Microfluidic particle tracking technique towards white blood cell subtype counting and serum protein quantification

Microfluidic technologies have gained wide acceptance in the past decade as diagnostics tools in clinical setting world-wide. This is primarily due to the fact that microfluidic technologies enable rapid, quantitative assays from small amount of physiological sample in an easy-to-use, portable platform. In this work, we will describe a microfluidic technique that can be built upon to count white blood cell subtypes or serum protein from a drop of blood. Traditionally, researchers have counted white blood cell subtypes by capturing them. However, an elegant and more accurate way to do the same is by exploiting the transitory interactions between the antigen on the surface of the cell and a cognate antibody. Cells expressing the antigen of interest will take longer to traverse a microchannel which has been coated with a cognate antibody compared to the cells which don't express that antigen. To our knowledge, no microfluidic assay exists which can rapidly count cells using this principle. Towards this end, we have developed a repeatable experimental technique to control the transit time and the order of particles in a microchannel. To least affect the uniformity of transit time, we have also optimized the geometry of pillars in the microchannel on which antibodies are functionalized