Force Sensing and Control in Robot-Assisted Suspended Cell Injection System

Stimulated by state-of-the-art robotic and computer technology, cell injection automation aims to scale and seamlessly transfer the human hand movements into more precise and fast movements of the micromanipulator. This chapter presents a robotic cell-injection system for automatic injection of batch-suspended cells. To facilitate the process, these suspended cells are held and fixed to a cell array by a specially designed cell holding device, and injected one by one through an "out-ofplane" cell injection process. Starting from image identifying the embryos and injector pipette, a proper batch cell injection process, including the injection trajectory of the pipette, is designed for this automatic suspended cell injection system. A micropipette equipped with a PVDF micro force sensor to measure real time injection force, is integrated in the proposed system. Through calibration, an empirical relationship between the cell injection force and the desired injector pipette trajectory is obtained in advance. Then, after decoupling the out-of-plane cell injection into a position control in X-Y horizontal plane and an impedance control in the Z- axis, a position and force control algorithm is developed for controlling the injection pipette. The depth motion of the injector pipette, which cannot be observed by microscope, is indirectly controlled via the impedance control, and the desired force is determined from the online X-Y position control and the cell calibration results. Finally, experimental results demonstrate the effectiveness of the proposed approach.