网格式柔性应变传感器的制备及应用

鉴于柔性应变传感器在人体运动监测、健康监测等领域的广泛应用,设计出兼具高灵敏度和大应变范围的柔性应变传感器具有重要的意义。本文基于Ecoflex-石墨烯复合材料,通过模板法制备了四边形和六边形网格式柔性应变传感器。通过对比两种不同网格结构传感器的应变范围与拉伸断裂极限,发现六边形网格柔性应变传感器的综合性能更优异,并在80%应变条件下进行拉伸/释放疲劳寿命检测,此传感器表现出良好的可靠性,同时该传感器在手肘关节运动和人体不同呼吸状况监测方面表现良好。将六边形网格柔性应变传感器组合构建多通道检测系统,实现了多种手势识别,这在人工智能和运动识别领域具有广阔的市场应用前景。     

Ceramics for chemical sensing

Many types of sensors have been developed to detect chemical species in the gas phase. These include optical based on color change or fluoresence, surface acoustic wave (SAW) devices, electrochemical, chemoresistive/semiconductive, field effect transistors (FET), metal-insulator-semiconductor (MIS) diode devices, and many other. Among these, resistive type sensors based on ceramic oxides are particularly attractive because of their low cost, wide range of applications and potential for use in electronic nose. This article focuses mainly on the resistive/semiconductive, especially the surface conductive ceramic oxide type gas sensors. The main emphasis is on the basic principles involving gas-solid reactions. Also discussed are selected applications with an emphasis on sensor design issues. Since SnO₂ can be used as a model system for oxide-based sensors, most of the discussions focuses on this system, though other systems are occasionally highlighted illustrating recent developments.     

Graphene‐Coated Spandex Sensors Embedded into Silicone Sheath for Composites Health Monitoring and Wearable Applications

This study presents a low‐cost, tunable, and stretchable sensor fabricated based on spandex (SpX) yarns coated with graphene nanoplatelets (GnP) through a dip‐coating process. The SpX/GnP is wrapped into a stretchable silicone rubber (SR) sheath to protect the conductive layer against harsh conditions, which allows for fabricating washable wearable sensors. Dip‐coating parameters are optimized to obtain the maximum GnP coating rate. The covering sheath is tailored to achieve high stretchability beyond the sensing limit of 104% for SpX/GnP/SR sensors. Adjustable sensitivity is attained by manipulating SpX immersion times broadening its application for a wide range of strains: Gauge factors as high as two orders of magnitude are achieved at tensile strains greater than ≈40%. The fabricated sensors are tested for two applications: First, the SpX/GnP sensors are integrated into composite fabrics (with no negative impact on the structural integrity of the part) for screening the yarn displacements, resin flow, solidification during the hot press forming process, and structural health monitoring under mechanical loads with minimal cross‐sensitivity to temperature/humidity. Second, the capability of SpX/GnP/SP sensors in detection of a wide range of bodily motions (from the joint motion to arterial blood pressure) is demonstrated.     

A New Low-Cost Electronic System to Manage Resistive Sensors for Gas Detection

In this paper, a new electronic system for gas detection is presented. Particular attention is focused on electronic noses that employ several resistive sensors. New resistive sensors may have high value due to new substances (TiO₂) or to low-cost fabrication process and, supposing to use these sensors together with traditional ones (SnO₂), a novel instrument to manage high-value resistive sensors varying over a wide range, from kilohms to gigohms is required. The proposed hardware approach is a modular architecture which takes advantage from an improved resistance-to-period converter, where sensors are DC powered. Experimental results show a relative standard deviation below 0.01% and a relative displacement to the reference line less than 1% over six decades if commercial resistors are considered. A prototype has been realized to manage up to eight sensors, detect and estimate substance concentrations, and communicate results to the Internet.     

