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.

► Tapered channels are fabricated using an ultrafast laser system with a Gaussian beam profile.
► Three transparent materials are tested (soda–lime, borosilicate glasses, and PDMS elastomer).
► Model for the channel width and depth is presented.
► Optical microscopy is used to characterize the channel cross-section.
► Channel depth is a linear function of the number of pulses per channel width.