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

Abstract

Microorganisms move in challenging environments by periodic changes in body shape. In 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 realize 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 microswimmers. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies.

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Figure 1: Locomotion based on travelling-wave features, from nature to technology.
Figure 2: Deformation of microrobots made of soft active materials wirelessly controlled by dynamic light fields.
Figure 3: Force- and torque-free swimming of a cylindrical microrobot driven by light-controlled travelling-wave deformations.
Figure 4: In-plane controlled locomotion of disc-shaped microrobots.

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Acknowledgements

This work was in part supported by the European Research Council under the ERC Grant agreements 278213 and 291349, and the DFG as part of the project SPP 1726 (microswimmers, FI 1966/1-1). S.P. acknowledges support by the Max Planck ETH Center for Learning Systems. We thank A. Posada for help with the movies and figures.

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Contributions

S.P., A.G.M. and P.F. proposed the experiment; S.P., A.G.M. and K.M. built the structured light set-up; H.Z., C.P., D.M. and D.S.W. synthesized the LCE and formed the cylindrical samples; S.P. performed the experiments and numerical simulations; S.P. and T.Q. fabricated the disc by photolithography; S.P., A.G.M., A.S.-C., N.K. and F.G. characterized the LCE material by SAXS; S.Y.R. and E.L. developed the analytical theory model; S.P., A.G.M. and P.F. wrote the manuscript with contributions from all authors.

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Correspondence to Peer Fischer.

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Palagi, S., Mark, A., Reigh, S. et al. Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots. Nature Mater 15, 647–653 (2016). https://doi.org/10.1038/nmat4569

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