Zeta Potential Measurements For Surface Modification Of Plastic Substrates For Nanofluidic Biosensors

Polymeric materials have revealed their great potentials in micro- and nano- fluidic devices for biosensing. Their advantages include low cost, various physicochemical properties, well-developed fabrication, and surface modification protocols comparing with traditional materials such as silicon or glass. Surface modification consists an essential step in fabrication of polymer-based biosensors. A proper characterization is required to justify the effectiveness of modifications on polymer surface. For nanofluidic devices, special phenomena such as overlapped electrical double layer, ion rectification and electroosmosis flow can dominate the behavior of single molcules. The concept of surface charge density plays a key role in nanofluidic devices due to its effects on electrophoresis and electroosmosis in the nanostructures. For example, a polymeric materials with low surface charge density is preferred for DNA translocation. Thus, the measurement technique of surface charge density is promising to select a proper material for nanofluidic sensor and assess the performance of polymer after surface modification. This work presents zeta potential measurements on PMMA, a common thermoplastic polymer, which is treated by UV/Ozone irradiation, O2 plasma, covalent crosslinking of 3-(3- dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS). And determine the optimal surface activation protocol via monitoring zeta potentials for different treatment conditions. Finally, lambda-Exonuclease (휆-Exo) will be anchored on the EDC/NHS functionalized PMMA surfaces and the effectiveness of binding biomolecule will be studied