All-in-one 3D acceleration sensor based on coded liquid–metal triboelectric nanogenerator for vehicle restraint system

Vehicle restraint systems play an irreplaceable role to limit passenger injuries when an accident occurs, in which, the 3D acceleration sensor (AS) is an essential component to detect the collision position and force. However, there are some defects for commercial sensors such as passive sensing, low sensitivity and high manufacturing cost. Here, we report a lightweight, high-sensitivity, low-cost and self-powered 3D AS based on a liquid–metal triboelectric nanogenerator (LM-TENG). In view of the coded strategy of the electrodes, the 3D AS retains the smallest size, lowest weight and highest integration compared to the currently reported self-powered AS. The fabricated sensor possesses wide detection range from 0 to 100 m/s² in the horizontal direction and 0 to 50 m/s² in the vertical direction at a sensitivity of 800 mV/g. The open-circuit voltage shows a negligible decrease after continuously operating for 100,000 times, showing excellent stability and durability. Furthermore, the 3D AS is demonstrated as a part of the airbag system to spot the collision position and force of the car simultaneously. This work will further promote the commercialization of TENG-based sensor and exhibits a prospective application in the vehicle restraint system.     

纸基碳纳米管薄膜/叉指结构的超灵敏宽量程压力传感器（英文）

柔性压力传感器因其在可穿戴设备和人机交互界面中的潜在应用而备受关注.特别是在实际应用中,人们对具有高灵敏度、宽测量范围和低成本的压力传感器有很大需求.基于此,我们研制出了一种测量范围宽的超灵敏压力传感器.该传感器是以碳纳米管(CNT)均匀溶液直接喷在纸表面作为敏感材料,用光刻技术制成的叉指电极为结构.由于CNT大的比表面积、纸的多孔结构以及CNT与叉指电极有效接触的协同作用,压力传感器实现了从0到140 kPa的宽测量范围,并在15,000个测试周期内表现出良好的稳定性.对于纸基碳纳米管薄膜/叉指状结构(PCI)压力传感器,敏感材料与叉指电极之间的连接区域在较小的压力范围内占主导地位,而敏感材料的内部变化在大的压力区域起主导作用.此外PCI压力传感器不仅具有2.72 kPa-1(直到35 kPa)的高灵敏度,还可以检测小重量,如一颗绿豆(约8 Pa).当压力传感器贴附到人体表面时,可以监测生理信号,如手腕运动、脉搏跳动和语音识别.此外,压力传感器的阵列能够识别空间压力分布,有望实际应用于人机交互界面.     

A self-powered temperature-sensitive electronic-skin based on tribotronic effect of PDMS/PANI nanostructures

A new self-powered temperature-sensitive electronic-skin (e-skin) for real-time monitoring body temperature without external electricity power was fabricated from patterned polydimethylsiloxane/polyaniline (PDMS/PANI) nanostructures. The e-skin can be feasibly attached on the human body and driven by the mechanical motion energy through triboelectric effect. The outputting triboelectric impulse of the PDMS/PANI units is significantly dependent on the local surface temperature of the e-skin, serving as both the power source and temperature sensing signal. The outputting current of the e-skin increases with increasing surface temperature of the device. Under applied bending deformation, the response of the e-skin is up to 63.6 for 38.6 °C. The e-skin can detect minimum temperature change of 0.4 °C. The working mechanism can be ascribed to the coupling effect of triboelectric and semiconductor properties (tribotronic effect). A practical application of the e-skin attaching on the human body for detecting the body temperature range of 36.5–42.0 °C has been simply demonstrated. This work provides a viable method for real-time monitoring body temperature, and can promote the development of wearable temperature sensors and self-powered multifunctional nanosystems.     

Large‐Area Integrated Triboelectric Sensor Array for Wireless Static and Dynamic Pressure Detection and Mapping

Large‐area flexible pressure sensors are of paramount importance for various future applications, such as electronic skin, human–machine interfacing, and health‐monitoring devices. Here, a self‐powered and large‐area integrated triboelectric sensor array (ITSA) based on coupling a triboelectric sensor array and an array chip of CD4066 through a traditional connection is reported. Enabled by a simple and cost‐effective fabrication process, the size of the ITSA can be scaled up to 38 × 38 cm². In addition, unlike previously proposed triboelectric sensors arrays, which can only react to the dynamic interaction, this ITSA is able to detect static and dynamic pressure. Moreover, through integrating the ITSA with a signal processing circuit, a complete wireless sensing system is present. Diverse applications of the system are demonstrated in detail, including detecting pressure, identifying position, tracking trajectory, and recognizing the profile of external contact objects. Thus, the ITSA in this work opens a new route in the direction of large‐area, self‐powered, and wireless triboelectric sensing systems.     

