Fabrication of post-hydrophilic treatment-free plastic biochip using polyurea film

A novel low-temperature bonding method was developed by using polyurea film as intermediate layers. A microchip with a microchannel having a highly hydrophilic surface was realized by pretreatment with vacuum ultraviolet light irradiation under an oxygen atmosphere (VUV/O₃). The bonding temperature is low enough to use thermo-plastic channel plates such as PMMA (poly(methyl methacrylate)) with negligible deformation of the channel structure. The results of contact angle measurements indicate the highly hydrophilic surface of the microchannel was retained after the bonding process. There was no leakage or obstacles to smooth fluidic flow at the bonded interface. For actual micro-biochip fabrication with this method, the post-hydrophilic treatment after bonding process is unnecessary.