Ultra-Wide Range,High Sensitivity Piezoresistive Sensor Based on Triple Periodic Minimum Surface Construction

Flexible piezoresistive sensors with biological structures are widely exploited for high sensitivity and detection. However, the conventional bionic structure pressure sensors usually suffer from irreconcilable conflicts between high sensitivity and wide detection response range. Herein, a triple periodic minimum surface (TPMS) structure sensor is proposed based on parametric structural design and 3D printing techniques. Upon tailoring of the dedicated structural parameters, the resulting sensors exhibit superior compression durability, high sensitivity, and ultra–high detection range, that enabling it meets the needs of various scenes. As a model system, TPMS structure sensor with 40.5% porosity exhibits an ultra–high sensitivity (132 kPa⁻¹ in 0–5.7 MPa), wide detection strain range (0–31.2%), high repeatability and durability (1000 cycles in 4.41 MPa, 10000 s in 1.32 MPa), and low detection limit (1% in 80 kPa). The stress/strain distributions have been identified using finite element analysis. Toward practical applications, the TPMS structural sensors can be applied to detect human activity and health monitoring (i.e., voice recognition, finger pressure, sitting, standing, walking, and falling down behaviors). The synergistic effects of MWCNTs and MXene conductive network also ensure the composite further being utilized for electromagnetic interference shielding applications.     

Optimization of gas-sensitive polymer arrays using combinations of heterogeneous and homogeneous subarrays

Results for optimizing an array of conducting polymer gas sensors for sensing one of five analytes in the presence of up to four interferents are presented. The optimized array consists of subarrays of homogeneous (like) sensors contributing to a larger heterogeneous array of up to ten points (unlike sensors) in multidimensional sensor space. The optimization techniques presented here are linear, since the polymer sensors in their useful (low concentration) operating range exhibit linear and additive response characteristics. The optimization of these arrays produces maximum separability between analytes, demonstrating the trade-off between the addition of both information and variability induced by increasing the size of the heterogeneous array. Optimization results for sensing acetone, hexane, THF, toluene, and ethanol in the presence of interferents result in array sizes that are significantly less than the maximum available number of sensors (ten in the heterogeneous partition of the array). This result adds fuel to the argument that fewer sensors are better; the argument for more sensors, however, is also made in the context of the electronic nose systems where significant chemical diversity is required. Homogeneous subarrays of up to four elements each improve the separability of analytes in these optimized heterogeneous arrays by over 10% and also effectively flag broken or unhealthy sensors in a manner that is independent of analyte and concentration.     

Developing an intelligent control system of automatic window motor with diverse wireless sensor network devices

This invention system involves hardware, firmware and software to develop an intelligent control system of automatic window motor with diverse wireless sensor network (WSN) devices for health and environmental monitoring. The parts of this invention are improved by implementing the WSN mote into environmental sensors that may detect temperature, humility, toxic gas, smog or aerosol, etc. With embedded system design, these sensors are capable of delivering WSN signal packets based on ZigBee protocol that follows the IEEE 802.14.4 standards. The primary hardware of the system is the window motor with circuit design by integrating micro control unit (MCU), radio frequency (RF) and WSN antenna to receive command. The firmware developed under embedded system can bridge hardware and software to control the window at the specified position. At the back end, the control system software can manage diverse sensor data and provide the interface for remote monitoring.     

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。     

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.     

Coverage probability analysis of IEEE 802.16 system with smart antenna system over stanford university interim fading channels

The IEEE 802.16 system, a promising wireless communication system, has a maximum transmission range of 50 km according to the IEEE 802.16 standard. In reality, the transmission range and coverage probability of an IEEE 802.16 system vary for different wireless scenarios. Evaluating the transmission range and coverage probability of an IEEE 802.16 system prior to implementation is important. Hence, the Stanford University Interim (SUI) channel model in IEEE 802.16 specifications is suitable for evaluating the performance of IEEE 802.16 systems. To generate an effective method for predicting coverage, this study uses the SUI channel model to analyse the coverage probability of an IEEE 802.16 system. Furthermore, this study utilises a smart antenna system (SAS) to enhance IEEE 802.16 system performance. In terms of different antenna heights of the Base Transceiver Station and Customer Premises Equipment, the performance evaluation results show that the cell radius with the SAS is at least 30% more than that without the SAS.     

Self-powered pressure sensor for ultra-wide range pressure detection

The next generation of sensors should be self-powered,maintenance-free,precise,and have wide-ranging sensing abilities.Despite extensive research and development in the field of pressure sensors,the sensitivity of most pressure sensors declines significantly at higher pressures,such that they are not able to detect a wide range of pressures with a uniformly high sensitivity.In this work,we demonstrate a single-electrode triboelectric pressure sensor,which can detect a wide range of pressures from 0.05 to 600 kPa with a high degree of sensitivity across the entire range by utilizing the synergistic effects of the piezoelectric polarization and triboelectric surface charges of self-polarized polyvinyldifluoride-trifluoroethylene (P(VDF-TrFE)) sponge.Taking into account both this wide pressure range and the sensitivity,this device exhibits the best performance relative to that of previously reported self-powered pressure sensors.This achievement facilitates wide-range pressure detection for a broad spectrum of applications,ranging from simple human touch,sensor networks,smart robotics,and sports applications,thus paving the way forward for the realization of next-generation sensing devices.Moreover,this work addresses the critical issue of saturation pressure in triboelectric nanogenerators and provides insights into the role of the surface charge on a piezoelectric polymer when used in a triboelectric nanogenerator.     

