MXene-Based Elastomer Mimetic StretchableSensors: Design, Properties, and Applications

Flexible sensors based on MXene-polymer composites are highly prospective for next-generation wearable electronics used in human-machine interfaces.One of the motivating factors behind the progress of flexible sensors is the steady arrival of new conductive materials.MXenes,a new family of 2D nanomaterials,have been draw-ing attention since the last decade due to their high electronic conduc-tivity,processability,mechanical robustness and chemical tunability.In this review,we encompass the fabrication of MXene-based polymeric nanocomposites,their structure-property relationship,and applications in the flexible sensor domain.Moreover,our discussion is not only lim-ited to sensor design,their mechanism,and various modes of sensing platform,but also their future perspective and market throughout the world.With our article,we intend to fortify the bond between flexible matrices and MXenes thus promoting the swift advancement of flexible MXene-sensors for wearable technologies.

Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Preparation and Performance Study of PVA-Based Flexible Sensors

Flexible sensors have great potential for monitoring human body motion signals. This paper presents a flexible sensor that uses zinc oxide (ZnO) to improve the mechanical properties and electrical conductivity of PVA hydrogel. The composite hydrogel has excellent conductive properties and high strain sensitivity, making it suitable for motion monitoring. The PVA/ZnO conductive hydrogel is tested on various body parts, showing effective feedback on movement changes and good electrical signal output effects for different motion degrees, confirming its feasibility in flexible sensors. The sensor exhibits good mechanical properties, electrical conductivity, and tensile strain sensing performance, making it a promising sensor material. It can accurately monitor wrist bending, finger deformation, bending, and large-scale joint movements due to its wide monitoring range and recoverable strain. The results show that the PVA/ZnO conductive hydrogel can provide effective feedback in flexible sensors, which is suitable for use in motion monitoring.

The Flow Measurement of Multiphase Flow Based on the Conductance Sensor

Oil-gas-water three-phase flow in the pipe is commonly encountered in the petroleum and nature gas industry. Its flow patterns are complex and always changeable, so it’s difficult to be measured and is becoming one of the most important subjects. Moreover, most of the oil fields in China are in such a high water fraction period that measures must be taken to meet the needs of the actual production. A conductance sensor which is widely used in the measurements of oil-water two-phase flow is used to measure the flow rate of the three-phase flow based on the research of the characteristics and the correlation theory, and a new technical solution which is suitable for measuring the oil-gas-water three-phase flow is established. A series of tests demonstrate that it’s feasible to use the conductance sensor in the measurements of oil- gas-water three-phase flow.

A Novel Thin Film Resistive Humidity Sensor Based on SolubleConjugated Polymer:(propionic acid)-co-(propargyl alcohol)

A novel soluble conjugated copolymer (propionic acid)-co-(propargyl alcohol) (PA-co-OHP) has been synthesized for the first time using a new palladium acetylide catalyst Pd(PPh3)(2)(C=CC(CH3)(2)OH)(2)(PPB). Thin film resistive humidity sensor based oil the copolymer doped with HClO4 was prepared. The impedance of the sensor changed from 10(3)similar to 10(7) Omega in 95%similar to 30%RH, and the response of that is very quick (<6 sec.). Preliminary results show the copolymer is a promising humidity sensitive material.

Fluorescent-Dye Doped Thin-Film Sensors for the Detection of Alcohol Vapors

Fluorescence sensors based on a trifluoroacetophone compound doped in ethyl cellulose (EC) thin films have been developed for the detection of methanol, ethanol, and 2-propanol (isopropanol, PriOH) vapors. Thin-film sensors are prepared with 4-dibutylamino-4’-(trifluoroacetyl)stilbene (Chromoionophore IX or CIX) as the fluorescent dye and its solution in EC was spin-coated onto glass slides. The luminescence intensity of the dye (555 nm) is quenched when exposed to alcohol vapor. Tested in the range of ca. 0 - 1.5?× 104 ppm (wt) for MeOH and EtOH, and ca. 0 - 2.3 × 104 ppm for PriOH, the sensors gave detection limits of 9, 13, 21 ppm and quantification limits of 32, 43, and 70 ppm, respectively. To enhance the sensitivity of the sensors, TiO2 particles have been added to the films to induce Mie scattering, which increases the incident light interaction with the sensing films. The sensors in this work have been designed to work in a multianalyte platform for the simultaneous detection of multiple gas analytes.

