Machine Learning‑Enhanced Flexible Mechanical Sensing

To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performances of sensor devices and the data processing capabilities of the device’s software.Significant research efforts have been devoted to improving materials,sensing mechanism,and configurations of flexible sensing systems in a quest to fulfill the requirements of future technology.Meanwhile,advanced data analysis methods are being developed to extract useful information from increasingly complicated data collected by a single sensor or network of sensors.Machine learning(ML)as an important branch of artificial intelligence can efficiently handle such complex data,which can be multi-dimensional and multi-faceted,thus providing a powerful tool for easy interpretation of sensing data.In this review,the fundamental working mechanisms and common types of flexible mechanical sensors are firstly presented.Then how ML-assisted data interpretation improves the applications of flexible mechanical sensors and other closely-related sensors in various areas is elaborated,which includes health monitoring,human-machine interfaces,object/surface recognition,pressure prediction,and human posture/motion identification.Finally,the advantages,challenges,and future perspectives associated with the fusion of flexible mechanical sensing technology and ML algorithms are discussed.These will give significant insights to enable the advancement of next-generation artificial flexible mechanical sensing.

Advances in flexible and wearable pH sensors for wound healing monitoring

Wound healing has been recognized as a complex and dynamic regeneration process and attracted increasing interests on its management.For effective wound healing management,a continuous monitoring on the wound healing based on sensors is essential.Since pH has been found to play an important role on wound healing process,a variety of pH sensors systems for wound healing monitoring have been greatly developed in recent years.Among these pH sensors,flexible and wearable pH sensors which can be incorporated with wound dressing have gained much attention.In this review,the recent advances in the development of flexible and wearable pH sensors for wound healing monitoring have been comprehensive summarized from the range of optical and electrochemical bases.

Advanced flexible humidity sensors:structures,techniques,mechanisms and performances

Flexible humidity sensors are widely used in many fields,such as environmental monitoring,agricultural soil moisture content determination,food quality monitoring and healthcare services.Therefore,it is essential to measure humidity accurately and reliably in different conditions.Flexible materials have been the focusing substrates of humidity sensors because of their rich surface chemical properties and structural designability.In addition,flexible materials have superior ductility for different conditions.In this review,we have summarized several sensing mechanisms,processing techniques,sensing layers and substrates for specific humidity sensing requirements.Aadditionally,we have sorted out some cases of flexible humidity sensors based on different functional materials.We hope this paper can contribute to the development of flexible humidity sensors in the future.

Two-dimensional materials:From mechanical properties to flexible mechanical sensors

Two-dimensional(2D)materials have great potential in the fields of flexible electronics and photoelectronic devices due to their unique properties derived by special structures.The study of the mechanical properties of 2D materials plays an important role in next-generation flexible mechanical electronic device applications.Unfortunately,traditional experiment models and measurement methods are not suitable for 2D materials due to their atomically ultrathin thickness,which limits both the theoretical research and practical value of the 2D materials.In this review,we briefly summarize the characterization of mechanical properties of 2D materials by in situ probe nanoindentation experiments,and discuss the effect of thickness,grain boundary,and interlayer interactions.We introduce the strain-induced effect on electrical properties and optical properties of 2D materials.Then,we generalize the mechanical sensors based on various 2D materials and their future potential applications in flexible and wearable electronic devices.Finally,we discuss the state of the art for the mechanical properties of 2D materials and their opportunities and challenges in both basic research and practical applications.

全纳米纤维离电式柔性压力传感器的制备及性能研究

为解决传统的电容式压力传感器灵敏度低的问题,基于聚丁二酸丁二醇酯对苯二甲酸丁二醇酯(PBST)和离子液体(ILs),采用静电纺丝技术制备离子介电层(ILs/PBST),并利用离电式压力传感机制开发了一种灵敏、透气的全纳米纤维离电式柔性压力传感器。该器件具有超高灵敏度(902.4 kPa-1,0~6 kPa)和快速响应/恢复时间(147 ms/147 ms),能够快速稳定地监测多种人体运动及生理信号。此外,三维多孔纳米纤维网络赋予其良好的透气性,确保其长期佩戴的舒适性,该器件有望应用在智能医疗领域。

