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Electromagnetic vibration energy harvesters are promising for the power supply of wireless sensor nodes, small electronic devices, and wearable electronics. Conventional electromagnetic harvesters usually increase output by increasing the size of coils and magnets, limiting the improvement of energy conversion efficiency and power density. In this study, multilayer microelectromechanical system (MEMS) coils were prepared using flexible electronics, and their high integration performance in arbitrary space was utilized to greatly improve the utilization of the space magnetic field by the electromagnetic harvester. The core magnet of the generator was magnetically balanced to achieve levitation, which improved the sensitivity and reduced fatigue damage compared with traditional spring structures. The wound coils on the top and bottom of the magnet and the flexible coils on the sides worked together to improve the energy efficiency and output of the devices. The output performance of the device with different number distributions was simulated using mathematical models to obtain the optimal structural parameters. The results show that by introducing flexible multilayer MEMS coils on the side surface of the energy harvester, the open-circuit voltage of the energy generators increased from 7 to 10 V by more than 43%. Flexible multilayer MEMS coils can enhance energy conversion rates and possess compact dimensions, making them suitable for integration onto complex surfaces. After the vibration energy harvesting system testing, the maximum peak power of the harvester was 7.1 mW at an acceleration of 1 gand a resonant frequency of 11 Hz with a resistor of 3.5 internal resistance. Moreover, a 470 µF capacitor can be charged to 3.5 V within 10 s to drive a hygrothermograph to work for more than 80 s and can supply a light bulb continuously. This strategy shows the great potential of vibration-energy-driven electromagnetic generators for powering small electronics in limited spaces.

Harvesting low-frequency vibration energy in the environment can provide electrical energy for mobile electronic devices. In this article, a bidirectional driving vibration energy harvester is presented based on the electromagnetic induction. The bidirectional driving component of the energy harvester converts the reciprocating linear motion driving energy into the unidirectional rotation. In addition, the two sets of generators are rectified first, and then connected in series to reduce the voltage rang, which is conducive to energy management and storage, and reduces energy loss. The results show that its average output power is 53.28 mW when the acceleration is 9 m/s2. At a running speed of 8 km/h, the average output power of the energy harvester installed on the human torso is 41.07 mW. At the same time, it can provide real-time energy supply for temperature hygrometer, calculator, and Bluetooth module. It is a novel method for the harvest and utilization of vibration energy, and has great significance for solving the current energy long-term demand of electronic devices.

The flexoelectricity polarization of nanoscale dimensions has a natural advantage in realizing highly sensitive pressure sensors in 2-D. Furthermore, as typical 2-D material materials, graphene was often combined for pressure sensors. As the result of a high dielectric constant, Pb(Zr $_{{0}.{52}}$ Ti0.48)O3(PZT) nanofilm could produce large surface polarization potential when subjected to external weak force. Then, fermi-level graphene on the surface of PZT film can be regulated by polarization electric field, which weak pressure signals’ sensor. We report on a novel graphene-based PZT pressure sensor with high sensitivity, fast response time, and weak pressure signals based on the flexoelectricity enhancement effect. The simulation of the graphene/PZT composite structure by COMSOL multiphysics and MATLAB indicates that the strain gradient of the PZT film is as high as $10^{{5}}$ . Combining the high flexoelectricity coeffcient of PZT with outstanding carrier transport of graphene, graphene-based PZT pressure sensor except high sensor expects exhibition highly sensitive, with an average sensitivity of 0.01 kPa $^{-{1}}$ , a faster response time as 0.06 s, and signal to noise ratio (SNR) is 61.9 dB in the range of pressure from 0.098 to 9.8 kPa. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity. This graphene/PZT-based pressure sensor will have great potentials for highly sensitive weak pressure signal detection.

In our daily lives, low-frequency kinetic energy primarily manifests as vibrations. However, effective harnessing of low-frequency kinetic energy remains a formidable challenge. This paper proposes a rope-driven rotor that rotates around an axis and consists of an ultra-high-molecular-weight polyethylene (UHMWPE) wire wrapped around a metal shaft. The rotor can convert ultra-low frequency vibration/linear motion into rapid rotation by pressing the top at low frequencies and driving the rope for a quick release. The harvester can generate up to 36.25 mW power using a 0.1-mm-diameter UHMWPE wire as the rotor when periodically pressed down to 20 mm at a frequency of 1 Hz. A simple power generation floor is assembled, generating 28.58-mW power with a matching load at a frequency of 1.5 Hz. Moreover, the harvester can increase the charging voltage of a 0.47-F supercapacitor from 0 to 6.8 V within 10 min. In addition, the harvester can harvest energy through a light finger press motion, and the energy obtained can also support the continuous operation of multiple electronic devices concurrently. This study introduces an effective method for harvesting ultra-low frequency energy and has great prospects in the field of power generation floor and human movement energy harvesting.

