Self-Assembly of Microsystems Using Non-Contact Electrostatic Traps

Self-assembly has been proposed to address problems in the integration of MEMS and optoelectronic systems, and also to relax yield constraints in wafer-scale systems such as active-matrix LCDs. The essence of the approach is to fabricate large numbers of microstructures, and then place them at predetermined sites on a target substrate. The sites are designed to have an affinity for the microstructures, e.g. via electrostatic or magnetic forces. Random mechanical vibration then enables large numbers of microstructures to be “annealed” into precise registration with the sites. A critical problem, however, is posed by static friction. When structures adhere to the substrate or each other, their progress toward optimal, precise registration is halted. For this reason, a new type of self-assembly binding site is proposed, wherein a microstructure is electrostatically trapped and levitated a short distance above the target substrate. The levitation effect is passively stable, so that large numbers of binding sites may be distributed over the substrate without need for feedback control sensors or circuitry. The site design is simple enough that relatively low-resolution lithography suffices for fabrication, and a broad range of materials may serve as target substrates.