3D-Molding of Microfluidic Devices

Multilayer elastomeric device fabrication by replication molding requires a method for bonding together layers. In our development of solvent-resistant microfluidics, the goal with each promising new material or coating was to fabricate multilayer chips to evaluate crossed-channel valve performance and ultimately to implement functional elastomeric devices. However, determining a reliable adhesion process was often a significant obstacle (see Chapters 3, 4, and 5). Because methods can rarely be re-used in different material systems, development of bonding protocols was time consuming , slowing progress and limiting the number of materials that could be thoroughly investigated. Generic bonding methods such as gluing are generally not useful due to the presence of easily clogged microfeatures on the bonding surfaces and due to the incompatibility of glues with many solvents that might be flowed through channels. Surface chemistry modification and partial curing techniques are usually required. To speed up our investigations, we developed a novel replication molding procedure based on sacrificial 3D wax molds, which eliminates the need for layer bonding entirely. A single mold contains a 3D pattern of fluid and control channels and a complete multilayer elastomeric device can be cast in a single step. We have demonstrated functional crossed-channel microvalves in elastomeric devices cast from these molds. While the resulting devices are of lower quality than those obtained by silicon wafers patterned with photoresist, this technique accelerates the ability to evaluate oper