New Strategies for Sampling, Analysing and Understanding Aerosols

气溶胶是分散在空气中的液滴固体颗粒的集合，包括烟雾，雾，海雾和车辆污染颗粒。颗粒大小可以从纳米（百万分之一毫米）到毫米级。气溶胶影响健康、能见度和气候，并在向肺部输送药物、通过喷雾干燥进行纳米结构工程设计以及输送燃烧燃料方面得到越来越多的技术应用。这项研究将探讨在理解气溶胶方面所面临的一些基本挑战。理解气溶胶对人类健康影响的关键是了解它们在吸入和呼出时是如何转化的。在呼吸道内的潮湿环境中，水蒸气会凝结在吸入的颗粒上，导致颗粒尺寸增大。这可能会影响它们渗透到肺部的深度，较小的颗粒渗透得更深。通过改变肺部对潮湿环境的反应，可以增强药物向肺部的靶向递送。此外，空气传播的病毒，如流感病毒的传播可能受到呼气和吸气时湿度变化的影响。同样，在大气科学中，了解气溶胶颗粒如何受到湿度的影响以预测云滴的大小至关重要。了解颗粒大小随湿度的变化对于了解颗粒散射和吸收阳光的能力及其对气候的影响也至关重要。因此，本项目的重点是了解颗粒物的大小如何随湿度变化，以及颗粒物对光的散射和吸收效率，了解颗粒物的化学成分，以解释其对健康和环境的影响，特别是在污染的城市环境中，以及了解颗粒物如何随时间发生化学变化。水在我们的环境中无处不在，并在很大程度上调节气溶胶的组成。然而，许多化学品不溶于水。对于许多污染物，如被认为具有致癌性和致突变性的多环芳烃，以及用于作物生产的许多农用化学品来说，情况尤其如此。这些化学品可能非常易溶，并在有机液体中浓缩。该项目的一个关键主题是了解含有水溶性和不溶性化学物质的气溶胶液滴的特性，并了解化学物质如何溶解到气溶胶中的有机相。事实上，许多有机成分可能会在我们的环境中发生化学反应，进一步的主题将是探索气溶胶中可能发生的化学反应以及它如何影响气溶胶特性。从药物输送到肺部，到燃烧中燃料液滴的蒸发，颗粒的喷雾干燥以及颗粒在大气中的生长，了解颗粒改变尺寸和成分的速率也至关重要。例如，在使用计量剂量吸入器时挥发性溶剂蒸发期间发生的过程关键地决定了活性药物向肺的递送。当液滴快速蒸发时形成的固体结构由喷雾干燥中溶剂蒸发的速度控制。对这些非常快速的过程的研究是一个进一步的主题。最后，对非常小样品体积的分析和化学反应有相当大的兴趣，这导致了芯片实验室技术的发展。通常，溶液流过非常小的制造通道，以允许对微升样品进行测量。该项目的最后一个主题将是利用激光束移动粒子并控制化学反应，控制仅含皮升样本（十亿分之一立方厘米）的气溶胶液滴中的反应。

Aerosols are a collection of solid particles of liquid droplets dispersed in air and include smoke, fog, sea spray and pollution particles from vehicles. Particle sizes can range from the nanometre (a millionth of a millimetre) to the millimetre scale. Aerosols influence health, visibility, and climate and are finding increased technological application in the delivery of drugs to the lungs, the engineering of nanostructures through spray drying, and the delivery of fuels for combustion. This research will examine some of the fundamental challenges faced in understanding aerosols.A key to understanding the impact of aerosols on human health is to understand how they are transformed as they are inhaled and exhaled. In the humid environment found within the respiratory tract, water vapour can condense on inhaled particles leading to growth in size. This can influence their depth of penetration into the lungs, with smaller particles penetrating deeper. The targeted delivery of drugs to the lungs may be enhanced by altering their response to a humid environment. Further, the transmission of airborne viruses, such as the influenza virus, may be influenced by the humidity changes on exhalation and inhalation. Similarly, in atmospheric science it is crucial to understand how aerosol particles are influenced by humidity in order to predict the size of cloud droplets. Understanding the change in particle size with humidity is also critical for understanding the ability of particles to scatter and absorb sunlight and their impact on climate. Thus, key themes of this project will be to understand how particles change in size with humidity and their efficiency in scattering and absorbing light.It is also essential to know the chemical composition of particles to interpret their impact on health and the environment, particularly in polluted urban environments, and to understand how particles are chemically changed over time. Water is ubiquitous in our environment and largely regulates the composition of aerosol. However, many chemicals are not soluble in water. This is particularly true for many pollutants such as polycyclic aromatic hydrocarbons, which are considered to be carcinogenic and mutagenic, and for many of the agrochemicals that are used in crop production. Such chemicals may be very soluble and become concentrated in organic liquids. A key theme of this project will be to understand the properties of aerosol droplets that contain both water soluble and insoluble chemicals, and to understand how chemicals can dissolve into the organic phase within an aerosol. Indeed, many of the organic components may undergo chemical reactions in our environment and a further theme will be to explore the chemistry that can occur in aerosol and how it influences aerosol properties. From the delivery of drugs to the lungs, to the evaporation of fuel droplets in combustion, the spray drying of particles, and the growth of particles in the atmosphere, understanding the rate at which particles can change size and composition is also crucial. For example, the processes occurring during the evaporation of a volatile solvent in the use of metered does inhalers critically determine the delivery of active pharmaceuticals to the lungs. The solid structures formed when liquid droplets rapidly evaporate are controlled by how quickly the solvent evaporates in spray drying. Studies of these very rapid processes are a further theme.Finally, there is considerable interest in the analysis and chemical reactions of very small sample volumes, and this has led to the development of lab-on-a-chip technology. Commonly, solutions flow through very small fabricated channels to allow measurements on micro-litre samples. A final theme of this project will be to control reactions in aerosol droplets containing only picolitres of sample, a billionth of cubic centimetre, using laser beams to move particles around and control chemistry.