Low-cost irreversible blue diode laser transmission welding of poly(methyl methacrylate)-based microfluidics

Thermoplastics have been widely used as bulk material for microfluidic devices in biological and medical applications. One of the critical steps in chip fabrication is bonding: substrate (usually with fabricated microchannels) is bonded with a cover plate to seal the microchannel. This study proposes a low-cost PMMA (polymethyl methacrylate)-based microfluidic chip bonding method using blue diode laser transmission welding. Conventional PMMA substrate is transparent to the blue diode laser (445 nm in wavelength) used in this study, to achieve the transmission welding with the low-cost blue diode laser, PMMA substrate was custom-made with the addition of light-absorbing additives. Thus, the laser beam can transmit through PMMA cover plate (without light-absorbing additives) and absorbed on the surface of PMMA substrate (with light-absorbing additives). The absorbed laser energy converts to heat and finally achieves a stable bonding between the substrate and cover plate. Compared with the conventional bonding method for thermoplastic-based microfluidics, such as thermal fusion bonding and adhesive/chemical bonding, the proposed bonding method achieved a higher bonding strength without contaminating the microchannel with adhesives and organic solvents. The proposed low-cost and rapid bonding method could have wide application potential in the field of point-of-care diagnostic devices.

Automated summary

This study proposes a low-cost PMMA-based microfluidic chip bonding method using blue diode laser transmission welding. Compared with traditional bonding methods, this method achieves higher bonding strength without contaminating the microchannel.