3D double-faced interlock fabric triboelectric nanogenerator for bio-motion energy harvesting and as self-powered stretching and 3D tactile sensors

Combining triboelectric nanogenerator (TENG) and textile materials, wearable electronic devices show great application prospects in biomotion energy harvesting and multifunctional self-power sensors in this coming intelligent era. However, fabrication method by rigidly stitching two or more individual fabrics together and working mode that must cooperate with external materials, make textile-based TENG bulky, stiff, uncomfortable and hinder their range of application. Here, by using a double needle bed flat knitting machine technology, a 3D double faced interlock fabric TENG (3DFIF-TENG) is designed as self-powered, stretchable and substrate-free wearable TENG sensors (such as a bending sensor to detect arm bending degree, pressure sensors) and energy harvesting devices. Besides, due to the unique 3D structure and after improving the structure by knitting a woven fabric-TENG in the middle layer, the 3DFIF-TENG can be further used as a multifunctional sensors, such as a 3D tactile sensor. Besides, by knitting a woven fabric-TENG in the middle layer of the 3DFIF-TENG, it can be further used as a multifunctional sensor, such as a 3D tactile sensor. The substrate-free and 3D structure design in this paper may provide a promising direction for self-powered, stretchable wearable devices in energy harvesting, human motion or robot movement detection, and smart prosthetics.     

Electrohydrodynamic (EHD) inkjet printing flexible pressure sensors with a multilayer structure and periodically patterned Ag nanoparticles

Flexible pressure sensors are widely employed for accurate pressure sensing on geometrically complex surfaces. As sensing materials, silver nanoparticles (AgNPs) have high electrical conductivity but relatively poor sensitivity as a trade-off. In this work, electrohydrodynamic (EHD) inkjet printing was utilized to directly write patterns of AgNPs tracks with periodic geometries on the flex-substrate surface. The patterns in which the as-printed AgNPs tracks, with a width of several tens of micrometres, exhibited a piezoresistive effect. This work confirmed that introducing multilayered structures into the flexible pressure sensors with AgNPs patterns was a practical path to improve the sensing sensitivity, with the assistance of soft packaging material of Polydimethylsiloxane (PDMS). The sensitivity was improved more than tenfold after fourfold overlapping of the as-printed single-layer sensor. Experimental tests, formula calculations, and numerical simulations of the sensors were conducted. It was concluded that the as-printed single-layer sensor with the AgNPs pattern of concave regular hexagonal structure (CRHTS) had better sensing performance than that of grid-type structure (GTS) or wave-type structure (WTS). For the two-layered CRHTS sensor, the dynamic and quasi-static sensing response characteristics, response recovery duration, cyclic stability, and ability to discriminate different strain frequencies were further measured and analysed. The working principle of the flex sensors was discussed based on the Percolation Theory and the Tunneling Effect. Some application demonstrations of the sensors were also exhibited. The structural design and EHD inkjet printing fabrication path facilitate the development of more versatile flex sensors.

     

Transparent triboelectric nanogenerators and self-powered pressure sensors based on micropatterned plastic films

Transparent, flexible and high efficient power sources are important components of organic electronic and optoelectronic devices. In this work, based on the principle of the previously demonstrated triboelectric generator, we demonstrate a new high-output, flexible and transparent nanogenerator by using transparent polymer materials. We have fabricated three types of regular and uniform polymer patterned arrays (line, cube, and pyramid) to improve the efficiency of the nanogenerator. The power generation of the pyramid-featured device far surpassed that exhibited by the unstructured films and gave an output voltage of up to 18 V at a current density of ～0.13 μA/cm(2). Furthermore, the as-prepared nanogenerator can be applied as a self-powered pressure sensor for sensing a water droplet (8 mg, ～3.6 Pa in contact pressure) and a falling feather (20 mg, ～0.4 Pa in contact pressure) with a low-end detection limit of ～13 mPa.     

