On-demand patterning of protein matrixes inside a microfluidic device

On-demand immobilization of proteins at specific locations in a microfluidic device would advance many types of bioassays. We describe a strategy to create a patterned surface within a microfluidic channel by electrochemical means, which enables site-specific immobilization of protein matrixes and cells under physiological conditions, even after the device is fully assembled. By locally generating hypobromous acid at a microelectrode in the microchannel, the heparin-coated channel surface rapidly switches from antibiofouling to protein-adhering. Since this transformation allows compartmentalizing of multiple types of antibodies into distinct regions throughout the single microchannel, simultaneous assay of two kinds of complementary proteins was possible. This patterning procedure can be applied to conventional microfluidic devices since it requires only some electrodes and a voltage source (1.7 V, DC).