基于ZnO复合材料的芯片式pH和温度传感器

可穿戴传感器可以方便地监测汗液pH、体表温度等信号,以此判断人体的健康状况,因而吸引了广泛注意。本研究制备了一种用于检测人体皮肤表面温度及汗液pH的芯片式传感器。pH传感器为ZnO/聚苯胺(PAni)微纳米结构,在不同pH溶液中的表面电位不同,灵敏度达120mV/pH。温度传感器为ZnO/还原氧化石墨烯(rGO)复合材料,用简单的滴落涂布法在聚对苯二甲酸乙二醇酯/氧化铟锡(PET/ITO)导电电极表面修饰一层ZnO/rGO。随着温度的升高, ZnO/rGO复合材料的电阻下降,其电阻变化量的灵敏度达–0.67%/℃。两种传感材料可以集成在一个微小的芯片上,获得的多功能传感器表现出较高的稳定性,在皮肤表面pH和温度检测方面具有潜在的应用价值。     

Enhanced gas sensing performance of SnO2/α-MoO3 heterostructure nanobelts

Extremely high sensitivity and low working temperature of gas sensors are realized from SnO(2)/α-MoO(3) heterostructure nanobelts. Their sensitivity against 500 ppm ethanol is up to 67.76 at the working temperature of 300?°C, which is higher than that of bare α-MoO(3) and SnO(2) nanostructures. Also the working temperature can be lowered down to 120?°C. Such behaviors are attributed to the variation of the junction barrier at the SnO(2)/α-MoO(3) interface. The present results imply that heterostructured 1D nanomaterials may yield gas sensors with improved characteristics, and can be applied to a wide range of gas sensors.     

Three-step precise robotic peg-hole insertion operation with symmetric regular polyhedral objects

Robotic peg-hole insertion operation, the most widely used assembly model, has been extensively investigated. The objective is to design strategies, or hardware, in order to enable a robot to achieve the assembly operation with: (1) higher accuracy than that obtainable directly from the resolution of the robot, (2) a cost lower than manual labour prices and, (3) an operation time in the range from 1.0 to 2.5 secs. There are many strategies provided through the use of specially designed hardware, for example, force sensors and robotic flexible wrists. However, it is difficult to achieve robotic peg-hole insertion with high accuracy, low cost and high speed. In previous work, strategies were designed to achieve the assembly operations without using force sensors or RCC (H. Qiao, B. H. Dalay, J. A. G. Knight, 1996, Robotic assembly operation strategy investigation without force sensors through the research on contact point location and range of peg movement. Proceedings of the IMechE, Journal of Engineering Manufacturing , Vol. 210, pp. 289-307). The strategy development in our work is based on the back-projection concept and the analysis of the allowable range of the peg system, which is constrained by the geometry of the hole system. The allowable range of the peg in the peg-hole system has been established, and features of this allowable range have been studied in detail. Compared with our previous strategies, this paper provides a strategy where the number of the required operational steps is reduced and the assembly process is simplified. The validity of this new method and the allowable initial range of the strategy are also studied. The key point in this paper are as follows: (a) establishing the general allowable range for the peghole system with symmetrical regular polyhedral objects, rather than for the round peg-hole system only, (b) studying the characteristics about this allowable range in more detail and finding out simplified strategies by their utilization, and finding out the allowable initial range for the peg-hole system in the new strategy. This strategy only includes three steps with the peg: (i) first rotated around an axis normal to its axis, (ii) then pushed towards the hole, (iii) then rotated back and inserted into the hole. This paper develops a particular strategy with the following characteristics: (1) it can perform the assembly operation fast, reliably and precisely, (2) there is no need to use force sensors or flexible wrists (3) the operation is simplified through the use of contact forces between the peg and the hole. There are three steps involved in the operation process. This method has been successfully applied to the cylindrical peg-hole insertion operation based on a 29.99 mm diameter peg and a hole with a diameter clearance of 0.02 mm. The operational time averages 1.5 sec. The strategy has been further verified through the simulation process. In addition, other issues about the strategy investigation, which may lead to new strategies, have been discussed.     

