Integration of polymer and metal microstructures using liquid-phase photopolymerization

In this paper we demonstrate, using a fabrication technique, liquid-phase photopolymerization (Lp(3)) for the relatively fast and low-cost integration of thick polymers and electroformed metal microstructures to develop a range of microfluidic components and systems. Liquid-phase UV-photosensitive polymers, similar to negative-tone photoresists, are used to create both polymer microstructures and molds to define electroformed metal (here, nickel-Ni) microstructures. This fabrication process can act as a stand-alone or appended one; it is gentle to allow processing after a metal structure has been released since fabrication occurs only at designated areas on a substrate, i.e. no spinning/casting of photosensitive materials, and self-planarization is achieved since photopolymerization of polymers occurs in the liquid phase. Photopatterned polymer and electroformed Ni microstructures are fabricated using Lp(3) with a low-end (low-cost) lithographic system. A variety of functional microfluidic components and systems, e.g., an active and a passive chaotic micromixer, and gear trains, are fabricated by utilizing a sequential step-and-repeat Lp(3) process to demonstrate the integration of polymers and metals.