Observation of Microorganism Galvanotaxis using High-speed Three-dimensional Tracking System

Our goal is to utilize microorganisms as micro-robots by using galvanotaxis (locomotor response to electrical stimulus). To reach this goal, observation of three-dimensional galvanotaxis must be achieved. Our group has proposed the technique for autofocusing cells by using the diffraction pattern that appears, which we call DepthFrom-Diffraction method. In this paper, we propose a novel three-dimensional tracking system incorporating the Depth-From-Diffraction method and the border-following algorithm to observe galvanotaxis of Paramecium cells. Experimental results shows that the system successfully captured the first ever three-dimensional galvanotactic motion of Paramecium cells.