Control of Multiple Heterogeneous Magnetic Microrobots in Two Dimensions on Nonspecialized Surfaces

In this paper, we propose methods to control multiple untethered magnetic microrobots (called Mag- ${\bm \mu }$Bots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-${\bm \mu }$ Bots that are geometrically designed to respond uniquely to the same applied magnetic fields. By controlling the magnetic field waveforms, individual and subgroups of Mag-${\bm \mu }$ Bots are able to locomote in a parallel but dissimilar fashion. The control of geometrically dissimilar Mag- ${\bm \mu }$Bots and a group of identically fabricated Mag- ${\bm \mu }$Bots are investigated, and control strategies are developed for 1-D and 2-D motion. This is accomplished by learning the velocity response of each microrobot to various control signals and using the uniqueness of each microrobot response to achieve independent control. The effect of high-level control parameters are investigated in simulation and in experiments, and the simultaneous independent global positioning of two and three microrobots is demonstrated in 2-D space. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as microfluidic systems and biomanipulation.