Using CO2-laser bugle for ultrasonic bonding of thermoplastic microfluidic devices

A novel method for ultrasonic bonding of thermoplastic microfluidic devices was demonstrated. When the CO2 laser beam scanned around the microchannel of the microdevice, a small bulge, which was called CO2 laser bulge (LB), was formed in the rim of the laser-ablated groove (LG). After applying the ultrasonic energy the LB was melted and the bonding process was achieved. In this method, the molten LB flowed into the LG, which addressed the issues of controlling the molten polymer flow between the bonding interfaces. Moreover, there was no need for fabricating the complicated and customized energy director, which will make it simple and flexible. The relationship between the laser parameters and the LB height was investigated. The ultrasonic bonding parameters were optimized. The influence of the LB height on the bonding strength was studied. The results showed that the thermoplastic microdevice can be successfully bonded by using this method. The channel loss was 0.42 ± 0.25 μm in depth and 0.32 ± 0.02 μm in width. The liquid leakage was not observed in the experiment. The bonding strength can be 1.92 ± 0.31 MPa. Hence, it can be a potential method for the bonding of microfluidic devices.