A self-healing and conductive ionic hydrogel based on polysaccharides for flexible sensors

In this study,we proposed a self-healing conductive hydrogel based on polysaccharides and Li+to serve as flexible sensors.At first,the oxidized sodium alginate(OSA)was obtained through the oxidation reaction of sodium alginate(SA).Then OSA,carboxymethyl chitosan(CMC),and agarose(AGO)were dissolved in LiCl solution,respectively.Finally,the hydrogel was obtained through heating,mixing,and cooling processes.Because of the Schiff base structure and hydrogen bonding,the hydrogel demonstrates good mechanical and self-healing properties.The presence of Li+provides good conductivity for the hydrogel.In addition,we demonstrated the application of the hydrogel as the flexible sensors.It can perceive the process of pressing Morse code with the index finger as a pressure sensor and monitor sliding movement of the thumb as the strain sensor to browse the web with the mobile phone.Thus,the selfhealing conductive hydrogel may have potential applications in flexible wearable sensors.

Wearable and stretchable conductive polymer composites for strain sensors:How to design a superior one?

Wearable and stretchable strain sensors have potential values in the fields of human motion and health monitoring,flexible electronics,and soft robotic skin.The wearable and stretchable strain sensors can be directly attached to human skin,providing visualized detection for human motions and personal healthcare.Conductive polymer composites(CPC)composed of conductive fillers and flexible polymers have the advantages of high stretchability,good flexibility,superior durability,which can be used to prepare flexible strain sensors with large working strain and outstanding sensitivity.This review has put forward a comprehensive summary on the fabrication methods,advanced mechanisms and strain sensing abilities of CPC strain sensors reported in recent years,especially the sensors with superior performance.Finally,the structural design,bionic function,integration technology and further application of CPC strain sensors are prospected.

用于运动状态监测的纸基柔性摩擦电传感器

为解决柔性摩擦电传感器制备流程复杂、成本高、不够环保等问题,设计了一种基于纸基导电银浆的低成本柔性摩擦电传感器。当外部压力由5 N增大至50 N时,其输出电压和输出电流逐渐增大,在频率为1 Hz、幅值为50 N的外部压力作用下,输出电压的峰值约为7.52 V。当外部压强在17~173 kPa的范围内变化时,输出电压峰值与压强呈分段线性关系。当外部压力的频率变化时,输出电压保持不变。结果表明,该传感器压力传感性能良好。当应用于运动传感中时,该传感器能够感知肘关节、腕关节的弯曲角度,并能有效区分走、快走、跑3种运动类型以及踮脚、深蹲、抱腹跳3种健身动作,计算人体行走频率与健身动作次数,在人体运动状态监测等领域具有良好的应用价值。

基于电导率对相对介电常数补偿的土壤含水率电容传感器标定方法

针对土壤含水率电容传感器检测精度低,标定模型对盐渍土壤的适用性不高等问题,提出基于电导率对相对介电常数补偿的含水率电容传感器标定法。在标准溶液中建立相对介电常数与传感器输出电压关系对数模型(R^(2)=0.983),进一步基于二元二次回归分析法,建立标准溶液电导率对相对介电常数补偿的相对介电常数与传感器输出电压及电导率的回归标定模型(R^(2)=0.979)。对传感器进行土壤含水率标定,建立土壤体积含水率与相对介电常数关系的三阶多项式标定模型(R^(2)=0.996)。对两步标定模型进行实测,结果表明:土壤电导率为0~2 dS/m时,体积含水率检测最大误差从未电导率补偿时0.0383 m^(3)/m^(3)降至电导率补偿后0.0127m^(3)/m^(3),最大相对误差从12.0200%降至6.2241%。结果表明,在不同电导率的同类土壤中,使用基于电导率对相对介电常数补偿的含水率传感器标定法能明显提高土壤含水率检测精度和对不同电导率土壤(黄土)的适用性。

CMC/PAM/LiCl复合离子导电水凝胶及传感性能

柔性力敏传感器能够将外界的机械刺激转换为相应的电信号,在可穿戴电子设备、电子皮肤、智能机器人等领域得到了广泛的应用。为满足以上应用需求,材料需要具有可变形、拉伸、回弹、导电等性能、较高的灵敏度及较好的重现性。因此,基于双网络结构,以羧甲基纤维素(CMC)与聚丙烯酰胺(PAM)为原料,设计并制备了一种离子水凝胶,并且,探究了交联剂及无机盐含量对水凝胶力学性能及导电性能的影响。结果表明,二者之间的内在相互作用赋予了水凝胶较好的力学强度(150 kPa)及拉伸/回弹性(可压缩/拉伸循环1 000次以上),同时具有较高的透明度,其值为69.1%。将其用作组装压力传感器,具有较高的灵敏度(S=7.13 kPa-1)及较好的重现性(1 000次);将其用作组装应变传感,其仍可以表现出及时的响应(50/60 ms)及较好的稳定性(1 000次)。因此,水凝胶有望应用于人体及智能机器人的活动监测及人机界面等领域。

