Micromanipulator control for grasping and orienting zebrafish larva

This paper presents a simple-structure micromanipulator for grasping and orienting zebrafish (Danio rerio) larva. Compared with complicated handling systems that are based on microfluidic chip, the designed 4-DOF manipulator that has three translations and one rotation allows operators to manipulate larva automatically in a more controllable manner. One glass pipette is mounted at the end of manipulator to rotate larva (about the microscope optical axis) in two dimensions to appropriate gestures where larva's tail is parallel with pipette. Pipette tip is then driven to approach the tail, and the micro pump that is connected with the pipette runs to hold part of larva's tail. Precisely rotating manipulator arm effectively ensures flexible orientation of grasped larva in the third dimension. In order to suppress the rotation oscillation of pipette tip, we have developed an online calibration method to compensate rotation error. We have also provided a simple extremum searching algorithm to automatically rotate larva body to special gestures that are commonly used in experiments (such as dorsal or lateral gestures). Experimental results show the performance of designed manipulator and verify the validity of presented control methods.