Post Bonding Modification of Microfluidic Channel Materials for the Manufacture of Bioanalytical Devices
Zhan Gao1, Chang-Soo Kim2, and David B. Henthorn1. (1) Department of Chemical and Biological Engineering, University of Missouri-Rolla, 143 Schrenk Hall, Rolla, MO 65409, (2) Department of Electrical and Computer Engineering, Dept. of Biological Sciences, University of Missouri-Rolla, Rolla, MO 65409
There has been increased interest in the use of negative-tone photoresist materials as structural components in microfluidic devices. However, the traditional steps used to seal a microchannel (heat, pressure, etc.) may be incompatible with biomolecular components often used in the development of bioanalytical devices. In this work, we have demonstrated a technique for post bonding functionalization of the photoresist SU-8 using thin polymer films. First, a photoactive initiator is conjugated on the SU-8 surface using a hydrogen abstraction technique. The now photoactive surface is then brought in contact with various monomeric species, with UV light used to induce a surface initiated polymerization reaction. Wettability of the normally hydrophobic SU-8 material was markedly enhanced by grafting hydrogels comprised of either 2-hydroxyethylmethacrylate (HEMA) monomer or macromonomers of poly(ethylene glycol) (PEG). The static water contact angle of freshly prepared SU-8 was reduced from 78° to 35° using grafted pHEMA hydrogels, and further reduced to 8° using PEG-rich hydrogels. Surface bound hydrogel layers containing the enzyme glucose oxidase were prepared to evaluate the applicability of the technique to integration of biomolecular components. In addition, incorporation of analyte-sensitive fluorophore layers was also investigated.