1,721,013 research outputs found
Micromachined optical flow cell for sensitive measurement of droplets in tubing
Full text linkHere a micromachined flow cell with enhanced optical sensitivity is presented that allows high-throughput analysis ofmicrodroplets. As a droplet flows through multiple concatenated measurement points, the rate of enzymatic reaction in thedroplet can be fully characterized without stopping the flow. Since there is no cross-talk between the droplets, the flow cell iscapable of continuously measuring biochemical assays in a droplet flow and thus is suitable to be used for continuous point-ofcarediagnostics monitoring. This paper describes the design and operation of the device and its validation by application to theaccurate and continuous quantification of glucose concentrations using an oxidase enzymatic assay. The flow cell forms animportant component in the miniaturization of chemical and bio analyzers into portable or wearable devices
Continuous measurement of enzymatic kinetics in droplet flow for point-of-care monitoring
Full text linkDroplet microfluidics is ideally suited to continuous biochemical analysis, requiring low sample volumes and offering high temporal resolution. Many biochemical assays are based on enzymatic reactions, the kinetics of which can be obtained by probing droplets at multiple points over time. Here we present a miniaturised multi-detector flow cell to analyse enzyme kinetics in droplets, with an example application of continuous glucose measurement. Reaction rates and Michaelis–Menten kinetics can be quantified for each individual droplet and unknown glucose concentrations can be accurately determined (errors <5 %). Droplets can be probed continuously giving short sample-to-result time (~30 s) measurement. In contrast to previous reports of multipoint droplet measurement (all of which used bulky microscope-based setups) the flow cell presented here has a small footprint and uses low-powered, low-cost components, making it ideally suited for use in field-deployable devices
Microscale computed tomography (µCT) imaging of leak pathways for optimised leak-free 3D printed fluidics
No full text3D printing is a highly attractive method for manufacturing micro- and milli-fluidic devices due to fast fabrication times and low barrier to entry. Of the common 3D printing methods, fused filament fabrication (FFF) is the most accessible but is also susceptible to leakages if using default printer settings. Here we combine microscale computed tomography (µCT) X-ray imaging with bulk leak testing to understand the fundamental structural reasons why leakages occur and the effect of optimising print parameters. In contrast to previous recommendations, we show that the amount of infill can be reduced as required, with print bodies being intrinsically porous regardless of infill. Instead we find it is solely channel wall quality that determines whether leaks will occur. In keeping with previous reports, we see that smaller layer heights (<0.1 mm) and increased flow rates (>100 % compared to recommended rate) are key to preventing leakage and show this is because of their positive effect on channel wall formation. A key consequence of being able to maintain channel integrity whilst using low infill values is that print times and material costs can be greatly reduced (over 50 % time and cost savings for the test pieces used here) without compromising device performance
Sensitive absorbance measurement in droplet microfluidics via multipass flow cells
No full textAbsorbance measurement is a useful analytical tool that can be used along with colorimetric assays to measure a wide range of analytes. However, since sensitivity is directly proportional to path length, sensitive measurements in microfluidic channels are inherently challenging. This is especially true for droplet microfluidics where the lensing at the droplet/carrier interface further constrains path length. In this study, we developed multipass flow cells assembled with squared PTFE tube with parallel mirrors on both sides, laser diode and detector. The devices featured affordable low power components, and was made using simple fabrication techniques making it accessible to a wide range of researchers. In testing it allowed multiple reflection of light in the detection chamber, which significantly increased the optical path length by 8 times. The flow cell was used to quantify the phosphate levels in water samples from a tidal chalk river which could not be measured with a simple single-pass flow cell
Trends in microfluidic systems for in situ chemical analysis of natural waters
Full text linkSpatially and temporally detailed measurement of ocean, river and lake chemistry is key to fully understanding the biogeochemical processes at work within them. To obtain these valuable data, miniaturised in situ chemical analysers have recently become an attractive alternative to traditional manual sampling, with microfluidic technology at the forefront of recent advances. In this short critical review we discuss the role, operation and application of in situ microfluidic analysers to measure biogeochemical parameters in natural waters. We describe recent technical developments, most notably how pumping technology has evolved to allow long-term deployments, and describe how they have been deployed in real-world situations to yield detailed, scientifically useful data. Finally, we discuss the technical challenges that still remain and the key obstacles that must be negotiated if these promising systems are to be widely adopted and used, for example, in large environmental sensor networks and on low-power underwater vehicles
Materials and methods for droplet microfluidic device fabrication
Full text linkSince the first reports two decades ago, droplet-based systems have emerged as a compelling tool for microbiological and (bio)chemical science, with droplet flow providing multiple advantages over standard single-phase microfluidics such as removal of Taylor dispersion, enhanced mixing, isolation of droplet contents from surfaces, and the ability to contain and address individual cells or biomolecules. Typically, a droplet microfluidic device is designed to produce droplets with well-defined sizes and compositions that flow through the device without interacting with channel walls. Successful droplet flow is fundamentally dependent on the microfluidic device – not only its geometry but moreover how the channel surfaces interact with the fluids. Here we summarise the materials and fabrication techniques required to make microfluidic devices that deliver controlled uniform droplet flow, looking not just at physical fabrication methods, but moreover how to select and modify surfaces to yield the required surface/fluid interactions. We describe the various materials, surface modification techniques, and channel geometry approaches that can be used, and give examples of the decision process when determining which material or method to use by describing the design process for five different devices with applications ranging from field-deployable chemical analysers to water-in-water droplet creation. Finally we consider how droplet microfluidic device fabrication is changing and will change in the future, and what challenges remain to be addressed in the field
A droplet microfluidic sensor for point-of-care measurement of plasma/serum total free thiol concentrations
No full textTotal free thiols are an important marker of the whole-body redox state, which has been shown to be associated with clinical outcome in health and disease. Recent investigations have suggested that increased insight may be gained by monitoring alterations of redox state in response to exercise and hypoxia and to monitor redox trajectories in disease settings. However, conducting such studies is challenging due to the requirement for repeated venous blood sampling and intensive lab work. Droplet microfluidic sensors offer an alternative platform for developing a point-of-care testing approach using small sample volumes and automated systems to complement or ultimately replace laboratory testing. Here we developed a small, portable droplet microfluidic sensor that can measure total free thiol concentrations in 20 μL human plasma (or serum) samples, providing a reading in less than 10 min. This system features a novel method to enhance the mixing of reagent and analyte in droplets containing viscous biological fluids. The results in a range of real-world human plasma samples showed equivalence with current standard laboratory assays while reducing sample volume requirements 9-fold and fully automating the process. Micro hematocrit capillaries allowed testing of capillary blood samples collected by fingerprick lancing. The system was used to monitor total free thiols using fingerprick samples in healthy volunteers and revealed significant changes in total free thiols in response to food intake and exercise. This device has the potential to improve our ability to conduct physiological studies of total free thiol level changes and improve our understanding of redox physiology, which may ultimately be applied in redox medicine to improve patient care
Detecting nitrite in water using a metal organic framework paper-based analytical device
No full textMicrodialysis/ultrafiltration-integrated droplet microfluidic sensors for decoding nitrate dynamics in soil
No full textDataset in support of the thesis 'A droplet microfluidic redox sensor'
No full textA dataset to accompany the thesis 'A Droplet Microfluidic Redox Sensor'. Contains CSV files and the necessary processing code to extract the data forming the key results presented in the thesis. </span
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