Traditionally chemicals in the aquatic environment (e.g. nitrate, phosphate) are measured by manual collection and laboratory analysis of discrete water samples. Microfluidic sensors offer an attractive alternative: by taking and analysing samples autonomously in the environment, they remove the need for manual sampling and allow real-time monitoring of water composition and quality. The current state-of-the-art sensors are not widespread due to a range of issues, most notably complicated fluidic control and their inefficient use of chemical reagent. This increases the size of the sensor and its power consumption, limits the frequency that measurements can be taken and duration the sensor can be deployed each time. Droplet microfluidics (in which nanolitre 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 higher analytical throughput and much more efficient use of consumables (reagent consumption being orders of magnitude lower). We have previously developed and demonstrated the first-ever droplet microfluidic sensor prototype for measuring nitrate and nitrite that uses drastically lower reagent consumption relative to the current state of the art. In this project we will mature the technology and demonstrate it in real-world operation in partnership with end users, including a UK public body and Chinese water company. These demonstrations will help us to refine the sensor, demonstrate its effectiveness, and ready it for commercial exploitation.

Water pollution, in the form of nutrient enrichment and algal blooms, causes water quality problems across the globe, resulting in health risks and large costs to water managers and regulators tasked with ensuring clean water supply and healthy rivers, lakes and reservoirs. Monitoring of water chemistry is essential for complying with relevant regulations and maintaining water security. Nutrient chemistry is typically measured by manual sampling and later laboratory analysis. The laborious, discrete, non-real-time nature of this method means that pollution events cannot be suitably characterised in a timely manner or can sometimes be missed completely. Low frequency and single nutrient measurement also currently limits our ability to understand processes or forecast future conditions accurately. The challenge the project addresses: Recent innovations and the development of high-frequency nutrient auto-analysers have the potential to transform our understanding of nutrient/pollutant sources and dynamics. This move to near real-time data provides the opportunity to significantly improve how catchments are managed and resources are protected. They are therefore of great potential interest to water companies and regulators, as evidence of meeting water quality targets and identifying pollutant sources. However, state-of-the-art commercial nutrient auto-analyser instruments are expensive to purchase (e.g. £20-35K per device), and expensive to run with high reagent costs and service contracts, they can be unreliable. In addition, conventionally, individual nutrients are monitored by different devices, resulting in prohibitively high costs for multiple separate nutrient systems. This is a critical barrier to the widespread adoption of nutrient monitoring sensors in freshwaters.

Silicon Photonics, the technology of electronic-photonic circuits on silicon chips, is transforming communications technology, particularly data centre communications, and bringing photonics to mass markets, utilising technology in the wavelength range 1.2 micrometres - 1.6 micrometres. Our vision is to extend the technical capability of Silicon Photonics to Mid -Infrared (MIR) wavelengths (3-15 micrometres), to bring the benefits of low cost manufacturing, technology miniaturisation and integration to a plethora of new applications, transforming the daily lives of mass populations. To do this we propose to develop low-cost, high performance, silicon photonics chip-scale sensors operating in the MIR wavelength region. This will change the way that healthcare, and environmental monitoring are managed. The main appeal of the MIR is that it contains strong absorption fingerprints for multiple molecules and substances that enable sensitive and specific detection (e.g. CO2, CH4, H2S, alcohols, proteins, lipids, explosives etc.) and therefore MIR sensors can address challenges in healthcare (e.g. cancer, poisoning, infections), and environmental monitoring (trace gas analysis, climate induced changes, water pollution), as well as other applications such as industrial process control (emission of greenhouse gases), security (detection of explosives and drugs at airports and train stations), or food quality (oils, fruit storage), to name but a few. However, MIR devices are currently realised in bulk optics and integrated MIR photonics is in its infancy, and many MIR components and circuits have either not yet been developed or their performance is inferior to their visible/near-IR counterparts. Research leaders from the Universities of Southampton, Sheffield and York, the University Hospital Southampton and the National Oceanography Centre will utilise their world leading expertise in photonics, electronics, sensing and packaging to unleash the full potential of integrated MIR photonics. We will realise low cost, mass manufacturable devices and circuits for biomedical and environmental sensing, and subsequently improve performance by on-chip integration with sources, detectors, microfluidic channels, and readout circuits and build demonstrators to highlight the versatility of the technology in important application areas. We will initially focus on the following applications, which have been chosen by consulting end users of the technology (the NHS and our industrial partners): 1) Therapeutic drug monitoring (e.g. vancomycin, rifampicin and phenytoin); 2) Liquid biopsy (rapid cancer diagnostics from blood samples); 3) Ocean monitoring (CO2, CH4, N2O detection).

For centuries, human activities have impacted our rivers by shifting the sources and combinations of physical, biological and chemical drivers and pressures. However, our understanding of their impact on ecosystems has been limited by viewing each in isolation and not considering their combined effects. Significant reductions in some regulated pollutants (such as nitrogen and phosphorus) have been achieved in recent decades. However, even with these improvements, we are witnessing declining water quality of our rivers, and the resulting loss of freshwater species and biota. The picture that we see is made evermore complex by the increasing numbers of different types of emerging contaminants of concern (e.g. pharmaceuticals, pesticides, illicit drugs, micro plastics etc.). This means that our freshwater species are being challenged by a bewildering combination of pollutant cocktails (mixtures) whose effects are poorly understood. At the same time, climate-change driven shifts in water quantity (more frequent floods, longer periods of low flow) and warming waters are expected not only to be influencing the function, physiology, abundance and biological timings of freshwater ecological communities directly, but also the delivery and potential toxicity of these cocktails respectively. It is not simply the water pathway that we need to consider, but also the re-mobilisation of contaminants and the changing patterns of exposure that potentially magnify the effects on biota (i.e. organism sensitivity). Our wastewater systems and combined sewer overflows transport these emerging pollutants from our cities and towns into our freshwater environment. Increasing urbanisation and changes in rainfall intensity and its seasonality, different catchment processes all have the potential to increase inputs of these emerging contaminants to the environment and freshwater species that live there. Substantial knowledge gaps remain around the effects of hydro-climatic and land use changes in combination with the different mixtures of chemicals on freshwater species. Our research will address these gaps by embracing the digital revolution through innovative technologies and transformative data analytics to deliver a step change in our knowledge and understanding. Our approach has three strands. The first will turn a spotlight on a typical catchment encompassing rural to urban land uses through rigorous investigations that will deliver high temporal resolution data. This will provide new understanding of acute/event-based impacts on freshwater ecosystems. Secondly, we will use national scale datasets and cutting edge data analytics tools to investigate the impacts of longer-term exposure to pollutant cocktails across the UK on water quality and ecosystem health. This will provide new understanding of chronic/long term impacts on freshwater ecosystems. Thirdly, we will integrate our new evidence base and understanding into a risk-based probabilistic model. The model will allow the exploration of the relationships between environmental change, declining river quality, multiple pollutants and ecosystem impacts. Our research will develop the evidence base to understand changing pollutant sources, delivery pathways and the environmental tolerances and boundaries within which organisms can thrive and flourish (i.e. the ecosystem safe space). Together, MOT4Rivers will inform priorities for policy, regulation and investment to design cost effective programmes of measures to promote and enhance sustainable freshwater ecosystems under a changing climate.