Delivery of minimally dispersed liquid interfaces for sequential surface chemistry using a microfluidic probe

We present a novel method for sequential delivery of reagents to a reaction site with minimal dispersion of their interfaces using the microfluidic probe. To minimize dispersion, we transport the reagents in segmented flow and passively remove the oil phase in close proximity to the apex, allowing only the aqueous phase to reach the surface. We demonstrate two examples of assays: measurements of reaction-kinetics and protein response to localized chemical stimuli on surface.