电容式柔性压力传感器的性能优化原理及研究进展

作为可穿戴电子器件的重要分支，柔性压力传感器在人机交互、健康监测等方面具有广阔的应用前景。随着新型材料与新的器件制备策略的不断开发，柔性压力传感器的力学与电学性能不断被优化以适应不同的应用需求。相较于其他传感器，电容式柔性压力传感器具有灵敏度高、功耗低、响应快的优势。电容式柔性压力传感器的性能优化主要通过改变器件的结构参数来实现，如电极有效正对面积、电极间距、有效介电常数等。主要方法策略包括新型纳米材料的应用、新型微结构设计和新型复合材料的开发。主要优化原理有四种：（1）通过改变电极表面粗糙度来改变电极有效正对面积；（2）在电极或介电层中引入空气层以降低弹性模量；（3）在介电层中引入空气或高介电常数材料来改变有效介电常数；（4）通过复合材料在介电层中形成微电容以改变总体电容变化。在电容式柔性压力传感器的性能优化研究中存在一个共性问题，即高灵敏度与宽检测范围之间总是存在一种制约关系。在一定压力范围内，尤其是低压范围，灵敏度提升往往会使器件较易达到压缩饱和而使检测范围有限，即线性度较差。近年来，研究者们着眼于高灵敏度与宽检测范围之间的制约问题，对介电层的梯度结构设计及混合响应机制进行探索，...     

基于多向冷冻法制备的高灵敏度柔性电容式压力传感器

近年来柔性电容压力传感器因兼具优异的力学性能和良好的灵敏性，广泛应用于医学诊断、电子皮肤、人工智能等重要领域。本文围绕提升电容式柔性传感器的灵敏度为目标，设计了一种基于多向冷冻工艺构筑的三维交联网络结构多壁碳纳米管(MWCNTs)/聚二甲基硅烷(PDMS)海绵为介质层的柔性电容式压力传感器，并对该传感器的制造过程、传感机制、响应性能和人体适用性进行表征。结果表明：通过多向冷冻法可成功构建三维网络结构MWCNTs/PDMS海绵介质层，且此介质层组装的柔性电容式压力传感器具有较高灵敏度(～1.94 kPa^-1)、低检测限(～4 Pa)、快响应时间(～250 ms)、良好稳定性及人体适用性。该柔性传感器在可穿戴电子产品中具有良好的应用前景。     

新型三明治结构聚二甲基硅氧烷/聚偏氟乙烯-纳米Ag线/聚二甲基硅氧烷柔性应变传感器的制备与性能

为了提升柔性应变传感器性能，采用静电纺丝技术制备聚偏氟乙烯(PVDF)静电纺丝膜后，将自制纳米Ag线(AgNWs)抽滤在PVDF静电纺丝膜表面，作为导电层。采用聚二甲基硅氧烷(PDMS)对导电层进行双面固化，制备了系列导电层中不同AgNWs含量的新型三明治结构的PDMS/PVDF-AgNWs/PDMS柔性应变传感器，并对其性能进行表征和分析。结果表明，静电纺丝膜的引入明显改善了PDMS/PVDF-AgNWs/PDMS柔性应变传感器的各项性能，减少了滞后现象，增加了传感器的灵敏度和可重复性，并大幅提升了使用寿命。当导电层中AgNWs质量为 0.030 g，应变达到10%时，PDMS/PVDF-AgNWs/PDMS柔性应变传感器灵敏度的传感系数可达143.85。对PDMS/PVDF-AgNWs/PDMS柔性应变传感器进行30天可重复试验后，在设定位移为5 mm、每天拉伸20次的条件下，PDMS/PVDF-AgNWs/PDMS柔性应变传感器的初始电阻值仅比初次试验时增加了约2 Ω，较最大位移时的电阻值可忽略不计。      

电极与介电层褶皱接触对压电式柔性电子皮肤性能的影响

提出了一种基于压电效应制备柔性电子皮肤的简单方法。为了研究纳米改性对柔性电子皮肤各层性能的影响，首先以纳米SiO₂粒子作为改性体，以聚二甲基硅氧烷(PDMS)作为基体，制备出SiO₂/PDMS复合柔性衬底，解决了在PDMS上磁控溅射沉积电极材料产生裂纹的现象，成功获得能够稳定工作的柔性电极。然后用钛酸钡/碳纳米管/聚二甲基硅氧烷(BaTiO₃/CNTs/PDMS)复合材料作为功能层，制备出一种五层结构的高灵敏性柔性电子皮肤，并找到一种通过改变基板粗糙度的简单方法构建电极与介电层的褶皱接触，进而提升柔性电极的电导率与柔性电子皮肤的压电响应信号。      

