Physics and Astronomy › Condensed Matter Physics

Micro and Nano Robotics

Works Count: 30439

Wikipedia

Description

This cluster of papers explores the hydrodynamics, self-propulsion, and collective behavior of active matter, including swimming microorganisms, colloidal particles, and nanomotors. It covers a wide range of topics such as biomedical applications, catalytic nanomotors, fluid dynamics, and the interactions of active particles in complex environments.

Keywords

Hydrodynamics; Micro/Nanomotors; Self-Propulsion; Colloidal Particles; Swimming Microorganisms; Bacterial Motion; Biomedical Applications; Catalytic Nanomotors; Fluid Dynamics; Collective Behavior

Athermal Phase Separation of Self-Propelled Particles with No Alignment

2012-06-08

Yaouen Fily , M. Cristina Marchetti

We study numerically and analytically a model of self-propelled polar disks on a substrate in two dimensions. The particles interact via isotropic repulsive forces and are subject to rotational noise, … We study numerically and analytically a model of self-propelled polar disks on a substrate in two dimensions. The particles interact via isotropic repulsive forces and are subject to rotational noise, but there is no aligning interaction. As a result, the system does not exhibit an ordered state. The isotropic fluid phase separates well below close packing and exhibits the large number fluctuations and clustering found ubiquitously in active systems. Our work shows that this behavior is a generic property of systems that are driven out of equilibrium locally, as for instance by self propulsion.

View PDF Chat

Biomedical Applications of Untethered Mobile Milli/Microrobots

2015-02-01

Metin Sitti , Hakan Ceylan , Wenqi Hu +4 more

Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size … Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biomedical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

View PDF Chat

Analysis of the swimming of microscopic organisms

1951-11-22

Geoffrey Ingram Taylor

Large objects which propel themselves in air or water make use of inertia in the surrounding fluid. The propulsive organ pushes the fluid backwards, while the resistance of the body … Large objects which propel themselves in air or water make use of inertia in the surrounding fluid. The propulsive organ pushes the fluid backwards, while the resistance of the body gives the fluid a forward momentum. The forward and backward momenta exactly balance, but the propulsive organ and the resistance can be thought about as acting separately. This conception cannot be transferred to problems of propulsion in microscopic bodies for which the stresses due to viscosity may be many thousands of times as great as those due to inertia. No case of self-propulsion in a viscous fluid due to purely viscous forces seems to have been discussed. The motion of a fluid near a sheet down which waves of lateral displacement are propagated is described. It is found that the sheet moves forwards at a rate 2π 2 b 2 /λ 2 times the velocity of propagation of the waves. Here b is the amplitude and λ the wave-length. This analysis seems to explain how a propulsive tail can move a body through a viscous fluid without relying on reaction due to inertia. The energy dissipation and stress in the tail are also calculated. The work is extended to explore the reaction between the tails of two neighbouring small organisms with propulsive tails. It is found that if the waves down neighbouring tails are in phase very much less energy is dissipated in the fluid between them than when the waves are in opposite phase. It is also found that when the phase of the wave in one tail lags behind that in the other there is a strong reaction, due to the viscous stress in the fluid between them, which tends to force the two wave trains into phase. It is in fact observed that the tails of spermatozoa wave in unison when they are close to one another and pointing the same way.

Bacteria Swim by Rotating their Flagellar Filaments

1973-10-01

Howard C. Berg , Robert A. Anderson

Artificial bacterial flagella: Fabrication and magnetic control

2009-02-09

Li Zhang , Jake J. Abbott , Lixin Dong +3 more

Inspired by the natural design of bacterial flagella, we report artificial bacterial flagella (ABF) that have a comparable shape and size to their organic counterparts and can swim in a … Inspired by the natural design of bacterial flagella, we report artificial bacterial flagella (ABF) that have a comparable shape and size to their organic counterparts and can swim in a controllable fashion using weak applied magnetic fields. The helical swimmer consists of a helical tail resembling the dimensions of a natural flagellum and a thin soft-magnetic “head” on one end. The swimming locomotion of ABF is precisely controlled by three orthogonal electromagnetic coil pairs. Microsphere manipulation is performed, and the thrust force generated by an ABF is analyzed. ABF swimmers represent the first demonstration of microscopic artificial swimmers that use helical propulsion. Self-propelled devices such as these are of interest in fundamental research and for biomedical applications.

Light-Driven Motion of Liquids on a Photoresponsive Surface

2000-06-02

Kunihiro Ichimura , Sang-Keun Oh , Masaru Nakagawa

The macroscopic motion of liquids on a flat solid surface was manipulated reversibly by photoirradiation of a photoisomerizable monolayer covering the surface. When a liquid droplet several millimeters in diameter … The macroscopic motion of liquids on a flat solid surface was manipulated reversibly by photoirradiation of a photoisomerizable monolayer covering the surface. When a liquid droplet several millimeters in diameter was placed on a substrate surface modified with a calix[4]resorcinarene derivative having photochromic azobenzene units, asymmetrical photoirradiation caused a gradient in surface free energy due to the photoisomerization of surface azobenzenes, leading to the directional motion of the droplet. The direction and velocity of the motion were tunable by varying the direction and steepness of the gradient in light intensity. The light-driven motion of a fluid substance in a surface-modified glass tube suggests potential applicability to microscale chemical process systems.

Living Crystals of Light-Activated Colloidal Surfers

2013-02-01

Jérémie Palacci , Stefano Sacanna , Asher Preska Steinberg +2 more

Spontaneous formation of colonies of bacteria or flocks of birds are examples of self-organization in active living matter. Here, we demonstrate a form of self-organization from nonequilibrium driving forces in … Spontaneous formation of colonies of bacteria or flocks of birds are examples of self-organization in active living matter. Here, we demonstrate a form of self-organization from nonequilibrium driving forces in a suspension of synthetic photoactivated colloidal particles. They lead to two-dimensional "living crystals," which form, break, explode, and re-form elsewhere. The dynamic assembly results from a competition between self-propulsion of particles and an attractive interaction induced respectively by osmotic and phoretic effects and activated by light. We measured a transition from normal to giant-number fluctuations. Our experiments are quantitatively described by simple numerical simulations. We show that the existence of the living crystals is intrinsically related to the out-of-equilibrium collisions of the self-propelled particles.

Statistical Mechanics of Interacting Run-and-Tumble Bacteria

2008-05-29

Julien Tailleur , M. E. Cates

We consider self-propelled particles undergoing run-and-tumble dynamics (as exhibited by E. coli) in one dimension. Building on previous analyses at drift-diffusion level for the one-particle density, we add both interactions … We consider self-propelled particles undergoing run-and-tumble dynamics (as exhibited by E. coli) in one dimension. Building on previous analyses at drift-diffusion level for the one-particle density, we add both interactions and noise, enabling discussion of domain formation by ``self-trapping,'' and other collective phenomena. Mapping onto detailed-balance systems is possible in certain cases.

View PDF Chat

Onset of Collective and Cohesive Motion

2004-01-15

Guillaume Grégoire , Hugues Chaté

We study the onset of collective motion, with and without cohesion, of groups of noisy self-propelled particles interacting locally. We find that this phase transition, in two space dimensions, is … We study the onset of collective motion, with and without cohesion, of groups of noisy self-propelled particles interacting locally. We find that this phase transition, in two space dimensions, is always discontinuous, including for the minimal model of Vicsek et al. [Phys. Rev. Lett. 75, 1226 (1995)]] for which a nontrivial critical point was previously advocated. We also show that cohesion is always lost near onset, as a result of the interplay of density, velocity, and shape fluctuations.

View PDF Chat

Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk

2007-07-27

Jonathan R. Howse , Richard Jones , Anthony J. Ryan +3 more

The motion of an artificial microscale swimmer that uses a chemical reaction catalyzed on its own surface to achieve autonomous propulsion is fully characterized experimentally. It is shown that at … The motion of an artificial microscale swimmer that uses a chemical reaction catalyzed on its own surface to achieve autonomous propulsion is fully characterized experimentally. It is shown that at short times it has a substantial component of directed motion, with a velocity that depends on the concentration of fuel molecules. At longer times, the motion reverts to a random walk with a substantially enhanced diffusion coefficient. Our results suggest strategies for designing artificial chemotactic systems.

View PDF Chat

Controlled Propulsion of Artificial Magnetic Nanostructured Propellers

2009-05-04

Ambarish Ghosh , Peer Fischer

For biomedical applications, such as targeted drug delivery and microsurgery, it is essential to develop a system of swimmers that can be propelled wirelessly in fluidic environments with good control. … For biomedical applications, such as targeted drug delivery and microsurgery, it is essential to develop a system of swimmers that can be propelled wirelessly in fluidic environments with good control. Here, we report the construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields. The propellers are made via nanostructured surfaces and can be produced in large numbers. The nanopropellers can carry chemicals, push loads, and act as local probes in rheological measurements.

Dynamical Clustering and Phase Separation in Suspensions of Self-Propelled Colloidal Particles

2013-06-05

Ivo Buttinoni , Julian Bialké , Felix Kümmel +3 more

We study experimentally and numerically a (quasi) two dimensional colloidal suspension of self-propelled spherical particles. The particles are carbon-coated Janus particles, which are propelled due to diffusiophoresis in a near-critical … We study experimentally and numerically a (quasi) two dimensional colloidal suspension of self-propelled spherical particles. The particles are carbon-coated Janus particles, which are propelled due to diffusiophoresis in a near-critical water-lutidine mixture. At low densities, we find that the driving stabilizes small clusters. At higher densities, the suspension undergoes a phase separation into large clusters and a dilute gas phase. The same qualitative behavior is observed in simulations of a minimal model for repulsive self-propelled particles lacking any alignment interactions. The observed behavior is rationalized in terms of a dynamical instability due to the self-trapping of self-propelled particles.

