Effect of Fluence and Pulse Overlapping on Fabrication of Microchannels in PMMA/PDMS Via UV Laser Micromachining: Modeling and Experimentation

Abstract

This article presents modeling and experimental investigations on the effects of process parameters and the viability of directly fabricating microchannels in polymethyl methacrylate (PMMA) and polydimethylsiloxane (PDMS) polymers which are suitable for the fabrication of microfluidic devices due to their biocompatibility and transparent properties. Experimental work was conducted using a solid-state Nd:YAG laser with 355 nm ultraviolet (UV) wavelength and 5 ns pulse duration at various energy densities and pulse overlapping (PO). The study was focused on understanding the effects of two main process parameters: fluence and PO. This study closely investigates the effect of varying process parameters on the ablation depth and profile achieved and the resultant microchannel dimensional quality. It presents findings indicating that both process parameters have strong effects on the profile shape and variability of the microchannel width and depth. For PMMA polymer, the lowest dimensional variability for the microchannel profile is obtained with low fluence values and highest PO factor, whereas for PDMS polymer, it was observed that microchannel width and depth decreased linearly with increasing fluence and increased nonlinearly with increasing scanning rate. Further, process modeling is utilized for predicting microchannel profile and ablation depth, and these predictions were validated with experimental results obtained with pulsed laser micromachining at UV wavelength.