Flexible Battery-Free Wireless Sensor Array Based on Functional Gradient-Structured Wood for Pressure and Temperature Monitoring

Approximately 4.5% to 7.0% of hospitalized patients suffer from pressure ulcers. Mitigating risks for pressure ulcers through sensors remains a challenge and a high requirement. A simple, low-cost, battery-free, multi-parameter passive wireless flexible sensor (MPWFS) for all-around pressure and temperature monitoring to prevent pressure ulcers is developed. The pressure sensing unit is fabricated with functional gradient-structured balsa wood and has high sensitivity of 0.34 kPa⁻¹ with a wide detection range of 0–20 kPa. The temperature sensing unit, which is 0.4 mm × 0.2 mm, is embedded in the surface of the pressure sensing unit, enabling temperature monitoring with a resolution of 0.1 °C. The flexible Radio Frequency energy-harvesting unit, data acquisition, and processing, as well as Bluetooth-Low-Energy wireless transmission, are integrated within a 20 mm × 20 mm unit. It acquires continuous temperature and pressure data without a battery at any position more than 1 m away from the power transmitter. Moreover, the combination of the sensor array design with a mobile terminal provides the MPWFS's various benefits, including tracking changes in the supine posture, warning about pressure ulcers, and monitoring falls out of bed. This study presents a new method for long-term bedridden patient care.     

Wearable,Human‐Interactive,Health‐Monitoring,Wireless Devices Fabricated by Macroscale Printing Techniques

Wearable human‐interactive devices are advanced technologies that will improve the comfort, convenience, and security of humans, and have a wide range of applications from robotics to clinical health monitoring. In this study, a fully printed wearable human‐interactive device called a “smart bandage” is proposed as the first proof of concept. The device incorporates touch and temperature sensors to monitor health, a drug‐delivery system to improve health, and a wireless coil to detect touch. The sensors, microelectromechanical systems (MEMS) structure, and wireless coil are monolithically integrated onto flexible substrates. A smart bandage is demonstrated on a human arm. These types of wearable human‐interactive devices represent a promising platform not only for interactive devices, but also for flexible MEMS technology.     

无源无线声表面波压力传感器研究

无源无线传感器可对快速移动或旋转等环境下的物体进行参数测量,具有无源无线等优势。为此,采用声表面波(SAW)技术和无线射频技术研究实现了一种结构简单的无源无线声表面压力传感器。基于CC1101无线射频模块实现对SAW压力传感器感知信息的无线接收。推导出CC1101射频收发模块的阻抗匹配网络的传递函数,通过MATLAB和Multism软件进行分析和仿真,确定了匹配网络的元件参数,使射频模块工作频率可调;设计并实现了传感器样机。试验结果表明,该无源无线SAW压力传感器具有精度高,稳定性好的特点,为其工程化提供了依据。     

Full‐Textile Wireless Flexible Humidity Sensor for Human Physiological Monitoring

Textile‐based electronic techniques that can in real‐time and noncontact detect the respiration rate and respiratory arrest are highly desired for human health monitoring. Yarn‐shaped humidity sensor is fabricated based on a sensitive fiber with relatively high specific surface area and abnormal cross‐section. The response and recovery time of the yarn‐shaped humidity sensor is only 3.5 and 4 s, respectively, with little hysteresis, because of the hydrophobic property of these functional fibers and the grooves on the surface of the fibers, which is much faster than those of the commercial polyimide materials. Moreover, a battery‐free LC wireless testing system combined with the yarn‐shaped sensor is fabricated, which is further successfully imbedded into the intelligent mask to detect human breath. Based on the detection of LC wireless testing system, the frequency of 50.25 MHz under the exhaled condition shifts to 50.86 MHz under the inhaled situation of humidity sensor. In essence, the functional yarns with proper structure, would be an excellent candidature to the yarn‐shaped humidity sensor, in which there are good performance and wide application possibilities, eventually offering a facile method for the wireless detection of human physiological signals in the field of electronic fabrics.     

Textile‐Based Flexible Tactile Force Sensor Sheet

The next generation of electronics will include human‐interactive flexible sensor sheets to monitor health. One approach is to realize practical macroscale low‐cost sensor arrays to monitor pressure distribution and health conditions without directly attaching a device onto the body. However, practical requirements such as reliability, scalability, and washability are not often discussed as most studies focus on the sensing sensitivity and validations. This study demonstrates an all textile‐based tactile force sensor sheet that covers the above requirements. By considering the device design and materials, high reliability/repeatability (≈250 000 cycles at ≈5 kPa) and washability are realized. These are important factors for practical applications for human‐interactive macroscale sensor sheets. In addition to the fundamental characteristics, pressure distribution mapping and respiration rate monitoring are confirmed by placing the sensor sheets on a bed, chair, and floor.     

