IT15. Transport and reactions in microfluidic immunosensors

There is a growing interest on microfluidic immunosensors for use as point-of-care diagnostic devices. In typical microfluidic immunosensors, the channel walls are functionalized with antibodies through intermediate linker molecules. The carrier fluid containing the antigens flows through the channels, and the antigens diffuse and electromigrate to the walls as the carrier fluid is convected along the channel. This interplay of the coupled phenomena of convection-diffusion-electromigration which affects the capture efficiencies and thus the detection limits, is an important aspect in the design of microfluidic immunosensors, and will be the main theme of the talk. The diffusion is governed by the velocity profile, which in turn is governed by the interaction of the carrier fluid molecules with the surface antibodies; and electromigration is governed by the electrical double layer. Some experimental results will be presented. Surface engineering (physical and chemical) was used to study the factors affecting these energies (substrates and underlying stack of self assembled linker molecules) and significant tunability of the energies of the surface antibodies was achieved. The effects of the surface engineering on the fluid flow characteristics in pressure driven antibody-functionalized silicon microchannels, and the molecular capture will be highlighted. This knowledge can be utilized to design more efficient microfluidic immunosensors.