基于CNTs/PDMS介电层的柔性压力传感特性研究

提出一种基于MEMS工艺的柔性压力传感器制备方法.采用MEMS工艺制备柔性压力传感器模板,结合纳米压印技术、射频磁控溅射技术和PDMS软光刻工艺在PDMS柔性基底上制备了具有"V"型阵列微结构的Ag薄膜平行板电极,基于碳纳米管(CNTs)/PDMS聚合物的压电容特性,制备出电容式柔性压力传感器.针对不同尺寸的压力传感器进行对比测试,本文制作的压力传感器的灵敏度能够达到3.98% kPa-1,具有良好的重复性,在智能穿戴和电子皮肤等方面有着广阔的应用前景.     

基于黑磷烯/氧化石墨烯双介质层的柔性电容式压力传感器

设计并制备了由黑磷烯/氧化石墨烯双层材料为介质层的电容式柔性压力传感器,该传感器结构以ITO为电容上下极板,PET为柔性基底,并对该传感器进行了系统的性能测试与分析。着重研究了该传感器在不同压力量程内的灵敏度,进而分析了其温度漂移特性。测试结果表明,以黑磷烯/氧化石墨烯薄膜为双介质层的电容式柔性压力传感器在0～3.12 kPa压力量程内灵敏度可达到1.60 kPa^-1。同时,对该传感器和以氧化石墨烯薄膜为单介质层的传感器进行了弯曲应变性能的对照实验,可知具有双介质层的传感器结构能够显著提高传感器的输出特性。     

基于PI衬底的柔性MEMS电容式触觉力传感器设计与制作

论述了一种可应用于机器人或医学修补技术的触觉传感器及其在旋涂的柔性聚酰亚胺衬底的新制作方法.该传感器是由多层无机和有机薄膜组成的柔性薄膜结构.结合传感器结构特点及各结构层材料的加工性能,进行工艺优化整合.尤其首次在载体硅片与PI衬底之间引进PDMS分离层,使得柔性器件的分离工艺大大简化.最后得到一种简单、低廉且与常规MEMS技术兼容的工艺.所制的传感器结构轻薄,可挠性好,且能贴附在任意形状的物体表面同时实现法向力和切向力的测量.     

基于 ＧＮＰｓ/ ＰＤＭＳ 复合薄膜的柔性压阻传感器制备及性能研究

目前柔性压力传感器已被用于众多领域,其中压阻薄膜是柔性压力传感器的核心。本文将石墨烯纳米片（GNPs）与聚二甲基硅氧烷（PDMS）复合,通过倒模的方法制备压阻薄膜,经测试,GNPs浓度为8%时,材料具有较好的性能。以此为基础,制备了压敏结构间距为1.2 mm,直径大小为1.0 mm的GNPs/PDMS基压阻传感器,经测试,所制备的传感器加载响应为340 ms,卸载响应速度为260 ms,并具有较好的稳定性,同时,基于该压阻式柔性压力传感器实现了人体手腕关节处压力信号的测试。     

基于柔性电极结构的薄膜电容微压力传感器

基于柔性电极结构,本文设计、制作了薄膜电容微压力传感器,在阐述传感器工作原理的基础上,提出了两种设计思路,即基于柔性纳米薄膜的电容式微压力传感器和具有微结构的柔性电极薄膜电容式微压力传感器,并结合传感器的结构和柔性材料的加工特性,进一步提出了相应的力敏特性材料结构优化思路和加工流程,利用该流程得到了一种结构轻薄、工艺简单、高灵敏度的微压力传感器。经测试,本文制作的压力传感器的灵敏度能够达到218 fF/mmHg,在智能穿戴和可植入压力检测等领域显示出较好的应用前景。     

基于柔性衬底的三维生物刺激微电极阵列研究

设计了一种基于聚酰亚胺薄膜的三维生物刺激微电极阵列,用于植入式人造视网膜应用.采用非硅MEMS技术,在柔性衬底上制备出具有生物相容性和化学稳定性,电极高度为80 μm的生物刺激电极阵列,通过PDMS牺牲层实现器件从基底的完整释放.实验中器件以聚酰亚胺和PDMS封装,电极柱和焊盘均镀金,从而提高电极的生物相容性.采用三电极法对微电极进行了电化学性能测试,在10-1～105Hz频率范围内,其阻抗为1.5～0.3 kΩ.制造出的器件尺寸小,质量轻,可靠性高,机械柔性好,符合生物电刺激要求.     

