Dynamic Response of Swimming Paramecium Induced by Local Stimulation using a Threadlike-Microtool

In this letter, an approach for realizing local area stimulation of single motile microorganism ( Paramecium ) by a microtool is described. In order to overcome the hydrodynamic drag force acting on the thin and long tool in the fluidic environment, a magnetic compensation approach to improve the positioning accuracy of the metallic microtool is introduced. The permanent magnets’ arrangement that reduced the vertical component and enhanced the horizontal component of the magnetic force is modeled and clarified through numerical simulations and actual experiments on the microtool with a diameter of 50 μm. As a result, the positioning accuracy of the microtool using the magnetic compensation is improved to approximately 200 μm. Finally, the performance and practicality of the integrated platform are confirmed by conducting experiments on a freely swimming Paramecium . By virtue of the low fluidic disturbance generated by the microtool, the stimulation did not cause a tracking failure and the dynamic reaction of the Paramecium is confirmed without any immobilization manners for the first time ever. The avoiding reactions in response to mechanical stimulation are evaluated by analysing the captured image data with a spatial resolution of less than 5 μm and a time resolution of less than 5 ms.