Automated Control of Microparticle Swarm in a Rotating Gradient-Based Magnetic Field

The magnetic micromanipulation of swarm microparticles has attracted considerable attention because of its advantages of non-invasiveness, high drug-carrying capacity, and easy observation in the targeted delivery in in-vivo environments. This paper presents an automated control scheme for the magnetic micromanipulation of microswarms in a rotating gradient-based field. Different from the rotating uniform magnetic field generated by Helmholtz coils, the rotating gradient-based field is a type of convergent field established by sequentially powering each coil of the electromagnetic coil system. By changing the coil currents, the field can rotate while driving the microswarm to a pre-determined position, facilitating the swarm localization and tracking. According to the preliminary motion characterization of the swarm in the rotating gradient-based field, an intuitive trapping dynamic model which can simplify the analysis of swarm dynamics is established to facilitate controller design. Based on this model, a super-twisting sliding mode estimator is first designed to estimate the position of the microswarm as well as the disturbances caused by parameter variations and unmodeled dynamics. A robust controller is then developed based on the estimator. In this way, closed-loop manipulation of the microswarm to follow a desired trajectory in the rotating gradient-based field is realized, and the system’s behavior has been significantly improved due to the capability to estimate disturbances. The proposed control scheme for the rotating gradient-based field has the potential to avoid volume loss and unexpected drug diffusion of the swarm when facing complex in-vivo environments. The stability of the control scheme is proved by the Lyapunov approach. Experiments are finally performed to demonstrate the effectiveness of the proposed control approach in a collision-free environment and in a simulated channel. © 2024 IEEE.