Scratch drive actuator with mechanical links for self-assembly of three-dimensional MEMS

The self-assembling of three-dimensional (3-D) MEMS from polysilicon surface micromachined part is very attractive. To avoid risky external manipulation, the practical use of integrated actuator to perform the assembling task is required. To that goal, this paper presents detailed characteristics of the electrostatic surface micromachined scratch drive actuator (SDA). First, from numerous SDA test, it results that this actuator is able to produce a threshold force of 30 mu N, with a yield above 60%. With polysilicon devices consisting of SDA mechanically linked to buckling beam, a horizontal force of 63 mN have been demonstrated with +/-112 V pulse, and up to 100 mu N can be obtain with higher voltage. With buckling beams, displacements up to 150 mu m have been obtained in the vertical direction. The generation of vertical force of 10 mu N was confirmed with a 100 mu m displacement producing in 1 nJ work in the vertical direction. Finally, SDA proves to overcome the usual sticking of surface machined polysilicon by producing enough vertical force to completely release wide polysilicon plate (500 mu m x 50 mu m) without external manipulation. The above characteristic, both in terms of structure releasing and vertical/horizontai forces and displacements provide the SDA with the capability of self-assembling complex 3-D polysilicon part, opening new integration capabilities and new application held of MEMS.