Reconfigurable artificial microswimmers with internal feedback

Self-propelling microparticles are often proposed as synthetic models for biological microswimmers, yet they lack the internally regulated adaptation of their biological counterparts. Conversely, adaptation can be encoded in larger-scale soft-robotic devices but remains elusive to transfer to the colloidal scale. Here, we create responsive microswimmers, powered by electro-hydrodynamic flows, which can adapt their motility via internal reconfiguration. Using sequential capillary assembly, we fabricate deterministic colloidal clusters comprising soft thermo-responsive microgels and light-absorbing particles. Light absorption induces preferential local heating and triggers the volume phase transition of the microgels, leading to an adaptation of the clusters' motility, which is orthogonal to their propulsion scheme. We rationalize this response via the coupling between self-propulsion and variations of particle shape and dielectric properties upon heating. Harnessing such coupling allows for strategies to achieve local dynamical control with simple illumination patterns, revealing exciting opportunities for developing tactic active materials. Changing the propulsion of simple artificial colloidal microswimmers usually proceeds by globally tuning the strength of the driving mechanism. Alvarez et al. implement an independent reconfiguration scheme, bringing small active particles one step closer to adaptive, autonomous behaviour.The authors thank Peter Schurtenberger and Heiko Wolf for insightful discussions, Walter Richtering for providing the microgels, and Philippe Nicollier for assisting with the substrate fabrication. L.I. and L.A. acknowledge financial support from the Swiss National Science Foundation (SNSF) Grant PP00P2-172913/1 and the European Soft Matter Infrastructure (EUSMI) proposal number E190900328. M.K. acknowledges SNCF support through grant 200021L-185052