Microfabricated 3D polymeric structure with SU-8

Abstract

Arbitrarily complex 3-D polymeric structures with a resolution of under 100 nm are fabricated by two-photon absorption polymerization (TPAP) by an ultra-short pulsed laser. This method can be applied to many scientific and engineering fields such as micro/nano-optics, MEMS, microfluidic system, and so on. Many 3-D structures by TPA fabrication have been made. However the structures made with an acrylate-based prepolymer material have seriously structural problems, such as shrinkage, collapse, distortion, etc. These problems make the fabrication of a large and fine 3-D structure difficult. Using an epoxy-based material like SU-8, which is widely used in the conventional lithography, the problems above can be prevented. Although SU-8 is designed for the UV lithography, a two-photon absorbing dye and proton acid generator can make it a base prepolymer material for the two-photon absorption polymerization. We studied the size of voxel or the resolution of fabrication from the SU-8 structures under the various fabrication conditions such as the laser output power and the exposure time. We demonstrated 3-D micro/nano structures with SU-8 and compared them with same structure with SCR-500.