Visually Servoed Orientation Control of Biological Cells in Microrobotic Cell Manipulation

摘要

In automated microrobotic injection of mouse embryos, high-speed cell orientation control is important for avoiding damage of cellular organelles. This paper presents a visual servoing system for automated cell orientation control, which overcomes the limitations in state-of-the-art techniques for embryo immobilization and orientation. An in-house developed device is used for immobilizing many mouse embryos into a regular pattern. Due to commercial unavailability, a compact motorized rotational microscopy stage is developed for orienting the polar body of mouse embryos away from the injection site. The polar body is identified by a pattern recognition algorithm and subsequently tracked by a visual tracking algorithm with a translation-rotation-scaling motion model, providing image position feedback to an image-based visual servo controller that is responsible for keeping the embryo inside the field of view during cell orientation. The transformation between the coordinate frame of the embryo holding device and that of the cell positioning stage (XY translational) is accurately calibrated during visually servoed orientation of the first target embryo. High-speed, automatic cell orientation is then conducted on other embryos in the same batch of immobilized cells through coordinate transformation and 3-DOF closed-loop position control. Experimental results demonstrate that the cell orientation system is capable of precisely orienting mouse embryos at 720 degrees/sec.