面向人体运动检测的水凝胶基柔性应变传感器设计

在可穿戴电子设备迅猛发展的背景下,构建面向人体运动检测的可穿戴柔性应变传感器成为目前传感器研究的重点之一。基于聚丙烯酰胺(PAM)、纤维素纳米晶(CNCs)、单宁酸(TA)构建了一种导电水凝胶基柔性应变传感器。机械性能与电学性能测试结果表明,相较于其他柔性应变传感器,聚丙烯酰胺-纤维素纳米晶-单宁酸导电水凝胶基柔性应变传感器具有超长的拉伸范围(0%~2 900%)、较好的黏附性、快速的响应时间(280 ms)和良好的稳定性(超320次加载-卸载循环)。该传感器对人体关节弯曲的大应变与喉部活动的小应变等运动信号具备良好的检测功能,可用作人体运动检测的柔性可穿戴传感器。

聚乙烯醇/角蛋白/碳纳米管自愈合导电水凝胶的构建

为了进一步提高聚乙烯醇水凝胶的力学性能和导电灵敏性,本文以聚乙烯醇(PVA)为原料,以羊毛角蛋白(KE)和三氯化铝(AlCl_(3))为交联剂,添加碳纳米管(CNT)作为导电载体,制备出具有互穿双网络结构的自愈合导电水凝胶。通过扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)等测试手段对PVA/KE/CNT复合水凝胶进行测试分析。结果表明,AlCl_(3)中的Al^(3+)与角蛋白中的—COOH、—OH配位络合促使角蛋白间相互交联形成团簇,同时AlCl_(3)中的Al^(3+)也与PVA中的—OH交联形成紧密结构,增强了水凝胶的强度和韧性,CNT被两种交联结构紧紧包裹并赋予水凝胶导电性能。CNT的加入使复合水凝胶的韧性增加,添加质量分数为4%和5%的CNT可明显提升材料的强度;所制备的水凝胶都具有较好的自愈合性能,在一定范围内的自愈合性能与愈合时长成正比,12 h的愈合时长效果最佳;加入CNT使水凝胶电阻下降,添加质量分数为2%~5%的CNT后水凝胶电阻分别为8.98、4.56、3.81、3.12 kΩ。这种力学性能、自愈性能和导电性能均良好的水凝胶与人体运动检测应用具有天然的柔韧匹配性,在电子皮肤和柔性传感器领域有很好的应用前景。

氢气传感器在电解制氧系统中的应用研究

针对电解制氧系统中氢气浓度测量受环境因素影响大、测量准确性低等问题,选取了半导体型、催化燃烧型、热导型三类不同原理的氢气传感器,对其在电解制氧系统中的应用进行了试验验证,并对试验结果进行了讨论,分析了各类氢气传感器的使用局限性。

用于应变传感器的自愈合抗冻离子水凝胶

近年来,导电水凝胶在电子驱动器、医疗监测传感器及可穿戴设备等领域的应用备受关注。然而,多数凝胶机械强度低、寿命短、抗冻性能差,从而导致低温下无法使用。为了解决该问题,以聚乙烯醇、离子液体1-丁基-3-甲基咪唑四氟硼酸盐和植酸为原料,在水与二甲基亚砜(DMSO)二元溶液中借助多重氢键及离子基团间的静电作用实现了超分子自组装,制备出一种可用于应变传感的自愈合、耐低温多功能离子水凝胶。研究发现在凝胶中引入DMSO,凝胶表现出优异的抗冻能力;同时,调节DMSO的含量可优化凝胶的强度和韧性,当DMSO体积分数为40%时,最大拉伸强度和断裂伸长率分别可达4.43 MPa和869.1%。该离子水凝胶在低温应变传感器、智能可穿戴响应元件等领域展现出较好的应用潜力。

