CO₂-laser micromachining of PMMA: The effect of polymer molecular weight

This paper reports an investigation on the effects of laser power and processing speed on the depth, width and surface profiles of microchannels manufactured from polymethyl methacrylate (PMMA) of various molecular weights. The CO₂ laser employed has a wavelength of 10.6 νm and a maximum power of 25 W. The power used for channel fabrication varied between 0.275 and 2.5 W and the cutting speed ranged from 7.0 to 64 mm s^-1. It is observed that the channel depth varies linearly with an increase in laser power at a particular speed. For a prescribed laser power, the channel depth decreased with an increase in laser speed for all the grades of PMMA. The channel width increased with an increase in laser power but decreased with an increase in speed. There is a decrease in the depth of the microchannels with an increase in the molecular weight of PMMA. Though the width decreases with an increase in molecular weights of PMMA, 96.7 kDa PMMA has a smaller width than 120 kDa PMMA which is due to the formation of bulges on the channel rim. The surface profiles of the microchannels were examined by a scanning electron microscope. It is observed that pore formation increased with an increase in molecular weight. © 2008 IOP Publishing Ltd.