Self-Assembled Magnetic Surface Swimmers

Snezhko, Alexey; Belkin, Maxim; Aranson, Igor S.; Kwok, W. K.

doi:10.1103/physrevlett.102.118103

Cited by 189 publications

(212 citation statements)

References 21 publications

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Section: Introductionmentioning

confidence: 99%

“…These challenges mean that most artificial microrobots actually have no actuators. Rather, they are in most cases rigid monolithic structures, either pushed by chemical reactions 15 or directly 4 manipulated by torques or forces applied by external magnetic fields [16][17][18][19][20] .Alternatively, they consist of flexible materials embedding, at best, a small number of passive degrees of freedom (DOFs) 21,22 .In macroscale robots, one approach to increase the number of DOFs has been to adopt soft bodies, capable of biomimetic actuation [23][24][25][26][27][28] . However, these approaches have resisted miniaturization.…”

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confidence: 99%

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

et al. 2016

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Microorganisms move in challenging environments by periodic changes in body shape. By contrast, current artificial microrobots cannot actively deform, exhibiting at best passive bending under external fields. Here, by taking advantage of the wireless, scalable and spatiotemporally selective capabilities that light allows, we show that soft microrobots consisting of photoactive liquid-crystal elastomers can be driven by structured monochromatic light to perform sophisticated biomimetic motions. We realized continuum yet selectively addressable artificial microswimmers that generate travelling-wave motions to self-propel without external forces or torques, as well as microrobots capable of versatile locomotion behaviours on demand. Both theoretical predictions and experimental results confirm that multiple gaits, mimicking either symplectic or antiplectic metachrony of ciliate protozoa, can be achieved with single microrobots. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies. 3Mobile micro-scale robots are envisioned to navigate within the human body to perform minimally invasive diagnostic or therapeutic tasks 1,2 . Biological microorganisms represent the natural inspiration for this vision. For instance, microorganisms successfully swim and move through a variety of fluids and tissues.Locomotion in this regime, where viscous forces dominate over inertia (low Reynolds number), is only possible through non-reciprocal motions demanding spatiotemporal coordination of multiple actuators 3 . A variety of biological propulsion mechanisms at different scales, from the peristalsis of annelids (Fig. 1a) to the metachrony of ciliates (Fig. 1b), are based on the common principle of travelling waves (Fig. 1c). These emerge from the distributed and self-coordinated action of many independent molecular motors 4,5 .Implementing travelling wave propulsion in an artificial device would require many discrete actuators, each individually addressed and powered in a coordinated fashion (Fig. 1d). The integration of actuators into microrobots that are mobile poses additional hurdles, since power and control need to be distributed without affecting the microrobots' mobility. Existing microscale actuators generally rely on applying external magnetic 6-10 , electric 11 , or optical 12,13 fields globally over the entire workspace. However, these approaches do not permit the spatial selectivity required to independently address individual actuators within a micro-device. Nevertheless, complex non-reciprocal motion patterns have been achieved by carefully engineering the response of different regions in a device to a spatially uniform external field 13,14 .The drawback is that this complicates the fabrication process, inhibits down-scaling and constrains the device to a single predefined behaviour. These challenges mean that most artificial microrobots actually have no actuators. Rather...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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

et al. 2016

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“…[17]) or by intrinsic self-propulsion mechanisms [18], opening the possibility for lane formation and related dynamical phenomena. Examples of swimmers with anisotropic (e.g., magnetic) interactions have been studied in [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Lane formation in a driven attractive fluid

2016

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We investigate non-equilibrium lane formation in a generic model of a fluid with attractive interactions, that is, a two-dimensional Lennard-Jones (LJ) fluid composed of two particle species driven in opposite directions. Performing Brownian Dynamics (BD) simulations for a wide range of parameters, supplemented by a stability analysis based on dynamical density functional theory (DDFT), we identify generic features of lane formation in presence of attraction, including structural properties. In fact, we find a variety of states (as compared to purely repulsive systems), as well as a close relation between laning and long wavelength instabilities of the homogeneous phase such as demixing and condensation.

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“…In experimental studies, various artificial systems have been reported on, each showing interesting individual features. The systems can be categorized either as interface bound surfers [26][27][28][29], micro-machines [30][31][32], Janus particles [33][34][35][36][37] or active emulsions [38][39][40][41][42][43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

Dimensionality matters in the collective behaviour of active emulsions

et al. 2016

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Abstract. The behaviour of artificial microswimmers consisting of droplets of a mesogenic oil immersed in an aqueous surfactant solution depends qualitatively on the conditions of dimensional confinement; ranging from only transient aggregates in Hele-Shaw geometries to hexagonally packed, convection-driven clusters when sedimenting in an unconfined reservoir. We study the effects of varying the swimmer velocity, the height of the reservoir, and the buoyancy of the droplet swimmers. Two simple adjustments of the experimental setting lead to a suppression of clustering: either a decrease of the reservoir height below a certain value, or a match of the densities of droplets and surrounding phase, showing that the convection is the key mechanism for the clustering behaviour.

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Self-Assembled Magnetic Surface Swimmers

Cited by 189 publications

References 21 publications

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

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

Lane formation in a driven attractive fluid

Dimensionality matters in the collective behaviour of active emulsions

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