Photoresist as a sacrificial layer by dissolution in acetone

We report here a detailed study of sacrificial layer dissolution of photoresist by acetone in microchannels. The effects of channel geometry as well as photoresist characteristics such as thermal cycles and UV exposure are considered and tested. Test channels were designed and fabricated ranging in height from 2 µm to 6 µm, widths from 10 µm to 80 µm, and lengths up to 2 mm. Channels were formed by encapsulating a sacrificial photoresist layer between two layers of parylene. Sacrificial layer dissolution in acetone was monitored using time lapse digital photography through a microscope and the captured data plotted and analyzed. The data support a diffusion limited model for photoresist dissolution in acetone. Individual parameters in the diffusion limited model are tested and validated through a number of controlled experiments. These results and the final model are important for the design and fabrication of micro-fluidic systems based on the parylene-photoresist sacrificial system