基于聚二甲基硅氧烷柔性传感器的研究进展

与传统应变传感器相比,柔性传感器的柔韧性、可穿戴性和实时监测是独特的优点,近年来柔性传感器快速发展并应用于医疗检测、可穿戴设备等多方面,由于聚二甲基硅氧烷(PDMS)的优异理化性质,常作为柔性传感器基底。文中总结了近年来用PDMS作为柔性传感器基底的研究工作,首先对PDMS纳米复合材料的传感机理进行详细的介绍,包括压阻式、电容式与压电式传感机制;然后对以碳纳米管(CNT)、石墨烯与纳米银等为纳米填料的PDMS基柔性传感器进行了详细综述;最后,对PDMS基柔性传感器的研究现状及存在的问题进行了总结并做出展望。     

基于聚二甲基硅氧烷柔性传感器的研究进展EI北大核心CSCD

与传统应变传感器相比,柔性传感器的柔韧性、可穿戴性和实时监测是独特的优点,近年来柔性传感器快速发展并应用于医疗检测、可穿戴设备等多方面,由于聚二甲基硅氧烷(PDMS)的优异理化性质,常作为柔性传感器基底。文中总结了近年来用PDMS作为柔性传感器基底的研究工作,首先对PDMS纳米复合材料的传感机理进行详细的介绍,包括压阻式、电容式与压电式传感机制;然后对以碳纳米管(CNT)、石墨烯与纳米银等为纳米填料的PDMS基柔性传感器进行了详细综述;最后,对PDMS基柔性传感器的研究现状及存在的问题进行了总结并做出展望。     

基于微结构的柔性压力传感器设计、制备及性能

随着科技的快速发展,电子皮肤和柔性可穿戴设备由于在人体运动、健康监测、智能机器人等领域具有重要应用而引起了人们广泛的关注。传统的基于贵金属或金属氧化物半导体的压力传感器成本高、柔韧性差,而新型的基于微结构的柔性压力传感器具有灵敏度高、应变范围宽、低成本、低功耗、响应速度快等优势,在电子皮肤和柔性可穿戴设备等方面发挥重要作用,成为当前柔性电子材料与器件主要研究热点之一。本文系统总结了近年来颇受关注的基于金字塔形、微球形、微柱形、仿生结构、褶皱等不同柔性基底微结构和多孔导电聚合物材料的柔性压力传感器在材料选择、结构设计、制备方法、传感性能等方面取得的重要进展,并对柔性压力传感器的未来发展进行了展望。      

气溶胶微喷射打印柔性应变传感器及性能研究

目的 研究气溶胶微喷射打印工艺在制备柔性应变传感器方面的可行性。方法 利用气溶胶微喷射打印工艺不受限于柔性基底且打印定位精度高的优势,通过等离子清洗技术增大PDMS表面附着力,使用纳米银墨水与PDMS基底制作用于人体运动检测的电阻式柔性应变传感器。结果 通过等离子清洗PDMS基底表面,解决了打印过程中柔性应变传感器因PDMS表面纳米银液滴凝聚而产生的不导电问题。探究了气溶胶微喷射打印工艺参数对打印银线宽度的影响规律,发现增大鞘气流量或缩小喷头内径能有效减小打印线宽。利用高精度万用表检测由气溶胶微喷射打印制备的传感器在受力时产生的电信号,测试传感器在无应力状态下导电性良好且稳定,计算出传感器应变在3.5%内且灵敏度可达163.84。将传感器用于人体手指部位的运动监测,证明其具有检测微小信号的能力。结论 气溶胶微喷射打印工艺可用于制备所需要的柔性应变传感器,该传感器在智能穿戴设备方面具有一定应用潜力。     

4H-SiC MEMS高温电容式压力敏感元件设计

为了研制Si C高温电容式MEMS压力敏感元件以满足高温环境下压力参数测量,设计了一种基于P型4H-Si C减薄抛光工艺制备高温变间隙电容式压力传感器敏感元件结构方法;通过数值仿真,研究了敏感元件的性能,得到敏感元件输出电容随压力、温度的变化曲线;通过微机械加工工艺制备出了Si C电容式高温压力传感器敏感元件,研制出Si C电容式高温压力传感器原理样机,通过模拟高温压力传感器样机工作环境,搭建了高温微压测试平台并对原理样机进行性能测试;结果显示,样机在873.15 K下能够正常工作,灵敏度为18.7 f F/k Pa,非线性为12.60%,迟滞为0.47%,能够满足解调电路拾取压力信号.     