View PDF Chat

Meso-scale turbulence in living fluids

2012-08-20

H. H. Wensink , Jörn Dunkel , Sebastian Heidenreich +4 more

Turbulence is ubiquitous, from oceanic currents to small-scale biological and quantum systems. Self-sustained turbulent motion in microbial suspensions presents an intriguing example of collective dynamical behavior among the simplest forms … Turbulence is ubiquitous, from oceanic currents to small-scale biological and quantum systems. Self-sustained turbulent motion in microbial suspensions presents an intriguing example of collective dynamical behavior among the simplest forms of life and is important for fluid mixing and molecular transport on the microscale. The mathematical characterization of turbulence phenomena in active nonequilibrium fluids proves even more difficult than for conventional liquids or gases. It is not known which features of turbulent phases in living matter are universal or system-specific or which generalizations of the Navier–Stokes equations are able to describe them adequately. Here, we combine experiments, particle simulations, and continuum theory to identify the statistical properties of self-sustained meso-scale turbulence in active systems. To study how dimensionality and boundary conditions affect collective bacterial dynamics, we measured energy spectra and structure functions in dense Bacillus subtilis suspensions in quasi-2D and 3D geometries. Our experimental results for the bacterial flow statistics agree well with predictions from a minimal model for self-propelled rods, suggesting that at high concentrations the collective motion of the bacteria is dominated by short-range interactions. To provide a basis for future theoretical studies, we propose a minimal continuum model for incompressible bacterial flow. A detailed numerical analysis of the 2D case shows that this theory can reproduce many of the experimentally observed features of self-sustained active turbulence.

View PDF Chat

Microscopic artificial swimmers

2005-10-01

Rémi Dreyfus , Jean Baudry , Marcus Roper +3 more

On the squirming motion of nearly spherical deformable bodies through liquids at very small reynolds numbers

1952-05-01

M. J. Lighthill

Large-amplitude elongated-body theory of fish locomotion

1971-11-16

M. J. Lighthill

The elongated-body theory of the reactive forces on a fish moving in water (that is, forces resulting from the inertia of associated water movements) is extended so that a prediction … The elongated-body theory of the reactive forces on a fish moving in water (that is, forces resulting from the inertia of associated water movements) is extended so that a prediction of instantaneous reactive force between fish and water is obtained for fish motions of arbitrary amplitude, regular or irregular (§2). A preliminary application of the theory to the balance of reactive thrust and resistive drag in regular carangiform swimming of fishes with slender caudal fins is made (§3). Comparison with data (Bainbridge 1963) on the dace Leuciscus suggests that an important feature of this balance may be a substantial enhancement of drag for such fishes when swimming movements commence, an enhancement here interpreted in terms of a boundary-layer-thinning mechanism first suggested by Dr Quentin Bone.

Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport

2012-01-02

Soichiro Tottori , Li Zhang , Famin Qiu +3 more

A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always … A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts.

Spontaneous motion in hierarchically assembled active matter

2012-11-01

Tim Sanchez , Daniel T. N. Chen , Stephen J. DeCamp +2 more

View PDF Chat

Flocks, herds, and schools: A quantitative theory of flocking

1998-10-01

John Toner , Yuhai Tu

We present a quantitative continuum theory of ``flocking'': the collective coherent motion of large numbers of self-propelled organisms. In agreement with everyday experience, our model predicts the existence of an … We present a quantitative continuum theory of ``flocking'': the collective coherent motion of large numbers of self-propelled organisms. In agreement with everyday experience, our model predicts the existence of an ``ordered phase'' of flocks, in which all members of even an arbitrarily large flock move together with the same mean velocity $〈\stackrel{\ensuremath{\rightarrow}}{v}〉\ensuremath{\ne}0.$ This coherent motion of the flock is an example of spontaneously broken symmetry: no preferred direction for the motion is picked out a priori in the model; rather, each flock is allowed to, and does, spontaneously pick out some completely arbitrary direction to move in. By analyzing our model we can make detailed, quantitative predictions for the long-distance, long-time behavior of this ``broken symmetry state.'' The ``Goldstone modes'' associated with this ``spontaneously broken rotational symmetry'' are fluctuations in the direction of motion of a large part of the flock away from the mean direction of motion of the flock as a whole. These ``Goldstone modes'' mix with modes associated with conservation of bird number to produce propagating sound modes. These sound modes lead to enormous fluctuations of the density of the flock, far larger, at long wavelengths, than those in, e.g., an equilibrium gas. Our model is similar in many ways to the Navier-Stokes equations for a simple compressible fluid; in other ways, it resembles a relaxational time-dependent Ginsburg-Landau theory for an $n=d$ component isotropic ferromagnet. In spatial dimensions $d>4,$ the long-distance behavior is correctly described by a linearized theory, and is equivalent to that of an unusual but nonetheless equilibrium model for spin systems. For $d<4,$ nonlinear fluctuation effects radically alter the long distance behavior, making it different from that of any known equilibrium model. In particular, we find that in $d=2,$ where we can calculate the scaling exponents exactly, flocks exhibit a true, long-range ordered, spontaneously broken symmetry state, in contrast to equilibrium systems, which cannot spontaneously break a continuous symmetry in $d=2$ (the ``Mermin-Wagner'' theorem). We make detailed predictions for various correlation functions that could be measured either in simulations, or by quantitative imaging of real flocks. We also consider an anisotropic model, in which the birds move preferentially in an ``easy'' (e.g., horizontal) plane, and make analogous, but quantitatively different, predictions for that model as well. For this anisotropic model, we obtain exact scaling exponents for all spatial dimensions, including the physically relevant case $d=3.$

View PDF Chat

Catalytic Nanomotors: Autonomous Movement of Striped Nanorods

2004-09-21

Walter F. Paxton , Kevin C. Kistler , Christine C. Olmeda +6 more

Rod-shaped particles, 370 nm in diameter and consisting of 1 μm long Pt and Au segments, move autonomously in aqueous hydrogen peroxide solutions by catalyzing the formation of oxygen at … Rod-shaped particles, 370 nm in diameter and consisting of 1 μm long Pt and Au segments, move autonomously in aqueous hydrogen peroxide solutions by catalyzing the formation of oxygen at the Pt end. In 2−3% hydrogen peroxide solution, these rods move predominantly along their axis in the direction of the Pt end at speeds of up to 10 body lengths per second. The dimensions of the rods and their speeds are similar to those of multiflagellar bacteria. The force along the rod axis, which is on the order of 10-14 N, is generated by the oxygen concentration gradient, which in turn produces an interfacial tension force that balances the drag force at steady state. By solving the convection-diffusion equation in the frame of the moving rod, it was found that the interfacial tension force scales approximately as SR2γ/μDL, where S is the area-normalized oxygen evolution rate, γ is the liquid−vapor interfacial tension, R is the rod radius, μ is the viscosity, D is the diffusion coefficient of oxygen, and L is the length of the rod. Experiments in ethanol−water solutions confirmed that the velocity depends linearly with the product Sγ, and scaling experiments showed a strong dependence of the velocity on R and L. The direction of motion implies that the gold surface is hydrophobic under the conditions of the experiment. Tapping-mode AFM images of rods in air-saturated water show soft features that are not apparent in images acquired in air. These features are postulated to be nanobubbles, which if present in hydrogen peroxide solutions, would account for the observed direction of motion.

A Method for Measuring Chemotaxis and Use of the Method to Determine Optimum Conditions for Chemotaxis by Escherichia coli

1973-01-01

Julius Adler

SUMMARY: Chemotaxis of a bacterium such as Escherichia coli is assayed by measuring the number of organisms attracted into a capillary tube containing an attractant. Rate of bacterial accumulation in … SUMMARY: Chemotaxis of a bacterium such as Escherichia coli is assayed by measuring the number of organisms attracted into a capillary tube containing an attractant. Rate of bacterial accumulation in capillaries and a concentration-response curve for l-aspartate taxis are presented and interpreted, and the effect of bacterial concentration is reported. Other parameters of the assay were studied, such as the volume of fluid in the capillary and the size of the capillary opening. The concentration gradient of chemical was also described. Escherichia coli chemotaxis requires EDTA to allow motility, a buffer to maintain the pH at its optimum near neutrality, and l-methionine if it cannot be synthesized. Under certain conditions there is stimulation by inorganic ions, either by K+ or, less effectively, by Na+. Chemotaxis is dependent on temperature, there being a 20-fold increase in the number of bacteria accumulating in a capillary when the temperature is raised from 20 to 30 °C.

Hydrodynamics of soft active matter

2013-07-19

M. Cristina Marchetti , Jean‐François Joanny , Sriraṁ Ramaswamy +4 more

This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical … This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are ``dry'' systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or ``wet'' systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

Soft robotics: a bioinspired evolution in robotics

2013-04-17

Sangbae Kim , Cecilia Laschi , Barry A. Trimmer

Hydrodynamic Attraction of Swimming Microorganisms by Surfaces

2008-07-17

Allison P. Berke , Linda Turner , Howard C. Berg +1 more

Cells swimming in confined environments are attracted by surfaces. We measure the steady-state distribution of smooth-swimming bacteria (Escherichia coli) between two glass plates. In agreement with earlier studies, we find … Cells swimming in confined environments are attracted by surfaces. We measure the steady-state distribution of smooth-swimming bacteria (Escherichia coli) between two glass plates. In agreement with earlier studies, we find a strong increase of the cell concentration at the boundaries. We demonstrate theoretically that hydrodynamic interactions of the swimming cells with solid surfaces lead to their reorientation in the direction parallel to the surfaces, as well as their attraction by the closest wall. A model is derived for the steady-state distribution of swimming cells, which compares favorably with our measurements. We exploit our data to estimate the flagellar propulsive force in swimming E. coli.

View PDF Chat

Nanomotor rotates microscale objects

2006-03-01

Rienk Eelkema , Michael M. Pollard , Javier Vicario +5 more

View PDF Chat

Hydrodynamic Fluctuations and Instabilities in Ordered Suspensions of Self-Propelled Particles

2002-07-15

Robert Simha , Sriraṁ Ramaswamy

We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) Nematic SPP suspensions are always absolutely … We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) Nematic SPP suspensions are always absolutely unstable at long wavelengths. (ii) SPP suspensions support novel propagating modes at long wavelengths, coupling orientation, flow, and concentration. (iii) In a wave number regime accessible only in low Reynolds number systems such as bacteria, polar-ordered suspensions are invariably convectively unstable. (iv) The variance in the number N of particles, divided by the mean <N>, diverges as <N >(2/3 ) in polar-ordered SPP suspensions.

