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 closedloop 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 threedimensional motion. A closedloop 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 closedloop 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.

MagneticNeedleAssisted Micromanipulation of Dynamically SelfAssembled Magnetic Droplets for Cargo Transportation Dynamic selfassembly is treated as a promising approach for generating a robotic swarm to perform coordinated tasks, and the assembled pattern can be tuned by regulating the energy input. However, location of a dynamically assembled pattern is hard to be determined, especially under global fields, such as magnetic field. In this paper, we report the formation and manipulation of dynamic selfassembled droplets at the airliquid interface with the assistance of a magnetic needle. Affected by the locally induced field gradient near the needle, reconfigurable assembled droplets are obtained with higher timeefficiency, and the location of the pattern can be determined. The pattern is reversibly tuned to exhibit expansion and shrinkage by adjusting the height of the needle. Assembled droplets are able to be steered via following the needle in a controlled manner. Moreover, cargo is trapped by exploiting the induced rotational flow around the droplets, and it can also be caged into the central area of the pattern and transported to the desired location. The proposed method opens new prospects of using energydissipative pattern as an untethered endeffector for microrobotic manipulation.