A universal bonding method for preparation of microfluidic biosensor

Sealing is one of the inevitable process in microfluidic chip fabrication to form complex networks for the biosensing applications. Currently, only a few materials can be used in microfluidic biosensor due to the lack of reliable bonding technique for most materials. To solve the problem of versatility for chip sealing, a novel adhesive bonding method as simple as “tear off–paste on” is developed. PDMS is mixed with a small amount of polyethylenimine solution to prepare a sticky thin layer, which works like a tape to paste on different materials. Various substrates including glass, plastic, metal and ceramics are used for preparation of microfluidic chips with good bonding strength. This method is appealing for its compatibility to traditional replication method using PDMS and SU8 channel mold while the small surface structures of channel walls can be retained. This method is reliable and versatile for microfluidic biosensor sealing, especially for those with biological sensitive recognition elements on the surfaces since neither aggressive chemicals, high temperature nor high-energy plasma is used. The applicability of the developed method is demonstrated to fabricate a novel long-term cell culture 3D microfluidic chip which keeps bacteria viable for more than 7 days.