Ionophore‐Based Biphasic Chemical Sensing in Droplet Microfluidics

Abstract

Droplet microfluidics is an enabling platform for high‐throughput screens, single‐cell studies, low‐volume chemical diagnostics, and microscale material syntheses. Analytical methods for real‐time and in situ detection of chemicals in the droplets will benefit these applications, but they remain limited. Reported herein is a novel heterogeneous chemical sensing strategy based on functionalization of the oil phase with rationally combined sensing reagents. Sub‐nanoliter oil segments containing pH‐sensitive fluorophores, ionophores, and ion‐exchangers enable highly selective and rapid fluorescence detection of physiologically important electrolytes (K+, Na+, and Cl−) and polyions (protamine) in sub‐nanoliter aqueous droplets. Electrolyte analysis in whole blood is demonstrated without suffering from optical interference from the sample matrix. Moreover, an oil phase doped with an aza‐BODIPY dye allows indication of H2O2 in the aqueous droplets, exemplifying sensing of targets beyond ionic species.Die Ölphase in einem Tröpfchenmikrofluidiksystem wird mit rational kombinierten Sensoreagenzien funktionalisiert. Auf diese Weise werden die Ölsegmente zu chemischen Sensoren für spezifische Analyte in wässrigen Tröpfchen. Diese biphasische Sensorplattform ermöglicht die Detektion eines breiten Spektrums von Analyten, einschließlich ionischer, polyionischer und nichtionischer Spezies.