Ultra-Precise High-Speed Untethered Manipulation of Magnetic Scanning Microprobe in Aqueous Solutions

This article describes the design and development of an integrated system that renders ultra-precise and high-speed, untethered manipulation of a single magnetic scanning microprobe in aqueous solutions under a microscope. The system uses a six-input-three-output hexapole electromagnetic actuator to control the magnetic gradient force exerted on the probe and a three-dimensional vision-based motion tracking system to enable feedback control. The control system has three core functions that enables superior manipulation of the magnetic microprobe. The six-input-six-output closed-loop magnetic flux control significantly suppresses the effect of magnetic hysteresis and greatly increases the bandwidth of magnetic flux generation. The optimal flux allocation solves four issues in multipole magnetic force generation: redundancy; coupling; nonlinearity; and position-dependency. The position-dependent discrete-time motion control law determines the required force for stabilization and tracking. These three core functions have been implemented using a high-speed field programmable gate array (FPGA) system. Experiments have verified that the use of digital control technology, high-speed electronics, mathematical modeling, and real-time computation has achieved superior manipulation of a single magnetic microprobe in aqueous solutions.