基于PDMS海绵介质层的电容式柔性压力传感器

柔性压力传感器以其低成本和大的检测范围等优势广泛的应用于电子皮肤和可穿戴传感器领域。本文通过在PDMS中填充碳酸氢铵材料,制备了大面积高密度具有微观结构的PDMS海绵介质层,通过简易的方法完成了柔性压力传感器的制备。与以往的柔性压力传感器相比,制备的PDMS海绵介质层由于气孔的存在更容易在受到压力时发生形变,拥有高的灵敏度(0.23 kPa^-1)、大的检测范围(0～50 kPa)、稳定的重复性(>1 000循环)以及快的响应时间(<150 ms)。通过对不同厚度、不同大小的PDMS海绵介质层进行测试,利用厚度为1.5 mm,大小为8 mm×8 mm的PDMS海绵作为压力传感器的介质层实现了力的实时检测。     

基于LCP衬底的柔性湿度传感器研究

介绍了一种新型柔性电容式湿度传感器.该柔性电容式湿度传感器采用液晶高分子聚合物(LCP)作为衬底,金属铜(Cu)作为叉指电极,聚酰亚胺(PI)作为湿度传感器的湿敏介质.LCP衬底的应用使得该传感器具有良好的柔性和可弯曲性.该柔性湿度传感器与传统硅基湿度传感器相比较具有成本低廉、结构简单、制作方便等优点.该柔性湿度传感器在25℃下的平均灵敏度为0.04%pF/%RH,最大回滞为±4.16%RH,其平均灵敏度在25℃~70℃范围内受温度影响较小.在25℃下其响应时间和恢复时间分别为36 s和39 s.该柔性湿度传感器可以应用于环境湿度检测、人工电子皮肤系统和可穿戴设备等领域.     

基于柔性微电极的高灵敏度MEMS电化学地震检波器

为了进一步降低微机电系统(MEMS)电化学地震检波器敏感电极的加工成本,提升传感器的灵敏度,推动其在地球物理勘探等领域的发展,提出了一种基于柔性微电极结构的新型MEMS电化学地震检波器.与基于硅衬底制作敏感电极相比,敏感电极的制作方法可以通过有效减小电极间距,大幅度提升传感器的灵敏度,大幅降低工艺成本.介绍了柔性微电极的加工工艺流程,并对传感器的性能进行了测试.结果表明:提出的地震检波器较基于硅衬底微电极器件灵敏度提高了一个数量级.     

碳纳米管/PDMS复合材料柔性阵列压力传感器制备与实验

以碳纳米管（CNTs）作为导电填料,聚二甲基硅氧烷（PDMS）为基体材料,采用溶液法制备出CNTs/PDMS导电复合材料。研究了碳纳米管浓度对复合材料的电学特性和压阻特性的影响规律,得到碳纳米管在PDMS中的渗滤区域。通过复合材料的压力灵敏度优化碳纳米管浓度。以制备的复合材料为敏感材料,FPCB工艺加工的柔性基板为电极,设计制备了一种简单结构和工艺的柔性阵列压力传感器。用零电势法设计了阵列电阻读出电路与LabVIEW实现的上位机配合,实现信号读取和显示。最后通过一个应用实例表明,该柔性阵列压力传感器及信号处理系统可以实现压力分布与大小的实时监测,可为柔性阵列压力传感器设计与制备提供参考。     

A flexible PDMS capacitive tactile sensor with adjustable measurement range for plantar pressure measurement

A flexible capacitive tactile sensor with adjustable characteristics, i.e., measurement range and sensitivity, has been developed. The proposed sensor is designed for large pressure measurement; therefore, polydimethylsiloxane (PDMS) material is selected as the material of the dielectric layer between the parallel plate electrodes of the sensor. Since the elasticity of the PDMS material can be adjusted by the mixing ratio of PDMS pre-polymer and curing agent during formation, sensors in different measurement ranges, i.e., 240–1,000 and 400–3,000 kPa, and corresponding sensitivities, i.e., 2.24 and 0.28 %/MPa, were respectively constructed and demonstrated. These measurement ranges are suitable for most of the biomechanical applications, especially for plantar pressure measurement. Moreover, because the output of the sensor, i.e., capacitance, is highly influenced by the dimension of the sensor structure, each sensor consists of four independent capacitance elements. The output of each sensor is averaged by four capacitances for single force measurement. This could improve the measurement accuracy in practical situation. Also, linearity of the measurement response could be enhanced and it was shown by the R-squared values in two measurement ranges, i.e., 0.9751 and 0.9881, respectively. The proposed sensor is flexible and miniaturized and has the potential to be applied to biomechanical applications.     

