Droplet microfluidic based sensors for high resolution chemical sensing on autonomous underwater vehicles

海洋中的化学过程是地球自然生命周期的基础。例如，海洋生态取决于营养物质（如硝酸盐和磷酸盐）在何处和以何种数量运输，因为这些营养物质构成食物链的最终基础。海洋也与大气处于动态平衡，是世界如何适应人为二氧化碳影响的内在因素。因此，更好地了解海洋化学动力学不仅具有学术意义，而且还将导致更好地保护海洋生物和改进了解和预测气候变化的模型，但要正确了解海洋化学，我们必须能够准确测量环境中化学物种的时空分布以及它们如何对不同刺激作出反应。然而，浩瀚的海洋带来了一个后勤问题--我们如何能够保护如此庞大而复杂的水体？一个令人信服的答案是使用配备化学传感器的自主水下航行器（AUV）。AUV可以在不需要人工干预的情况下一次前往偏远地区数月，因此提供了一种高效的方式来收集有关海洋化学动力学的信息。（自动采样和分析水使用实验室化验）提供最好的分析性能（准确度、精度、灵敏度），但存在资源（动力、流体）使用效率低和测量频率低的问题，限制了它们对AUV的适用性。针对这一点，在这次研究期间，我将开发一种基于液滴微流体的新型化学传感器。液滴微流体技术涉及分散在沿着沿着数百微米宽的管道流动的油流中的离散水滴的产生、操纵和测量。由于液滴体积非常小（亚微升），因此可以快速精确地进行化学处理和测量，这意味着液滴微流体技术为环境的连续采样和化学分析提供了一条快速高效的途径。虽然液滴微流体技术是一种经过验证并广泛应用于实验室分析化学的工具，但它现在才进入第一批现场部署的设备。在这项研究中，我将推动改进现场部署液滴微流体的灵敏度，测量频率和适用性，以开发适用于AUV的液滴微流体传感器。这些传感器将是高效的（低功耗和液体使用），能够以高灵敏度（这意味着它们可以在广泛的海洋环境中使用）和高测量频率（在移动车辆上使用时转化为丰富详细的空间数据）测量几种不同的化学参数。这一项目将是朝着广泛、常规使用传感器监测海洋环境化学变化，特别是在自动潜航器上的化学变化迈出的关键一步。这将导致化学传感器成为未来环境科学中无处不在的工具，最终在整个海洋的静态系泊和远洋自动驾驶车辆上大量部署。

Chemical processes within the oceans underpin the planet's natural cycles of life. Marine ecology, for example, depends on where and in what quantity nutrients (such as nitrate and phosphate) are transported, as these constitute the ultimate base of the food chain. The oceans are also in dynamic equilibrium with the atmosphere and are intrinsic to how the world will adjust to the effects of anthropogenic carbon dioxide. Thus better understanding of oceanic chemical dynamics is not only of academic interest, but will also lead to better protection of marine life and improved models to understand and predict climatic change.To properly understand ocean chemistry, however, we must be able to accurately measure the temporal and spatial distributions of chemical species within the environment and how they change in response to different stimuli. The vastness of the oceans provides a logistical problem however - how can we possibly characterise such a large and complex body of water? One compelling answer to this is to employ autonomous underwater vehicles (AUVs) equipped with chemical sensors. AUVs can travel to remote locations for months at a time without need of human interaction and as such offer a highly efficient way to gather information about the chemical dynamics of the ocean.The current state-of-the-art chemical sensors (which automatically sample and analyse the water using miniaturised laboratory assays) provide superlative analytical performance (accuracy, precision, sensitivity) but suffer from inefficient use of resources (power, fluid) and low measurement frequencies - limiting their applicability to AUVs. In response to this, during this fellowship I will develop a new type of chemical sensor based around droplet microfluidics. Droplet microfluidics involves the generation, manipulation and measurement of discrete droplets of water dispersed within a stream of oil flowing along tubing hundreds of microns in width. As the droplet volumes are so small (sub-microlitre), chemical treatments and measurements can be quickly and precisely performed, meaning droplet microfluidics offers a rapid and highly efficient route to continuous sampling and chemical analysis of the environment.While droplet microfluidics is a proven and widely used tool for laboratory-based analytical chemistry, it is only now making its way into the first field-deployable devices. In this fellowship I will drive improvements in the sensitivity, measurement frequency and applicability of field-deployable droplet microfluidics to develop droplet microfluidic sensors suitable for use on AUVs. The sensors will be highly efficient (low power and fluid use), capable of measuring several different chemical parameters with high sensitivity (meaning they can be used in a wide range of marine environments) and at high measurement frequencies (which translates into richly detailed spatial data when used on moving vehicles). This project will be a key step towards the widespread, routine usage of sensors to monitor chemical change in the marine environment, in particular on AUVs. It will lead to chemical sensors being a ubiquitous tool in environmental science in the future, eventually deployed in large volumes throughout the oceans on static moorings and ocean-going autonomous vehicles.