基于溶剂蒸发的孔隙率控制技术提高软电容式压力传感器的灵敏度
Summary
提出了一种基于溶剂蒸发技术的简单且具有成本效益的制造方法，以优化软电容式压力传感器的性能，该方法通过使用不同质量比的模塑PDMS/甲苯溶液在介电层中的孔隙率控制来实现。
Abstract
软压力传感器在软机器人和触觉界面中发展“人机”触觉方面发挥着重要作用。具体而言，具有微结构聚合物基质的电容式传感器因其高灵敏度、宽线性范围和快速响应时间而进行了相当大的努力探索。然而，传感性能的提高通常依赖于介电层的结构设计，这需要复杂的微细加工设施。本文介绍了一种简单且低成本的方法来制造多孔电容式压力传感器，该方法使用基于溶剂蒸发的方法调节孔隙率，从而提高了灵敏度。该传感器由多孔聚二甲基硅氧烷 （PDMS） 介电层组成，该介电层与由弹性导电聚合物复合材料 （ECPC） 制成的顶部和底部电极粘合。通过将碳纳米管（CNTs）掺杂的PDMS导电浆料刮涂成模具图案的PDMS薄膜来制备电极。为了优化介电层的孔隙率以增强传感性能，PDMS溶液用不同质量分数的甲苯稀释，而不是过滤或研磨成不同尺寸的糖孔形成剂（PFA）。甲苯溶剂的蒸发允许快速制造具有可控孔隙率的多孔介电层。结果表明，当甲苯与PDMS的比例从1：8提高到1：1时，灵敏度可以提高两倍。这项工作中提出的研究提供了一种低成本的方法来制造具有可调传感器参数的软感觉机械感受器的完全集成的仿生软机器人抓手。
Introduction
近年来，柔性压力传感器因其在软机器人1，2，3，“人机”触觉界面4，5和健康监测6，7，8中不可或缺的应用而受到关注。通常，压力传感的机制包括压阻式 1，4，7、压电式 2，6、电容式 2、3，9、10、11、12、13 和摩擦电8传感器。其中，电容式压力传感器因其高灵敏度、低检测限（LOD）等特点，成为触觉传感中最有前途的方法之一。
为了获得更好的传感性能，柔性电容式压力传感器引入了微金字塔2，9，14，微柱15和微孔9，10，11，12，13，16，17等各种微结构，并优化了制造方法以进一步提高传感水平这种结构的性能。然而，这些结构中的大多数都需要复杂的微细加工设施，这大大增加了制造成本和操作难度。例如，微金字塔作为软压力传感器中最常用的微观结构，依靠光刻定义和湿蚀硅片作为成型模板，这需要精密设备和严格的洁净室环境9，14。因此，可以通过简单的制造工艺和低成本原材料制造，同时保持高传感性能的微孔结构（多孔结构）最近引起了越来越多的关注9，10，11，12，13，16，17.这将讨论，以及改变PFA及其量的缺点，作为使用我们的分数控制方法的动机。
本文提出了一种基于溶剂蒸发技术的简单、低成本的方法来制备孔隙率可控的多孔柔性电容式压力传感器。完整的制造过程包括多孔PDMS介电层的制造，电极的刮擦涂层以及三个功能层的粘合。具体而言，本工作创新性地利用一定质量比的PDMS/甲苯混合溶液，基于糖/赤藓糖醇混合物模板制备了多孔PDMS介电层。同时，均匀的PFA粒径确保了均匀的孔形貌和分布;因此，可以通过改变PDMS/甲苯质量比来控制孔隙率。实验结果表明，通过将PDMS/甲苯质量比从1：8提高到1：1，可以将所提出的压力传感器的灵敏度提高两倍以上。光学显微镜图像也证实了由于不同的PDMS/甲苯质量比而导致的微孔壁厚的变化。优化后的软电容式压力传感器具有较高的传感性能，灵敏度和响应时间分别为3.47% kPa−1 和0.2 s。该方法实现了快速、低成本且易于操作的多孔介电层的制造，具有可控的孔隙率。
Protocol
1. 多孔PDMS介电层软电容式压力传感器的制备 多孔PDMS介电层的制造按照以下步骤准备糖/赤藓糖醇多孔模板。用孔径为270μm和500μm的样品筛过滤糖。选择粒径在270-500μm范围内的糖。注意：只要均匀性在公差范围内，更大或更小的糖粒径也是可以接受的。糖颗粒的直径将影响后续步骤中制造的多孔PDMS层的孔径，但不会完全确定孔径。 将赤藓糖醇（见 <stron…
Representative Results
集总糖/赤藓糖醇多孔模板的照片如图3A所示。 图3B显示了具有刮擦涂层ECPC图案的柔性电极层。图3C显示了用所提出的方法制造的带有多孔介电层的软电容式压力传感器。基于PDMS/甲苯溶液制备了4个多孔PDMS介电层，质量比分别为1：1、3：1、5：1和8：1。显示不同结构的孔形貌的光学显微镜图像如图3D</stro…
Discussion
本工作提出了一种基于溶剂蒸发的简单方法控制孔隙率，一系列实验结果证明了其可行性。虽然多孔结构已广泛应用于柔性电容式压力传感器，但孔隙率控制仍需进一步优化。与改变PFA 11，12，13，18，19的粒径和聚合物底物与PFA 17，20的比例的现有方法不同</sup…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作得到了中国国家自然科学基金资助62273304。
