3D Micromanipulation of Particle Swarm Using a Hexapole Magnetic Tweezer

This article discusses the design, modeling, and application of a powerful hexapole magnetic tweezer system for closed-loop 3D swarm control applications. The system consists of six sharp tapered magnetic poles that are integrated with six electromagnetic coils and mounted on two yokes composed of 3D printed magnetic material. Magnetic field gradients are generated at the sharp tips of the magnetic poles when current is applied through the attached electromagnetic coils. Different combinations of current input can interact with magnetized microparticles to create three-dimensional motion. A closed-loop control algorithm based on image processing and hardware integration through MATLAB was developed to automatically operate external power supplies connected to the magnetic tweezer system. Coordinate system transformation is utilized to transform the tilted actuation coordinates, by virtue of the system hardware configuration, to the measurement coordinates used during experiments and analysis. This magnetic tweezer system has the advantage of a larger working space and higher magnetic field strengths when compared to several other similar designs. The magnetic tweezer system allows for more diverse applications within the microscale, such as microparticle swarm control, cell penetration, and cell therapy. Experimental analysis performed in this article demonstrates the closed-loop navigation of a microparticle swarm moving freely in both 2D and 3D environments. Results show highly consistent trajectories within the swarm with only a few fluctuations due to microflows. This system will keep being updated and optimized to investigate the performance of microparticles in in vivo environments.