Control of a particular Micro-Macro positioning system applied to cell Micromanipulation.

International audienceBiological research requires new tools for cell micromanipulations. Currently, biological cell sizes range from a few to hundreds of micrometers, their manipulation therefore belonging to the field of microrobotics. This paper presents a new wireless micromanipulation system which allows cells placed in a droplet of liquid to be pushed on a glass slide. The cell micropusher is a ferromagnetic object which follows the movement of a permanent magnet located under the glass slide. It has been proved in previous works that two kinds of micropusher movements can induce a movement of the pushed object: turning the micropusher around the contact point (rotation), or moving the micropusher in translation. Rotation allows an object to be placed with a precision below 1 μm ,but acts within a narrow range. Translation allows placement of an object with lower accuracy, but within a wide range. We propose a specific coarse-fine control strategy to push an object, with good precision, within a wide range. Furthermore, experimentation on polystyrene balls of 50 μm in diameter, and immature human oocytes of 150 μm in diameter are presented