View PDF Chat

OctoMag: An Electromagnetic System for 5-DOF Wireless Micromanipulation

2010-10-08

Michael P. Kummer , Jake J. Abbott , Bradley E. Kratochvil +3 more

We demonstrate five-degree-of-freedom (5-DOF) wireless magnetic control of a fully untethered microrobot (3-DOF position and 2-DOF pointing orientation). The microrobot can move through a large workspace and is completely unrestrained … We demonstrate five-degree-of-freedom (5-DOF) wireless magnetic control of a fully untethered microrobot (3-DOF position and 2-DOF pointing orientation). The microrobot can move through a large workspace and is completely unrestrained in the rotation DOF. We accomplish this level of wireless control with an electromagnetic system that we call OctoMag. OctoMag's unique abilities are due to its utilization of complex nonuniform magnetic fields, which capitalizes on a linear representation of the coupled field contributions of multiple soft-magnetic-core electromagnets acting in concert. OctoMag was primarily designed to control intraocular microrobots for delicate retinal procedures, but it also has potential uses in other medical applications or micromanipulation under an optical microscope.

View PDF Chat

Emergence of macroscopic directed motion in populations of motile colloids

2013-11-01

Antoine Bricard , Jean-Baptiste Caussin , Nicolas Desreumaux +2 more

View PDF Chat

Hydrodynamics and phases of flocks

2005-06-10

John Toner , Yuhai Tu , Sriraṁ Ramaswamy

View PDF Chat

Fluid Mechanics of Propulsion by Cilia and Flagella

1977-01-01

Christopher E. Brennen , Howard Winet

The field of fluid mechanics is rapidly advancing, driven by unprecedented volumes of data from experiments, field measurements, and large-scale simulations at multiple spatiotemporal scales. Machine learning (ML) offers a … The field of fluid mechanics is rapidly advancing, driven by unprecedented volumes of data from experiments, field measurements, and large-scale simulations at multiple spatiotemporal scales. Machine learning (ML) offers a wealth of techniques to extract ...Read More

View PDF Chat

The hydrodynamics of swimming microorganisms

2009-08-25

Eric Lauga , Thomas Powers

Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion … Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming, tens of micrometers and below. At this scale, inertia is unimportant and the Reynolds number is small. Our emphasis is on the simple physical picture and fundamental flow physics phenomena in this regime. We first give a brief overview of the mechanisms for swimming motility, and of the basic properties of flows at low Reynolds number, paying special attention to aspects most relevant for swimming such as resistance matrices for solid bodies, flow singularities and kinematic requirements for net translation. Then we review classical theoretical work on cell motility, in particular early calculations of swimming kinematics with prescribed stroke and the application of resistive force theory and slender-body theory to flagellar locomotion. After examining the physical means by which flagella are actuated, we outline areas of active research, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers and the optimization of locomotion strategies.

View PDF Chat

Chemically Powered Micro‐ and Nanomotors

2014-12-12

Samuel Sánchez , Lluís Soler , Jaideep Katuri

Abstract Chemically powered micro‐ and nanomotors are small devices that are self‐propelled by catalytic reactions in fluids. Taking inspiration from biomotors, scientists are aiming to find the best architecture for … Abstract Chemically powered micro‐ and nanomotors are small devices that are self‐propelled by catalytic reactions in fluids. Taking inspiration from biomotors, scientists are aiming to find the best architecture for self‐propulsion, understand the mechanisms of motion, and develop accurate control over the motion. Remotely guided nanomotors can transport cargo to desired targets, drill into biomaterials, sense their environment, mix or pump fluids, and clean polluted water. This Review summarizes the major advances in the growing field of catalytic nanomotors, which started ten years ago.

A spherical envelope approach to ciliary propulsion

1971-03-15

J. R. Blake

In this paper, an attempt has been made to model the dynamics of ciliary propulsion through the concept of an ‘envelope’ covering the ends of the numerous cilia of the … In this paper, an attempt has been made to model the dynamics of ciliary propulsion through the concept of an ‘envelope’ covering the ends of the numerous cilia of the microscopic organism. This approximation may be made in the case when the cilia are close together, as can occur in the case of the symplectic metachronal wave (i.e. the wave travels in the same direction as the effective beat). For simplicity, a spherical model has been chosen, and the analysis which follows is a correction to Lighthill's (1952) paper on squirming motions of a nearly spherical organism. The velocity and efficiency compared to the work done in pushing an inert organism are obtained, and compared to that of a ciliated organism.

The Rotary Motor of Bacterial Flagella

2003-06-01

Howard C. Berg

▪ Abstract Flagellated bacteria, such as Escherichia coli, swim by rotating thin helical filaments, each driven at its base by a reversible rotary motor, powered by an ion flux. A … ▪ Abstract Flagellated bacteria, such as Escherichia coli, swim by rotating thin helical filaments, each driven at its base by a reversible rotary motor, powered by an ion flux. A motor is about 45 nm in diameter and is assembled from about 20 different kinds of parts. It develops maximum torque at stall but can spin several hundred Hz. Its direction of rotation is controlled by a sensory system that enables cells to accumulate in regions deemed more favorable. We know a great deal about motor structure, genetics, assembly, and function, but we do not really understand how it works. We need more crystal structures. All of this is reviewed, but the emphasis is on function.

Influence of interfaces on microbial activity

1990-03-01

Mark C.M. van Loosdrecht , J. Lyklema , Willem Norde +1 more

Bacterial adhesion in natural and artificial systems has been critically reviewed to investigate the influences exerted by the presence of interfaces. Numerous investigations have demonstrated that, in the presence of … Bacterial adhesion in natural and artificial systems has been critically reviewed to investigate the influences exerted by the presence of interfaces. Numerous investigations have demonstrated that, in the presence of a solid phase, the activity of bacterial cultures is changed. Reviewing relevant literature, two problems were encountered. One is of an experimental nature. Due to lack of similarity in experimental conditions, disparate experiments often cannot be compared; their results may even appear conflicting. The other problem is of an interpretational nature: several hypothetical theories exist which try to explain the effect of surfaces on microbial activity. These theories often confuse changes in the medium and limitations in mass transfer which are due to the presence of solid surfaces (indirect influences) with changes in cell properties (direct influences). Whenever a surface is reported to influence the metabolism of bacteria, the action is found almost exclusively to be due to changes in the medium or environment and is therefore indirect. Based on data reported in the literature, and by using thermodynamic and kinetic considerations, it is concluded that so far neither experimental nor theoretical evidence exists for a direct influence of interfaces on microbial activity.

View PDF Chat

Swimming in Circles: Motion of Bacteria near Solid Boundaries

2005-10-26

Eric Lauga , Willow R. DiLuzio , George M. Whitesides +1 more

View PDF Chat

Motility-Induced Phase Separation

2015-01-12

M. E. Cates , Julien Tailleur

Self-propelled particles include both self-phoretic synthetic colloids and various micro-organisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: … Self-propelled particles include both self-phoretic synthetic colloids and various micro-organisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: the steady state is then independent of kinetic parameters. In contrast, self-propelled particles tend to accumulate where they move more slowly. They may also slow down at high density, for either biochemical or steric reasons. This creates positive feedback which can lead to motility-induced phase separation (MIPS) between dense and dilute fluid phases. At leading order in gradients, a mapping relates variable-speed, self-propelled particles to passive particles with attractions. This deep link to equilibrium phase separation is confirmed by simulations, but generally breaks down at higher order in gradients: new effects, with no equilibrium counterpart, then emerge. We give a selective overview of the fast-developing field of MIPS, focusing on theory and simulation but including a brief speculative survey of its experimental implications.

View PDF Chat

Transient assembly of active materials fueled by a chemical reaction

2015-09-03

Job Boekhoven , Wouter E. Hendriksen , Ger J. M. Koper +2 more

Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular organization. Continuous energy supply maintains these transient biomolecular assemblies far from thermodynamic equilibrium, unlike typical synthetic systems … Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular organization. Continuous energy supply maintains these transient biomolecular assemblies far from thermodynamic equilibrium, unlike typical synthetic systems that spontaneously assemble at thermodynamic equilibrium. Here, we report the transient self-assembly of synthetic molecules into active materials, driven by the consumption of a chemical fuel. In these materials, reaction rates and fuel levels, instead of equilibrium composition, determine properties such as lifetime, stiffness, and self-regeneration capability. Fibers exhibit strongly nonlinear behavior including stochastic collapse and simultaneous growth and shrinkage, reminiscent of microtubule dynamics.

Microrobots for Minimally Invasive Medicine

2010-07-01

Bradley J. Nelson , I. Kaliakatsos , Jake J. Abbott

Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new … Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical microrobots; second, to explore the potential impact of medical microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical microrobots.

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

2016-02-15

Stefano Palagi , Andrew G. Mark , Shang Yik Reigh +7 more

View PDF Chat

Active Particles in Complex and Crowded Environments

2016-11-23

Clemens Bechinger , Roberto Di Leonardo , Hartmut Löwen +3 more

Differently from passive Brownian particles, active particles, also known as self-propelled Brownian particles or microswimmers and nanoswimmers, are capable of taking up energy from their environment and converting it into … Differently from passive Brownian particles, active particles, also known as self-propelled Brownian particles or microswimmers and nanoswimmers, are capable of taking up energy from their environment and converting it into directed motion. Because of this constant flow of energy, their behavior can only be explained and understood within the framework of nonequilibrium physics. In the biological realm, many cells perform directed motion, for example, as a way to browse for nutrients or to avoid toxins. Inspired by these motile microorganisms, researchers have been developing artificial particles that feature similar swimming behaviors based on different mechanisms; these manmade micro- and nanomachines hold a great potential as autonomous agents for healthcare, sustainability, and security applications. With a focus on the basic physical features of the interactions of self-propelled Brownian particles with a crowded and complex environment, this comprehensive review will put the reader at the very forefront of the field, providing a guided tour through its basic principles, the development of artificial self-propelling micro- and nanoparticles, and their application to the study of nonequilibrium phenomena, as well as the open challenges that the field is currently facing.

