Surface micromachining on a polymethylmethacrylate substrate using visible laser-induced backside wet etching with a KMnO4 solution as an absorber

In this paper, the authors report a method for continuous trench micromachining on polymethylmethacrylate (PMMA). Visible laser-induced backside wet etching (v-LIBWE) on PMMA using a potassium permanganate (KMnO4)-based absorber liquid was studied. PMMA is widely used in microfluidic devices for chemical and biological applications. Conventional micromachining of channels in the PMMA substrate using CO2 lasers achieves the smallest feature of approximately 85 μm. In this study, a continuous 12 μm-wide trench etching on PMMA was achievable by v-LIBWE using a 532 nm nanosecond pulsed laser. The etching threshold is ∼10 J/cm2, which corresponds to the average power of 58 mW for the repetition rate of 10 kHz. The authors also determined that the lowest scanning speed of 2 mm/s was necessary for the v-LIBWE of PMMA to generate the crack-free surface. Our study provides a new perspective and a convenient approach for the micromachining of the polymer substrate using v-LIBWE.