Harvesting energy from human movement and converting it into electricity is a promising method to address the issue of sustainable power supply for wearable electronic devices. Using traditional energy harvesters for practical applications is difficult due to their low output power. In this paper, an energy harvester with high power and efficiency is reported based on the principle of electromagnetic induction. It adopts a tiny compound mechanism comprising symmetrical lever-sector gear, which can amplify the vertical displacement of the human heel of 1.44 times without affecting the flexibility and comfort of human movement. The lever-sector gear and gear acceleration mechanism can achieve high output power from the tiny vertical movements of the heel. The results demonstrated that the average power and energy harvesting efficiency of the device are 1 W and 63%, respectively. Moreover, combining a novel controllable electric switch and energy management circuit allows the energy harvester to be worn by individuals with different weights and functions as a continuous real-time power supply for various electronic devices (mobile phones, smartwatches, etc.). Therefore, this research provides a new approach for the highly efficient harvesting of human motion energy and sustainable power supply of wearable electronics.

Heterovalent doped (K0.48-0.07xNa0.52-0.43xBi0.5x)(Nb0.95-0.95xSb0.05-0.05xZrx)O3ceramics were fabricated using conventional solid-state reaction. Then, the phase structures, dielectric, ferroelectric, and electric-strain properties were investigated. The compositions were tuned to be located at polymorphic phase boundary with increasing heterovalent Bi3+and Zr4+doping levels. A large strain of 0.19% was obtained at relatively low electric fields of 30 kV/cm in the composition of x = 0.04. The normalized large-signal d33∗ values were approximately 633 pm/V under a low driving electric field of 30 kV/cm, which were comparable or larger than the values reported for other lead-free families. The large strains obtained can be attributed to the formation of nanodomains and high-density domain walls, which were confirmed by the observations of domain morphology using transmission electron microscopy (TEM) technique. Excellent temperature stability of the strain properties of the x = 0.04 sample could be ascribed to the sluggish behaviour for the local structural heterogeneity in heterovalent-ion doped KNN ceramic. Theoretical simulations revealed that the Zr4+produce the local stress at the BO6octahedra and Bi3+could yield off-centering of AO12ployhedron due to the nature of Bi 6slone pair electrons, which induced lattice expansion and local distortions in the sample. The local displacements are strongly anisotropic in heterovalent-ion doped system. It is believed that random local fields exist in these compositions owing to the eixstence of charge distribution. Such heterovalent doping of Bi3+and Zr4+could destory simultaneously the orthorhombic symmetry and the short-range ferroelecctric order, leading to the formation of complex nanodomains and local structral hetergenenity. Heterovalent doping may, therefore, offer a new avenve to design novel K0.5Na0.5NbO3(KNN) -based materials for their mutifunctional applications.

With the rapid development of microelectronics and flexible electronics technology, self-powered sensors have significant application prospects in human-machine interface systems and Internet of Things. However, piezoelectric- and triboelectric-based sensors have low current output and are easily affected, while electromagnetic-based sensors are difficult to miniaturize. This work proposes a high-density stacked microcoil integrated microminiaturized electromagnetic vibration energy harvester (EVEH). The double-layer high-density microcoil is fabricated on both sides of the flexible polyimide substrate interconnected via the central through-hole. Owing to reduced single coil line width, line spacing, and stacked structure, the number of turns can be substantially enhanced. Moreover, the relative position of the coils and magnet has a considerable influence on the performances; due to the huge change rate in magnetic flux when the coil is placed in the radial direction of the magnet than in the axial direction, the open-circuit voltage in the radial direction is 10 times greater. The microcoil can maintain good performance at high, low temperatures and under bending conditions. When the distance between the ends of the coil changes from 2 to 20 mm in 2 mm steps, the bending angle of the coil changes from 45° to 270° in 45° steps; furthermore, when the coil is exposed to −40 and 60°C conditions, the coil resistance is maintained at approximately 447 Ω. The peak open-circuit voltage of three-piece microcoils reaches 0.41 V at 4 Hz under 2g, and the output voltage and current increase with an increasing number of stacked layers. These excellent properties indicate that EVEH can be used for self-powered acceleration sensing. The sensitivity is measured to be 0.016 V/(m/s2) with a correlation coefficient of 0.979 over the acceleration range of 1–18 m/s2. Thus, the developed microminiaturized EVEH has enormous potential for self-powered sensing applications in confined spaces and harsh environments.

