WP1 - Microhandling

This work package deals with the development of a reconfigurable and low-cost microgripper, which will be integrated in the demonstrator. Currently the microgrippers available on the market are monolithic structures based only on MEMS processes. As all the functions are realized in the same process (actuator, end-effector), these grippers are not reconfigurable and each application requires the design, fabrication and test of new tweezers.

Microhandling achievements

New actuation principle was developed based on piezoelectric multilayered do-bimorphs actuators, allowing 2 degrees-of-freedom continuous motion of both gripper fingers on 100 µm stroke. Thanks to this new actuation principle, and the reduction of the analog input amplitude for piezoelectric drive from +/- 150 V to +/- 20V, electronics is far less expensive and much easier to integrate. Piezoelectric behavior as gripping principle is better, with less than 10 % coupling effect on both degrees-of-freedom and 150 % of increasing stroke comparing to the first high voltage piezoelectric gripper device.

Innovative tool exchanger was developed to interface the actuators and the manipulating end-effectors in order to achieve fast and easy replacement of this fragile parts. Thermal melting adhesive was used thanks to a compact thermal control inside the gripper to fix and unfix at will the end-effectors to the piezoelectric actuators. Fragile and high precision end-effector replacement takes less than one minute to change with bare hands, with more than 90% of success (without damaging the end-effectors). This result is much better than the previous device, where changing end-effectors required a dedicated robotic system or to dismount the actuators with a changing time about half-an-hour.

Low voltage gripper prototype was designed in two versions, a first one with high stroke (100 µm) which was characterized with 150% of increased stroke comparing to the previous version. The maximum force of gripping was characterized thanks to the CSEM load cell at 40 mN maximum. The second version is a high force gripper with low stroke (6 µm) but a high gripping force which was characterized as well at 1,7 N (more than 40 times greater). Pulling test on micro-assembled device showed that the maximum pulling force could reach 300 mN, and that is beyond numerous destructive test already done in microelectronic industry.