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

CO(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 100-500 mu m 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 0.45 to 1.35 W and the scanning speeds ranged from 2 to 14 mm/s. The width of fabricated channels ranged from 44 to 240 mu m and their depths ranged from 22 to 130 mu m. Physical models were developed for predicting the depth and the profile of laser-ablated channels. The profile model incorporates the threshold fluence for CO(2) 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%. (c) 2007 American Institute of Physics.