The ferroelectric diode is a promising candidate for memory, rectifier system, and logic devices. Conductive domain wall (CDW) is essential to ferroelectric diodes. A permanent CDW-based unipolar two-terminal ferroelectric diode-like cell with enhanced conductivity is demonstrated here. Through poling engineering on LiNbO3 ferroelectric single-crystal thin film, diode-like cells with much smaller size than conventional diode is created in significantly efficient way. Throughout 5880 h, the CDW has maintained consistent operation around $\mu \text{A}$ rather than pA. The ferroelectric diode-like cell is fatigue-resistant for 500 cycles and retains its conductivity for 2400 h. In addition, the conductivity of a diode-like cell has increased from 0.2 to $16 ~\mu \text{A}$ via charge injection and parallel connection of multiple cells. Finally, the “OR” logic gate is assembled using the cells. These ferroelectric cells can be used as a diode-like component in large-scale integrated circuits and have potential applications in nanoelectronic logic devices.

A single longitudinal mode (SLM) parity-time (PT) symmetric Brillouin fiber laser (BFL) based on z-cut lithium niobate phase modulator (LN-PM) Sagnac loop with Hz level linewidth is proposed and experimentally verified. A 10 km single-mode fiber provide SBS gain, while an LN-PM Sagnac loop consisting of an LN-PM and two polarization controllers (PCs) is used to achieve PT symmetry. Two mutually linked feedback loops supporting orthogonally polarized light are created by utilizing inherent birefringence of LN waveguide from LN-PM without electrical signal modulation. One of the feedback loops experiences gain in a clockwise direction and the other loss in a counterclockwise direction. The polarization state of the stokes injected into the LN-PM is controlled by adjusting the PC, and SLM BFL can be achieved when the gain and loss are well matched and exceed the coupling coefficient to break the PT symmetry. Compared with existing BFL studies, this design does not call for frequency matching of several composite cavity structures or precise control of ultra-narrow bandwidth bandpass filters. In addition, a frequency-locking system based on Pound-Drever-Hall technology is employed to lessen the instability and external disturbances brought on by the ring cavity. In the experiment, the linewidth of PT symmetry BFL based on LN-PM Sagnac loop is 3.85 Hz, according to the measured linewidth of 77 Hz at the −20 dB power point. A 65 dB optical signal-to-noise ratio and a 43 dB maximum side mode suppression ratio are measured. Furthermore, the PT symmetry BFL's wavelength is tuned between 1550 and 1550.41 nm.

Flexible pressure sensors have broad application prospects, such as human motion monitoring and personalized recognition. However, their applicability is limited by complex structures, low output performance, low sensitivity, and narrow measurement range. In this study, we report a single-electrode spongy triboelectric sensor (SSTS) mainly composed of spongy composite multi-walled carbon nanotubes/polydimethylsiloxane (MWCNT/PDMS) film and conductive fabric, which can simultaneously generate contact electrification and electrostatic induction coupling in a single-electrode contact-separation mode. The SSTS combines the triboelectric effect, properties of doping material, and spongy porous structure (soft sugar as a sacrificial template). An SSTS with an MWCNT content of 10 wt% and a porosity of 64% exhibits high sensitivity, a wide measurement range, and excellent linearity. It also displays two sensitivity regions (slopes): 1.324 V/kPa from 1.5 to 28 kPa in the low-pressure range and 0.096 V/kPa from 28 to 316.5 kPa in the high-pressure range, with linearities of 0.980 and 0.979, respectively. Furthermore, the SSTS delivers a high-performance output and high stability, thus enhancing the monitoring of hand pressure changes, human movement, personalized spatial recognition, and other detection tasks. This new strategy for human motion monitoring shows great potential in the healthcare fields, sports rehabilitation, and human-computer interactions.

The research on flexible pressure sensors has drawn widespread attention in recent years, especially in the fields of health care and intelligent robots. In practical applications, the sensitivity of sensors directly affects the precision and integrity of weak pressure signals. Here, a pressure sensor with high sensitivity and a wide measurement range composed of porous fiber paper and 3D patterned electrodes is proposed. Multi-walled carbon nanotubes with excellent conductivity were evenly sprayed on the fiber paper to form the natural spatial conducting networks, while the copper-deposited polydimethylsiloxane films with micro-pyramids array were used as electrodes and flexible substrates. Increased conducting paths between electrodes and fibers can be obtained when high-density micro-pyramids fall into the porous structures of the fiber paper under external pressure, thereby promoting the pressure sensor to show an ultra-high sensitivity of 17.65 kPa−1in the pressure range of 0–2 kPa, 16 times that of the device without patterned electrodes. Besides, the sensor retains a high sensitivity of 2.06 kPa−1in an ultra-wide measurement range of 150 kPa. Moreover, the sensor can detect various physiological signals, including pulse and voice, while attached to the human skin. This work provides a novel strategy to significantly improve the sensitivity and measurement range of flexible pressure sensors, as well as demonstrates attractive applications in physiological signal monitoring.

