Design and Control of a Porous Helical Microdrill with a Magnetic Field for Motions

Magnetically controlled microrobots have attracted wide attention in noninvasive therapy. However, it is challenging to design a microrobot with both low motion resistance and multi-mode motions control. Here, we design a 100 μm helical drill-like microrobot with biodegradable materials GelMA and HAMA. The microrobot is optimized with surface pores to reduce the resistance and alternately rotates and oscillates in composite magnetic fields. Inspired by the dimpled surface of the golf ball to reduce the pressure drag via fluid transition, the microdrill is modified with 98 dimples over its surface to effectively reduce the movement resistance. Considering hyperviscosity tasks, a control strategy to dynamically switch rotating and oscillating composite magnetic fields is performed with visual recognition of the local environment, which actuates the microdrill to move flexibly. The experiment demonstrates that the swimming step-out frequency of the dimpled microdrill is improved 44.5% to 13 Hz, and swimming velocity of the dimpled microdrill is improved by 13.7% to 25.3 μm/s. Furthermore, the microdrills can be degraded by collagenase in a concentration of 0.35 mg/mL, which shows good biocompatibility and is anticipated to be applied in microsurgery and untethered therapies in the future. (This work was supported by National Key R&D Program of China under grant number 2019YFB1309701, and0 National Natural Science Foundation of China under grant number 62073042).