Etude du comportement mécanique des microbulles. Application à la conception d'une table actionnée pour la micromanipulation en milieu liquide.

摘要

The scope of this thesis is micromanipulation in liquid media. This scientific field aims at understanding the relevant phenomena existing during the manipulation in a liquid of microcomponents having a size between 1µm and a few millimeters. This work focuses on the study of surface tension forces in immersed media. The main idea is to use gas bubbles as actuation mean in a liquid, and requires to study the mechanical properties of these bubbles. The originality of the approach is the combination of two effects: surface tension and gas compressibility. The first step was the study of an efficient mean to generate a single bubble of predefined size. Volume controlled bubble generation being a promising method, we have then developed a model to predict the size of a bubble, and emphasized the possible existence of a growing instability. An analytic dimensionless study allowed to define a criterion to predict the existence of this instability. The second step aimed at the mechanical characterization in quasi static equilibrium of a gas bubble caught between two solids. The purpose is to predict the force generated by the bubble, together with its stiffness. The model implemented allowed to infer interesting properties, notably a high compliance whose value is controllable by fluidic parameters. This compliance property being very important during micromanipulation, a demonstrator making use of gas bubbles has been designed and manufactured. It consists in a compliant microtable actuated by three bubbles. This work opens the way to new actuation or sensing means, using the transduction between fluidic and mechanic energy operated by a capillary bridge.