自愈性石墨烯基柔性传感器研究进展

自愈性柔性传感器具有良好的传感性、机械性能和自愈性,相较于传统柔性传感器,可以修复因形变造成的损伤,使用寿命长。石墨烯基复合材料具有优良的力学性能和高导电性,在制备自愈性柔性传感器领域获得广泛关注。重点论述自愈性石墨烯基柔性传感器实现自愈的机理,即基于可逆共价键如Diels-Alde(D-A)反应、可逆二硫键、可逆硼酸酯键等的自愈,及基于可逆非共价键,如氢键、金属配位键和基于双动态键的自愈。总结了制备此种传感器的基质材料,主要为聚二甲基硅氧烷、聚氨酯、聚丙烯酸、聚乙烯醇基等,并对比了不同基质材料制备的自愈性石墨烯基传感器的各项性能。最后对自愈性石墨烯基柔性传感器目前存在的问题进行讨论,对其未来进行展望。

针织结构温度传感器用镀银纱线的性能

为了保证针织结构温度传感器的传感性能,文章运用FLUKE289数字万用表、V-2030T微电脑加热平台等设备测试了10种典型镀银纱线在伸直与模拟线圈弯曲状态下的电阻值,分析了光照氧化和水洗条件对纱线导电性能的影响,并得到了线密度、纱线状态、温度、光照氧化时间、水洗次数与电阻之间的关系。结果表明:10种镀银纱线的单位电阻在1.245~18.788Ω,温度电阻关系拟合R 2在0.89425~0.99040,具有良好的导电性和感温性,复丝越多的纱线电阻越小,线密度适中偏小的纱线感温性能更好;纱线的弯曲状态不会改变温度电阻规律,但会略微降低其感温线性度和导电性;光照氧化和水洗都会导致纱线导电性能变差;综合分析可设计复丝数适中偏少、捻丝结构的镀银纱线制备针织结构温度传感器。

高强度双网络结构木基复合凝胶的制备及性能

以木材为原料,通过脱基质处理获得木材纤维骨架,在其多孔结构中利用原位聚合法构建以聚乙烯醇(PVA)/聚丙烯酰胺(PAM)为双网络结构填充相的高强度木基复合凝胶。通过调控PVA及PAM在复合凝胶体系中的质量比,系统研究制备所得木基复合凝胶的宏/微观形貌、力学性能、光学性能及表面化学性能等变化规律。结果表明:在聚丙烯酰胺/木材纤维骨架中引入少量PVA,通过构建双网络结构,能够有效提升木基复合凝胶的力学性能,其最大拉伸强度可达16.47 MPa,断裂伸长率约为11.61%。将木基复合凝胶作为柔性基材组装构建传感器件,电导率为1.8 S/m,发现木基传感器在多种形变下均表现出稳定可重复的相对电流信号变化。

Soft-template synthesis of hierarchically porous structured polydimethylsiloxane toward flexible capacitive pressure sensor

Flexible pressure sensors play an important role in the field of monitoring, owing to their inherent safety and the fact that they are embedded at the material level. Capacitive pressure sensors have been proven to be quite versatile, with the ability to change the sensitivity and monitoring range by modifying the pore structure of the dielectric layer(elastic modulus). In this paper, capacitive pressure sensors are devised, comprising hierarchical porous polydimethylsiloxane. Due to the inherent hollow and hierarchical micropore structure, the capacitive pressure sensor allows operation at a wider pressure range(~1000 kPa) while maintaining sensitivity(6.33 MPa-1) in the range of 0–300 k Pa. Subsequently, the capacitance output model of the sensor is optimized, which provides an overall approximation of the experimental values for the sensor performance. Additionally, the signal response of the“break up the whole into parts”(by analysis of the whole sensor in parts) is simulated and outputted by the finite element analysis. The simplified analysis model provides a good understanding of the relationship between the local pressure and the signal response of the pressure sensor. For practical applications, seal monitoring and rubber wheel pressure array system are tested, and the proposed sensor shows sufficient potential for application in large deformation elastomer products.

用于柔性传感的双形状记忆MXene基水凝胶的制备及性能研究

兼具优良导电性和多重形状记忆多功能水凝胶柔性传感器的构筑极具挑战。通过分子设计采用自由共聚和冷冻-解冻法将MXene纳米片引入兼具温度响应的高分子聚乙烯醇和金属离子响应的聚丙烯酸网络中,制备了具有双重形状记忆的导电水凝胶并构筑了应变传感器。采用透射电镜、扫描电镜、X射线衍射及傅里叶红外光谱等技术研究了该纳米片和复合水凝胶的形貌及结构,研究了MXene含量对该水凝胶力学性能、导电性能及形状记忆性能的影响规律。研究表明:MXene纳米片均匀分散在复合水凝胶中,且与水凝胶网络通过氢键交联,这不仅强化了该水凝胶的力学性能,而且提高了双重形状记性水凝胶的形状固定率。其中,复合水凝胶的抗拉强度提升至236.10 kPa,是纯水凝胶的7.3倍,对铁离子的形状固定率从69.44%增加至94.44%,对温度响应的形状固定率从63.89%增加至88.89%。该水凝胶传感器的信号在多次快速拉伸应变循环下表现出色的连续性和一致性,这为环境适应性柔性传感器的构筑提供了新思路。

