Low-cost hybrid bonding between thermoplastics and PDMS with differential adhesive tape for microfluidic devices

Abstract

Bonding is the key process in the fabrication of close-channel microfluidic devices. In the general fabrication approach of microfluidic devices, the substrate was processed with various kinds of microfabrication methods for the formation of the microchannel, then a cover plate (the same or different material to the substrate) was bonded to the substrate to enclose the microchannel. Various bonding methods have been previously reported which mainly focused on the bonding between thermoplastics or polydimethylsiloxane (PDMS)–glass bonding. In the past few years, the hybrid bonding between thermoplastics and PDMS was found to be useful to lower the cost and increase the flexibility of PDMS-based microfluidics, and the current approaches for thermoplastic–PDMS bonding are usually involved a series of chemical treatment processes (e.g., salinization). To simplify the bonding process between thermoplastic and PDMS, in this study, a low-cost, low-residue, easy-to-process bonding method was proposed with the help of silicone/acrylic differential double-sided adhesive tape. The differential tape consists of a silicone adhesive layer on one side and an acrylic adhesive layer on the other side, and during the hybrid bonding process, the silicone adhesive layer was bonded with PDMS substrate after a corona treatment process, while the acrylic adhesive layer bonded directly with the thermoplastic plate (polymethyl methacrylate and cyclic olefin copolymer) under the room temperature through a roller laminator. The whole hybrid bonding process is simple and without a chemical surface treatment process, and the bonding strength is also comparable to conventional bonding approaches. More importantly, the enclosed channel on PDMS substrate has consistent properties (e.g., water contact angle) on all four side walls, which may have significant advantages in sophisticated microfluidic applications like droplet generation. The bonding strength tests and biocompatibility tests were also conducted in this study.