Indoor body-area channel model for narrowband communications

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described.     

多孔硅在传感器中的应用研究进展

多孔硅由于其制备方法简单、拥有极大的内表面积、广泛的孔径尺寸、可控的表面改性以及与传统硅集成技术兼容等特点,成为传感器件中理想的敏感材料。简述了多孔硅电化学传感器和光学传感器的研究进展,包括多孔硅湿度传感器、多孔硅气敏传感器、多孔硅有机蒸气传感器、多孔硅生物传感器。最后指出了阻碍多孔硅基传感器商业化的影响因素,并展望了多孔硅传感器的发展方向。     

A history of medical and biological imaging with polyvinylidene fluoride (PVDF) transducers

Polyvinylidene fluoride (PVDF) is a ferroelectric polymer with unique properties suitable for use in a wide range of medical and biological imaging applications. Most notable among these is its low acoustic impedance, which matches that of the body reasonably well, and its flexible mechanical properties. This paper traces the exploitation of PVDF as a transducer material from its early beginnings for thyroid and breast imaging to its current well-established applications in ultrasound biomicroscopy. Although PVDF's electromechanical properties fall short of composite ceramic materials in the traditional diagnostic frequency range, it has significant advantages in the 25-to 100-MHz range. Design criteria for high frequency transducers are reviewed, and examples of relevant medical and biological images are used to illustrate the excellent image quality obtained with this remarkable material.     

自供能柔性氧化石墨烯湿度传感器的喷墨印刷制备及性能研究

呼吸频率及呼吸模式检测可用于医疗诊断以及人体健康评估。传统的医学检测器件体积大、能耗高、使用不便捷。针对高性能、低成本、便携式电子产品的迫切需求, 本工作利用氧化石墨烯材料自发极化后对湿度敏感的特性, 通过喷墨印刷方法制备了一种可以实现自供能的平面型湿度传感器。所制备的传感器对湿度响应呈现为线性关系, 并且具有优异的灵敏度、快速响应和恢复特性、多次循环稳定性和长期老化稳定性等特性。基于该传感器可以实现对于人体呼吸频率和呼吸模式等的检测。制备的湿度传感器具有制作简单、成本低、不易受人体行动及外界环境干扰等优点, 适用于实时监测呼吸频率和呼吸模式。     

An Information Fusion-Based Multiobjective Security System With a Multiple-Input/ Single-Output Sensor

In the framework of sensor fusion, multiple sensors corresponding to the number of physical variables that must be measured are used. In this paper, we propose a novel sensing approach that simultaneously deals with heterogeneous physical variables with a sensor. It is fundamentally different from sensor fusion. The proposed approach takes into consideration the fact that any sensor that detects a certain physical variable is influenced to a degree by other physical variables, which are designated as noise. The objective in conventional sensor design has been the minimization of noise. In contrast, the proposed approach takes advantage of sensors that are easily influenced by many physical variables and makes full use of the multisensing characteristics of these sensors. The system designed using this concept has advantages in terms of cost performance and system simplification compared to existing approaches. This concept can be realized by developing a novel multiple-input/single-output sensor that can detect various variables, including pressure, acceleration, temperature and incandescent light emission, by a single device. We apply the sensor to monitor the symptoms of fire, earthquakes, and break-ins for the purpose of home security. The proposed security system is realized through statistical signal processing and machine learning techniques     

A novel strain sensor based on graphene composite films with layered structure

The use of graphene for strain sensors has attracted enormous attention due to its prominent mechanical and electrical properties. In this paper, we report on the preparation and characterization of a novel type of strain sensor based on graphene composite films with layered configuration. Highly reliable and sensitive composite films strain sensors based on graphene were produced from solution processed graphene flakes by spray coating method. The layered strain sensor which could sustain a large tensile deformation (25% strain) demonstrated high sensitivity to mechanical strain with gauge factors of 6–35. And the sensitivity of this type of strain sensors can be tuned over a relatively wide range of values by adjusting the deposition parameters. What’s more, the layered composite films are more durable compared with the fragile pure graphene films. In addition the main mechanisms are investigated, resulting in theoretical models which predict very well the observed behavior.