Single‐Thread‐Based Wearable and Highly Stretchable Triboelectric Nanogenerators and Their Applications in Cloth‐Based Self‐Powered Human‐Interactive and Biomedical Sensing

The development of wearable and large‐area fabric energy harvester and sensor has received great attention due to their promising applications in next‐generation autonomous and wearable healthcare technologies. Here, a new type of “single” thread‐based triboelectric nanogenerator (TENG) and its uses in elastically textile‐based energy harvesting and sensing have been demonstrated. The energy‐harvesting thread composed by one silicone‐rubber‐coated stainless‐steel thread can extract energy during contact with skin. With sewing the energy‐harvesting thread into a serpentine shape on an elastic textile, a highly stretchable and scalable TENG textile is realized to scavenge various kinds of human‐motion energy. The collected energy is capable to sustainably power a commercial smart watch. Moreover, the simplified single triboelectric thread can be applied in a wide range of thread‐based self‐powered and active sensing uses, including gesture sensing, human‐interactive interfaces, and human physiological signal monitoring. After integration with microcontrollers, more complicated systems, such as wireless wearable keyboards and smart beds, are demonstrated. These results show that the newly designed single‐thread‐based TENG, with the advantage of interactive, responsive, sewable, and conformal features, can meet application needs of a vast variety of fields, ranging from wearable and stretchable energy harvesters to smart cloth‐based articles.     

Printed Flexible Strain Sensor Array for Bendable Interactive Surface

An interactive surface using bending gestures as the input is proposed by integrating a flexible strain sensor array and a flexible display screen. To create such a flexible strain sensor array, formation of a reliable interconnection between the elastic sensitive regions and the rigid contact regions is vital to achieve required sensitivity and durability. In this work, a new design with an added interconnect layer on top of the interface regions is used to reduce the bending induced local stress. A stretchable conductive composite by blending carbon black (CB) with polydimethylsiloxane (PDMS) and Ecoflex (CB‐PDMS/Ecoflex) is developed for the interconnect layer. CB‐PDMS/Ecoflex is compatible with the blade coating for facile processing, and demonstrates a similar low Young's modulus as that of the sensitive region composed of silver nanowires and PDMS. Printing processes are developed to fabricate a 4 × 9 flexible strain sensor array based on the proposed design and the interconnect layer. It is shown that the sensor with CB‐PDMS/Ecoflex interconnect layer can sustain more than 3000 bending cycles. Finally, the sensor array is integrated with a flexible active‐matrix organic light‐emitting diode display to construct the bendable interactive surface, demonstrating the capability of controlling the ball movement via bending gestures.     

基于轮胎电容阻抗和SAWR的胎压传感器

介绍了一种由轮胎电容阻抗和声表面波谐振器(SAWR)组成的轮胎压力传感器,该传感器利用轮胎内部钢丝层的不同钢丝与钢丝间的橡胶组成的电容阻抗进行轮胎压力的测量,轮胎压力的变化会引起轮胎电容阻抗的变化,轮胎电容阻抗的变化通过声表面波谐振器转化为频率变化无线发射出去,从而实现轮胎压力的无源无线测量。根据理论分析设计了该传感器的实验系统并进行实验测试研究,实验测试结果表明,设计的传感器具有较高的测量精度。因此,该文提出的传感器设计方案可行。     

基于无线SAW压力传感器的FADS研究

嵌入式大气数据系统（FADS）是先进的大气数据系统。由于SAW压力传感器能进行无线测量，将无线SAW压力传感器应用于FADS，与MIMU相结合使之成为廉价的微型组合导航系统。研究了FADS的基本原理、无线双单端SAW谐振器压力传感器的基本原理以及相关应用电路模块，并利用HP Esoft软件和SAW谐振器等效电路对无线SAW压力传感器进行了仿真。研究表明，无线SAW传感器能应用到先进的大气数据系统，具有重要的应用价值。     

基于无线SAW压力传感器的FADS研究

嵌入式大气数据系统(FADS)是先进的大气数据系统。由于SAW压力传感器能进行无线测量,将无线SAW压力传感器应用于FADS,与MIMU相结合使之成为廉价的微型组合导航系统。研究了FADS的基本原理、无线双单端SAW谐振器压力传感器的基本原理以及相关应用电路模块,并利用HP Esoft软件和SAW谐振器等效电路对无线SAW压力传感器进行了仿真。研究表明,无线SAW传感器能应用到先进的大气数据系统,具有重要的应用价值。     

Textile‐Based Triboelectric Nanogenerators for Self‐Powered Wearable Electronics

Wearable smart electronic devices based on wireless systems use batteries as a power source. However, recent miniaturization and various functions have increased energy consumption, resulting in problems such as reduction of use time and frequent charging. These factors hinder the development of wearable electronic devices. In order to solve this energy problem, research studies on triboelectric nanogenerators (TENGs) are conducted based on the coupling of contact‐electrification and electrostatic induction effects for harvesting the vast amounts of biomechanical energy generated from wearer movement. The development of TENGs that use a variety of structures and materials based on the textile platform is reviewed, including the basic components of fibers, yarns, and fabrics made using various weaving and knitting techniques. These textile‐based TENGs are lightweight, flexible, highly stretchable, and wearable, so that they can effectively harvest biomechanical energy without interference with human motion, and can be used as activity sensors to monitor human motion. Also, the main application of wearable self‐powered systems is demonstrated and the directions of future development of textile‐based TENG for harvesting biomechanical energy presented.     

