Experimental and theoretical analysis of direct-write laser micromachining of polymethyl methacrylate by CO2 laser ablation

Abstract

C O 2 laser micromachining provides a flexible and low-cost means for the rapid prototyping and manufacturing of miniaturized polymer systems such as polymethyl methacrylate (PMMA) microfluidic chip devices. In this paper, the relationships between the process variables (profile and depth of laser-ablated channels) and the process parameters (laser power and scanning velocity) are investigated. In contrast with the fabrication of 100–500μm wide channels reported in previous work, we focus on the fabrication of narrower channels using low laser power which can reduce the cost of the fabrication system and low scanning speeds. In this work, the laser power used for channel fabrication ranged from 0.45to1.35W and the scanning speeds ranged from 2to14mm∕s. The width of fabricated channels ranged from 44to240μm and their depths ranged from 22to130μm. Physical models were developed for predicting the depth and the profile of laser-ablated channels. The profile model incorporates the threshold fluence for CO2 laser ablation of PMMA to account for the partial ablation across the beam diameter. Our models are in excellent agreement with experimental results, with a maximum deviation of approximately 5%.