Enhanced Locomotion of Shape Morphing Microrobots by Surface Coating

Abstract

Mobile microrobots with shape morphing capability show great advantages for conducting tasks in complex environments. Combination of magnetically driven locomotion and stimuli-responsive shape morphing is an effective strategy to realize these microrobots. However, most existing microrobots fabricated by the combination strategy are of low locomotion efficiency due to the limited amount of magnetic material loaded. Herein, a novel scheme for coating the magnetic nanoparticles (NPs) on the surface of microrobot is proposed to increase the magnetic material loading amount. Theoretical analyses demonstrate that, below a critical size at microscale, surface coating NPs can load more magnetic material than embedding NPs into the volume due to the high surface area-to-volume ratio. Microrobots with both shape morphing and enhanced magnetically driven locomotion are fabricated by coating magnetic NPs on the surface of stimuli-responsive hydrogel microstructures. It is experimentally demonstrated that surface coating ensures that the microstructure has not only an efficient locomotion but also an excellent deformability. A four-claw microgripper is fabricated, which is smaller and has higher magnetically driven locomotion speed than the most existing shape morphing microrobots. This microgripper demonstrating carrying and delivery capabilities is of immediate interest to microobject manipulation and minimally invasive surgery.