193 nm ArF laser ablation and patterning of chitosan thin films

This paper reports laser ablation studies on spin-coated biopolymer chitosan films, β-l,4-1inked 2-amino-2-deoxy- d -glucopyranose. Chitosan has been irradiated using an ArF laser emitting at 193 nm. An ablation threshold of F T = 85±8 mJ cm −2 has been determined from etch rate measurements. Laser-ablated chitosan is characterised using white light interferometry, scanning electron microscopy, and thermo-gravimetric analysis. Laser ablation of chitosan is discussed in terms of thermal and photoacoustic mechanisms. Heat transfer is simulated to assist in the understanding of laser-irradiated chitosan using a finite-element method and the software package COMSOL Multi-Physics™. As a demonstrator, a micro-array of square structures in the form of a crossed grating has been fabricated by laser ablation using a mask projection scanning method. The initial investigations show no evidence of thermal damage occurring to the adjacent chitosan when operating at a moderately low laser fluence of 110 mJ cm −2 .