Surface modification of polymers by vacuum ultraviolet Illumination containing low wavelength below 160 nm and microfluidic applications of irradiated polycarbonate

Microfluidic devices are applied in various fields including medicine and drug discovery. Recently, plastics are used for the device due to low cost. One of the challenges is the bonding process. A bonding method that preserves the microstructure is required. Recently, room temperature bonding methods using vacuum ultraviolet (VUV) light have been reported, but the applicable materials are limited. Here, we propose a new method using VUV with a wavelength shorter than 160 nm. As a result of the surface analysis, it was confirmed that the substrate surface becomes hydrophilic upon VUV irradiation. As a result of the bonding test, it was confirmed that it was possible to bond polycarbonate (PC) to each other (maximum bonding force: 2.03 MPa), PC to glass (maximum bonding force: 10.72 MPa), and cyclic olefin polymer to glass (maximum bonding force: 3.51 MPa), which have not been reported so far. The results suggest that one of these bonding mechanisms is the addition of hydrophilicity by VUV irradiation. Based on the results, for the first time, a PC-made microfluidic device was successfully developed using the bonding method. This result greatly contributes to the development of the manufacturing process of plastic microfluidic devices.