View PDF Chat

Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water

2017-02-01

Hyunwoo Yuk , Shaoting Lin , Chu Ma +3 more

Abstract Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the … Abstract Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the capabilities of leptocephali will enable new applications in diverse fields. However, existing hydrogel actuators, mostly osmotic-driven, are intrinsically low-speed and/or low-force; and their camouflage capabilities have not been explored. Here we show that hydraulic actuations of hydrogels with designed structures and properties can give soft actuators and robots that are high-speed, high-force, and optically and sonically camouflaged in water. The hydrogel actuators and robots can maintain their robustness and functionality over multiple cycles of actuations, owing to the anti-fatigue property of the hydrogel under moderate stresses. We further demonstrate that the agile and transparent hydrogel actuators and robots perform extraordinary functions including swimming, kicking rubber-balls and even catching a live fish in water.

View PDF Chat

Micro/nanorobots for biomedicine: Delivery, surgery, sensing, and detoxification

2017-03-01

Jinxing Li , Berta Esteban‐Fernández de Ávila , Wei Gao +2 more

Micro- and nanoscale robots that can effectively convert diverse energy sources into movement and force represent a rapidly emerging and fascinating robotics research area. Recent advances in the design, fabrication, … Micro- and nanoscale robots that can effectively convert diverse energy sources into movement and force represent a rapidly emerging and fascinating robotics research area. Recent advances in the design, fabrication, and operation of micro/nanorobots have greatly enhanced their power, function, and versatility. The new capabilities of these tiny untethered machines indicate immense potential for a variety of biomedical applications. This article reviews recent progress and future perspectives of micro/nanorobots in biomedicine, with a special focus on their potential advantages and applications for directed drug delivery, precision surgery, medical diagnosis and detoxification. Future success of this technology, to be realized through close collaboration between robotics, medical and nanotechnology experts, should have a major impact on disease diagnosis, treatment, and prevention.

View PDF Chat

A soft robot that navigates its environment through growth

2017-07-19

Elliot W. Hawkes , Laura H. Blumenschein , Joseph A. Greer +1 more

Across kingdoms and length scales, certain cells and organisms navigate their environments not through locomotion but through growth. This pattern of movement is found in fungal hyphae, developing neurons, and … Across kingdoms and length scales, certain cells and organisms navigate their environments not through locomotion but through growth. This pattern of movement is found in fungal hyphae, developing neurons, and trailing plants, and is characterized by extension from the tip of the body, length change of hundreds of percent, and active control of growth direction. This results in the abilities to move through tightly constrained environments and form useful three-dimensional structures from the body. We report a class of soft pneumatic robot that is capable of a basic form of this behavior, growing substantially in length from the tip while actively controlling direction using onboard sensing of environmental stimuli; further, the peak rate of lengthening is comparable to rates of animal and robot locomotion. This is enabled by two principles: Pressurization of an inverted thin-walled vessel allows rapid and substantial lengthening of the tip of the robot body, and controlled asymmetric lengthening of the tip allows directional control. Further, we demonstrate the abilities to lengthen through constrained environments by exploiting passive deformations and form three-dimensional structures by lengthening the body of the robot along a path. Our study helps lay the foundation for engineered systems that grow to navigate the environment.

View PDF Chat

Small-scale soft-bodied robot with multimodal locomotion

2018-01-24

Wenqi Hu , Guo Zhan Lum , Massimo Mastrangeli +1 more

Ferromagnetic soft continuum robots

2019-08-21

Yoonho Kim , German Alberto Parada , Shengduo Liu +1 more

A submillimeter-scale, soft continuum robot navigates through highly constrained environments by steering based on magnetic actuation. A submillimeter-scale, soft continuum robot navigates through highly constrained environments by steering based on magnetic actuation.

Collective motion

2012-03-21

Tamás Vicsek , Anna Zafeiris

View PDF Chat

The Mechanics and Statistics of Active Matter

2010-07-29

Sriraṁ Ramaswamy

Active particles contain internal degrees of freedom with the ability to take in and dissipate energy and, in the process, execute systematic movement. Examples include all living organisms and their … Active particles contain internal degrees of freedom with the ability to take in and dissipate energy and, in the process, execute systematic movement. Examples include all living organisms and their motile constituents such as molecular motors. This article reviews recent progress in applying the principles of nonequilibrium statistical mechanics and hydrodynamics to form a systematic theory of the behaviour of collections of active particles -- active matter -- with only minimal regard to microscopic details. A unified view of the many kinds of active matter is presented, encompassing not only living systems but inanimate analogues. Theory and experiment are discussed side by side.

View PDF Chat

Physics of microswimmers—single particle motion and collective behavior: a review

2015-04-28

Jens Elgeti , Roland G. Winkler , Gerhard Gompper

Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible … Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.

View PDF Chat

Anisotropic fluids

1959-01-01

J. L. Ericksen

Reconfigurable robust microrobot collectives with large force output enabled by gradient magnetic fields

2025-06-25

Zichen Xu , Wei Ge , Qingsong Xu | Science Advances

Robot collectives offer a promising solution for complex assignments that are nearly impossible for individual robots to execute. In microscopic scenarios, organizing microrobot collectives is now governed by agent-agent physical … Robot collectives offer a promising solution for complex assignments that are nearly impossible for individual robots to execute. In microscopic scenarios, organizing microrobot collectives is now governed by agent-agent physical interactions. However, the existing methods are insufficient to produce robust connections and fail to tolerate harsh environments. We propose a strategy to efficiently program microrobots into reconfigurable robust collectives to operate in various dynamic environments. Magnetic collectives are produced to achieve reconfigurable pattern transformation with considerable structural enhancement via well-designed gradient magnetic fields. The strong gradient magnetic field-induced connections among individual microrobots enable a record-breaking 700-fold output force enhancement, and 0.2-gram microrobot collectives generate Newton-level output forces. The proposed reconfigurable microrobot collectives provide a stable and promising approach to executing droplet, fluid, and solid manipulations via powerful output forces. These results may have implications for further understanding of self-assembly, particle systems, microrobot collectives, smart dust, and related microscopic multiagent behaviors.

Autonomous chemo-metabolic construction of anisotropic cell-in-shell nanobiohybrids in enzyme-powered cell microrobots

2025-06-25

N. Kim , Sang Yeong Han , Hyeong Bin Rheem +2 more | Science Advances

Living organisms use intricate strategies to adapt and survive in response to potentially lethal environment changes. Inspired by cryptobiosis in nature, researchers have pioneered approaches to create cell-in-shell nanobiohybrids, aiming … Living organisms use intricate strategies to adapt and survive in response to potentially lethal environment changes. Inspired by cryptobiosis in nature, researchers have pioneered approaches to create cell-in-shell nanobiohybrids, aiming to endow cells with enhanced protection and exogenous functions. Yet, these methods still lack the biological autonomy intrinsic to natural cellular responses. Here, we present an innovative chemo-metabolically coupled strategy for the autonomous construction of cell-in-shell structures in cell growth medium. Our system harnesses ethanol fermentation by Saccharomyces cerevisiae, chemically coupled with an enzymatic cascade involving alcohol oxidase and horseradish peroxidase, to drive the nanoshell formation of polydopamine. The integration of autonomous shell formation with cellular proliferation produces anisotropic cell-in-shell structures, which can serve as enzyme-powered cell microrobots, upon conjugation with urease. Our autonomous system enables the creation of cell-in-shell nanobiohybrids with dynamic and adaptive environmental interactions, paving the way for transformative applications in synthetic biology, such as artificial cells, as well as advancements in cell-based therapies.

Does nematic order allow groups of elongated cells to sense electric fields better?

2025-06-25

Kurmanbek Kaiyrbekov , Brian A. Camley | PLoS ONE

Collective response to external directional cues like electric fields helps guide tissue development, regeneration, and wound healing. In this study we focus on the impact of anisotropy in cell shape … Collective response to external directional cues like electric fields helps guide tissue development, regeneration, and wound healing. In this study we focus on the impact of anisotropy in cell shape and local cell alignment on the collective response to electric fields. We model elongated cells that have a different accuracy sensing the field depending on their orientation with respect to the field. With this framework, we assume cells are better sensors if they can align their long axes perpendicular to the field. Elongated cells often line up with their long axes in the same direction — “nematic order” – does a nematic cell-cell interaction allow groups of cells to share information about their orientation to sense fields more accurately? We use simulations of a simple model to show that if cells orient themselves perpendicular to their average velocity, alignment of a cell’s long axis to its nearest neighbors’ orientation can in some circumstances enhance the directional response to electric fields. We also show that cell-cell adhesion modulates the accuracy of cells in the group.

Photocatalytic microrobots for treating bacterial infections deep within sinuses

2025-06-25

Haidong Yu , Xurui Liu , Yabin Zhang +7 more | Science Robotics

Microrobotic techniques are promising for treating biofilm infections located deep within the human body. However, the presence of highly viscous pus presents a formidable biological barrier, severely restricting targeted and … Microrobotic techniques are promising for treating biofilm infections located deep within the human body. However, the presence of highly viscous pus presents a formidable biological barrier, severely restricting targeted and minimally invasive treatments. In addition, conventional antibacterial agents exhibit limited payload integration with microrobotic systems, further compromising therapeutic efficiency. In this study, we propose a photocatalytic microrobot through a magnetically guided, optical fiber–assisted therapeutic platform specifically designed to treat bacterial infections in deep mucosal cavities. The microrobots comprising copper (Cu) single atom–doped bismuth oxoiodide (BiOI), termed CBMRs, can be guided and tracked by real-time x-ray imaging. Under external magnetic actuation, the illuminated region from the magnetically guided optical fiber synchronously follows the CBMR swarm, enabling effective antibacterial action at targeted infection sites. Upon continuous visible-light irradiation, the resultant photothermal effect substantially reduces the viscosity of pus on inflamed mucosal tissues, enhancing the penetration capability of the CBMR swarm by more than threefold compared with baseline conditions. Concurrently, atomic-level design of CBMRs facilitates robust generation of reactive oxygen species, enabling efficient biofilm disruption and reductions in bacterial viability. We validated the effectiveness of this integrated optical fiber–assisted microrobotic platform in a rabbit sinusitis model in vivo, demonstrating its potential for clinically relevant infection therapy.

