An automated robotic system for high-speed microinjection of Caenorhabditis elegans

The tiny nematode worm Caenorhabditis elegans has long been a popular model organism for genetic, developmental, and biochemical studies in which worm microinjection plays a critical role. This paper presents an automated robotic system for high-speed injection of C. elegans with an efficiency more than 10 times faster than that of a proficient injection technician. To facilitate the injection process, a multilayer, hydraulically-controlled polydimethylsiloxane (PDMS) microfluidic device is developed to rapidly load, immobilize, flush, sort and collect individual worms. In addition, a newly proposed contact detection algorithm is adopted to find the optimal injection position along the z axis within the microscope view field. The direction and location of the needle tip are identified online based on an effective image processing algorithm. According to continuous injection of 40 worms, our system is able to perform worm injection at a speed of 6.6 worms per minute with a pre-sorting success rate of 77.5% (post sorting: 100%). The superior performance provided by the system will significantly facilitate large-scale transgenic studies and biomolecule screening on C. elegans.