MICROMOLDING OF POLYMERS IN CAPILLARIES - APPLICATIONS IN MICROFABRICATION

This paper describes the use of micromolding in capillaries (MIMIC) to produce complex polymeric microstructures supported on different subs trates and the applications of these microstructures in microfabricati on. Patterned microstructures of several organic polymers-polyurethane , polyacrylate, and epoxy-were formed by molding in enclosed, continuo us channels formed by conformal contact between a solid support and an elastomeric mold whose surface had been patterned with a relief struc ture having micrometer-scale dimensions. A liquid prepolymer filled th ese channels by capillary action and was allowed to cure photochemical ly or thermally. The mold was then removed. Polymeric microstructures formed on films of Saran Wrap could be folded into different shapes, w hile these microstructures retained their forms; they could also be st retched uniaxially to generate microstructures having distorted forms. The patterned polymeric microstructures formed on SiO2, glass, and me tals (Au, Ag, and Cr) could be used directly as resists in the selecti ve etching of underlying substrates. Free-standing polymeric microstru ctures fabricated by lift-off were used as disposable masks to generat e patterned microfeatures of metals on the surfaces of both planar and nonplanar substrates in two different procedures: (a) evaporation of gold through the polymeric mask supported on a substrate; (b) formatio n of patterned self-assembled monolayers (SAMs) by exposure of a silve r film covered by a polymeric mask to hexadecanethiol (HDT) in vapor, followed by selective etching of the regions that were not exposed; to HDT (that is, the parts of the surface protected by the mask) in an a queous solution containing K2S2O3 and K3Fe(CN)(6)/K4Fe(CN)(6).