Ocean intelligent buoy is important for ocean environment monitoring. With the increase of requisite sensors and transportable data, a long power supply has become a problem to be solved urgently. In this work, a hybrid nanogenerator integrating triboelectric, piezoelectric, electromagnetic, photovoltaic, and thermotropic units is proposed to maximize ocean ambient energy harvesting, which includes static energy (solar and thermal energy) and dynamic energy (wave energy). Compared with a device with a single energy conversion mechanism, this structural design breaks the limit of harvesting time and natural conditions during the energy harvesting process, thereby increasing the harvested energy. Static energy harvesting is realized by the thermoelectric (TG) and photovoltaic (PV) units located inside the device and the PV unit attached to the device surface. Results show that the maximum open-circuit voltage and short-circuit current are 5 V and 41 mA in the external PV and 1.33 V and 49 mA in the internal PV under 30000 Lux illumination, respectively. The open-circuit voltage and short-circuit current of the TG unit are 5 V and 15 mA, respectively. The core component of the dynamic generation unit is the gimbal used to harvest wave energy by the triboelectric nanogenerator (TENG), piezoelectric generator (PENG), and electromagnetic generator. When the frequency is 2.4 Hz, the maximum peak-to-peak power of the TENG, PENG, and EMG are 0.25, 1.58, and 13.8 mW, respectively. Finally, an intelligent ocean buoy is fabricated by the integration of an energy harvester, a power management circuit, sensors, a microcontroller, and a wireless communication module. Driven by static and dynamic energy, temperature signal, humidity signal, GPS signal, and sound signal are sent to the receiving terminal wirelessly. The ocean energy harvester proposed in this work is of great significance for ocean energy harvesting and ocean wireless monitoring systems.

Effective collection, recognition, and analysis of sports information is the key to intelligent sports, which can help athletes to improve their skills and formulate scientific training plans and competition strategies. At present, wearable electronic devices used for movement monitoring still have some limitations, such as high cost and energy consumption, incompatibility of suitable flexibility and personalized spatial structure, dissatisfactory data analysis methods, etc. In this work, a novel three-dimensional-printed thermoplastic polyurethane is introduced as the elastic shell and friction layer, and it endows the proposed customizable and flexible triboelectric nanogenerator (CF-TENG) with personalized spatial structure and robust correlation to external pressure. In practical application, it exhibits highly sensitive responses to the joint-bending motion of the finger, wrist, or elbow. Furthermore, a pressure-sensing insole and smart ski pole based on CF-TENG are manufactured to build a comprehensive sports monitoring system to transmit the athletes’ motion information from feet and hands through the plantar pressure distribution and ski pole action. To recognize the movement status, the self-developed automatic peak recognition algorithm (P-Find) and machine learning algorithm (subspace K-Nearest Neighbors) were introduced to accurately distinguish the four typical motion behaviors and three primary sub-techniques of cross-country skiing, with accuracy rates of 98.2% and 100%. This work provides a novel strategy to promote the personalized applications of TENGs in intelligent sports.

Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces. Pressure sensors with high sensitivity, wide measurement range, and low-cost are now highly desired for such practical applications. In the present investigation, an ultrasensitive pressure sensor with wide measurement range has been successfully fabricated. Carbon nanotubes (CNTs) (uniformly sprayed on the surface of paper) comprise the sensitivity material, while lithographed interdigital electrodes comprise the substrate. Due to the synergistic effects of CNT’s high specific surface area, paper’s porous structure, interdigital electrodes’ efficient contact with CNT, our pressure sensor realizes a wide measurement range from 0 to 140 kPa and exhibits excellent stability through 15,000 cycles of testing. For the paper-based CNT film/interdigitated structure (PCI) pressure sensor, the connection area between the sensitive material and interdigital electrodes dominates in the low-pressure region, while internal change within the sensitive materials plays the leading role in the high-pressure region. Additionally, the PCI pressure sensor not only displays a high sensitivity of 2.72 kPa−1(up to 35 kPa) but also can detect low pressures, such as that exerted by a resting mung bean (about 8 Pa). When attached to the surface of a human body, the pressure sensor can monitor physiological signals, such as wrist movement, pulse beats, or movement of throat muscles. Furthermore, the pressure sensor array can identify the spatial pressure distribution, with promising applications in human-machine interactive interfaces.