全纤维电容式传感器的结构设计及其性能

由于受柔性电容式传感器介电层弹性模量的限制,目前电容器的性能如灵敏度等难以达到应用要求,为提高传感器的传感性能,以聚吡咯复合蚕丝织物作为织物电极,羊毛纤维集合体作为介电层构建全纤维的电容式压力传感器,对电极的织物结构和纤维集合体高度进行优化分析;对传感器的电学及传感性能进行测试,并进行了应用探索。结果表明:面密度为69 g/m^(2)素绉缎聚吡咯复合织物方阻最小,为42Ω/□;纤维电容器以素绉缎聚吡咯复合织物作为电极,羊毛纤维集合体为介电层,且高度为1.4 cm时传感性能最优,在频率为10 kHz、电容最高为66 pF、压力为0~5 N范围内灵敏度最高为1.08 N^(-1)。该电容式传感器具有良好的稳定性,有望应用于肢体运动监测与公共场合安全监测中。

导电复合材料涂覆式全织物基柔性压阻传感器制备

针对目前织物基柔性压阻传感器制备工艺相对复杂、导电材料与织物结合度有限等问题,提出以聚二甲基硅氧烷(PDMS)-多壁碳纳米管(MWCNTs)/炭黑(CB)为导电复合材料涂覆非织造布制备压敏层,采用微滴喷射技术在织物表面直接成形叉指型金属电极,制备织物基柔性压阻传感器的方法。当CB与MWCNTs质量比为3∶2时,对不同MWCNTs填充量下导电复合材料形态及制备的压敏层微观形貌观察,并研究其对传感器灵敏度的影响,最后对制得传感器的性能及应用进行测试。结果表明:导电材料在PDMS中分散均匀,导电复合材料与织物结合紧密;当MWCNTs质量分数为2.5%时,所制传感器灵敏度最高可达0.353 kPa^(-1),检测范围为0~25 kPa,响应/恢复时间为150/200 ms,最低检测限约为49 Pa,具有良好的重复稳定性(约1 600次)。此外,该传感器可识别出手指按压以及手指和腕部弯曲的压力信号,可应用于人体健康、运动等信号监测。

聚吡咯/氨纶长丝的应变传感性能与应用

为制备应用于运动监测方面的柔性拉伸应变传感器,探索拉伸型应变传感材料自身长度及拉伸应变对运动监测效果的影响,将表面聚合吡咯的氨纶长丝裁剪成不同长度进行循环拉伸测试,通过扫描电子显微镜和红外光谱仪对氨纶长丝和聚吡咯/氨纶长丝的微观形貌及化学结构进行表征,并测试分析了不同长度的聚吡咯/氨纶长丝在不同速率下拉伸不同应变时的电力学性能。结果表明:通过原位聚合可使聚吡咯完全覆盖氨纶长丝表面,所得聚吡咯/氨纶长丝在500%的应变范围内应力最高可达21.0 MPa;灵敏度值在0%~63%和118%~243%应变范围内分别为1.82和43.3,在800 mm/min速率下拉伸10%应变的响应时间为200 ms。为探索聚吡咯/氨纶长丝与实际应用的匹配性,测试了不同长度聚吡咯/氨纶长丝在连续循环拉伸过程中的电阻变化,归纳其电阻变化特性,并将有效长度1 cm的聚吡咯/氨纶长丝固定在食指第2关节处以监测手指关节的重复弯曲。

导电水凝胶在柔性可穿戴传感器的应用研究进展

目的概述导电水凝胶在柔性可穿戴传感器方面的研究情况,挖掘其作为传感器件的应用潜能。方法查阅大量相关的文献,对导电水凝胶在柔性可穿戴传感领域的最新进展进行归纳与总结。按水凝胶网络分类的4种导电水凝胶,总结归纳其设计、合成、结构和潜在应用。讨论导电水凝胶的导电性、力学性能、黏附性、防冻性能、自愈性能和各式响应性等功能性能的影响因素,总结自黏性、防冻性、自修复和其他多种优秀性能的柔性可穿戴传感器。结论导电水凝胶是一种具有多功能的独特刺激响应性的功能材料,在柔性可穿戴传感领域进行深入探究具有重大意义。

基于PDMS的柔性压阻式传感器的研究进展

近年来,以聚二甲基硅氧烷(PDMS)为主体材料的柔性压阻式传感器的发展十分迅速,在人体运动及健康监测、电子皮肤、智能机器人等领域中具有广阔的应用前景。本文首先介绍了柔性压阻式传感器的传感机理及主要性能指标,然后重点综述了基于PDMS的柔性压阻式传感器的研究进展,特别是在PDMS与不同导电填料结合制备传感器以及微结构构建两个方面进行了详细阐述,最后指出了当前该领域存在的一些问题,并对其发展方向进行了展望。