The microscale physics has several specific effects that are mainly manifested by the predominance of contact and surface forces (van der Vaal, electrostatic and capillar forces) over volumic forces (weight), the small inertia of microsystems which causes high dynamics, the small signal-to-noise ratio, the fragility of microparts, the dependency of the environment conditions (temperature, humidity, etc) and the high nonlinearity in the active materials used for the actuation at this scale.

All these specific effects at the microscale increases the difficulty of modeling microsystems and indentifying their parameters. Thus, nonlinear and robust control approaches need to be used to compensated the model nonlinearity and uncertainity. In addition, several care needs to taken for the dynamic control in order to accurately control microsystems without breaking the microparts and to prevent unsuccessful tasks.

During my PhD, a two-smart-fingers microgripper has been designed and fabricated. Each of the microgripper fingers is composed of an active piezoelectric microgripper with a piezoresistive force sensorized end-effector. The developed microgripper presents very interesting static and dynamic performances for both actuation and force sensing. The developed microgripper is shown in the following figure.

The micrassembly of hybrid MOEMS is one of our applications. The main motivation of this application is systems miniaturization which is of great interest last years for several reasons (space saving, energy saving, reduction of signal noises, favorable scale effects, etc). Clean room micromachining becomes everyday more challenging to fabricate complex MOEMS (Micro-Opto-Electro-Mechanical Systems). MOEMS assembly brings a very interesting alternative because it enables to integrate together several components fabricated through several and often incompatible microfabrication processes.

The automation of microassembly enbales to increase the precision, reduce assembly time and increase the dexterity of the microassembly tasks at a scale where the human cannot sense and may even not see what is hapening. The automation by integrating sensors and cameras is necessary to successfully accomplish the tasks.

These works are performed in collaboration with the MN2S department of FEMTO-ST.