Materials
| 3D printer | Zhejiang Qidi Technology Co., Ltd | X-MAX | |
| 3D printing metarials | Zhejiang Qidi Technology Co., Ltd | 3D Printing Filament PLA 1.75 mm | |
| Carbon nanotubes (CNTs) | XFNANO | XFM13 | |
| Data acquisition (DAQ) | National Instruments | USB6002 | |
| Double side tape | Minnesota Mining and Manufacturing (3M) | 3M VHB 4910 | 1 mm thick |
| Electrode metal mold | Guangdong Shunde Molarobot Co., Ltd | This metal mold is a round metal plate with a flat bottom round groove and an embossed electrode pattern of 0.2 mm thick in the middle of the groove. | |
| Erythritol | Shandong Sanyuan Biotechnology Co.,Ltd. | ||
| Isopropyl Alcohol (IPA) | Sinopharm chemical reagent Co., Ltd | 80109218 | |
| LabVIEW | National Instruments | LabVIEW 2019 | |
| LCR meter | Keysight | EA4980AL | |
| Metal wire | Hangzhou Hongtong WIRE&CABLE Co., Ltd. | 2UEW/155 | |
| Microscope | Aosvi | T2-3M180 | |
| Numerical modeling software | COMSOL | COMSOL Multiphysics 5.6 | |
| Polydimethylsiloxane (PDMS) | Dow Chemical Company | SYLGAR 184 Silicone Elastomer Kit | Two parts (base and curing agent) |
| Sealing film | Corning | PM-996 | parafilm |
| Si wafer | Suzhou Crystal Silicon Electronic & Technology Co.,Ltd | ZK20220416-03 | Diameter (mm): 50.8 +/- 0.3 Type/Orientation: P/100 Thickness (µm): 525 +/- 25 |
| Silver conductive paint | Electron Microscopy Sciences | 12686-15 | |
| Stepping motor | BEIJING HAI JIE JIA CHUANG Technology Co., Ltd | 57H B56L4-30DB | |
| Sugar/erythritol template metal mold | Guangdong Shunde Molarobot Co., Ltd | This metal mold is a 5 mm thick square metal plate with a flat bottom square groove of 2.5 mm deep. | |
| Toluene | Sinopharm chemical reagent Co., Ltd | 10022819 |
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Cite This Article
Zhu, Z., Cao, Y., Chi, H., Wang, X., Hou, D. Sensitivity Enhancement of Soft Capacitive Pressure Sensors Using a Solvent Evaporation-Based Porosity Control Technique. J. Vis. Exp. (193), e65143, doi:10.3791/65143 (2023).