Light-adaptive motility in self-propelled microswimmers

Many recent studies aim to emulate key features of biological microswimmers, such as autonomous motion, adaptability, and sensing, using synthetic microscale equivalents. However, unlike their biological counterparts, most synthetic active colloidal systems can adjust the motility only through modulations of their driving force. Thus, such systems lack true adaptation, i.e., they cannot reconfigure their motility in response to stimuli orthogonal to the propulsive one. While in larger-scale robotic devices adaptation can be embedded in the material itself, via so-called physical intelligence, demonstrations of this principle at the colloidal scale remain sparse.

We developed microswimmers with an optically-controllable activity by fabricating silica Janus particles (JPs) with a photo-responsive titania hemisphere. Our JPs self-propel in response to an external AC electric field through electrohydrodynamic flows. Upon local illumination, the conductivity of the titania hemisphere increases, allowing for the adaptation of the propulsion velocity. We employ dynamic illumination landscapes that demonstrate a broad range of control schemes over the particles. We believe that this platform opens intriguing possibilities for the development of adaptive artificial microswimmers leading to interesting emergent behaviour.