Integration of PDMS membranes into thermoplastic microfluidic packages

This project proposes a novel process to integrate a polydimethylsiloxane (PDMS) membrane into a polycarbonate (PC) microfluidic device. A novel composite material was manufactured by adhesively laminating UV/ozone pretreated PDMS to polycarbonate using Loctite 3105 UV curable adhesive. Hot embossing of this composite produced a microstructured substrate of PC with an adhesively bonded PDMS layer at the surface. This PDMS surface was then exposed to an oxidative media such as oxygen plasma or UV radiation to produce a highly activated PDMS surface that can adhere to itself upon contact. The use of a novel system of PC bonded to PDMS using a UV curable adhesive resulted in adhesion of sufficient strength and durability to withstand the hot embossing process. Optimizing the UV curing parameters maximized joint strength for PC to PDMS bonds. The surface chemistry of the delaminated PDMS was analyzed and used to determine the dependence of adhesive failure mode on UV/ozone treatment parameters. The research conducted proves that an adhesively laminated composite of PDMS and PC can be embossed in a reproducible way with both semi-circular and rectangular tools. The dimensions of the embossed channels can also be modeled in terms of both the embossing parameters and the UV exposure parameters. In summary, this technique can be used to fabricate microfluidic structures in a controlled fashion, and when combined with oxidative exposure of PDMS surfaces, offers an effective way to integrate PDMS membranes into thermoplastic microfluidic devices.