基于仿生微结构的柔性触觉传感器

FLEXIBLE TACTILE SENSORS BASED ON BIONIC MICROSTRUCTURES

万永彪

11649118

硕士

信息功能材料与器件

郭传飞

2018-05-27

2018-07-06

哈尔滨工业大学

深圳

柔性触觉传感器是一种将触觉信号转换电信号的电子器件，在可穿戴电子设备、健康监测、运动监测、软体机器人、人机交互、以及人工智能等领域有着巨大的应用前景。围绕电阻型、电容型、压电型、摩擦电型这四种传感机制，科学家们已经证明微结构能有效提高柔性触觉传感器的性能，例如微金字塔、微柱子、微半球以及微槽等各种微结构被用于制备超灵敏的柔性触觉传感器。然而这些微结构通常通过传统的光刻技术、化学刻蚀方法，其制备过程复杂、耗时、价格昂贵。制备低成本、简易、高性能的柔性触觉传感器成为当前的一大挑战。基于仿生微结构，本文围绕电容型柔性触觉传感器，致力于提高其灵敏度、压力传感范围，大大降低其制备成本。取大自然中的植物作为原始模板，通过两次转印，复写出植物表面的微结构用于制备柔性触觉传感器。首先，以荷叶为模板，复写出具有高深宽比、稀疏微塔结构的聚二甲基硅氧烷（PDMS）薄膜，再喷涂超细银纳米线（AgNWs）作为下电极。喷涂有 AgNWs的透明聚酰亚胺（CPI）一面作为上电极、另一面作为为介电层。最后将上电极、介电层、下电极组装成三明治结构，而制成柔性触觉触觉传感器。该器件具有较高的灵敏度（1.2 kPa−1）、较快的响应速度（36 ms）、较低的监测限（0.8 Pa），以及较高的可靠性，能循环探测至少 100000 次。通过有限元模拟分析得出高深宽比、稀疏的微结构能有效提高器件的灵敏度。如此高的性能使得该器件能实现运动监测、气流探测。其次，以天鹅绒竹芋叶子为模板，制备了具有整齐微圆锥阵列结构的碳纳米管/聚二甲基硅氧烷（CNT/PDMS）复合薄膜作为下电极，结合聚乙烯醇（PVA）介电层、平面 CNT/PDMS 上电极，封装成电容型柔性触觉传感器。器件具有较高的灵敏度（4.7 kPa−1）、较低的检测限（0.6 Pa）和较高的可靠性，能稳定循环检测10000 次，实现人体运动检测、气流检测。所制备的触觉传感器阵列各点能独立的识别对应压力。此外，以天鹅绒竹芋叶子为模板，还制备了仿生微结构离子凝胶薄膜，将其作为介电层，结合 AgNWs 电极构筑三明治结构柔性触觉传感器。微结构离子凝胶与电极形成电双层，极大的提高了器件的灵敏度（54.31 kPa−1）。另外器件还具有超低的压力检测限（0.1 Pa），较快的响应速度（29 ms），能监测出脉搏跳动，实现假肢与人、物体环境的传感交互。为了获取更加廉价的柔性触觉传感器，我们免去繁琐的倒模复写过程，直接利用自然材料作为介电层，制备了简易的柔性触觉传感器。新鲜的植物里含有大量离子液体，使得植物与电极界面同样形成电双层，大大提高了器件的响应电容。经过临界点干燥处理过的植物作为介电层，能提高器件性能的稳定性。用多个器件集成的二维传感器阵列能做出了多点力的识别，可用于可穿戴电子设备、人工智能等领域。使用仿生微结构或直接利用自然材料制备柔性触觉传感器，能大大简化制备工艺，降低制备成本，符合可持续发展理念，对构建环境友好型柔性电子体系具有重要意义。

