Fabrication of an integrated microfluidic device based on a heat-sensitive poly(N-isopropylacrylamide) polymer and micromachining protocols for programmed bio-molecular patterning

Due to their broad application in biochemical analysis, the miniaturized and integrated microfluidic devices which can give a biochemically Active phase for diagnostic capabilities on single chips are very important in contemporary research. Here, we present an integrated microfluidic device applicable to sample preparation, like the controlled patterning of target biomolecules, like proteins or cells, with a smart polymer-modified temperature-addressable microelectrode that is thermally switched between hydrophilic and hydrophobic states. The device is composed of a bulk-micromachined Si device and a hot-cast poly(dimethyl siloxane) (PDMS) device. The microelectrode a array has been integrated into a micro-hot plate having an embedded microheater and temperature sensors on 2-mu m thick silicon oxide/silicon nitride/silicon oxide (O/N/O) stacking layer, and is designed to adsorb and release biomolecules with low power consumption and rapidness in a microfluidic chamber. To provide the heat-responsive activity to the microelectrode surface, the electrode surface was modified with poly(N-isopropylacrylamide) (PNIPAAm), which shows a rapidly reversible hydrophilic-to-hydrophobic transition in response to temperature changes. In this study, design, fabrication and its characterization of the microfluidic device with NHS PNIPAAm surface modifications on the dendrimer monolayer conjugated microelectrode were carried out. And then, the synthesis and the confirmation of surface modification with the smart polymer by grazing FT-IR spectroscopy and contact angle analyzer were demonstrated. The microfluidic devices would be directly applicable to a portable battery-powered biochemical system. (C) 2007 Elsevier B.V. All rights reserved.