On the use of CO2 laser induced surface patterns to modify the wettability of poly(methyl methacrylate) (PMMA)

CO₂ lasers can be seen to lend themselves to materials processing applications and have been used extensively in both research and industry. This work investigated the surface modification of PMMA with a CO₂ laser in order to vary the wettability characteristics. The wettability characteristics of the PMMA were modified by generating a number of patterns of various topographies on the surface using the CO₂ laser. These induced patterns were trench and hatch with scan dimensions of 50 and 100 μm. Through white light interferometry, it was found that for all laser patterned samples, the surface roughness had significantly increased by up to 3.1 μm. The chemical composition of selected samples was explored using X-ray photoelectron spectroscopy and found that the surface oxygen content had risen by approximately 4 at%. By using a sessile drop device it was found that, in comparison to the as-received sample, 50 μm dimensions gave rise to a more hydrophilic surface; whereas 100 μm dimensions gave rise to either no change in contact angle or an increase making the PMMA hydrophobic. This can be explained by combinations of surface roughness and γp contributing to the observed contact angle, in addition to the possibility of different wetting regimes taking place owed to the variation of topographies over the as-received and laser patterned samples.