Ultrafast laser machining of tapered microchannels in glass and PDMS

The ability to fabricate tapered microchannels with customizable cross sections in a variety of materials is highly desirable for microfluidic applications. This article examines ultrafast laser machining of tapered microchannel trenches in both hard (soda-lime and borosilicate glasses) and soft (PDMS elastomer) transparent solids. A simple model for channel width and depth as a function of processing parameters and threshold fluence is presented. Estimated channel sizes from the model are in good agreement with experimental results. We also show that the channel depth is a linear function of the number of laser pulses per channel width. All measurement data are found to collapse onto a single curve, which can serve as a useful guide for micromachining of tapered channels in transparent materials. (C) 2011 Elsevier Ltd. All rights reserved.