Effective removal of water-soluble azo dyes by cubic MgO micromotors

2025-06-24

Yanxia Nan , Bo-Seon Kang , Xiaole Mei +2 more | Environmental Technology

As one of the main dyes in the textile industry, azo dyes have a serious impact on the ecological environment and health through their wastewater discharge. It has become crucial … As one of the main dyes in the textile industry, azo dyes have a serious impact on the ecological environment and health through their wastewater discharge. It has become crucial to develop effective methods for removing these substances. Currently, research on micro-nano technology is underway to develop new micro-nano systems and materials that can rapidly and effectively remove pollutants and heavy metals from water. This study reported the successful preparation of cubic magnesium oxide (MgO) micromotors dynamic nanomaterials through chemical deposition-hydrothermal-ion sputtering and explored the adsorption performance and mechanism of MgO micromotors on methyl orange (MO) azo dye. The surface morphology, composition and motion trajectory of nanomaterials were analysed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET automatic specific surface area and pore size analyser, X-ray diffraction (XRD), upright optical microscopy and NIS-Elements software. The MgO micromotors exhibit a mean square displacement of 4.599 μm2 and an average velocity of 3.87 ± 0.54 μm/s in a 6% H2O2 solution, demonstrating their self-propulsion ability in static water. Furthermore, the adsorption capacity of MgO micromotors for MO is significantly enhanced with increasing H2O2 concentration, reaching a removal rate as high as 97.46% at a 6% H2O2 concentration. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that a strong chemical bond (coordinate bond) was formed between the negatively charged anionic azo dye MO and the MgO micromotors which could be hydrolysed to produce easily dissociated magnesium hydroxide (Mg(OH)2) in aqueous solution, resulting in enhanced adsorption properties.

Self-alignment and anti-self-alignment suppress motility-induced phase separation in active systems

2025-06-24

Marco Musacchio , Alexander P. Antonov , Hartmut Löwen +1 more | The Journal of Chemical Physics

In this article, we investigate the impact of self-alignment and anti-self-alignment on collective phenomena in dense active matter. These mechanisms correspond to effective torques that align or anti-align a particle's … In this article, we investigate the impact of self-alignment and anti-self-alignment on collective phenomena in dense active matter. These mechanisms correspond to effective torques that align or anti-align a particle's orientation with its velocity, as observed in active granular systems. In the context of motility-induced phase separation (MIPS)-a non-equilibrium coexistence between a dense clustered phase and a dilute homogeneous phase-both self- and anti-self-alignment are found to suppress clustering. In particular, increasing self-alignment strength first leads to flocking within the dense cluster and eventually to the emergence of a homogeneous flocking phase. In contrast, anti-self-alignment induces a freezing phenomenon, progressively reducing particle speed until MIPS is suppressed and a homogeneous phase is recovered. These results are supported by scaling arguments and are amenable to experimental verification in high-density active granular systems exhibiting self- or anti-self-alignment.

Arrested development and traveling waves of active suspensions in nematic liquid crystals

2025-06-24

NULL AUTHOR_ID | Physical Review Fluids

Recent Advancements in Near-Infrared Light-Propelled Nanomotors for Biomedical Applications

2025-06-24

Yina Su , Guizhen Xu , Wei Wu +4 more | ACS Biomaterials Science & Engineering

Nanomotors (NMs) achieve autonomous motion by converting external energy into mechanical work, enabling them to perform complex tasks on demand. Among the various propulsion mechanisms for NMs, near-infrared (NIR) light … Nanomotors (NMs) achieve autonomous motion by converting external energy into mechanical work, enabling them to perform complex tasks on demand. Among the various propulsion mechanisms for NMs, near-infrared (NIR) light propulsion has attracted significant attention due to its excellent biocompatibility, deep tissue penetration, minimal damage to normal tissues, precise on/off control, and rapid response. Furthermore, NIR propulsion can be integrated with other propulsion mechanisms to overcome the limitations of single-mode systems. In this review, we explore the design of NIR light-propelled NMs, categorizing their mechanisms into three types: (1) photothermal propulsion, (2) NIR light-triggered bubble propulsion, and (3) photothermal-bubble dual-driven propulsion systems. We also highlight the applications of NIR light-propelled NMs in treating diseases such as tumors, thrombosis, and bacterial infections. In addition, the challenges and future prospects for the development of NIR light-propelled NMs are also discussed.

Magnetic Multifunctional Module Multiphasic Maneuver Mimicking Multienzyme Magic

2025-06-24

Yongyi Zeng , Xinjian Yin , Yating Zou +4 more | Journal of Agricultural and Food Chemistry

Coimmobilizing multiple proteins onto a single nanosupport holds great promise for mimicking natural multiprotein complexes and creating efficient cascade biocatalytic systems. However, controlling the spatial arrangement and loading ratio of … Coimmobilizing multiple proteins onto a single nanosupport holds great promise for mimicking natural multiprotein complexes and creating efficient cascade biocatalytic systems. However, controlling the spatial arrangement and loading ratio of different proteins poses a significant challenge, and coimmobilization often requires purified proteins. In this study, we developed a plug-and-display, sequential, and tunable coimmobilization strategy by combining Catcher/Tag pairs with HaloTag technology for the first time. We designed a chloroalkane-functionalized magnetic multifunctional module multiphasic maneuver mimicking multienzyme magic platform that combines HaloTag, SpyCatcher, DogCatcher, etc., allowing for rapid and stable capture of enzymes functionalized with corresponding Tags. By varying the number and order of Catchers or switching the tags, the spatial arrangement and loading ratio of different enzymes can be precisely controlled. The immobilized enzymes demonstrated high protein loading capacity and retained their catalytic activity. Moreover, the magnetic beads preserved their responsiveness, facilitating easy enzyme separation and recovery. This system also efficiently captured target enzymes directly from cell lysates, streamlining the immobilization process while reducing the time and cost. These findings represent a significant improvement over current methods for diverse advanced, sustainable, and biomedical applications.

Displaying In Vivo “Assembly–Disassembly” Cascade with “Off–On–Off” Magnetic Resonance Imaging Signals in Tumor

2025-06-24

Haidong Xu , Xianbao Sun , Zheng Huang +6 more | Journal of the American Chemical Society

"Assembly-Disassembly" cascade has been utilized as a highly effective approach for tumor theranostics, but its real-time in vivo monitoring remains challenging. Current strategies face a fundamental trade-off between penetration depth … "Assembly-Disassembly" cascade has been utilized as a highly effective approach for tumor theranostics, but its real-time in vivo monitoring remains challenging. Current strategies face a fundamental trade-off between penetration depth and real-time nature, while there is still no report on integrating both features to display this dynamic cascade in a living organism. In this work, we develop a gadolinium (Gd) probe Cys(StBu)-Asp-Asp-Asp-Asp-Lys-Lys(DOTA(Gd))-CBT (Gd-AD) to display an in vivo "Assembly-Disassembly" cascade via T1-weighted "Off-On-Off" 1H magnetic resonance imaging (MRI) signals. Under reduction conditions, Gd-AD undergoes a CBT-Cys click reaction to assemble into a Gd nanoparticle, with enhanced 1H MRI signals of 59.3% and 25.4% in cells and in tumors, respectively ("Off-On"). Upon enterokinase (ENTK) cleavage, the nanoparticle disassembles, rendering decreased 1H MRI signals of 23.4% and 15.2% in cells and in tumors, respectively ("On-Off"). A scrambled control probe Asp-Asp-Asp-Asp-Lys-Cys(StBu)-Lys(DOTA(Gd))-CBT (Gd-A), which responds to reduction and ENTK to assemble into a Gd nanoparticle with "Off-On" 1H MRI signals, is designed and studied in parallel. During 1 h tumor imaging, while Gd-A only displays "Off-On" 1H MRI signals, Gd-AD clearly shows "Off-On-Off" signals to reflect the "Assembly-Disassembly" cascade of Gd nanoparticles in tumor. We expect that our strategy of real-time display of in vivo "Assembly-Disassembly" cascade could help people to optimize their nanodrug-based tumor theranostics in the near future.

Self‐Assembly and Collective Locomotion Behavior of Swarm Microrobot

2025-06-23

Qilong Cheng , Yunhao Tai , Yuteng Liu +7 more | Small

Abstract Collective behaviors in microrobots achieve self‐assembly and execute complex tasks through swarm microrobot interactions and collaboration, which possess significant potential in biomedical applications. However, challenges such as swarm stability … Abstract Collective behaviors in microrobots achieve self‐assembly and execute complex tasks through swarm microrobot interactions and collaboration, which possess significant potential in biomedical applications. However, challenges such as swarm stability and diversity, and adaptability to complex environments remain to be addressed. In this study, magnetically anisotropic hydrogel microrobots are developed to explore the potential of assembly behavior and collective locomotion driven by the interactions of multiple microrobots. In this, microrobots with distinct magnetic particle arrangements exhibit different critical frequencies under magnetic fields, which play a pivotal role in governing their assembly behavior and collective locomotion. By categorizing microrobots with varying critical frequencies into separate units, the dynamic behaviors and collective modes of these units are investigated under rotating magnetic fields. Through precise regulation of magnetic field parameters and analysis of interaction mechanisms, efficient and stable collective modes are demonstrated. Furthermore, diverse collective modes and reversible self‐assembly dynamics of swarm microrobots are comprehensively investigated, with a specific focus on the biomedical application of linearly arranged microrobot swarms in targeted delivery. This work proposes a novel approach for achieving static assembly and controlled collective locomotion in microrobots, offering innovative insights into the design and implementation of swarm microrobots for biomedical engineering applications.

Robust and Fast‐Transforming Soft Microrobots Driven by Low Magnetic Field

2025-06-23

Yuanyuan Wang , Haili Qin , Niu Liu +3 more | Advanced Materials

Abstract Magnetically driven soft microrobots, characterized by their small size, soft structure, and responsiveness to magnetic fields, offer unique advantages such as high maneuverability, biocompatibility, and remote control, making them … Abstract Magnetically driven soft microrobots, characterized by their small size, soft structure, and responsiveness to magnetic fields, offer unique advantages such as high maneuverability, biocompatibility, and remote control, making them suitable for a variety of applications across multiple fields. Achieving low‐power actuation for microrobots is more accessible, safer, and cost‐effective, dependent on the precise quality and arrangement of their magnetic domains. However, traditional approaches integrating multi‐domain magnetic microstructures often introduce trade‐offs between mechanical stability and responsiveness. Here, a magnetic domain assembly method is presented for the fabrication of robust soft microrobots with fast transforming behaviors powered by low magnetic fields (3–15 mT). By developing a composite ink containing polyacrylamide chains grafted onto magnetizable single‐domain ferromagnetic NdFeB nanostructures, precise control over domain orientation within ultrafine filaments (80 µm) is achieved by magnetic field‐assisted 3D printing process, allowing complex and rapid shape morphing in under 1 s, even with less than 2 wt.% NdFeB. This uniform magnetic alignment results in a tenfold increase in mechanical toughness and impressive stretchability (1600%). With top‐performing actuation performance at low magnetic fields, the microrobots demonstrate multimodal locomotion and robust tasking capabilities, showcasing their transformative potential for next‐generation soft robotics.