空间光学遥感器精密次镜调整机构设计及试验

随着空间光学遥感器地面分辨率逐步提高,长焦距、大口径相机成为重点研究方向。为了克服重力变化、复合材料变形等因素带来的天地不一致性的问题,次镜调整成为校正光学遥感器离焦和主次镜相对位置变化的关键技术之一。将次镜柔性支撑、精密直线驱动与柔性铰链传动技术相结合,设计了一套高精度次镜调整机构。首先介绍了该套机构的光机构成、工作原理及传动链路,然后对超轻次镜、高精度直线致动、高精度调焦传动等设计分别进行了阐述,最后介绍了力学环境试验后的调整精度测试情况。试验结果表明,该套精密调整机构实测调整行程大于±120μm,轴向调整步距精度0.18μm(3σ值),调整行程内次镜的最大平移误差为1.30μm,最大倾斜误差为1.93″,具有调整范围宽、调整精度高的特点,满足空间光学遥感器精密次镜调整的要求,已成功在轨应用于北京三号B卫星0.5 m级高分辨率空间相机。

柔性可穿戴湿度传感器的研究进展

柔性可穿戴智能设备如智能手表、手环等在日常生活中发挥着重要作用,尤其是在医疗保健和运动监测等方面。传统刚性湿度传感器件存在柔韧性差、体积庞大、质量大以及需要传统电池供电等缺陷,无法与人体力学相匹配,因而不能检测皮肤表明湿度变化,柔性可穿戴乃至可自供电的新型湿度传感器是传统湿度传感器的有效替代品。柔性可穿戴湿度传感器的吸湿主要依靠水分子的物理、化学吸附机制。湿敏材料主要有有机高聚物及无机低分子物。柔性可穿戴湿度传感器可分为电阻式、电容式、电压式湿度传感器。电阻式湿度传感器的电阻随环境湿度、交流频率的增加而逐渐减小,且灵敏度降低,但其具有良好的可重复使用性;电容式湿度传感器的电容随着湿度的增加而增大,响应恢复性和耐久性好;电压式湿度传感器既可以作为电压传感器使用,又可利用湿气发电,其电压随着湿度的增加而减小,响应恢复时间短,可循环使用性强。3种柔性湿度传感器在人体健康监测和环境湿度检测调控等方面具有重要作用。

纺织基柔性力学传感器的研究进展

随着近年来各领域对纺织基柔性力学传感器研究与应用不断深入,以纺织材料作为传感载体的纺织基柔性力学传感器在各领域的应用水平得到了进一步提升。通过对纺织基柔性力学传感器常用材料、制作方法、结构设计的总结分析,以及国内外相关研究回顾,综述了电阻式、电容式、压电式和多功能纺织基柔性力学传感器研究的最新进展。结合实际应用场景,提出现阶段研究存在所面临的挑战,并展望了纺织基柔性力学传感器的前景。

柔性压电器件及其可穿戴应用

可穿戴设备是能穿在身上,实时获取人体或环境信息并进行传递和处理的功能设备,在医疗健康、人工智能、运动娱乐等领域具有广阔的应用前景。随着可穿戴设备的发展,各类柔性传感器应运而生。基于压电效应的柔性力学传感器因具有感应频率宽、响应快、线性好、自供电等优势而备受关注。然而传统的压电材料多为脆性陶瓷和晶体材料,限制了其在柔性方面的应用。随着研究的深入,越来越多的柔性压电材料和压电复合材料不断涌现,给柔性可穿戴力学器件注入了新的发展活力。本文主要概括了柔性可穿戴压电器件的前沿进展,包括压电原理、柔性压电材料的制备与性能提升方法。此外,还详细总结了柔性可穿戴压电设备的主要应用方向,包括医疗健康和人机交互,以及遇到的挑战与机遇。

导电弹性体复合材料及其柔性力学传感器研究进展

为探究导电弹性体复合材料结构和组成对可穿戴力学传感器关键性能的影响规律,文中基于聚二甲基硅氧烷(PDMS)、Ecoflex硅胶和聚氨酯(PU)为柔性基体的导电弹性体复合材料研究进展,综述导电弹性体复合材料的制备方法,对比不同导电弹性体复合材料的性能差异,介绍导电弹性体复合材料在电阻式、电容式和静电式柔性力学传感器中的应用。

