近些年来，环境保护问题日益严峻，因而环境监测成为了科学研究中一个重要的方向；此外，由于人们长时间在室内工作、学习、生活，居家环境监测也越来越被重视。柔性湿度传感器具有成本低、体积小、易于与环境融合等特点，因而在未来的智能居家环境监测中有广阔的应用前景。然而，柔性湿度传感器的响应范围、稳定性、灵敏度等指标仍有待进一步提高。本文提出了一种基于电化学聚合聚吡咯的柔性湿度传感器，具体的研究内容如下：本文首先介绍了基于电化学聚合聚吡咯的柔性湿度传感器的制造工艺。采用电化学聚合方式，使用计时电势法进行聚合聚吡咯；然后以聚酰亚胺为基底、聚吡咯为敏感材料、铜为电极，制作三明治结构的柔性湿度传感器；铜电极与聚吡咯材料之间采用各向异性导电胶进行连接。随后，我们对传感器进行了测试。我们搭建了一个湿度传感器测试系统，并使用LCR测试仪测试了柔性湿度传感器的阻抗随相对湿度的变化情况。测试结果显示，上述柔性湿度传感器的湿度响应时间为286s（20% RH - 90% RH）、恢复时间为43s（90% RH - 20% RH）。此外，传感器在循环测试中表现出良好的重复性。实验后，我们对测试结果进行了理论分析：湿度升高时，聚吡咯吸附水蒸气，主要发生了化学吸附、物理吸附、氢键作用，从而导致导电性增强，引起阻抗减小；在吸附过程中，介电函数、弛豫时间等的变化也支持了上述结论。湿度传感器测试系统的原理如下：通过混合不同比例的不同湿度的气体，测试腔中的湿度可以连续改变。此外，通过设计一个快速切换装置，可以达到快速改变测试腔内气体湿度的目的，以供响应时间测试使用。之后，我们对该测试系统进行了理论分析和仿真验证，仿真的结果表明系统响应时间与测试腔的大小及气体流速有关，为系统设计及实施提供了参考。上述柔性湿度传感器加入通信模块后可以制成无线柔性湿度传感器，实现分布式湿度测试，并将数据汇总、以控制除湿机。为了分析分布式监测的优势，我们对多传感器、多除湿机的模型进行了仿真分析。结果表明：在分布式监测的情况下，传感器能更快速感应到湿度变化、并及时开启除湿机，控制室内湿度不至于上升过高、过快；而多除湿机的设置则可以更快进行除湿、使室内恢复到舒适湿度。此外我们还提出了除湿机数量优化的方法。
In recent years, environmental problems are becoming more and more serious, leading to research on environmental monitoring. What’s more, people are spending lots of time working, learning, and living in their homes. As a result, home environment monitoring gets attention. Due to its low costs, small volume, and compatibility with various surfaces, flexible humidity sensors have potentials in environmental monitoring in smart homes. However, the response range, stability, and sensitivity of the flexible humidity sensors still need improvement. In this thesis, we introduce a flexible humidity sensor based on electrochemically polymerized polypyrrole. The contents of this thesis are described as follows:We first introduce the fabrication process of the flexible humidity sensor based on electrochemically polymerized polypyrrole. Polypyrrole is synthesized through electrochemical polymerization by chronopotentiometry method. Polyimide is then used as the substrate, and the copper electrodes are connected to polypyrrole sensitive material through the anisotropic conductive film. As a result, a sandwich-structured sensor is built and will be tested.During the tests, we build a test system and use it during the experiments. We utilize the LCR tester to test the impedance change of the fabricated flexible humidity sensor when relative humidity (RH) changes. The test results show that the response time of the sensor from 20% RH to 90% RH is 286s, and the recovery time of the sensor from 90% RH to 20% RH is 43s. The flexible humidity sensor also shows satisfying repeatability during cyclic tests. Then, we give a theoretical analysis of the experimental results. When relative humidity is rising, polypyrrole is able to adsorb water molecules by chemical adsorbing, physical adsorbing, and hydrogen bond, leading to higher electrical conductivity and lower impedance of polypyrrole. What’s more, the dielectric function and relaxation time changes during the adsorbing process also give the same results.The principle of the designed humidity sensor test system is: by mixing different amounts of dry and wet gas, humidity in the test chamber can be adjusted continuously. In addition, a rapid switch is designed to change the humidity in the test chamber quickly during response time tests. After theoretical analysis and simulation, we conclude that the response time of the test system is related to the volume of the test chamber and the gas flow rate. The results will guide us in the design and implementation of the test system.Finally, the wireless flexible humidity sensors can be built by connecting a communication module to the above-mentioned flexible humidity sensor. The wireless sensors can be distributed in home to test the humidity distribution. And these data will be collected and used to control dehumidifiers. In order to analyze the advantages of distributed monitoring, we simulate different models with multi-sensors and multi-dehumidifiers. The simulation results show that: in the case of distributed monitoring, the distributed sensors can detect the humidity changes quickly and turn on the dehumidifiers in time. And the distributed sensors will control dehumidifiers to keep humidity from rising too high and too fast. The settings of multiple dehumidifiers can dehumidify faster and recover the room environment to comfortable humidity levels. In addition, we also put forward a method to optimize the number of dehumidifiers in home.