基于SAW谐振器无源无线传感器编码方法研究

为简化声表面波(SAW)传感器的编码过程,提出了一种基于SAW谐振器的编码方法,通过多个不同中心谐振频率的SAW谐振器分别连接不同的负载阻抗进行传感器的编码。设计了传感器的具体结构,建立了传感器的等效电路模型,利用ADS仿真软件对中心谐振频率分别为868MHz和915MHz的2个SAW谐振器组成的传感器进行仿真,结果表明,SAW谐振器外接1pF与4pF的阻抗,其谐振频率差可达200³00kHz。根据仿真结果,设计制作了不同编码的2个传感器,一个不外接阻抗,一个外接10pF的阻抗,测试谐振频率差别可达39.75300kHz。根据仿真结果,设计制作了不同编码的2个传感器,一个不外接阻抗,一个外接10pF的阻抗,测试谐振频率差别可达39.75⁴0.2kHz,因此,SAW谐振器外接不同阻抗时谐振频率的差异明显,基于SAW谐振器与外接阻抗的传感器编码方法是可行的。     

A Monocharged Electret Nanogenerator‐Based Self‐Powered Device for Pressure and Tactile Sensor Applications

This study reports a self‐powered pressure sensor based on a monocharged electret nanogenerator (MENG). The sensor exhibits great advantages in terms of high reliability, ease of fabrication, and relatively high sensitivity. The working mechanism of the MENG sensor is studied by both theoretical derivations and finite element analyses to determine the electric potential distribution during the device operation. The MENG sensor exhibits a stable open circuit voltage ≈10 V at a 30.8 kPa pressure and a corresponding sensitivity of 325 mV kPa^?1. The stability testing result shows that the device has only ≈5% attenuation after 10 000 cycles of repeated testing at 30.8 kPa pressure. Furthermore, it is found that the MENG sensor responds not only to a dynamic force but also a static force. Finally, a sensor array consisting of nine MENG sensor elements is fabricated. The testing results from the sensor array also reveal that a single touch of the sensor element can immediately light up an LED light at the corresponding position. This device holds great promise for use in future tactile sensors and artificial skin applications.     

基于无线传感器网络的智能灌溉系统研究

针对我国水资源紧缺以及农田节水灌溉的需求,根据现有的农田灌溉装备条件,应用领域作物、土壤、水源布点等情况,分析了目前实现精确农业亟待解决的关键技术问题,提出一套采用无线传感器网络技术、适合大面积农田智能灌溉控制方法。分析结果表明,该系统通过无线传感技术完成智能化灌溉,可很好地实现节水。且该系统工作稳定,具有一定的推广应用价值。     

基于MantisOS的无线传感器网络应用的研究

无线传感器网络具有很强的应用相关性,每一个应用程序开发都是基于特定的操作系统平台并针对具体的应用进行开发。为了更好地在MantisOS平台上开发应用程序,提出了一个Manti-sOS开发应用程序的模型,并应用于无线传感器网络防火监控应用程序的开发,取得了较好的效果。     

基于无线传感器网络的智能用电在线监控系统

针对传统建筑中由于电气线路接触不良、过载等易引发火灾,提出一种基于无线传感器网络的智能建筑电气安全监控系统,可动态设置智能插座的功率阈值,若超过阈值时,插座自动断开电源,以避免过载或影响同一分支电路的其他设备。测试结果表明,系统对过载反应快速准确,工作稳定可靠。该监控系统安装调试简便,可有效保障用电安全,具有较高的应用推广价值。     

分布式无线Ad Hoc传感器网络中的合成式波束形成

分布式无线Ad Hoc传感器网络中的合作式波束形成的性能分析是建立在随机阵理论和移动通信波束形成的基础上的。在分布式Ad Hoc传感器网络中,每个传感器节点有一个全向天线,且在簇中的节点传输同一信号,使信号在远区场的目标方向上叠加。波束的方向的随机性是由无线Ad Hoc网络结构决定的。介绍了随机阵理论和移动通信波束形成,接着介绍了系统模型,分析了波束的方向特性,着重讨论了平均方向性增益,推导出平均方向性增益的近似公式。     

基于集成压力传感器的无源胎压监控系统研究

汽车轮胎压力监测系统(TPMS),主要用于在汽车行驶时实时地对轮胎气压进行自动监测,对轮胎漏气和低气压进行报警,以保障行车安全,是当前汽车电子研究的一个热点。汽车轮胎的压力与温度是密切相关的,需要同时监控压力和温度信息。设计制作了一种压力温度集成传感器,可以同时监控汽车轮胎压力和温度的变化。基于这种集成压力传感器,设计了一种无源胎压监控系统。