Photodefinable PDMS thin films for microfabrication applications

In this work, direct patterning of polydimethylsiloxane (PDMS) is demonstrated by the addition of a UV-sensitive photoinitiator benzophenone. As an improvement to our previous work, patterns with both positive and negative features have been fabricated on the same substrate. Infrared spectroscopy was used to investigate photocrosslinking behavior and reaction chemistry of this new photodefinable PDMS (photoPDMS) material. Several applications of the photoPDMS process have been successfully demonstrated. Multi-layer structures and multi-level microfluidic chips can be easily fabricated using this photopatterning process. Patterned PDMS thin films can also be removed from the underlying substrates and used as shadow masks for defining patterns on both planar and non-planar surfaces. The photopatternable PDMS was also found to be biocompatible once un-reacted benzophenone is extracted from the cured film. Overall, photoPDMS offers a number of critical advantages over conventional PDMS processing, including elimination of master template fabrication, ability to process under ambient light processing conditions, positive-acting tone, low cost, and rapid and easy fabrication.