ChemMicroMan

Microhandling is a promising way to assemble microcomponents in order to manufacture a new generation of hybrid microelectromechanical systems. To achieve high repeatability in the positioning of micro-objects, typically in the range of 5 to 50 µm, micro-tools such as micro-tweezers or grippers are developed. However, at the scale of several micrometers, the adhesion phenomenon highly perturbs the micro-object release and positioning. This phenomenon is directly linked to both the object and the gripper surface chemical composition, but also to other features such as roughness, hydrophobic/hydrophilic state as well as surface charge. So, all these parameters must be precisely control to propose optimal conditions and strategies for a precise and reliable manipulation. For applications in microhandling, our objective is to use chemical functionalization by polymers to perform the following successive steps: grasping of a micro-object by a gripper, moving of the micro-object to position it above a surface, then release of the micro-object onto the surface, and sticking of the micro-object onto the functionalized surface. Consequently, the grasping of the micro-object must be reversible to further allow the release when the sticking of the micro-object must be irreversible to allow a permanent positioning of the micro-object. To perform these tasks, we propose chemical strategies based on polymer functionalization of surfaces. Indeed, the grasping of the micro-object will be performed using a gripper previously functionalized by polyelectrolytes assemblies since polyelectrolytes have a high charge density that will allow the creation of electrostatic interactions between the object and the gripper leading to a reversible adhesion to the gripper. Then, by modifying the pH of the medium in which the gripper and the micro-object are immersed, it will be possible to switch the interaction between the polyelectrolyte-modified gripper and the object from an attractive behavior to a repulsive one, and thus to release the micro-object. Finally, the irreversible sticking of the micro-object onto a surface will be performed thanks to electrodeposited polymers. Indeed, functionalization of a surface by electrodeposited polymers generally leads to a strong and irreversible interaction between the polymer and the surface (through covalent bonds), but also to a strong interaction between the polymer and the object. The nature of polyelectrolytes and electrodeposited polymers is very important. Concerning polyelectrolytes, polypeptides and multilayer films possessing both positive and negative functions in their structure will be used, as well as polyelectrolytes assemblies based on hydrogen bonding. Concerning electrodeposited polymers, new organic and electrochemical synthesis will be performed to obtain polymers possessing interesting terminal functions (polypyrroles functionalized by alkyl chains and terminated by carboxylic groups, polyaminobenzoic acids and original polysulfures electrosynthesized in non-aqueous solutions). In conclusion, the aim of ChemMicroMan project is to develop original chemical strategies, based on functionalization by polymers, in order to show the relevance of a new type of reliable submerged robotic microhandling principle, based on the functionalization by polymers and on the adjustment of the chemical properties of the liquid.