Label-Free Sensing in Microdroplet-Based Microfluidic Systems

Abstract

Droplet microfluidic systems have evolved as fluidic platforms that use much less sample volume and provide high throughput for biochemical analysis compared to conventional microfluidic devices. The variety of droplet fluidic applications triggered several detection techniques to be applied for analysis of droplets. In this review, we focus on label-free droplet detection techniques that were adapted to various droplet microfluidic platforms. We provide a classification of most commonly used droplet platform technologies. Then we discuss the examples of various label-free droplet detection schemes implemented for these platforms. While providing the research landscape for label-free droplet detection methods, we aim to highlight the strengths and shortcomings of each droplet platform so that a more targeted approach can be taken by researchers when selecting a droplet platform and a detection scheme for any given application.

Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

“…Based on the instantaneous droplet velocity u d , that is evident and directly measurable via optical or electrical measurement techniques [31], different explanatory approaches for the deviation of superficial velocity u 0 and droplet velocity u d have been reported.…”

Real-time impedimetric droplet measurement (iDM)

“…[7][8][9] The main motivations of performing a study in microdroplet form are the need for high throughput, low sample volume, automation and precision of the analytical output. 10 All of these features require the monitoring of droplets especially during the system development phase, where droplet formation and microchannel design are optimized. This study was inspired by the recently published work on automated droplet measurement systems using image processing techniques.…”

Surface-Enhanced Raman Scattering Spectroscopy and Microfluidics: Towards Ultrasensitive Label-Free Sensing

“…Several reports combining microdroplets-based strategies and Raman label-free detection have been published in the recent years. The use of microdroplets is beneficial as they act as individual microreactors, enhance fluid mixing and avoiding nanoparticle adsorption in the microfluidics channels, thus preventing the memory effect [ 79 ]. Several applications, analytes, and events have been demonstrated, such as the monitoring of nanoparticle assembly formation in microdroplets [ 80 ], presence of contaminants in water samples [ 81 ], tracing dyes and small atoms [ 82 , 83 ], or ultra-detection of drugs [ 30 ].…”