柔性力敏传感器发展现状

集高灵敏度、高柔韧性和易集成特点的柔性力敏传感器在电子皮肤、可穿戴设备、生物医药和人工智能等领域得到了广泛的研究。笔者通过总结压阻式、电容式、压电式和摩擦电型压力传感器近年来的研究进展,归纳分析了不同新型材料所制成传感器的优势和缺陷。在全面介绍了最新的柔性力敏传感器发展后,讨论了当下柔性传感器所存在的问题以及潜在的发展前景:探索新的传感原理,挖掘新型复合材料,研发性能优异的新型柔性力敏传感材料和器件。传感器综合性能的提升将是未来发展的方向。

宽范围高灵敏度的碳基柔性电容传感性能

为了改善柔性电容式传感器灵敏度与测量范围的问题,提出了一种易制备、无微结构的制备方法。以硅橡胶为柔性基底,碳纳米管和石墨烯为导电填料,采用机械共混和热固化工艺制备了柔性碳基介电层,选用铜箔作为传感器上下电极。研究分析了碳基填料和固化温度对介电层灵敏度与弹性模量的影响,并通过万能试验机与数字电桥构成测试回路对传感器传感性能进行测定分析。实验结果表明,混合填充与单组分填充相比灵敏度提高约10倍,较高的固化温度可以有效降低弹性模量;在30 kPa压力下灵敏度高达1.092 kPa-1且在循环载荷下表现出良好的稳定性,响应时间和恢复时间分别达到300 ms与260 ms,并且拥有较低的迟滞特性。

Adhesive hydrogels for bioelectronics

Benefiting from the unique advantages of superior biocompatibility,strong stability,good biodegradability,and adjustable mechanical properties,hydrogels have attracted extensive research interests in bioelectronics.However,due to the existence of an interface between hydrogels and human tissues,the transmission of electrical signals from the human tissues to the hydrogel electronic devices will be hindered.The adhesive hydrogels with adhesive properties can tightly combine with the human tissue,which can enhance the contact between the electronic devices and human tissues and reduce the contact resistance,thereby improving the performance of hydrogel electronic devices.In this review,we will discuss in detail the adhesion mechanism of adhesive hydrogels and elaborate on the design principles of adhesive hydrogels.After that,we will introduce some methods of performance evaluation for adhesive hydrogels.Finally,we will provide a perspective on the development of adhesive hydrogel bioelectronics.

冷冻限域聚合构建PHEMA/MMT/PVA复合水凝胶及力敏传感性能研究

基于高强韧材料基传感器的发展需求,构建特殊的导电路径以提高材料的灵敏度被认为具有很大的研究价值。通过冷冻铸造辅助聚合诱导相分离的新策略,得到了具有聚甲基丙烯酸羟乙酯(PHEMA)纳米球镶嵌的蒙脱土(MMT)/聚乙烯醇(PVA)双重取向结构的复合水凝胶。制备的水凝胶具有高机械强度(1.9 MPa)和高断裂韧性(2.3 MJ·m^(-3)),同时也拥有良好的耐压缩循环性能(100圈)。构建出的球镶嵌片层结构能够有效调控形变条件下水凝胶材料的离子导电路径,在应变过程中表现出优异的灵敏度(40%应变以下,GF为1.7;40%~100%之间,GF为2.28),超快的响应速度(120 ms),极短的弛豫时间(120 ms)和极低的检测极限(1%),并且能够监测细微变化,如吞咽、书写等,有望用于对人体生理信号和关节运动的全面监测。

基于柔性关节的草莓收获机器人自平衡系统设计

随着现代农业作业精细化发展,用于搭载农业作业工具的作业平台的行走机构要求具有更高的稳定性。以草莓采摘机器人行走机构为研究对象,在复杂的田间作业中,针对草莓采摘机器人行走机构会由于超静定问题产生“虚腿”现象,造成平台晃动甚至倾覆,设计了一种用于解决行走机构“虚腿”问题的自平衡系统,在保证支腿刚度的前提下,基于柔性关节传感器设计了轻负载动态自平衡系统。通过对支腿足端压力进行实时监测,避免“虚腿”出现,保证平台作业的稳定性。利用Matlab搭建模型进行仿真分析,表明模糊PID控制较常规PID控制在行走机构非线性系统中具有更好的控制性能。越障试验结果证明,研制的自平衡系统具有良好的平衡性能。