Visual Servoed Three-Dimensional Rotation Control in Zebrafish Larva Heart Microinjection System

Objective: Zebrafish larva heart microinjection is a widely used technique in cardiac disease study. Compared with intensively researched rotation control of spherical or nearly spherical targets with clear structures, such as cells and embryos, 3-D rotation control of zebrafish larva demands new techniques due to its nontransparent structures and irregular outlines. Methods: In this paper, we present a vision-servo system to automate the rotation process of zebrafish larva body. A switched control strategy is adopted to rotate zebrafish larva about the optical axis by using two micropipettes. Precisely rolling about larva body is performed, which involves a custom-designed rotational micromanipulator. A vision detection and online tracking algorithm is also developed to meet the requirement of visual servoing. With designed rotation control strategy, zebrafish larva heart can be adjusted to a desired orientation, which is often towards the injection pipette tip. Results: Experimental results show that the designed system is capable of achieving high success rate of 94% about $z$-axis rotation and 100% about $x$-axis with 50 trails. The system also performs an average speed of 44 s/larva with a satisfied rotation accuracy of 0.5$^\circ$ in the horizontal plane and 2.5$^\circ$ about its roll axis. Conclusion: The proposed strategy is effective in flexibly manipulating larvae in 3-D. Significance: The developed 3-D rotation control scheme is able to be applied to injection of various organs in zebrafish larva body for different experimental requirements.