Fatigue Resistant Aerogel/Hydrogel Nanostructured Hybrid for Highly Sensitive and Ultrabroad Pressure Sensing

Achieving high sensitivity over a broad pressure range remains a great challenge in designing piezoresistive pressure sensors due to the irreconcilable requirements in structural deformability against extremely high pressures and piezoresistive sensitivity to very low pressures. This work proposes a hybrid aerogel/hydrogel sensor by integrating a nanotube structured polypyrrole aerogel with a polyacrylamide (PAAm) hydrogel. The aerogel is composed of durable twined polypyrrole nanotubes fabricated through a sacrificial templating approach. Its electromechanical performance can be regulated by controlling the thickness of the tube shell. A thicker shell enhances the charge mobility between tube walls and thus expedites current responses, making it highly sensitive in detecting low pressure. Moreover, a nucleotide-doped PAAm hydrogel with a reversible noncovalent interaction network is harnessed as the flexible substrate to assemble the aerogel/hydrogel hybrid sensor and overcome sensing saturation under extreme pressures. This highly stretchable and self-healable hybrid polymer sensor exhibits linear response with high sensitivity (S_min > 1.1 kPa^?1), ultrabroad sensing range (0.12–≈400 kPa), and stable sensing performance over 10 000 cycles at the pressure of 150 kPa, making it an ideal sensing device to monitor pressures from human physiological signals to significant stress exerted by vehicles.     

Ultrasensitive Strain Sensor Based on Separation of Overlapped Carbon Nanotubes

Although there have been remarkable improvements in stretchable strain sensors, the development of strain sensors with scalable fabrication techniques and which both high sensitivity and stretchability simultaneously is still challenging. In this work, a stretchable strain sensor based on overlapped carbon nanotube (CNT) bundles coupled with a silicone elastomer is presented. The strain sensor with overlapped CNTs is prepared by synthesizing line‐patterned vertically aligned CNT bundles and rolling and transferring them to the silicone elastomer. With the sliding and disconnection of the overlapped CNTs, the strain sensor performs excellently with a broad sensing range (≥145% strain), ultrahigh sensitivity (gauge factor of 42 300 at a strain of 125–145%), high repeatability, and durability. The performance of the sensor is also tunable by controlling the overlapped area of CNT bundles. Detailed mechanisms of the sensor and its applications in human motion detection are also further investigated. With the novel structure and mechanism, the sensor can detect a wide range of strains with high sensitivity, demonstrating the potential for numerous applications including wearable healthcare devices.     

Highly Sensitive and Stretchable Resistive Strain Sensors Based on Microstructured Metal Nanowire/Elastomer Composite Films

High sensitivity and high stretchability are two conflicting characteristics that are difficult to achieve simultaneously in elastic strain sensors. A highly sensitive and stretchable strain sensor comprising a microstructured metal nanowire (mNW)/elastomer composite film is presented. The surface structure is easily prepared by combining an mNW coating and soft‐lithographic replication processes in a simple and reproducible manner. The densely packed microprism‐array architecture of the composite film leads to a large morphological change in the mNW percolation network by efficiently concentrating the strain in the valley regions upon stretching. Meanwhile, the percolation network comprising mNWs with a high aspect ratio is stable enough to prevent electrical failure, even under high strains. This enables the sensor to simultaneously satisfy high sensitivity (gauge factor ≈81 at >130% strain) and high stretchability (150%) while ensuring long‐term reliability (10 000 cycles at 150% strain). The sensor can also detect strain induced by bending and pressure, thus demonstrating its potential as a versatile sensing tool. The sensor is successfully utilized to monitor a wide range of human motions in real time. Furthermore, the unique sensing mechanism is easily extended to detect more complex multiaxial strains by optimizing the surface morphology of the device.     

Fiber loop ringdown for physical sensor development: pressure sensor

A new method of developing optical fiber pressure sensors by use of a fiber loop ringdown scheme is described. The fiber loop ringdown system is characterized in terms of the ringdown baseline stability, fiber transmission loss, and fiber refractive index. The overall sensor performance is demonstrated by use of sensing forces applied to the sensor head. The current device can sense pressures in the range of 0 to 9.8 x 10(6) Pa, converted approximately from the applied forces. The sensor's linear response, repeatability, detection sensitivity, measuring dynamic range, and temperature tolerance are explored.     

