Towards the Electronic Nose: Liquid Crystal Chemical Sensors.

该项目的背景是研究和利用液晶的独特性质来响应不同的气体，并充当传感器。微流体(在非常小范围内的流体行为)可以用来产生液晶液滴，它们的表面可以应用其他物质(被功能化)，以便在特定气体通过它们时做出反应。液晶的排列及其在不同刺激下的变化非常有说服力，本项目旨在研究不同气体下的这些变化，并利用这一知识。虽然这个项目可能只是理论上的，也可能是实验性的，但我建议走一条将两者结合起来的路线。例如，在利兹的高性能计算机ARC4等设备上进行建模的更具理论性的方法可以用来节省材料和实验室时间。我已经有了这方面的经验，以及丰富的Python经验(包括建模和数据分析)。这将节省整个项目的时间，从而实现更快的进度。我的学术能力通过我在学位期间一流的平均成绩得到了证明，这将使我能够深入研究理论方面，并迅速学习更多高级建模技术。此外，该模型还可用于确定液晶的各向异性弹性常数和表面力等属性如何影响液滴对刺激的响应。这将与实验数据进行比较，以检查对取向性质的理解；许多液晶物理都可以用数学来描述。该项目的成功将依赖于使用该理论来指导实验工作和对许多不同线索的调查：传感器行为如何与几何形状(例如，自由悬浮液滴、固定液滴或嵌入在多孔介质中的液晶)、表面排列和功能化有关。了解取向变化与液晶相或各向异性性质之间的关系。开始针对传感器的功能化表面进行设计和制造。计算分析结果。电学和光学响应的模式识别。目标是制造一种灵敏的、工作的电子鼻，对气体具有光学和电子响应，并将所获得的知识应用于其他传感器系统，如化学和生物传感器。在了解光学和电学变化的基础上，当化学物质经过它时，液晶排列的变化可以通过实验来理解，比如用偏振显微镜进行的实验。例如，可以查找颜色变化或电压变化。对于创建自动分析系统来说，后者会更简单，这可能使其更适合在现实环境中使用，并更适合非专家消费者。一个关键的目标是生产制造成本低廉的传感器，利用少量液晶材料的放大效应提供敏感但明显的效果。应用范围从工作环境中的气体传感到检查不同的挥发性有机污染物或其他气体，以确保健康和安全。然而，我希望它最终可能能够确定混合气体样本的组成，并成为更广泛的有用工具，例如在应对气候变化方面，简单的传感器帮助消费者确定空气质量。

The context of the project is to investigate and use the unique properties of liquid crystals to respond to different gases, and act as a sensor. Microfluidics (fluid behaviour on a very small scale) can be used to produce liquid crystal droplets, and their surfaces can have other substances applied to them (be functionalised) to allow a response when a certain gas is passed over them. The alignment of liquid crystals and their change under different stimuli can be very telling, and this project aims to investigate these changes under different gases, and utilise this knowledge. Whilst this project could be exclusively either theoretical or experimental, I propose to follow a route that combines both. For example, a more theoretical approach of modelling on equipment such as the high-performance computer ARC4 at Leeds could be used to save money on materials and time in the lab. I have already had experience in this, as well as extensive python experience (with both modelling and data analysis). This will save time in the project overall, allowing for more rapid progression. My academic competency evidenced through my high first class averages during my degree will allow me to investigate the theoretical side in depth and learn more advance modelling techniques quickly. In addition, the modelling can be used to determine how properties such as the anisotropic elastic constants and surface forces of the liquid crystals can influence the response of the droplets to stimuli. This will be compared to experimental data to check that the understanding of the alignment properties; a lot of liquid crystal physics can be described mathematically. The success of the project will rely on using the theory to steer the experimental work and investigations into a number of different threads:How sensor behaviour relates to geometry (e.g. freely suspended droplets, sessile droplets or liquid crystals embedded in porous media), surface alignment and functionalisation.Droplet sensitivity. Understanding the relationships between alignment changes and liquid crystal phase, or anisotropic properties.To begin to target functionalised surfaces for the Sensor design and fabrication.Computational analysis of the results. Pattern recognition for the electrical and optical responses.The target is to make a sensitive, working electronic nose, with both optical and electronic responses to gases and to apply the knowledge gained to other sensor systems, such as chemical and bio-sensors.Understanding the optical and electrical changes the liquid crystal alignment varies when a chemical has run over it can be understood by experiments such as those done with a polarising microscope. For example, a colour change can be looked for, or a voltage change. The latter would be simpler for creating an automated analysis system, which may make it more suitable for uses in the real-world environment, and by the non-expert consumer. A key aim is to produce sensors that are cheap to make, using the amplification effect from small quantities of liquid crystal materials to provide a sensitive but noticeable effect. Applications range from gas sensing in a working environment to check for different volatile organic contaminants or other gases, for health and safety. However, I'd hope that it may eventually to be able to determine the composition of a mixed gas sample, and be a useful tool more generally, such as in the fight against climate change, where simple sensors help air quality be determined by the consumer.