PNNL

Abstract

We present an integrated droplet-on-demand microfluidic platform for dispensing, mixing, incubating, extracting and analyzing by mass spectrometry pico- to nanoliter sized droplets. Droplet generation is accomplished using computer-controlled pneumatic valves. Controlled actuation of valves for different aqueous streams enables controlled dosing and rapid mixing of reagents within droplets in the droplet generation area or in a region with widening channel cross-section. Following incubation, which takes place while droplets travel in the oil stream, the droplet contents are extracted to an aqueous channel for subsequent ionization at an integrated nanoelectrospray emitter. As an initial demonstration of the platform, rapid enzymatic digestions of a model protein are performed in droplets and detected on-line by nanoelectrospray ionization mass spectrometry.