Coating-assisted laser micromachining of UHMWPE: Thermal control and microchannel optimisation using PDMS and PAA

Ultra-high molecular weight polyethylene (UHMWPE) is established as a material of choice in tribological and biomedical applications because of its superior impact resilience, low coefficient of friction, and outstanding wear resistance. Nevertheless, its intrinsic low thermal conductivity poses significant challenges during laser surface texture (LST), manifesting as thermal anomalies, including surface bulging and geometric distortion. In this study, we addressed these limitations by implementing a thermal regulation framework that integrates polymeric coatings, polyacrylic acid (PAA) and polydimethylsiloxane (PDMS), to mitigate thermally induced deformation in diode laser micromachining. A uniform coating thickness of 150 µm was applied through a controlled screen-printing protocol. The samples were then textured using a 520 nm, 4 W diode laser in a matrix of focal distances (22 to 54 mm) and scanning speeds (2 to 10 mm/s). Quantitative characterization of the resulting microchannels was conducted using confocal microscopy and profilometry, emphasizing dimensional metrics such as depth, width, and height of the curve. PDMS-coated substrates consistently demonstrated superior thermal stability and geometric accuracy among all configurations. At the optimal settings identified (38 mm focal distance, 4 mm/s scanning speed), microchannels exhibited a depth of 43.2 µm, a width of 35.2 µm and a minimal bulge height of 10 µm. This investigation contributes a scalable and cost-efficient approach to the advancing laser-based micromachining of UHMWPE, particularly in applications requiring precise surface architectures. The demonstrated integration of laser parameter optimization with polymer-based thermal modulation offers significant implications for designing and fabricating high-performance components in seawater-lubricated tribosystems and microfluidic biomedical platforms.