基于渗流型复合材料的电容式柔性压力传感器

A conventional capactive pressure sensor detects the applied pressure by the capacitance change that is resulted from the compression of the dielectric layers and the decreased distance between two electrodes. The sensitivity of this type of sensor is limited by the compliance of the dielectric layer. Although recent studies have shown that the sensitivity can be improved by introducing porous structure to the dielectric layer, it is still far from sufficient for centain applications. In this project, we propose to use the elastic composite filled with conductive fillers as the dielectric layer materials. When an external pressure is applied to the sensor, not only the decreased electrode distance, but also the dielectric constance increase from the compression of the composite, will increase the capacitance of the sensor. The combination of the two above effect will lead to a breakthrough in the sensitivity of the sensor. We will establish a structure-deformation-dielectric property change relationship of the composite material using simultaneous measurement of mechanical and dielectric properties, finite element analysis, and percolation theory. We will also investigate the critical factors for the dielectric change of the composite under applied pressure, and therefore optimize the dielectric layer design to maximize the sensor sensitivity. The results of the current proposed research will provide new ideas for flexible pressure sensor design, and promote its application in various areas, such as electronic skin, health mornitoring, and human-machine interaction.

传统的电容式柔性压力传感器通过受压过程中介电层压缩和电极间距减小所导致的电容变化来检测受压情况。然而，受到介电层柔韧性的限制，其灵敏度一直停留在较低范围。尽管近年来通过介电层中加入多孔结构等方法使得灵敏度有所提高，但仍与一些应用的要求存在明显差距。本项目采用柔性渗流型复合材料代替传统的纯弹性体作为电容式传感器的介电层，使得在受压过程中不仅电极间距变小会导致电容变大，同时复合材料介电常数的提高也会进一步增大电容。通过上述效应的叠加，带来压力传感器灵敏度的大幅度提升。本项目将通过力学和介电性质同步测量、有限元力学分析、渗流理论相结合的方法建立“材料结构-受压变形-介电性质变化”的函数关系，深入探索影响受压过程中介电常数变化的关键因素，从而优化介电层的组成结构以获得最大的灵敏度。研究成果将为柔性压力传感器的设计提供新思路，从而推动其在电子皮肤、医疗监测、人机交互等多方面的应用。

电容式柔性压力传感器依靠力的作用下极板间距离发生的变化来产生信号，其灵敏度受到介电层可压缩性能的限制，特别是在较大压力作用下，介电层模量迅速上升，灵敏度急剧下降。本项目从电容式柔性传感器灵敏度的调控出发，开展了介电层可压缩性提高与“介电常数-压缩比”调控的研究。具体来说，第一部分我们通过在聚二甲基硅氧烷（PDMS）介电层中复合膨胀微球制备了高灵敏度大测量（< 4.5 MPa）范围电容式压力传感涂层，并对工艺参数-涂层结构与性能进行了详细研究与总结，结果显示该复合涂层灵敏度达到纯PDMS介电层的22倍（0-50 Pa）。第二部分，设计制备了带刺镍球/PDMS渗流型复合介电涂层材料，并基于渗流理论建立了理论模型，实现了对介电层介电常数的可控动态调节，抵消了不同压力作用下模量变化引起的灵敏度变化，使得传感信号在大压力范围（达 1.7 MPa）下依然保持极好的线性。两种介电涂层在各类复杂的表面具有良好的涂附效果，并在质量测量、行为监测、水（气）压力测量等方面实现了示范性应用。