Automated Microrobotic Manipulation with Micron-scale Precision Using Multimodal Magnetic Microswarms

Untethered microrobots possess a promising perspective for micro-manipulation applications. With specifically designed morphologies and structures, microrobots are able to perform controllable delivery of target objects. However, the manipulation process still lacks autonomy, the picking, transporting, and releasing behaviors of microrobots need analysis. In this paper, we propose to achieve automated microrobotic manipulation with multimodal magnetic microswarms. The microswarm is composed of numerous Fe3O4 nanoparticles. When exposed to different dynamic magnetic fields (rotating magnetic field and oscillating magnetic field), the swarm could exhibit corresponding forms and generate attracting and repelling effects for micro-objects, respectively. Exploiting these two types of swarms, precise and controllable picking and releasing can be realized. The manipulation process is quantitatively divided into five stages, and a finite state machine (FSM) is presented to govern the transition between the stages. To guarantee accurate motion control of the swarm, a disturbance observer (DOB)-based super-twisting sliding mode control (STSMC) is designed. Experiments are conducted to validate the feasibility of the proposed manipulation scheme. The results demonstrate that the swarm is capable of automatically and effectively delivering micro-cargoes with different sizes to the target positions.