Flexible tactile sensor, a device for detecting external tactile stimuli, converts the stimuli into measurable or recordable electrical signals, which has the promising potentials for applications in field of wearable electronics, human healthcare, motion monitoring, soft robots, human-machine interactions and artificial intelligence. Focusing on four typical mechanisms including resistive, capacitive, piezoelectric, and triboelectric types, scientists have demonstrated the microstructures, such as micropyramid, micropillar, microhemisphere, and microgroove, can effectively enhance the sensitivity of flexible tactile sensors. However, the aforementioned microstructures were mainly obtained through traditional lithography techniques and chemical etching processes, which are complicated, costly, and time-consuming. It is an urgent challenge to develop highly sensitive and cost-effective flexible tactile sensors.In this paper, we reported several highly sensitive flexible tactile sensors based on bionic microstructures. The natural materials were used as the original templating mold. After two templating processes, the microstructures mimicking the surface of natural plants were successfully fabricated for high-performance flexible tactile sensors.Firstly, we fabricated the micropatterned polydimethylsiloxane (m-PDMS) film with the sparse and high-aspect-ratio microtowers molded from lotus leaf. The m-PDMS film was coated by using ultrathin silver nanowires (AgNWs) and used as bottom electrode. Colorless polyimide (CPI) with one-side-coated AgNWs was employed for dielectric layer as well as top electrode. By packaging in framework of sandwich-structured configuration with the bottom electrode, dielectric layer, and top electrode, we obtained flexible capacitive tactile sensors with a high sensitivity up to 1.2 kPa−1, a fast response time of 36 ms, a low limit of detection (LOD) of <0.8 Pa, and high robustness that can repeatedly tested at least 100,000 times. The finite-elemental analysis indicates that the sparse and high-aspect-ratio microtowers are critical to achieve high performances of the flexible tactile sensor. Such high performances mark the realizations of human motion monitoring, and gas flow detection.Secondly, we fabricated the carbon nanotube/polydimethylsiloxane (CNT/PDMS) composite conductive film with uniform microcones array, which was mold from Calathea zebrine leaf as bottom electrode. By sandwiching the microstrucutred bottom electrode, polyvinyl alcohol (PVA) dielectric layer, and flat CNT/PDMS top electrode, we obtained a capacitive flexible tactile sensor. The device displayed a high sensitivity of 4.7 kPa−1, a very low LOD of <0.6 Pa, and high reliability, which could be repeatedly work more than 10000 times and achieve human motion monitoring, gas flow detection. Each point of the as-fabricated sensors array can independently recognize the corresponding pressure.In addition, a bionic and ionic gel film was fabricated by replicating Calathea zebrine leaf as dielectric layer, and sandwiched by two flexible AgNWs electrodes to construct a flexible tactile sensor. Owing to the electric double layer (EDL) formed in the ionic-electronic interfaces between ionic gels and electrodes, the sensor exhibited a high sensitivity of 54.31 Pa−1, a fast response time of 29 ms, and ultralow LOD of <0.1 Pa. More importantly, the sensor could monitor the pulse and achieve the sensing interactions between the prosthetic and human, or between the prosthetic and environmental objects.To obtain more simple and inexpensive flexible tactile sensors, we directly used the natural materials as dielectric layer to fabricate flexible tactile sensors, which avoid the complicated replica processes. There are plenty of ionic liquids in fresh natural materials based dielectric layer, similarly resulting in remarkable EDL capacitances and a high sensitivity of the flexible tactile sensors. After critical point dry treatment, the natural materials based tactile sensors displayed a stable performance. The multi-component integrated sensors array enables the recognition of multi-point force, which offers the potentials in wearable electronics, artificial intelligence, and so forth.Manufacturing flexible tactile sensors based on bionic microstructures or directly using natural materials can greatly simplify the preparation process, cut the high cost, which is consistent with the concept of sustainable development and is of great significance for building an environment-friendly flexible electronic system.

柔性触觉传感器 仿生微结构 脉搏监测 运动监测 离子液体 电双层

flexible tactile sensors bionic microstructures pulse monitoring motion detection ionic liquid electric double layer

中文

联合培养

南方科技大学

万永彪. 基于仿生微结构的柔性触觉传感器[D]. 深圳. 哈尔滨工业大学,2018.