Emerging MXene-Based Flexible Tactile Sensors for Health Monitoring and Haptic Perception

Due to their potential applications in physiological monitoring, diagnosis, human prosthetics, haptic perception, and human–machine interaction, flexible tactile sensors have attracted wide research interest in recent years. Thanks to the advances in material engineering, high performance flexible tactile sensors have been obtained. Among the representative pressure sensing materials, 2D layered nanomaterials have many properties that are superior to those of bulk nanomaterials and are more suitable for high performance flexible sensors. As a class of 2D inorganic compounds in materials science, MXene has excellent electrical, mechanical, and biological compatibility. MXene-based composites have proven to be promising candidates for flexible tactile sensors due to their excellent stretchability and metallic conductivity. Therefore, great efforts have been devoted to the development of MXene-based composites for flexible sensor applications. In this paper, the controllable preparation and characterization of MXene are introduced. Then, the recent progresses on fabrication strategies, operating mechanisms, and device performance of MXene composite-based flexible tactile sensors, including flexible piezoresistive sensors, capacitive sensors, piezoelectric sensors, triboelectric sensors are reviewed. After that, the applications of MXene material-based flexible electronics in human motion monitoring, healthcare, prosthetics, and artificial intelligence are discussed. Finally, the challenges and perspectives for MXene-based tactile sensors are summarized.     

PVDF冲击压力传感器的制备和应用

PVDF（聚偏氟乙烯）及其共聚物压电计具有响应快、灵敏度高、测压范围宽等特点，是一种理想的冲击压力传感器。用它制作超高压力传感器的关键是必须解决传感器的一致性问题。本文对近年来国内外在此方面的工作进行了总结，给出了该类传感器的爆炸、高速撞击、高能脉冲激光辐照等压力测试方面的应用，并对该类传感器中存在的问题进行了归纳。     

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.     

Energy extraction for a self-energized pressure sensor

With the prolific use of sensors for manufacturing process monitoring, proper power supply and installation scheme has assumed an increasingly central role. Cable-based sensor powering, while commonly used on the factory floor, faces various real-world constraints. It is desirable that the power required by the sensors be "extracted" from the process being monitored itself to enable "self-energized" sensing. Such a novel design for a wireless pressure sensor for injection molding process monitoring is presented in this paper. The focus is on the energy extraction mechanism from the pressure transients exerted by the polymer melt during the injection molding process to power a piezoelectric signal transmitter, which digitally reconstructs the polymer melt pressure profile. An analytical model examining the energy conversion mechanism due to interactions between the mechanical strain and the electric field developed within the energy extraction device is first established. Using a coupled-field analysis, a numerical model is then developed to evaluate the electromechanical properties dependent upon the geometric effects of the energy extraction device. The two models are then compared with experimental results obtained from a functional prototype to evaluate the relevance of the assumptions made and the modeling accuracy. Preliminary experimental results describing the integration of the energy extraction device with the ultrasonic transmitter and the subsequent transmission of pressure information acoustically through a block of steel are also presented. The presented design introduces a new generation of self-energized sensors that can be employed for the condition monitoring of a wide range of high-energy manufacturing processes.     

Inhibition and activation of glucose oxidase bioanodes for use in a self-powered EDTA sensor

Self-powered sensors are able to automatically signal the presence of a specific analyte without the aid of an external power source, making them useful as potential devices for batteryless sensing. Here, we present a self-powered enzymatic ethylenediaminetetraacetic acid (EDTA) sensor based on the inhibition and subsequent activation of glucose oxidase (GOx)-based bioelectrodes within the framework of a biofuel cell. Although EDTA is not redox-active, it is detected by the activation of a Cu(2+)-inhibited GOx bioanode in either a typical amperometric sensor (using a standard three-electrode setup) or in a self-powered sensor where the GOx bioanode is coupled to a platinum cathode. The sensors are able to detect concentrations of EDTA that correspond to the amount of Cu(2+) that is used to inhibit the enzymatic electrode. The self-powered sensor shows a greater than 10-fold increase in power output when it is activated by the presence of EDTA. This represents the first time that a non-redox-active analyte has been detected in a self-powered sensor that turns on in the presence of said analyte.     

