Control of active particle motion by microstenciling precise surface patches

Active particles locally dissipate energy from their environment to function and are useful across disciplines given their dynamic and programmable behaviors. Altering particle shape or surface asymmetry has increased control of particle actuation for applications such as microrobotics, biomedicine, and environmental remediation. Making arbitrary active particles of precise shape and surface composition remains a significant challenge due to insufficient complexity in conventional fabrication methods. Thus, we developed a fabrication technique combining two-photon lithography and sacrificial stencil masking to deposit arbitrary metallic patches onto particles of any three-dimensional shape, with a limit of resolution as low as 0.2 µm. Using this method, we demonstrated enhanced control over active particle dynamics and provide a path to better understanding the structure-function relationship of active particles. Specifically, we studied electrokinetic spheres with tunable 3D trajectories, catalytic bent rods with chiral rotation, and steric magnetic particles forming self-limiting microrobots. Overall, this high-resolution microstenciling technique offers a versatile strategy to create well-defined active particles, enabling advanced applications in more complex environments.