Experimental and numerical study of untethered microswimmers with light-driven particle hinges

Light-driven microswimmers are studied numerically and experimentally in the forms of one-hinge "scallop" swimmers and two-hinge "Purcell" swimmers. Although the untethered microswimmers hold great potential in their applications, such as minimally invasive medicine and active environment monitoring, the study of microswimmers' locomotion on the length scale of mm to cm is often hindered by the availability of experimental techniques at microscale and the limited understanding of its flow physics. In this study, an electromicrofluidic (EMF) printing platform, that independently drives and assembles hydrogel droplets and suspended particles, is adapted to fabricate hydrogel scallop and Purcell swimmers with particle-embedded hinges driven by light. The response of the hinges, including folding angle, folding speed, and unfolding speed, are characterized. The locomotion trajectory and speed are characterized in experiments and compared with the numerical simulation. In particular, we studied numerically and experimentally the nonlinear impact to the flow dynamics and locomotion of microswimmers, since nonlinearity has been neglected in most of the previous studies based on Stokes flow assumption.