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,a nd microscale material syntheses.A nalytical methods for real-time and in situ detection of chemicals in the droplets will benefit these applications,but they remain limited. Reported herein is an ovel heterogeneous chemical sensing strategy based on functionalization of the oil phase with rationally combined sensing reagents.S ub-nanoliter oil segments containing pH-sensitive fluorophores,i onophores,a nd ion-exchangers enable highly selective and rapid fluorescence detection of physiologically important electrolytes (K + ,N a + , and Cl À )a nd polyions (protamine) in sub-nanoliter aqueous droplets.E lectrolyte analysis in whole blood is demonstrated without suffering from optical interference from the sample matrix. Moreover,a no il phase doped with an aza-BODIPY dye allows indication of H 2 O 2 in the aqueous droplets, exemplifying sensing of targets beyond ionic species.

Size Effect on the Reaction Rate of Surface Nanodroplets

“…The large surface-to-volume ratio of microdroplets is desirable for efficient mass transfer crossing the interface in biphasic reactions . In heterogeneous catalytic reactions, the catalyst adsorbed at the droplet surface has access to the compounds dissolved in both aqueous and organic phases. , Thanks to these advantageous features, droplet reactions are increasingly employed in drug discovery, synthesis of fine chemicals, biofuel conversion, , and fabrication of structured materials, , such as polymeric microcapsules or microspheres, porous membranes, lightweight materials, and food-grade foams . In tandem with fast analytic techniques, droplet reactions are indispensable in personalized medicine, , point-of-care diagnostics, anticounterfeiting, food safety, or environmental monitoring .…”

Hydrogel-Based Optical Ion Sensors: Principles and Challenges for Point-of-Care Testing and Environmental Monitoring

“…However, most of the real samples still need pretreatments such as centrifuge, filtering, and dilution, which is not user-friendly to untrained operators. So far, only a few works could determine ions in completely untreated samples such as whole blood. , On the other hand, many hydrogel-based sensors need a relatively stable detection environment such as a fixed pH or ionic strength, which brings limitations to their applications in complex samples. An optical sensor that automatically integrates sample pretreatment and the sensing components may be promising for the future .…”

First online X‐ray fluorescence characterization of liquid‐liquid extraction in microfluidics

“…In terms of chip design, guide structure [6][7][8][9][10] and droplet [2,[11][12][13][14][15][16] technologies require a highly stable flow rate with careful injection to maintain separation with higher risk of interface rupture. Recently, Dunne et al developed a flow technique based on magnetic flow freeing themselves from the excessive hydrostatic pressure stemming from wall friction.…”

“…[1,22] To avoid manual characterization and to exploit fully the automation capabilities of a microfluidic system, researchers implemented online characterization tools in microfluidic circuits. [1,5,15,[23][24][25] Spectroscopic techniques such as Raman, [26,27] infrared [24,[28][29][30] and UV-VIS [31] have been used extensively. However, only Hellé et al directly applied online characterization for studying L-L extraction processes.…”