Analysis according to the change in structure of ultrasonic sensors and the change in pressure inside the tank for measurement of fuel amounts in compressed natural gas (CNG) tank

The present study is a fundamental research for precise measurement of fuel amounts in a compressed natural gas (CNG) tank where an analysis of receiving sensitivity was conducted as a result of changes in the contact surface shape in the number of piezoelectric element of the ultrasonic sensor as well as in the internal pressure of the tank. Experiments were conducted as a function of changes in the contact surface shape between the ultrasonic sensor and outside of the aluminum tank and in the number of piezoelectric element as well as in the internal pressure of the tank. According to the experimental results, it could be confirmed that the maximum receiving sensitivity value was increased by about 60 % when the contact surface shape of the transmission and receiving ultrasonic sensors compared with the ultrasonic sensor in the Line-Line shape selected as the reference model was changed to the surface. As a whole, the highest receiving sensitivity values were observed when the transmission sensor of surface shape produced as multiple piezoelectric elements and the receiving sensor of surface shape produced as a single piezoelectric element were used. It could be confirmed that receiving sensitivities were improved at the same voltage value as a result of changes in the contact surface shape of the ultrasonic sensor and in the number of piezoelectric elements.     

Harvesting energy from extreme environmental conditions with cellulosic triboelectric materials

Triboelectric nanogenerators (TENGs), as a new energy conversion device in self-powered sensing devices, have been used at extreme environmental conditions, which poses great challenges to the structural stability and chemical tolerance of triboelectric materials. However, the low tolerance characteristics of traditional triboelectric materials limit their expansion in emerging applications. Cellulose, with its unique multidimensional structure and, controlled surface chemistry regulation advantages, shows great potential in resisting extreme environmental conditions and is emerging as a new candidate. This review aims to design and fabricate cellulosic triboelectric materials with exceptional tolerance, providing a perspective on the emerging applications of TENGs at extreme environmental conditions. First, the performance advantages and design principles of action of cellulosic triboelectric materials at extreme environmental conditions are described. Second, the importance of physical and chemical regulation strategies is discussed through the multi-scale perspective from macroscopic fiber bundles to microscopic cellulose molecules. It also presents the latest applications of cellulosic triboelectric materials at extreme environmental conditions such as wide temperature, high humidity, high corrosion, and radiation. Finally, the idea of how cellulosic triboelectric materials can further expand the development of TENGs application areas is presented.     

Nanocellulose intercalation to boost the performance of MXene pressure sensor for human interactive monitoring

The advent of smart and wearable electronics endows flexible pressure sensors with promising potentiality. Ti₃C₂T_x-based MXene is considered as one of attractive sensing materials for its metallic conductivity and adjustable interlayer. However, existing flexible MXene pressure sensor still requires a technical breakthrough that simultaneously possessing high sensitivity, fast response, and durability in low-pressure regime and excellent mechanical strength. Herein, a Ti₃C₂T_x-based pressure sensor with distinctly enhanced sensing functionality and mechanical strength is demonstrated though inserting high-strength of bacterial cellulose nanofibers to control the interlayer of MXene. By optimizing the bacterial cellulose content and MXene interlayer space, the resultant sensor device exhibits high mechanical strength (225 MPa), wide-sensing range with low detective limit (0.4 Pa), high sensitivity (up to 95.2 kPa^?1, in < 50 Pa region), fast response (95 ms) and outperformed repeatability (25,000 cycles), as well as low operation voltage of 0.1 V. For practical application demos, the sensor can monitor multiple human biologic activities, including subtle pressures (e.g., swallow, heartbeat and pulse), acoustic vibrations and gesture motions, and serve as electronic skin for mapping pressure distribution, elucidating the potential application in medical diagnosis, smart robotics and human-machine interfacing.

     

Transparent paper-based triboelectric nanogenerator as a page mark and anti-theft sensor

The triboelectric nanogenerator （TENG）, based on the well-known triboelectric effect and electrostatic induction effect, has been proven to be a simple, cost effective approach for self-powered systems to convert ambient mechanical energy into electricity. We report a flexible and transparent paper-based triboelectric nanogenerator （PTENG） consisting of an indium tin oxide （ITO） film and a polyethylene terephthalate （PET） film as the triboelectric surfaces, which not only acts as an energy supply but also as a self-powered active sensor. It can harvest kinetic energy when the sheets of paper come into contact, bend or slide relative to one another by a combination of vertical contact-separation mode and lateral sliding mode. In addition, we also integrate grating-structured PTENGs into a book as a self-powered anti-theft sensor. The mechanical agitation during handling the book pages can be effectively converted into an electrical output to either drive a commercial electronic device or trigger a warning buzzer. Furthermore, different grating-structures on each page produce different numbers of output peaks by sliding relative to one another, which can accurately act as a page mark and record the number of pages turned. This work is a significant step forward in self-powered paper-based devices.