Self-Propelling Active Particles & Self-Reconfiguring Assemblies from Remotely-Powered Thin Film Silicon Microdiodes

Locally energized particles that are powered by external fields (e.g., electrical, magnetic, and optical) have formed the basis of emerging classes of reconfigurable active matter. We describe how millions of electrically- and magnetically-responsive silicon microparticles can be made to draw energy from applied external fields and actively propel, repel, rotate, and perform on-demand sequential assembly and disassembly. We show how a number of electric field-based effects such as electrohydrodynamic (EHD) flows, induced-charge electrophoresis, and dielectrophoresis, can selectively power this suite of particles. Microparticles subjected to a lower ac frequency (< 10 kHz) can propel and repel from each other when placed in proximate contact. At higher external field frequencies, the microparticles are attracted to each other due to induced dipolar interactions. We also briefly show that magnetic field-based effects such as magnetohydrodynamic (MHD) flows can induce additional functionalities to similarly designed particles. The result is the ability to achieve customized locomotion, interactions, reversible assembly, and synchronous rotational torque on demand that could enable advanced applications such as remotely powered microsensors and reconfigurable computational systems.