Capacitive flexible pressure sensor: microfabrication process and experimental characterization

Kapton-based flexible pressure sensor arrays are fabricated using a new technology of film transfer. The sensors are dedicated to the non-invasive measurement of pressure/force in robotic, sport and medical applications. The sensors are of a capacitive type, and composed of two millimetric copper electrodes, separated by a polydimethylsiloxane (PDMS) deformable dielectric layer. On the flexible arrays, a very small curvature radius is possible without any damage to the sensors. The realized sensors are characterized in terms of fabrication quality. The inhomogeneity of the load free capacitances obtained in the same array is ±7 %. The fabrication process, which requires 14 fabrication steps, is accurate and reproducible: a 100 % transfer yield was obtained for the fabrication of 5 wafers gathering 4 sensor arrays each (215 elementary sensors). In the preliminary electro-mechanical characterization, a sensor (with a PDMS dielectric layer of 660 μm thickness and a free load capacitance of 480 fF) undergoes a capacitance change of 17 % under a 300 kPa normal stress.     

同面散射场电容式砂含水量传感器的研究

针对电容式砂含水量传感器的特殊结构,本文从同面散射场电容传感器的等效电容的分析出发,优化了电容极板的大小;使用有限元法分析了极板间距、极板对数以及极板结构对传感器灵敏度的影响;并对传感器的隔离板材料的介电常数选择问题进行了探讨。结果表明双电极小极板结构的普通陶瓷隔离的传感器结构尺寸小,灵敏度高。本研究对同面散射场电容式砂含水量传感器的结构参数优化有实际指导意义。     

Design and optimization of fully differential capacitive MEMS accelerometer based on surface micromachining

In this paper, design and simulation of a single-axial, capacitive, fully differential MEMS accelerometer based on surface micromachining with two proof masses is presented. So far, most surface micromachined capacitive accelerometers offered, employed differential interface circuits to measure capacitor variations. However, in the presented structure, the possibility of fully differential design is realized by dividing the proof mass to two electrically isolated parts that are located on a silicon nitride layer. By utilizing two proof masses and altering outputs and stimulation voltage, parasitic capacitor is reduced and the sensitivity is increased. Moreover, some sensor capacitors are embedded inside the proof mass, so that sensitivity could be increased in the limited area and electrode length could be reduced. Furthermore, analytic equations are derived to calculate the sensitivity, as well to optimize the sensor structure. The designed sensor has been simulated and optimized using COMSOL Multiphysics, where the simulation results show the mechanical and capacitive sensitivity of 29.8 nm/g and 15.8 fF/g, respectively. The sensor size is 1 mm × 1 mm that leads to excellent performance, regarding to the defined figure of merit.

     

High-performance capacitive humidity sensor with novel electrode and polyimide layer based on MEMS technology

A high-performance capacitive humidity sensor based on a newly designed electrode and a polyimide (PI) layer is presented in this paper. The humidity sensor consists of a substrate with a cavity, a bottom electrode, a PI sensing layer, and a comb-shaped top electrode with branches. The cavity structure of the substrate was formed to protect the top electrode. In order to enhance the performance of the sensor, the coated PI layer was etched by using an O₂ plasma asher in accordance with the top electrode passivation. After the PI etching, the humidity sensor showed a high sensitivity of 506 fF/% RH and a fast response time of less than 6 s, which is attributed to the increased contact area between the PI layer and moisture, and shortened moisture absorption path into the PI layer. Further characterizations were carried out to measure the effect of temperature, hysteresis, and stability. The humidity sensor showed a hysteresis of 2.05% RH, little temperature dependence, and stable capacitance value with maximum 0.28% error rate for 24 h.     

A novel thick-film ceramic humidity sensor

The paper describes the results of studies on the fabrication and characterisation of a thick-film humidity sensor based on the semiconducting metal oxide MnWO₄. The sensor element possesses a novel ‘sandwich’-configuration with a 40 μm porous MnWO₄ ceramic layer sandwiched by two 10 μm polarity-reversed, interdigitated metal films. Instead of traditional glass frits, LiCl powders are used as adhesion promoters for sintering the sensor paste. With this method, MnWO₄ powders with an average particle size of 3.0 μm are sintered at the standard thick-film firing temperature of 850°C. The sintered ceramic layer exhibits a porous structure. The novel electrode arrangement combines the advantages of humidity sensors in the form of a parallel capacitor with those in the form of an interdigital capacitor, permitting a high sensitivity and a fast response. The influence of temperature on the sensor characteristics has been compensated for by integrating a thick-film NTC resistor. The humidity sensor shows no cross-sensitivity to organic vapour. The organic contamination on the sensor surface can be burned out by heating the sensor element at about 400°C with the refresh heater printed on the back side of the substrate.