Motors based on photo-magnetic materials

2025-06-23

Boris Kichatov , Vladimir Sudakov , Alexey Korshunov | The Journal of Chemical Physics

Absorption of light by a substance does not change its magnetic properties. However, if redox reactions occur on the surface of a material when irradiated with light and a current … Absorption of light by a substance does not change its magnetic properties. However, if redox reactions occur on the surface of a material when irradiated with light and a current loop is formed, it turns into a magnet. This study reports a method for producing a new type of material-photo-magnets, which are capable of changing their magnetic properties when exposed to light. The simplest photo-magnet is a bimetallic plate made of two dissimilar metals, one part of which is coated with a semiconductor material-zinc oxide-and it is immersed in a solution of hydrogen peroxide. When exposed to light, holes and electrons are formed in the semiconductor, which take part in redox reactions during the decomposition of hydrogen peroxide. Since a current loop is formed in this case, the photo-magnet becomes a source of a magnetic field. In addition, any loop with current in a non-uniform magnetic field is affected by a force whose nature is determined by the action of the Lorentz force on moving charges. Therefore, on the basis of photo-magnets, it is possible to create motors that will move in a non-uniform magnetic field when irradiated with light.

Micro- and nanorobots for pioneering precision medicine and medical processing at the cellular level

2025-06-23

Palanirajan Vijayaraj Kumar , Foo Kai Tian , Le Yi Chia +3 more | International Journal of Intelligent Robotics and Applications

Microrobots in Colorectal Cancer Diagnosis

2025-06-23

Sneha Pallatt , Ashiq Shibili , Sibin Nambidi +3 more | CRC Press eBooks

In Vivo Perspective of Microrobots/Microbots in Colorectal Cancer

2025-06-23

Ravi Gor , Lurdes Queimado , Vengatesh Ganapathy +5 more | CRC Press eBooks

Bio-Nanotechnology and Microbots

2025-06-23

Bipin D. Lade , Ishfaq Ahmed | CRC Press eBooks

Microplate Active Migration Emerging From Light‐Induced Phase Transitions in a Nematic Liquid Crystal

2025-06-23

Antonio Tavera‐Vázquez , Danai Montalvan‐Sorrosa , Gustavo R. Pérez-Lemus +4 more | Advanced Functional Materials

Abstract Achieving precise control over the diverse equilibrium configurations and corresponding optical textures of motile liquid crystals (LCs) in response to a wide range of external stimuli is a formidable … Abstract Achieving precise control over the diverse equilibrium configurations and corresponding optical textures of motile liquid crystals (LCs) in response to a wide range of external stimuli is a formidable challenge. This complexity becomes even more intriguing when applied to far‐from‐equilibrium systems. In this work, we investigate how LC phase transitions are leveraged to achieve controlled self‐propulsion of colloids. To accomplish that, we designed quasi‐2D solid, micron‐sized, light‐absorbing platelets suspended in a thermotropic nematic LC. When exposed to light, these platelets self‐propel, generating localized nematic‐isotropic (NI) phase transitions. The system's dynamics are governed by temperature, light intensity, and confinement, giving rise to three regimes: a large 2D regime where the platelet‐isotropic phase bubble remains stationary with a stable NI interface; a compact motile‐2D regime where the NI interface is closer to the platelet; and a motile‐3D confinement regime, marked by the appearance of multipolar LC configurations. Furthermore, we employed continuum mean‐field simulations to predict stable platelet‐LC states in slab confinements. The approach gives insights crucial for designing far‐from‐equilibrium synthetic systems with controlled propulsion and tunable topological reconfigurations. This has implications for advancements in photonics and material sciences.

Viscotaxis of chiral microswimmer in viscosity gradients

2025-06-23

Takuya Kobayashi , Ryōichi Yamamoto | Journal of Fluid Mechanics

Microswimmers display an intriguing ability to navigate through fluids with spatially varying viscosity, a behaviour known as viscotaxis, which plays a crucial role in guiding their motion. In this study, … Microswimmers display an intriguing ability to navigate through fluids with spatially varying viscosity, a behaviour known as viscotaxis, which plays a crucial role in guiding their motion. In this study, we reveal that the orientation dynamics of chiral squirmers in fluids with uniform viscosity gradients can be elegantly captured using the Landau–Lifshitz–Gilbert equations, originally developed for spin systems. Remarkably, we discover that chiral swimmers demonstrate negative viscotaxis, tracing spiral trajectories as they move. Specifically, a chiral squirmer with a misaligned source dipole and rotlet dipole exhibits a steady-state spiral motion – a stark contrast to the linear behaviour observed when the dipoles are aligned. This work provides fresh insights into the intricate interplay between microswimmer dynamics and fluid properties.

View PDF Chat

Analysis of magnetic configuration and its effect on motion in magnetically actuated soft miniature robots within tubular confinement

2025-06-21

Afarin Khabbazian , Mir Behrad Khamesee , Veronika Magdanz | Journal of Micro-Bio Robotics

Soft, magnetically actuated robots offer promising potential for medical applications due to their simple fabrication, controllability, cargo loading ability and flexibility. This research focuses on the design, modeling, and behavior … Soft, magnetically actuated robots offer promising potential for medical applications due to their simple fabrication, controllability, cargo loading ability and flexibility. This research focuses on the design, modeling, and behavior of soft, millimeter-scale filamentous robots composed of Gelatin Methacrylate (GelMa) hydrogels and embedded with micromagnets for magnetic actuation. These robots are designed for navigation within the human urinary tract. The study investigates two distinct configurations: screw-like and fin-like robots, each responding differently to an external rotating magnetic field. The screw-like robots propel forward through synchronized helical motion, while the fin-like robots rely on interaction with surrounding surfaces for crawling motion. Experimental frequency response tests reveal that fin-like robots exhibit three times faster motion than screw-like robots in confined environments, reaching velocities of up to 18 mm/s. Additionally, the influence of micromagnet location inside the filaments on their propulsion dynamics is explored, highlighting the potential for optimized performance in medical applications requiring navigation through narrow channels, such as the ureter. Further optimization is proposed to enhance control and performance in more complex biological environments. The online version contains supplementary material available at 10.1007/s12213-025-00188-1.

Towards Fluorescence-Guided Autonomous Robotic Partial Nephrectomy on Novel Tissue-Mimicking Hydrogel Phantoms

2025-06-20

Ethan Kilmer , Joseph Chen , Jiawei Ge +7 more | Journal of Medical Robotics Research

Dual‐Driven Janus Nanomotors Combined with a Size‐Shrinkage Strategy for Enhanced Tumor Penetration and Synergistic Chemo/Photothermal/Photodynamic Therapy

2025-06-20

Xiaoxiao Wang , Yuxuan Guo , Xia Xu +5 more | Advanced Functional Materials

Abstract Further applications of nanotherapeutic systems are greatly hindered by their unsatisfactory tumor permeability. Therefore, achieving an optimal balance between long circulation time and deep penetration is imperative. Janus nanomotors … Abstract Further applications of nanotherapeutic systems are greatly hindered by their unsatisfactory tumor permeability. Therefore, achieving an optimal balance between long circulation time and deep penetration is imperative. Janus nanomotors have garnered significant attention owing to their distinctive asymmetric structure and exceptional active motility. Herein, a novel doxorubicin (DOX)‐loaded and glucose oxidase (GOx)‐modified Janus mesoporous organosilica‐AuPt nanomotor encapsulated in a metal–organic framework (MOF), namely DOX/GOx‐MSN‐AuPt@MOF, is developed for enhanced tumor penetration and synergistic chemo/photothermal/photodynamic therapy. In response to an acidic tumor microenvironment, the nanosystem underwent a process of size‐shrinkage from ≈170 to ≈40 nm, inducing the release of nanomotors. Nanomotors rely on excellent motility for deep penetration into tumors, driven by the combined action of a cascade reaction catalyzed by glucose oxidase‐AuPt, using glucose as fuel to produce oxygen, and thermal gradient generated by near‐infrared laser irradiation. Synergistic tumor treatment is achieved through the drug, DOX; reactive oxygen species generated during tandem catalysis; and localized high temperature. Effective aggregation, deep penetration, and outstanding anti‐tumor activity of the nanosystem are confirmed via 2D cells, 3D multicellular tumor spheroids, and tumor‐bearing mouse models. This study provides a new prospect for constructing a combined treatment system for deep tumor penetration.

A magnetically actuated microcatheter with soft rotatable tip for enhanced endovascular access and treatment efficiency

2025-06-20

Mei-Jie. ZHANG , Lidong Yang , Haojin Yang +7 more | Science Advances

Endovascular interventions require fast access to affected regions, followed by effective treatment. Catheterizations are effective approaches for treating vascular diseases; however, they face challenges in accessibility, efficiency, and invasiveness in … Endovascular interventions require fast access to affected regions, followed by effective treatment. Catheterizations are effective approaches for treating vascular diseases; however, they face challenges in accessibility, efficiency, and invasiveness in narrow, tortuous vascular systems. This study presents a submillimeter magnetically actuated soft rotatable-tipped microcatheter (MSRM) designed to access small blood vessels and provide efficient, minimally invasive therapeutic interventions for blood clot treatment. The MSRM’s rotatable tip design enhances accessibility and navigation speed through a rotation-assisted active steering strategy. Improved blood clot treatment efficiency is achieved through the MSRM’s multifunctionality: It can accelerate drug-blood clot interactions, mechanically break down blood clots, and retrieve clot debris. The low invasiveness is attributed to the soft material design and conservative actuation strategy. The performance of the MSRM is validated in both in vitro phantom studies and in vivo rabbit models, and the invasiveness is evaluated using a human placenta model.

