磁流变弹性体压容传感效应的磁场优化机制研究

In recent years, electronic skins based on flexible tactile sensors are obtaining growing interests in the fields of bionic robots, human-machine interaction, etc. Aiming at the contradiction between the key performance parameters of traditional tactile sensors, i.e., sensitivity and working range, our previous study has found that the new pressure-sensitive material—magnetorheological elastomer (MRE) presents significant piezo-capacitive effect. In addition, MRE possesses wide working range for its enhanced Young’s modulus. Accordingly, it can achieve a favorable balance between sensitivity and working range. When applying a compression, MRE’s capacitance changes in orders of magnitude due to the rearrangement of micro/nano particles distribution. Thus, the sensitivity directly depends on the initial particle distribution, which is determined by the curing magnetic field conditions. Therefore, by using a magnetic field to modulate the initial particle distribution, this project makes efforts to study the comprehensive optimization mechanism of sensitivity and working range theoretically and experimentally. Different from the random distribution in isotropic MRE, in the MRE cured in a magnetic field, there exists complex dense distribution of localized particles in the particle chains/clusters and wide-area random distribution of such chains/clusters. Based on this logic, local and wide-area series-parallel microcapacitors model are to be established respectively, thus the relationship between the macroscopic piezo-capacitive effect and microstructure parameters can be obtained. Finally, the magnetic field optimization mechanism of piezo-capacitive effect is to be determined, which would provide the basic theory for designing the flexible tactile sensor with both high sensitivity and wide working range.

近年来，基于柔性触觉传感材料的电子皮肤在仿生机器人、人机交互等领域备受关注。针对传统触觉传感器的关键性能参数—灵敏度和量程之间的对立问题，前期研究发现新型压敏材料磁流变弹性体存在显著的压容效应，且较大的杨氏模量使其可承受大检测压力，从而可兼顾灵敏度与量程的平衡。磁流变弹性体在压缩变形过程中因微纳米颗粒的空间结构重排而使其电容发生数量级变化，因此灵敏度直接决定于初始颗粒空间分布结构，而此初始结构又受磁场制备条件决定。据此，项目拟从理论和实验上研究磁流变弹性体经磁场调制的颗粒分布结构对灵敏度和量程的综合优化机制，且不同于零场下简单的颗粒随机分布，磁场制备下存在复杂的局域颗粒密集分布和广域颗粒链簇随机分布，据此分别建立局域和广域空间内的微电容串-并联模型，以获得宏观压容效应与微观空间分布结构参数间的联系，进而确定其与调制磁场之间的优化机制，为设计兼具高灵敏度和宽量程的柔性触觉传感器提供理论基础。

针对传统柔性触觉传感器的灵敏度与量程之间的对立问题， 项目以柔性磁流变弹性体为传感介质，开展了磁流变弹性体基柔性触觉传感单元的灵敏度和量程的磁场制备优化研究。设计和制备了一系列磁流变弹性体样品，建立了微观尺度的压容传感模型，研究制备磁场对由微观颗粒空间分布结构导致的灵敏度和量程等传感性能的优化机制、压容传感的电容蠕变与回复机制等。通过磁场制备优化获得的磁致链化型磁流变弹性体具有高压容传感灵敏度和相对较宽的线性测量量程，有效地解决了传感灵敏度和量程之间的对立难题。此外，通过初始化重复性测试途径，较好解决了因橡胶基体蠕变导致传感器在实际应用中的传感信号衰减问题。