Orientation Control of Biological Cells Under Inverted Microscopy

Orientation control of biological cells under inverted microscopes is important for cell birefringent imaging and micromanipulation. Taking our microrobotic mouse embryo injection research as an example, this paper presents a cell orientation control system operated under inverted microscopes. A compact motorized rotational stage for inverted microscopy was developed for orienting the polar body of mouse embryos away from the injection site to avoid damage of cellular organelles. An in-house developed microdevice was used for immobilizing many cells into a regular pattern. The polar body is 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 online calibration of coordinate transformation during visually servoed orientation of the first embryo. High-speed, automatic cell orientation is then conducted on other embryos in the same batch of immobilized embryos through coordinate transformation and 3-DOF closed-loop position control. Experimental results demonstrate that the cell-orientation system is capable of orienting mouse embryos at a high speed of 720°/s with an accuracy of 0.24°.