Fabrication of Microchannels on Aluminium-Coated Polymethyl Methacrylate (PMMA) Using a Low Power CO₂ Laser

The emergence of microfluidics as one of the most viable technologies for making various microfluidic devices has greatly enhanced miniaturization in several areas. The utilization of polymethyl methacrylate (PMMA) for making such devices using CO₂ lasers has significantly increased due to the flexibility, time, and cost-effectiveness involved. However, attaining microchannels with accurate dimensions is a challenge because of the resulting defects like bulges, high heat-affected zone (HAZ), and surface roughness (Ra). This paper presents a novel attempt to engrave rectangular microchannels on PMMA substrates using a CO₂ laser by coating the substrates with a thin layer of 1 μm thickness of 99.95% pure aluminium. The study investigated the effects of power, and speed on the quality of the microchannels. The fabrication was done on both coated and uncoated substrates under the same conditions and the results were compared. Power and speed ranged from 1.5 to 7.5 W and 5 to 17.5 mm/s, respectively. At 1.5 W and 17.5 mm/s, the aspect ratio increased by 37.16%. However, the microchannel depth, width, HAZ, and Ra all reduced by 44.66%, 59.68%, 29.44%, and 64.74% respectively. At 7.5 W and 5 mm/s, the aspect ratio increased by 81.46%. However, the microchannel depth, width, HAZ, and Ra all reduced by 21.84%, 54.64%, 32.36%, and 72.70% respectively. The coated substrates produced better microchannels than the uncoated ones.