Non-contact batch micro-assembly by centrifugal force

Due to the minute scale of MEMS, inertia forces are often neglected. However, we prove that these forces can be significant even if a microstructure's mass is <1 /spl mu/g (a 250 /spl mu/m /spl times/ 100 /spl mu/m mass with MUMPs poly1, poly2, and Au layers). We demonstrate that at this scale, mass inertia force can overcome surface forces and be used for non-contact self-assembly of MEMS structures. A centrifugal force was applied to hinged MUMPs#31 structures, causing these structures to self-assemble by rotating themselves 90/spl deg/ out of substrate plane and to lock themselves automatically to designed latches. This batch-assembly technique is very fast, low-cost, non-contact, and non-destructive. Moreover, we have successfully characterized the centrifugal forces needed to assemble these microstructures by integrating sensors on the same MUMPs chips to provide wireless signals that relate to the dynamic behavior of the microstructures. This is a very important result in terms of making feasible quantitative analyses of surface forces acting on surface micromachined MEMS devices.