Research on key technologies of quadrupole electromagnetic tweezer

Abstract

In this paper, the quadrupole electromagnetic tweezer installed in a fluorescent microscope was developed for the purpose of achieving precise control of magnetic microspheres’ motion trajectory. The key technologies of magnetic microsphere control and positioning by such quadrupole magnetic tweezers were systematically studied. An electromagnetic quadrupole magnetic tweezer system was designed and constructed, a current-magnetic force model of the quadrupole magnetic tweezer was established, and the magnetic force-current inverse force model was derived and simplified. A fluorescence microscopy imaging system was set up and the related program design was completed. The position of magnetic fluorescent microspheres was monitored by a high-speed CCD with sampling frequency of 200 Hz. A proportional-integral closedloop feedback controller was built up for magnetic microspheres. The experimental results demonstrated that the magnetic force range available at the center of the work area was [-80pN, 80pN]. Besides, magnetic microspheres were tested to possess a displacement resolution up to 400 nm as well as the capacity of moving in any direction in a two-dimensional plane. Based on the obtained results, it is expected that the quadrupole electromagnetic tweezer can function one of the effective devices for evaluation of cell mechanical properties.