Soft Microbot Traction on Structured Surfaces.

Microbots (μbots) have demonstrated significant potential for in vivo applications, such as targeted drug delivery. Rigid μbots, however, suffer from limited adaptability and poor reconfigurability, reducing their effectiveness in navigating complex physiological environments. As a result, soft μbots have garnered considerable recent attention due to their intrinsic deformability and potential biocompatibility. In previous work, we developed magnetic particle-based Pickering emulsion soft μbots that can be driven by magnetic fields. While these μbots roll on flat surfaces, they do so with significant slip, limiting traction and transport efficiency. Here, we demonstrate that substrate topography, specifically grooves, can lead to a combination of slip and no-slip motion, resulting in a distinct bimodal locomotion pattern and up to a 3-fold increase in traction. Furthermore, we show that traction can be systematically tuned with varying groove width and depth, identifying an approach to optimize the μbot performance across a range of topographically heterogeneous environments.