(496c) Photopatterned Surface Modification of Su-8 Photoresist for Lab-on-a-Chip Applications

Recently, the negative tone photoresist SU-8 has attracted attention as a possible material in the construction of bioanalytical microfluidic devices. Traditionally, bio-MEMS devices were fabricated from either glass or other silicon-based materials, but disadvantages such as harsh processing conditions have lead researchers to seek out alternatives. The epoxy-based photoresist SU-8 has garnered attention due to its design flexibility and ability to form high aspect ratio structures. Normally hydrophobic, various modifications have been made to SU-8 to improve wettability including variations in the bulk chemistry, treatment with oxygen plasma, and functionalization of the surface with chemical agents. We describe a new in situ surface modification whereby a photoinitiator is grafted to the SU-8 substrate, allowing for a number of possible surface chemistries. This technique, amenable to photopatterning, allows for the spatial control of surface properties and/or the growth of various polymer layers. Hydrophilic monomers (2-hydroxyethylmethacrylate, methacrylated polyethylene glycol) were photopolymerized using this surface grafted initiator, resulting in controlled enhancements in wettability. In addition, the growth of hydrogel layers containing covalently linked enzymes was also studied for the creation of microfluidic biosensors.