Abstract

Biochemical Assays in Variable Height Microfluidic Devices

Mark Burns, T. C. Chang Professor of Engineering, University of Michigan

Processing of solid particles in 3D-printed fluidic channels has the potential to expand the application space of microfluidic systems. As an example, selective binding of proteins, DNA, and other biological substances is used in assays to detect pathogens, diagnose disease, and guide patient treatment. The capture of these substances can take place in a bulk liquid phase, which is generally simpler, or on a solid surface, which provides the benefit of straightforward two-dimensional result interpretation. We combine these two techniques to achieve the best of both worlds. We use an antibody sandwich assay with the capture antibody immobilized on the solid surface of microbeads, each of which has a specific diameter corresponding to one protein in a multiplexed adsorption assay. The beads are then introduced into a microfluidic channel with varying heights, allowing each bead size to become trapped at a distinct location. This method effectively transforms a three-dimensional suspension into a two-dimensional layout, simplifying the reading of binding results. The channel is currently constructed using a variable etch of a glass substrate in hydrofluoric acid but we hope to use other techniques such as 3D printing to produce these chips. One printing technique we have developed, dual-wavelength stereolithography, could eventually fulfill this goal but the current resolution is too low.