具有超高灵敏度、宽工作范围、低检测限的3D气凝胶可穿戴压力传感器用于语音识别和生理信号监测（英文）

随着智能电子设备的快速发展,对同时具有超高灵敏度、宽工作范围、低检测限的可穿戴压力传感器的需求越来越大.本文开发了一种基于超轻(29.5 mg cm^-3)和弹性的3D壳聚糖/MXene (CS/MXene)复合气凝胶的压阻式压力传感器.由于CS和MXene之间的强静电吸引力,具有良好机械性能的CS/MXene气凝胶只需一步冷冻干燥即可获得,无需额外的化学处理.CS/MXene复合气凝胶压力传感器在小压力区(<1 kPa)和大压力区(1-20 kPa)的灵敏度分别为709.38和252.37 kPa^-1.在此压力范围下,其灵敏度是目前报道的同类型气凝胶压力传感器的最高值.此外,该传感器具有快速的响应时间(<120 ms)、1.4 Pa的超低检测限以及10,000次循环后几乎无衰减的良好稳定性.以上出色的性能不仅使得该传感器可用于检测肢体活动和空间压力分布等较大幅度的压力信号,而且还能准确检测脉搏、语音等微小压力信号.这种多功能的柔性压力传感器极大地拓宽了可穿戴电子器件在语音识别、健康监测和人机交互等诸多领域的应用范围.     

High Sensitivity,Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing

A pressure sensor based on irregular microhump patterns has been proposed and developed. The devices show high sensitivity and broad operating pressure regime while comparing with regular micropattern devices. Finite element analysis (FEA) is utilized to confirm the sensing mechanism and predict the performance of the pressure sensor based on the microhump structures. Silicon carbide sandpaper is employed as the mold to develop polydimethylsiloxane (PDMS) microhump patterns with various sizes. The active layer of the piezoresistive pressure sensor is developed by spin coating PEDOT:PSS on top of the patterned PDMS. The devices show an averaged sensitivity as high as 851 kPa^?1, broad operating pressure range (20 kPa), low operating power (100 nW), and fast response speed (6.7 kHz). Owing to their flexible properties, the devices are applied to human body motion sensing and radial artery pulse. These flexible high sensitivity devices show great potential in the next generation of smart sensors for robotics, real‐time health monitoring, and biomedical applications.     

In-situ sugar-templated porous elastomer sensor with high sensitivity for wearables

Fabrication of elastic pressure sensors with low cost, high sensitivity, and mechanical durability is important for wearables, electronic skins and soft robotics. Here, we develop high-sensitivity porous elastomeric sensors for piezoresistive and capacitive pressure detection. Specifically, a porous polydimethylsiloxane (PDMS) sponge embedded with conductive fillers of carbon nanotubes (CNTs) or reduced graphene oxide (rGO) was fabricated by an in-situ sugar template strategy. The sensor demonstrates sensitive deformation to applied pressure, exhibiting large and fast response in resistance or capacitance for detection of a wide range of pressure (0‒5 kPa). PDMS, as a high-elasticity framework, enables creation of sensors with high sensitivity, excellent stability, and durability for long-term usage. The highest sensitivities of 22.1 and 68.3 kPa⁻¹ can be attained by devices with 5% CNTs and 4% rGO, respectively. The geometrics of the sponge sensor is tailorable using tableting technology for different applications. The sensors demonstrate finger motion detection and heart-rate monitoring in real-time, as well as a capacitive sensor array for identification of pressure and shape of placed objects, exhibiting good potential for wearables and human-machine interactions.     

Natural Plant Materials as Dielectric Layer for Highly Sensitive Flexible Electronic Skin

Nature has long offered human beings with useful materials. Herein, plant materials including flowers and leaves have been directly used as the dielectric material in flexible capacitive electronic skin (e‐skin), which simply consists of a dried flower petal or leaf sandwiched by two flexible electrodes. The plant material is a 3D cell wall network which plays like a compressible metamaterial that elastically collapses upon pressing plus some specific surface structures, and thus the device can sensitively respond to pressure. The device works over a broad‐pressure range from 0.6 Pa to 115 kPa with a maximum sensitivity of 1.54 kPa^?1, and shows high stability over 5000 cyclic pressings or bends. The natural‐material‐based e‐skin has been applied in touch sensing, motion monitoring, gas flow detection, and the spatial distribution of pressure. As the foam‐like structure is ubiquitous in plants, a general strategy for a green, cost‐effective, and scalable approach to make flexible e‐skins is offered here.     

Fabrication of a flexible and transparent touch sensor using single-walled carbon nanotube thin-films

Reported herein are the fabrication and demonstration of a flexible and transparent touch sensor using carbon nanotube thin films (CNTFs). The CNTF was fabricated by vacuum filtration and was transferred CNTF to polydimethylsiloxane (PDMS) by water-assisted stamping method. The sheet resistance of the CNTF decreased by approximately 74% after HNO3 treatment. The CNTF touch sensor was fabricated similarly to the conventional four-wire touch screen structures. PDMS was used for the upper plate to absorb the tensile and compressive strain and polyethylene terephthalate (PET) for the lower plate to provide device stability during bending action. The CNTF touch sensor showed high optical transmittance (over 80%) and high sensitivity with the measured touch activation pressure of 23 kPa. Cyclic pressure (38 kPa) was applied at 0.5 Hz and good repeatability was found for several hundred cycles. The results show that the CNTF flexible touch sensor can be applied to future flexible electronic interfaces such as, e-paper and flexible displays.     

