The somatosensory system helps the human body to become aware of various stimuli and to interact with its surroundings. Humans are able to identify and to process abundant sensory information quickly ...due to their unique perception characteristics. As the largest sensory organ, skin has a large number of discrete receptors to sense and to transform stimuli of touch, pressure, pain, temperature, etc. into electrical signals, which are preprocessed at various levels before reaching the brain, greatly reducing the computational burden on the central nervous system. In addition, the conduction speed varies for different stimulus information, which simplifies the parallel processing of a variety of information. In this Perspective, we discuss a bioinspired design for a flexible smart sensor system by simulating the human somatosensory system. In this design, sensors with selective responses, signals separated in time sequences, and hierarchical information processing are adopted to optimize the sensing and perceiving processes, to reduce power consumption, and to improve the speed of a flexible smart sensor system.
Textile triboelectric nanogenerator (TENG) is a kind of smart textile technology that integrates traditional flexible and wearable textile materials with emerging and advanced TENG science, which not ...only embraces the capabilities of autonomous energy harvesting and active self-powered sensing, but also maintains original wearability and desired comfortability. With the help of the burden-free and self-sufficient wearable intelligent system, individuals can achieve convenient acquisition and efficient utilization of electric energy, which will help to promote the future development of human-oriented on-body electronics and artificial intelligence. Here, some fundamental knowledge and core elements, including the operational modes and corresponding service occasions, charge generation and transfer mechanisms, remaining challenges and potential solutions are comprehensively summarized and systematically discussed. Based on these analyses, a roadmap toward the scientific research and large-scale commercial application of textile TENGs in the next decade is highlighted at the end of the article. We believe that textile TENGs will become an indispensable part of daily clothing in the future, thus benefiting all humankind and human civilization.
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Physiological monitoring sensors have attracted increasing research interest due to their broad application potential in daily activities, sports performance and health status monitoring for next ...generation athletic/clinical technologies. Having high sensitivity and low power consumption are essential to realize these applications in advanced portable/remote forms. In this work, triboelectric nanogenerators (TENGs), which are based on expandable microspheres in a polydimethylsiloxane (PDMS) mixture, were constructed as self-powered pressure sensors with ultrahigh sensitivity for biological signal monitoring through a low-cost and simple processing technique. Different sensitivities can be obtained by adjusting the weight percentage of microspheres in the PDMS, and the output voltage of the sensor was analyzed by a theoretical model, which was consistent with the simulation results. The maximum sensitivity of the sensor can reach 150 mV/Pa so respiratory and pulse monitoring can be implemented by attaching the ultrasensitive pressure sensor to the chest and wrist of a human body, respectively.
Ultrasensitive pressure sensors based on triboelectric nanogenerator (TENG) is constructed with the mixture of expandable microspheres and polydimethylsiloxane (PDMS). The microspheres expanded after heating and microstructure forms on the triboelectrification layer’s surface. The sensitivity of the sensor can be tuned by adjusting the weight percentage of microspheres in PDMS. Subtle biological signals monitoring, including respiration and pulse, are demonstrated by attaching the flexible pressure sensor onto the chest and wrist of the human body, respectively. Display omitted
•Self-powered pressure sensors with tunable sensitivity are fabricated through a very simple and low-cost processing.•A sensitivity of 150 mV/Pa is achieved in the pressure sensor, which is the highest sensitivity realized by TENG-based pressure sensors.•Respiration and pulse monitoring are demonstrated by attaching the flexible pressure sensor onto the human body.
Single‐electrode triboelectric nanogenerators (SETENGs) significantly expand the application of triboelectric nanogenerators in various circumstances, such as touch‐pad technologies. In this work, a ...theoretical model of SETENGs is presented with in‐depth interpretation and analysis of their working principle. Electrostatic shield effect from the primary electrode is the main consideration in the design of such SETENGs. On the basis of this analysis, the impacts of two important structural parameters, that is, the electrode gap distance and the area size, on the output performance are theoretically investigated. An optimized electrode gap distance and an optimized area size are observed to provide a maximum transit output power. Parallel connection of multiple SETENGs with micro‐scale size and relatively larger spacing should be utilized as the scaling‐up strategy. The discussion of the basic working principle and the influence of structural parameters on the whole performance of the device can serve as an important guidance for rational design of the device structure towards the optimum output in specific applications.
A comprehensive theoretical model is developed for single‐electrode triboelectric nanogenerators. The real time output characteristics are calculated by different numerical calculation methods. A three‐capacitance equivalent circuit model is built to clarify the working principle of single‐electrode triboelectric nanogenerators. Finally, the impact of electrode gap distance and area size on the performance of the devices are investigated and strategies for the structural optimization are provided.
