Direct bonding of polymer/glass-based microfluidic chips with dry film photoresist

Dry film has been widely used as a low-cost photoresist in the print circuit board industry which consists of a thin layer of photoresist sandwiched between two protective polymer layers. In this research, a simple, cleanroom-free, low-cost and highly adaptable bonding method for various polymer and glass-based microfluidic systems was proposed using the cross-linked dry film photoresist. In this proposed approach, the uncross-linked dry film photoresist was sandwiched between substrates and cover plate, then using UV exposure for the crosslinking of the photoresist to reach a secured bonding, after bonding, a cleaning process for the removal of photoresist residuals trapped inside the microchannels was also applied. The proposed bonding method is highly adaptable for different kinds of polymer or glass-based microfluidic devices, even the hybrid bonding between polymer and glass substrates could be achieved, which is usually very challenging using the conventional bonding technologies. Comparing with the traditional adhesive bonding method, the proposed method is simple, low-cost and without the requirement for toxic organic solvents, in addition, the cleaning procedure proposed in this study could effectively remove the residual of the adhesives trapped in the microchannels.