CO 2 Laser Fabrication of a Passive continuous-flow T-shaped Polymethyl Methacrylate (PMMA) Micromixer

Since the emergence of microfluidics, the demand for microfluidic devices is ever increasing. Polymethyl methacrylate (PMMA) is extensively used to manufacture microfluidic devices because it is cheap, disposable, and biocompatible. CO 2 laser micromachining of PMMA is cheap, fast, and efficient. However, thermal defects affect the process. In this work, a passive continuous-flow T-shaped micromixer was fabricated using a low-power CO 2 laser. Microchannels were fabricated on PMMA substrates coated with a 1-µm layer of 99.95% pure aluminium. The power and speed of the laser varied from 1.5 to 7.5 W and 5 to 17.5 mm/s respectively. The effects of the deposited energy on surface roughness, heat-affected zone, and volumetric removal rate were examined. The microchannels were characterized to get the suitable dimensions for the micromixer’s microchannel which was fabricated at 3.0 W and 17.5 mm/s. The micromixer was bonded using the microwave welding technique and tested for leakage using purple dye by varying the flow pressure at intervals of 100 kPa for 20 min. Up to 1.5 MPa, no leakage occurred. Beyond 1.5 MPa, any increase in pressure resulted in leakage from the inlet tubes. Coating PMMA substrates with 99.95% pure aluminium before fabrication reduces thermal defects and improves efficiency.