Rotational self-assembly of complex microstructures by the surface tension of glass

A new process for self-assembly of microstructures based on rotation by surface-tension forces is described. Greatly improved materials compatibility, combined with controllable viscosity, is achieved by using a low-melting-point borophosphosilicate glass as the meltable material. Precise rotation is ensured by a mechanical rotation limiter acting on the bottom corner of the movable part. The limiter is constructed by a simple modification to the layout of the fixed and moving parts, so that only two lithographic steps are required to define the entire structure. Using this process, reliable self-assembly of complex Si-based microstructures is demonstrated, including simultaneous rotation of parts about orthogonal axes and rotation of parts attached to other rotating parts. (C) 1998 Elsevier Science S.A.