Bioinspired, piezoelectrically-actuated deployable miniature robots

2025-06-20

Hongyi Liu , Jun Sun , Yanhu Zhang +4 more | Materials Science and Engineering R Reports

Regulatable nanomotors for NIR-responsive, NO release and cuproptosis: Synergistic antifungal therapy

2025-06-20

Tao Li , Jing Zhao , Ji Zhang +3 more | Colloids and Surfaces B Biointerfaces

Bacteria Optimize Tumble Bias to Strategically Navigate Surface Constraints

2025-06-20

Antai Tao , Guangzhe Liu , Rongjing Zhang +1 more | Advanced Science

Abstract In natural environments, solid surfaces present both opportunities and challenges for bacteria. On one hand, they serve as platforms for biofilm formation, crucial for bacterial colonization and resilience in … Abstract In natural environments, solid surfaces present both opportunities and challenges for bacteria. On one hand, they serve as platforms for biofilm formation, crucial for bacterial colonization and resilience in harsh conditions. On the other hand, surfaces can entrap bacteria for extended periods and force them to swim along circular trajectories, constraining their environmental exploration compared to the freedom they experience in the bulk liquid. Here, through systematic single‐cell behavioral measurements, phenomenological modeling, and theoretical analysis, how bacteria strategically navigate these factors is revealed. It is observed that bacterial surface residence time decreases sharply with increasing tumble bias from zero, transitioning to a plateau at the mean tumble bias of wild‐type Escherichia coli (≈0.25). Furthermore, it is found that bacterial surface diffusivity peaks near this mean tumble bias. Considering the phenotypic variation in bacterial tumble bias, which is primarily induced by noise in gene expression, this reflects a strategy for bacterial offspring persistence: In the absence of stimulus cues, some bacteria swiftly escape from the nearby surface in case it lacks nutrients, while others, with longer surface residence times, explore this 2D environment most efficiently to find potential livable sites.

Elastic Displacements and Viscous Flows in Wedge-Shaped Geometries with a Straight Edge: Green’s Functions for Perpendicular Forces

2025-06-19

Abdallah Daddi‐Moussa‐Ider , Andreas M. Menzel | Journal of Elasticity

Magnetic-Driven Tubular Micromotors with Bases for Precise Positioning and Cargo Carrying

2025-06-19

Peiqi Chen , Ying Jia , Shutong Wang +3 more | Nanomanufacturing and Metrology

Abstract Micro/nanomotors present considerable potential in various fields, such as medical treatment, environmental remediation, and cell engineering. However, their restricted lifetime and issues in navigation control hinder their applications in … Abstract Micro/nanomotors present considerable potential in various fields, such as medical treatment, environmental remediation, and cell engineering. However, their restricted lifetime and issues in navigation control hinder their applications in cases requiring precise positioning without chemical fuels. Thus, we propose a tubular micromotor driven by external magnetic fields, enabling it to swim in water with accurate transport capabilities. The presented tubular micromotor incorporates a single-sided base, which increases the contact area to enable cargo delivery in liquid environments. The micromotor exhibits varied movement behaviors by applying different magnetic fields, and frequency modulation allows for control over movement velocity. Template-assisted electrochemical deposition is employed to achieve large-scale fabrication, which enables the construction of Ni–Au tubular micromotors with a single-sided base. In addition, the micromotor can trace a predefined path, which demonstrates its precise positioning ability. The cargo transport capability of the micromotor is further validated using polystyrene globules as cargo. This fuel-free tubular micromotor, which is driven by magnetic fields, provides a promising approach for precise cargo delivery. Its broad feasibility makes it suitable for various biomedical applications.

Micromotors Meet Collective (Bio)sensing: The Asset Behind the Assay

2025-06-19

Alberto Escarpa , Beatriz Jurado‐Sánchez | Analytical Chemistry

Micromotors are microscale devices with enormous potential for analytical (bio)sensing due to autonomous motion capabilities in extremely small sample volumes or for guided detection in localized hard-to-reach areas. These unique … Micromotors are microscale devices with enormous potential for analytical (bio)sensing due to autonomous motion capabilities in extremely small sample volumes or for guided detection in localized hard-to-reach areas. These unique features enable dynamic interactions with the analytes, offering considerable promise in microscale environments and opening new avenues for on-the-fly (bio)sensing strategies. By selecting and discussing the ideas and findings behind pioneering works, we offer our perspective on the current state of the art in the field of in vitro (bio)sensing approaches based on the micromotors classified according to their detection principle: motion-based, optical, and electrochemical sensing. We will also draw attention to current challenges and opportunities that have not yet been fully explored, in a landscape that is as exciting as it is changing.

Reconfigurable Underwater Robots with Dual-jet Piezoelectric Synthetic Jet Thrusters

2025-06-18

Kai Li , Hongze Zhang , ZhenHao Chen +3 more | International Journal of Mechanical Sciences

From actin to action

2025-06-18

Yu Shi | Nature Physics

Preparation of Morphology-Controlled Gel Particles from Small Molecules through Vortex Ring Freezing and Photopolymerization

2025-06-18

Yang Hou , Tian Qing-bo , Guoqiang Lu +3 more | ACS Applied Polymer Materials

Twist-induced networking and fast propagation of defects in three-dimensional active nematics

2025-06-18

NULL AUTHOR_ID | Physical Review Letters

Rapid Discovery of Sequence‐Encoded Magnetically Reconfigurable Microrobots Using Monte Carlo Simulations

2025-06-16

Collin C. Kemper , Kendra M. Kreienbrink , Hayden J. Tomazin +3 more | Advanced Intelligent Systems

Reconfigurable microrobots promise advancements in microsurgical tools, self‐healing materials, and environmental remediation by enabling precise, adaptive functionalities at small scales. However, predicting their behaviors a priori remains a significant challenge, … Reconfigurable microrobots promise advancements in microsurgical tools, self‐healing materials, and environmental remediation by enabling precise, adaptive functionalities at small scales. However, predicting their behaviors a priori remains a significant challenge, limiting the pace of design and discovery. To address this, a Monte Carlo simulation framework is presented for predicting the folding behavior of self‐assembled, sequence‐encoded microrobot chains composed of magnetic particles, enabling efficient exploration of their large design space. This computational framework employs metrics of radius of gyration, tortuosity, and symmetry score to map the design space, identify functional sequences, and predict likely folding behaviors before fabrication. The framework through experiments to demonstrate accuracy in capturing folding behaviors is validated. Statistical analysis reveals adherence to self‐avoiding walk principles from polymer theory, providing a foundation for understanding how input sequences drive folding capabilities. Moreover, the simulation surpasses current experimental capabilities, enabling exploration of novel microrobot designs, such as sequences incorporating mixtures of cubes and triangular prism subunits, which exhibit distinct compressive behaviors. Beyond the sequence‐encoded microrobots investigated in this study, this framework offers broad utility for the design of reconfigurable microscale systems by reducing reliance on experimental prototyping and accelerating discovery of new functional microrobots for use in biomedicine, materials engineering, and sustainability.

Light‐Driven Micromotors for Microscale Metal Ion Sensing Applications in Fluid Medium

2025-06-16

Srikanta Debata , R. N. Ram , Dhruv Singh | Particle & Particle Systems Characterization

Abstract Synthetic micromotors are at the forefront of technological advancements, offering innovative solutions for biomedical and environmental challenges. This study presents a unique design of light‐driven micromotors for the localized … Abstract Synthetic micromotors are at the forefront of technological advancements, offering innovative solutions for biomedical and environmental challenges. This study presents a unique design of light‐driven micromotors for the localized detection of copper (Cu 2 ⁺) metal ions. These micromotors have a Janus‐shaped spherical structure, featuring multiple layers: a photocatalytic layer for propulsion under UV light (320‐400 nm), a layer of dye molecules for fluorescence emission when excited by blue light (450 nm), and a magnetic‐responsive layer for guided swimming. The fluorescent dye used has the intriguing property of changing its fluorescent behavior in the presence of Cu 2 ⁺ metal ions in solution, allowing the micromotors to selectively and locally detect Cu 2 ⁺ ions. To quantify fluorescence variations, a spectrometer is utilized, confirming the system's sensitivity to metal ions in solutions. Controlled experiments are conducted to optimize and calibrate micromotors for precise Cu 2 ⁺ metal ion detection at targeted locations. The scalable design of these micromotors, featuring dual optical responsiveness and guided swimming, enables precise on‐demand sensing of metal ions. These features present the micromotors as mobile sensor units suitable for environmental remediation and sensing applications in various fields, including lab‐on‐a‐chip devices, water quality assessment, and the regulation of industrial waste disposal into water bodies.

Unraveling Charge Transport in Heterostructured Nanomotors for Efficient Photocatalytic Motion

2025-06-16

Yufen Chen , Chunyu Li , Rebeca Ferrer Campos +4 more | Nano Letters

Photocatalytic micro/nanomotors have emerged as promising tools for environmental remediation, biosensing, and targeted delivery. To enhance their light-driven propulsion, significant efforts have focused on engineering semiconductor heterostructures, which promote charge … Photocatalytic micro/nanomotors have emerged as promising tools for environmental remediation, biosensing, and targeted delivery. To enhance their light-driven propulsion, significant efforts have focused on engineering semiconductor heterostructures, which promote charge separation. However, a clear understanding of how these architectures govern photocatalytic mechanisms and influence motion performance remains limited. Here, we design a visible light-responsive nanomotor based on a Fe2O3-Pt-TiO2 trilayered heterostructure, combining narrow-bandgap α-Fe2O3 and wide-bandgap TiO2 with an intermediate Pt layer. Remarkably, Fe2O3-TiO2 nanomotors without the Pt layer exhibit only modest propulsion under visible light, whereas the inclusion of Pt significantly enhances their motility. Through advanced techniques, including in situ synchrotron radiation-based near-ambient pressure X-ray photoelectron spectroscopy and transient absorption spectroscopy, we reveal that Pt serves as an efficient electron mediator, enabling directional charge transfer across the heterojunction. This study provides fundamental insights into charge transport in multicomponent nanomotors and introduces a rational strategy for designing efficient photoactive systems.