Chemical and biological sensors have attracted great interest due to their importance in applications of healthcare, food quality monitoring, environmental monitoring, etc. Carbon nanotube ...(CNT)-based field-effect transistors (FETs) are novel sensing device configurations and are very promising for their potential to drive many technological advancements in this field due to the extraordinary electrical properties of CNTs. This review focuses on the implementation of CNT-based FETs (CNTFETs) in chemical and biological sensors. It begins with the introduction of properties, and surface functionalization of CNTs for sensing. Then, configurations and sensing mechanisms for CNT FETs are introduced. Next, recent progresses of CNTFET-based chemical sensors, and biological sensors are summarized. Finally, we end the review with an overview about the current application status and the remaining challenges for the CNTFET-based chemical and biological sensors.
We introduce an innovative design of a disk triboelectric nanogenerator (TENG) with segmental structures for harvesting rotational mechanical energy. Based on a cyclic in-plane charge separation ...between the segments that have distinct triboelectric polarities, the disk TENG generates electricity with unique characteristics, which have been studied by conjunction of experimental results with finite element calculations. The role played by the segmentation number is studied for maximizing output. A distinct relationship between the rotation speed and the electrical output has been thoroughly investigated, which not only shows power enhancement at high speed but also illuminates its potential application as a self-powered angular speed sensor. Owing to the nonintermittent and ultrafast rotation-induced charge transfer, the disk TENG has been demonstrated as an efficient power source for instantaneously or even continuously driving electronic devices and/or charging an energy storage unit. This work presents a novel working mode of TENGs and opens up many potential applications of nanogenerators for harvesting even large-scale energy.
An unstable mechanical structure that can self-balance when perturbed is a superior choice for vibration energy harvesting and vibration detection. In this work, a suspended 3D spiral structure is ...integrated with a triboelectric nanogenerator (TENG) for energy harvesting and sensor applications. The newly designed vertical contact–separation mode TENG has a wide working bandwidth of 30 Hz in low-frequency range with a maximum output power density of 2.76 W/m2 on a load of 6 MΩ. The position of an in-plane vibration source was identified by placing TENGs at multiple positions as multichannel, self-powered active sensors, and the location of the vibration source was determined with an error less than 6%. The magnitude of the vibration is also measured by the output voltage and current signal of the TENG. By integrating the TENG inside a buoy ball, wave energy harvesting at water surface has been demonstrated and used for lighting illumination light, which shows great potential applications in marine science and environmental/infrastructure monitoring.
Harvesting thermoelectric energy mainly relies on the Seebeck effect that utilizes a temperature difference between two ends of the device for driving the diffusion of charge carriers. However, in an ...environment that the temperature is spatially uniform without a gradient, the pyroelectric effect has to be the choice, which is based on the spontaneous polarization in certain anisotropic solids due to a time-dependent temperature variation. Using this effect, we experimentally demonstrate the first application of pyroelectric ZnO nanowire arrays for converting heat energy into electricity. The coupling of the pyroelectric and semiconducting properties in ZnO creates a polarization electric field and charge separation along the ZnO nanowire as a result of the time-dependent change in temperature. The fabricated nanogenerator has a good stability, and the characteristic coefficient of heat flow conversion into electricity is estimated to be ∼0.05–0.08 Vm2/W. Our study has the potential of using pyroelectric nanowires to convert wasted energy into electricity for powering nanodevices.
We demonstrate the first self-powered system driven by a nanogenerator (NG) that works wirelessly and independently for long-distance data transmission. The NG was made of a free cantilever beam that ...consisted of a five-layer structure: a flexible polymer substrate, ZnO nanowire textured films on its top and bottom surfaces, and electrodes on the surfaces. When it was strained to 0.12% at a strain rate of 3.56% S–1, the measured output voltage reached 10 V, and the output current exceeded 0.6 μA (corresponding power density 10 mW/cm3). A system was built up by integrating a NG, rectification circuit, capacitor for energy storage, sensor, and RF data transmitter. Wireless signals sent out by the system were detected by a commercial radio at a distance of 5–10 m. This study proves the feasibility of using ZnO nanowire NGs for building self-powered systems, and its potential application in wireless biosensing, environmental/infrastructure monitoring, sensor networks, personal electronics, and even national security.
We present a simple, cost-effective, robust, and scalable approach for fabricating a nanogenerator that gives an output power strong enough to continuously drive a commercial liquid crystal display. ...Utilizing the conical shape of the as-grown ZnO nanowires, a nanogenerator is fabricated by simply dispersing them onto a flat polymer film to form a rational “composite” structure. It is suggested that the geometry induced unipolar assembly of the conical nanowires in such a composite structure results in a macroscopic piezoelectric potential across its thickness by introducing a mechanical deformation, which may be responsible for driving the flow of the inductive charges between the top and bottom electrodes. A compressive strain of 0.11% at a straining rate of 3.67% s−1 produces an output voltage up to 2 V (equivalent open circuit voltage of 3.3 V). This is a practical and versatile technology with the potential for powering small size personal electronics.
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