MEMS-Capacitive Pressure Sensor Fabricated Using Printed-Circuit-Processing Techniques

Microelectromechanical systems (MEMS)-based capacitive pressure sensors are typically fabricated using silicon-micromachining techniques. In this paper, a novel liquid-crystal polymer (LCP)-based MEMS-capacitive pressure sensor, fabricated using printed-circuit-processing technique, is reported. The pressure sensor consists of a cylindrical cavity formed by a sandwich of an LCP substrate, an LCP spacer layer with circular holes, and an LCP top layer. The bottom electrode and the top electrode of the capacitive pressure sensor are defined on the top side of the LCP substrate and the bottom side of the top-LCP layer, respectively. An example pressure sensor with a diaphragm radius of 1.6 mm provides a total capacitance change of 0.277 pF for an applied pressure in the range of 0-100 kPa     

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human‐machine interfaces because of their simple device structure and easy‐readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low‐cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray‐coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa⁻¹ and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin.     

基于膨胀石墨/聚二甲基硅氧烷复合材料的柔性压力传感器及加热除冰的应用

积冰作为一种常见的自然现象,给航空、电力和道路交通等方面带来了极大安全隐患。本文利用膨胀石墨优异的导电性和聚二甲基硅氧烷良好的柔韧性与疏水性,制备具有探冰与电热除冰功能为一体的膨胀石墨/聚二甲基硅氧烷的复合材料(Expandable graphite/polydimethylsiloxane, EG/PDMS),并研究其疏水性、压阻性能和电热效应。结果表明,EG/PDMS复合材料传感器压力灵敏度最大为0.15 kPa?1,且能在10~110 kPa大范围内产生线性压阻反应;在电加热过程中,当输入电压为30 V、输入电流为0.05 A时,最高平衡温度为94.7℃,完全融化10 g冰的时间为166 s。EG/PDMS复合材料不仅可以监测其表面积冰厚度变化,还可通电加热除冰,在探冰/除冰领域具有较大的应用价值。      

Splashing-Assisted Femtosecond Laser-Activated Metal Deposition for Mold- and Mask-Free Fabrication of Robust Microstructured Electrodes for Flexible Pressure Sensors (Small 24/2023)

Flexible pressure sensors play an indispensable role in flexible electronics. Microstructures on flexible electrodes have been proven to be effective in improving the sensitivity of pressure sensors. However, it remains a challenge to develop such microstructured flexible electrodes in a convenient way. Inspired by splashed particles from laser processing, herein, a method for customizing microstructured flexible electrodes by femtosecond laser-activated metal deposition is proposed. It takes advantage of the catalyzing particles scattered during femtosecond laser ablation and is particularly suitable for moldless, maskless, and low-cost fabrication of microstructured metal layers on polydimethylsiloxane (PDMS). Robust bonding at the PDMS/Cu interface is evidenced by the scotch tape test and the duration test over 10 000 bending cycles. Benefiting from the firm interface, the developed flexible capacitive pressure sensor with microstructured electrodes presents several conspicuous features, including a sensitivity (0.22 kPa⁻¹) 73 times higher than the one using flat Cu electrodes, ultralow detection limit (<1 Pa), rapid response/recovery time (4.2/5.3 ms), and excellent stability. Moreover, the proposed method, inheriting the merits of laser direct writing, is capable of fabricating a pressure sensor array in a maskless manner for spatial pressure mapping.     

A contactless capacitive angular-position sensor

This paper presents an absolute capacitive angular-position sensor with a contactless rotor. The sensor is mainly composed of three parts: the capacitive sensing element, a signal processor, and a microcontroller. The electrically floating rotor can be either conductive or dielectric. For the dielectric material, we chose plastic, and for the conductive rotor, we chose aluminum. The sensing element has a redundant structure, which reduces mechanical nonidealities. The signal processor has a multicapacitance input and a single output, which is a period-modulated square-wave voltage. The microcontroller acquires output data from the processor and sends them to a PC, which calculates the rotor position. Theoretical analysis, supported by experimental results, show that the sensitivity to mechanical nonidealities of the sensing element is higher in the case of a conductive rotor. The resolution of the capacitive angular-position sensor over the full range (360/spl deg/) was better than 1". The measured nonlinearity was /spl plusmn/ 100" and /spl plusmn/ 300" for the dielectric and the conductive rotor, respectively.