Active nematics: a new approach to mechanobiology?

2025-06-16

Julia M. Yeomans , Saraswat Bhattacharyya , Mehrana R. Nejad | Liquid Crystals

Topological Magnetic Lattices for On-Chip Nanoparticle Trapping and Sorting

2025-06-16

Hongyang Xu , Xi Xie , Chuangye Zhang +3 more | Nano Letters

On-chip optical lattices based on surface plasmon polariton (SPP) fields have been shown to generate diverse novel topologies and potential for sorting nanoparticles. However, the reliance on metallic excitation in … On-chip optical lattices based on surface plasmon polariton (SPP) fields have been shown to generate diverse novel topologies and potential for sorting nanoparticles. However, the reliance on metallic excitation in SPP systems suffers from heavy ohmic loss and heat buildup. In this work, we propose a magnetic topological lattice based on Bloch surface waves (BSWs) excited on transparent dielectric multilayers, offering ultralong propagation ranges and markedly reduced thermal effects. In contrast to the conventional SPPs, rich topologies appear in the magnetic field and spin vector. Furthermore, large-scale dynamic manipulation as well as size-dependent sorting of nanoparticles is feasible by leveraging the ability to reconfigure lattice topologies via polarization and phase adjustments, which further expands its functional versatility. Our results provide new insight into optical topologies governed by magnetic fields and hold promise for application in other wave systems, including elastic and water waves.

Magnetic soft millirobot with simultaneous locomotion and sensing capability

2025-06-15

Weihong Zeng , Xinrui Ding , Yuan Jin +6 more | npj Flexible Electronics

Dynamics of rotating helices in a viscous fluid

2025-06-13

Chen Zang , Luke Omodt , Moumita Dasgupta +1 more | Journal of Fluid Mechanics

We investigate the dynamics of a pair of rigid rotating helices in a viscous fluid, as a model for bacterial flagellar bundle and a prototype of microfluidic pumps. Combining experiments … We investigate the dynamics of a pair of rigid rotating helices in a viscous fluid, as a model for bacterial flagellar bundle and a prototype of microfluidic pumps. Combining experiments with hydrodynamic modelling, we examine how spacing and phase difference between the two helices affect their torque, flow field and fluid transport capacity at low Reynolds numbers. Hydrodynamic coupling reduces the torque when the helices rotate in phase at constant angular speed, but increases the torque when they rotate out of phase. We identify a critical phase difference, at which the hydrodynamic coupling vanishes despite the close spacing between the helices. A simple model, based on the flow characteristics and positioning of a single helix, is constructed, which quantitatively predicts the torque of the helical pair in both unbounded and confined systems. Finally, we show the influence of spacing and phase difference on the axial flux and the pump efficiency of the helices. Our findings shed light on the function of bacterial flagella and provide design principles for efficient low-Reynolds-number pumps.

Mechanical Agitation Assisted Transmembrane Drug Delivery by Magnetically Powered Spiky Nanorobots

2025-06-13

Xiaojia Liu , Zihan Xu , Yanan Che +6 more | Research

Swarming intelligence in self-propelled micromotors and nanomotors

2025-06-13

Tania Patiño , Shuqin Chen , Ana C. Hortelão +2 more | Nature Reviews Materials

Autonomous self-propelled reduced graphene oxide hydrogel-CuO@rGO micromotors for high-efficiency removal of organic dye pollutant

2025-06-13

Zengze Liu , Ziwei Zheng , Yanlin Liu +3 more | Journal of Contaminant Hydrology

Dynamical modes of highly elastic loops settling under gravity in a viscous fluid

2025-06-13

Yevgen Melikhov , Maria L. Ekiel-Jeżewska | Journal of Fluid Mechanics

The settling of highly elastic non-Brownian closed fibres (called loops) under gravity in a viscous fluid is investigated numerically. The loops are represented using a bead–spring model with harmonic bending … The settling of highly elastic non-Brownian closed fibres (called loops) under gravity in a viscous fluid is investigated numerically. The loops are represented using a bead–spring model with harmonic bending potential and finitely extensible nonlinear elastic stretching potential. Numerical solutions to the Stokes equations are obtained with the use of HYDROMULTIPOLE numerical codes, which are based on the multipole method corrected for lubrication to calculate hydrodynamic interactions between spherical particles with high precision. Depending on the elasto-gravitation number $B$ , a ratio of gravitation to bending forces, the loop approaches different attracting dynamical modes, as described by Gruziel-Słomka et al. (2019 Soft Matt. 15 , 7262–7274) with the use of the Rotne–Prager mobility of the elastic loop made of beads. Here, using a more precise method, we find and characterise a new mode, analyse typical time scales, velocities and orientations of all the modes, compare them and investigate their coexistence. We analyse numerically the transitions (bifurcations) to a different mode at certain critical values of the elasto-gravitation number.

View PDF Chat

Nano-orchestrated magnetotactic-like navigation for electromagnetic theranostics and immune enhancement via photoautotrophic oxygenation, mild hyperthermia, and ferroptosis

2025-06-13

Chai-Hsien Hsiao , Yung‐Wei Lin , Chia‐Hung Liu +3 more | Journal of Nanobiotechnology

Abstract Overcoming the hypoxic tumor microenvironment (TME) and immune suppression remains a significant challenge in solid bladder tumor therapies. This study introduces a translational system of nano-orchestrated magnetotactic-like system, integrating … Abstract Overcoming the hypoxic tumor microenvironment (TME) and immune suppression remains a significant challenge in solid bladder tumor therapies. This study introduces a translational system of nano-orchestrated magnetotactic-like system, integrating photosynthetic oxygenation, remote hyperthermia, and ferroptosis to achieve comprehensive tumor eradication and immune activation. The developed system, composed of electromagnetic-responsive iron oxide nanoparticles (IO NPs) encapsulated within a glycol chitosan (GCS) matrix and coated onto Chlorella (CHL; CHL-GCS-IO NPs), exhibited versatility for precise magnetic targeting, photothermal-hypertehrmia and photosynthesis-driven oxygen generation under light irradiation. The CHL enhanced oxygen production by continuously alleviating hypoxia, boosting both electromagnetic therapeutic efficacies and ferroptosis-induced tumor cell death. Moreover, the multimodal CHL-GCS-IO NPs reprogrammed the TME, facilitating immune activation by promoting macrophage polarization towards the proinflammatory M1 phenotype, engaging cytotoxic T cells and natural killer cells, programmed death ligand 1 (PD-L1) downregulation, and driving dendritic cell reprogramming towards improved antigen presentation. In vivo, this approachsuggested significant tumor growth inhibition and prevented recurrence in bladder cancer models, highlighting its potential for robust and durable anticancer immunity. This magnetotactic-like CHL platform presents a highly promising theranostic strategy, merging multimodal therapies with immune modulation to tackle both direct and systemic challenges of solid bladder tumors. Graphical abstract

Capsule damage by an enclosed microswimmer

2025-06-13

Zhihan HUANG , Toshihiro Omori , Takuji Ishikawa | Journal of Fluid Mechanics

Capsules are widely used in bioengineering, chemical engineering and industry. The development of drug delivery systems using deformable capsules is progressing, yet the regulation of drug release within a capsule … Capsules are widely used in bioengineering, chemical engineering and industry. The development of drug delivery systems using deformable capsules is progressing, yet the regulation of drug release within a capsule remains a challenge. Meanwhile, a microswimmer enclosed in a capsule can generate a large lubrication force on the capsule membrane, which could result in deformation and mechanical damage to the membrane. In this study, we numerically investigate how a capsule can be damaged by an enclosed microswimmer. The capsule membrane is modelled as a two-dimensional neo-Hookean material, with its deformability parametrised by capillary number. An isotropic brittle damage model is applied to express membrane rupture, with the Lighthill–Blake squirmer serving as the microswimmer model. In a sufficiently small capillary number regime, pusher-type squirmers exhibit stable swimming along the capsule membrane, while neutral-type and puller-type squirmers exhibit swimming towards the membrane and remain stationary. As capillary number increases, the damage to the membrane increases and rupture occurs in all swimming modes. For pusher-type squirmers, the critical capillary number leading to rupture is dependent on the initial incidence angle, whereas neutral-type and puller-type squirmers are independent of the initial value. Furthermore, we present methods for controlling membrane damage by magnetically orienting the microswimmer. The findings reveal that a static magnetic field can orient the microswimmer, leading to membrane damage and rupture even for a capsule that cannot be damaged by free swimming, while controlling the swimming path with a rotating magnetic field enables soft membranes to maintain deformation without rupture.

Motile and Chemotactic Minicells and Minicell-Driven Biohybrids Engineered for Active Cargo Delivery

2025-06-12

Irina Kalita , Rémy Colin , Sarah Hoch +3 more | ACS Applied Materials & Interfaces

Bacterial minicells are submicrometer-sized spherical compartments produced by bacteria as a result of aberrant cell division. Minicells have a similar cellular composition to the parental bacteria but lack chromosomal DNA … Bacterial minicells are submicrometer-sized spherical compartments produced by bacteria as a result of aberrant cell division. Minicells have a similar cellular composition to the parental bacteria but lack chromosomal DNA and are thus unable to proliferate. Due to that, minicells have attracted attention as potential means of effector delivery in bioengineering and biomedical applications. However, until now, the efficiency of delivery by minicells has been limited by passive collisions with their targets. To develop minicell-based active delivery, here we engineer Escherichia coli strains generating motile minicells with enhanced swimming properties by introducing genetic modifications specifically targeting flagella number, length, and rotation speed. The engineered minicells preserve motility over an extended period of time and, in contrast to parental E. coli cells, increase their swimming speed for the intermediate viscosity of the medium. Despite their small size, minicells show an efficient chemotactic response and utilize the same chemotactic strategy as parental E. coli cells. Moreover, we develop a procedure for conjugating minicells with cargo particles and demonstrate that such minicell-driven biohybrid swimmers are chemotactic and thus capable of actively accumulating at the source of an attractant. These engineered chemotactic minicells and minicell-based biohybrids can serve as cargo delivery platforms with active targeting, thus overcoming the challenges posed by nontargeted therapies.