Addition of structural features and two-step adhesive bond method to improve bonding quality of thermoplastic microfiltration chip

This paper reports a thermoplastic microfiltration chip designed for operation in a high-pressure environment. Preventing leakage and ensuring a heterogeneous bond between the commercial membrane and thermoplastic substrate are two issues crucial to the performance of such devices. A commercial polycarbonate membrane was tightly bonded to the PMMA substrates by applying a novel two-step UV adhesive bond, and a ring-shape structural feature was created around the microchannel using a micromilling machine to facilitate sealing and improve bonding strength. Evaluation results were as follows: (1) the inclusion of a ring-shape structural feature in conjunction with two-step UV adhesive bond proved highly effective in the prevention of leakage and significantly increasing bonding strength to 13 bars; (2) widening the ring cavity structure led to an increase in bonding strength; however, the benefits diminished when the width of the ring exceeded 5.5 mm; (3) wider microchannels increased filtering efficiency, but reduced the bonding strength because of a reduction in bonding area; (4) fluorescence particles were successfully separated from silicon oil when the pressure within the top microchannel exceeded 5 bars at a flow rate of 0.1 ml/min.