Laser micromachining of glass substrates for microfluidics devices

Laser micromachining technique offers a promising alternative method for rapid production of microfluidic devices. However the effect of process parameters on the channel geometry and quality of channels on glass substrate has not been fully understood yet. Glasses are one of the most widely used substrates in microfluidics because of its rapid availability, inexpensiveness and superb optical and physical properties. In this research, we studied the effect of laser system parameters on the microchannel characteristics on glass substrates. A commercial CO2 laser system with three degrees of freedom (lateral, longitudinal and vertical) was used for fabricating microchannels on glass. The MUSE Full Spectrum laser system consists of a 45W laser tube, circulating water loop within the laser tube and air cooling of the substrate during machining process. Four laser system parameters - speed, power, focal distance and number of passes were varied to fabricate straight microchannels. The channel characteristics such as depth, width, shape and roughness were measured using scan electron microscope (SEM) and 3D profilometer. The results show that higher speed produces lower depth while higher laser power produces deeper channel. Out of focus laser machining produces wider but shallower channel. Results also show that the profile of microchannel can be controlled by increasing the number of passes. Roughness can be reduced by reducing speed. However in higher power and slower speed, glass breaks without forming a channel. Hence, optimum combination of all these four laser parameters are needed to fabricate a desired microchannel depending on applications. This comprehensive experimental investigation can provide a useful guidance to fabricate microchannels on glass substrate for various microfluidic applications.