Micromachined optical flow cell for sensitive measurement of droplets in tubing

Abstract

Here a micromachined flow cell with enhanced optical sensitivity is presented that allows high-throughput analysis of microdroplets. As a droplet flows through multiple concatenated measurement points, the rate of enzymatic reaction in the droplet can be fully characterized without stopping the flow. Since there is no cross-talk between the droplets, the flow cell is capable of continuously measuring biochemical assays in a droplet flow and thus is suitable to be used for continuous point-of-care diagnostics monitoring. This paper describes the design and operation of the device and its validation by application to the accurate and continuous quantification of glucose concentrations using an oxidase enzymatic assay. The flow cell forms an important component in the miniaturization of chemical and bio analyzers into portable or wearable devices.

Real-time impedimetric droplet measurement (iDM)

“…The optical droplet detection method involves the integration of a light source and detection unit into a microfluidic chip to measure droplet size, size distribution, shape, frequency, velocity and composition. [13][14][15][16][17][18][19][20][21][22] De Saint Vincent et al presented a realtime droplet detection system to measure droplet length, velocity and frequency using two photodiodes. 18 Although recent optical systems are usually on-chip and do not require bench-top hardware, they have low reproducibility due to the stringent alignment procedure between the light source and photodiodes.…”

“…The use of waveguides and apertures is a common practice to avoid the misalignment issues that lead to signal deterioration. 17,19,23 For electrical droplet detection, Niu et al reported a capacitive detection method for counting droplets and for droplet size, velocity and composition detection. 24 Elbuken et al made non-contact planar microelectrodes to measure microfluidic droplet size and velocity using an applicationspecific integrated circuit (ASIC).…”

The Rise of the OM-LoC: Opto-Microfluidic Enabled Lab-on-Chip

“…A modular optical unit has been recently demonstrated with a micro-milled LED system that encapsulates Polytetrafluoroethylene (PTFE) tubing in order to perform highthroughput absorbance measurements on droplets [169]. In this case, four detection cells are formed through LEDs in micro-milled holes.…”

Droplet-Based Microfluidics: Formation, Detection and Analytical Characterization

“…Bright-field microscopy also allows for the study of kinetics for nucleation of protein crystals within droplets [44] and colour detection of changes in BZ reaction in droplets [45]. Absorbance based detections of droplets are also carried out and provide robust and low-cost detections for colourimetric assays such as glucose, lactate and nitrate assay kinetics [46][47][48][49][50][51].…”