Droplet microfluidic based chemical sensors for rapid measurement of nutrients in water

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Traditionally most chemical parameters (e.g. nitrate, phosphate) in aquatic environment are measured by laboratory analysis of discrete water samples. Microfluidic sensors offer an attractive alternative: by taking and analysing samples autonomously in situ, they obviate sampling allowing larger datasets particularly when used in conjunction with autonomous systems.The current state-of-the-art sensors have temporal resolution of minutes due to Taylor dispersion (fluid flow effectively smears chemical composition within the device) and complex valve controls, making them high-cost and unsuitable for deployments requiring high frequency measurement - most notably on profiling vehicles (e.g. Argo floats, oceanic gliders) that rapidly transect the water column. Droplet microfluidics (in which nano litre water samples are taken and subsequently operated on as droplets within an immiscible oil) is a novel microfluidic method that, in addition to other advantages, crucially offers zero Taylor dispersion and much higher analytical throughput. This project will develop the first-ever droplet-flow based field-deployable sensor for autonomous systems. Low-cost, low-powered and fully functional; the device will be a step-change in high-frequency autonomous aquatic chemical analysis.