Automated Motion Control of a Microparticle Swarm in Liquids by a Single-Solenoid Electromagnetic Manipulation System

In recent years, magnetic field-controlled microparticles have demonstrated their superiority in biomedical applications. To improve the operation efficiency and imaging effect of microparticles, increasing numbers of researchers are devoted to driving a swarm composed of a group of microparticles. In this study, a new strategy for autonomously manipulating microparticle swarms in liquids via an electromagnetic coil system was investigated. Compared with the commonly used rotating magnetic field composed of multiple electromagnetic coils, the oscillating magnetic field drive system formed by a single electromagnetic coil reduces the occupied space meanwhile ensures the sufficient working space, making the microparticle movement more flexible while providing greater feasibility for good compatibility with imaging systems. Through designing the parameters of the input current, a vortex-shaped swarm can be formed, and the movement of the entire swarm can be pulled by controlling the coil position. Owing to the rotation of microparticles, the coefficient of the control input is unknown uncertainty. To solve this uncertainty problem, a sliding mode controller is used, and the chattering caused by the sliding mode surface is reduced using a saturation function. Lastly, the effectiveness of the proposed strategy is verified by simulation and experiments. Note to Practitioners—The motivation of this article is mainly to solve the problem of magnetic microparticle aggregation, aiming to form a stable swarm and automatically control the movement of the swarm. Most of the existing methods of aggregating microparticles to form a swarm are based on the creation of a rotating magnetic field by Helmholtz coils, which leads to the problem of spatial limitation. To solve this problem, this research uses one single solenoid to form a stable swarm, which provides more space for imaging equipment and objects requiring operation. The controlled movement of the stable swarm is achieved by manipulating the solenoid with a sliding mode controller. It reduces the impact of system uncertainties, allowing the swarm to automatically track a predefined path accurately. This will provide a new idea for the application of microparticles in the biomedical field.