Microfluidic Droplet Detection

Microfluidic Droplet Detection, Fig. 1 The schematics of three critical functions of droplet microfluidics (a) droplet production (encapsulation of sample... 

Microfluidic Droplet Detection, Fig. 3 Microlluidic droplet system enables delivery and analysis of complex chemical signals with multiple detection methods, (a) Schematic showing droplet-based chemical stimulation,... 

Fig. 11 Droplet-based single cell analysis, (a) Highly efficient encapsulation of single cells into microdroplets. Reproduced with permission Irom [119]. (b) Detection and analysis of low-abundance cell-surface biomarkers using enzymatic amplification in microfluidic droplets. Reproduced with permission Irom [125]...

A droplet detection microfluidic system with chirp excitation (Fig. 18) is shown in Fig. 19 [4]. 

Droplet-based optofluidics Electrical droplet detection Microfluidic droplet assays Microfluidic droplet characterization Optical droplet detection... 

The droplet detection methods described in this entry include fluorescence, surface-enhanced Raman scattering (SERS), electrochemistry, capacitive, and mass spectrometry. The integration of different detection approaches into the microfluidic droplet device typically involves MEMS and optics technologies. Several methods have been employed to address the integration of detection components with the droplet operation unit however, the task of maintaining overall system functionality remains a challenge. As a result, most of these methods are significantly sophisticated. Trends and issues associated with each detection method are presented. 

When a droplet passes through the sensing region, variations in capacitance can be detected in real time due to the contrast in dielectric properties between the aqueous solution and oil phase. Niu and coworkers employed a capacitance method to test the size and speed of droplets by integrating parallel electrodes across the droplet flow channel [8]. Based on the electric signal feedback, the microfluidic droplets can be counted, sorted out, or directed in an automated manner. However, this droplet content assay is limited to certain dielectric materials [9]. 

Casadevall i Solvas X, Niu X, Leeper K, Cho S, Chang S-I, Edel JB, de Mello AJ (2011) Fluorescence detection methods for microfluidic droplet platforms. J VisExpJoVE l-9... 

Elbuken C, Glawdel T, Chan D, Ren CL (2011) Realtime detection, control, and sorting of microfluidic droplets. Sens Actuat APhys 171 55-62... 

V. Srinivasan, V.K. Pamula, and R.B. Fair Droplet-Based Microfluidic Lab-on-a-Chip for Glucose Detection. Anal. Chim. Acta 507, 145 (2004). 

A. Huebner, M. Srisa-Ait, D. Holt, C. Abell, F. Hollfelder, A. J. deMello, and J. B. Edel, Quantitative detection of protein expression in single cells using droplet microfluidics, Chemical Communications, no. 12, pp. 1218-1220, 2007. 

J. Q. Boedicker, L. Li, T. R. Kline, and R. F. Ismagilov, Detecting bacteria and determining their susceptibility to antibiotics by stochastic confinement in nanoliter droplets using plug-based microfluidics. Lab on A Chip, vol. 8, no. 8, pp. 1265-1272, 2008. 

A digital microfluidic lab-on-a-chip based on electrowetting actuation of droplets has been demonstrated for the deteetion of 2,4,6-trinitrotoluene (TNT). We have used DMSO as a solvent instead of aeetone or acetonitrile which is commonly used. We have demonstrated a linear range of deteetion for TNT between 12.5 pg/mL - 50 pg/mL in less than 5 minutes. We have also demonstrated simultaneous deteetion of various eoneentrations of TNT and feasibility of detection of 2,4-dinitrotoluene (DNT). Future work would involve inereasing the detection limits of the system from pg/mL to ng/mL and simultaneous deteetion of other nitroaromaties sueh as DNT and TNB. 

Zhu et al. have developed a chip for heavy metal ion electrochemical detection". By controlling the microfluidics, a mercury droplet microelectrode is generated on the chip. Square wave stripping voltammetry is used for analysis. 

Srinivasan, V., Pamula, V. K., Fair, R. B. (2004). Droplet-based microfluidic lab-on-a-chip for glucose detection. Analytica ChimicaActa, 507, 145-150. 

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