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Triboelectric textile with wearable property and feasibility of large area preparation has presented a great prospect in effectively collecting energy from human body motion to provide power supply for diversified wearable electronics. Here, we report a stretchable triboelectric textile (STET) composed of wavy conductive-cloth poly(ethylene terephthalate) and a patterned stretchable electrode as basic knitting units, which can achieve multivariant energy harvest with low cost and good comfort. STET displays excellent output performances due to diversified working principles of contact-separation and contact-sliding modes. Interaction between the knitting units can generate open-circuit voltage with a peak-to-peak value of 350 V and instantaneous peak power of 1 mW; the stretched-released STET produces a peak voltage of 32 V, whereas tapping the STET with cotton twice gives contact-separation movements generating improved peak voltage and current. To prove the potential application, the STET is fixed onto different positions of a human body to effectively harvest multivariant human body motion energy. Therefore, this work provides a new approach applying stretchable triboelectric textile for power supply in wearable devices.

Flexible nanogenerators with advantages of conformal structure and easy assembly have become an appealing research field for wearable electronics recently. Here, an all-in-one filler-elastomer-based high-performance stretchable piezoelectric nanogenerator (SPENG) is reported. By mechanically shearing and uniformly dispersing high weight compositions of PZT particles and Ag-coated glass microspheres fillers into the identical solid state silicone rubber matrixes, the piezoelectric layer and electrode layers are prepared, respectively, and the SPENG can be fabricated in an all-in-one structure with tight adhesion and reliable durability, which is very important to the tension sensing and energy harvesting for the limb motion with large strain and variable degree of freedom. The stretchable energy harvester exhibits excellent output performances (Voc≈20 V, Isc≈0.55μA, 3.93μW/cm3) and can respond to different external stimulations (such as stretched, clustered, folded, twisted, etc.). The SPENG can be not only mounted on a joint to efficiently capture and convert random body kinetic energy into electricity as a power supply for portable electronics, but also used as the self-powered tension and gesture sensors to monitor dynamic motions. This work has demonstrated a great progress in stretchable electronics and energy harvesting technology, which may have important prospects in artificial intelligence and individualized medical care.

Energy harvesting is a key technology for the self-powered mode of wireless sensor nods and mobile terminals. A large number of devices have been developed to convert mechanical energy into electrical energy. Whereas great efforts have been made to improve the output performance, problems like energy dissipation, device life and response range still need to be addressed. Herein, we report a hybridized triboelectric-piezoelectric-electromagnetic nanogenerator efficiently harvesting vibration energy. Three harvest modes are integrated into a single device, whose core component is a magnetic levitation structure. On the one hand, it presents higher sensitivity than conventional spring or cantilever designs due to low energy loss, which favors the tiny energy harvesting like the slapping desk vibration and the running car vibration. On the other hand, the mechanical fatigue or damage can be avoided by the special structure design. Under 20Hz, triboelectric nanogenerator (TENG) can deliver a peak output power of 78.4μW, while the top (EMG2) and the bottom (EMG1) electromagnetic generator can provide a peak output power of 36mW and 38.4mW, respectively. Piezoelectric generator located at top (PEG2) and bottom (PEG1) can contribute a peak output power of 122mW and 105mW, respectively. The capacitor charge measurement reveals that unit combination performance is remarkably stronger than individual performance, and the combination of TENG+EMG1+EMG2+PEG1+PEG2 has the highest energy harvesting capacity. Finally, this device has been integrated into a wireless sensor system. Results show that the wireless sensor system can be activated and transmit temperature and vibration signal to control computer. This work has a vital significance to the development and application of the internet of things.

Recently, human physiological information wireless monitoring in real-time is particularly important in health analysis. As a solution, a non-contact wireless physiological monitoring system based on pyroelectric generator (PyG), whose core part consists of a wireless circuit processing module and a polyvinylidene fluoride (PVDF) film, has been successfully designed. Owing to the temperature change under the stimulation of an external heat source, the output voltage of the PyG self-powered flexible sensor increases with the heat source temperature variation in the range of 295–355 K. Furthermore, based on the natural temperature oscillation between the living body and surrounding environment, the sensor can realize human physiological information assessment, for example, temperature monitoring of the palms, fingers, respiratory heat signals from mouth or nose or non-contact spatial heat mapping recognition of finger movement via sensor array. On this basis, a portable wireless monitoring system was designed by integrating the intelligent sensor with a signal conditioning circuit, data conversion storage module, Bluetooth module, and power module. This system can acquire real-time human oral or nasal breathing signals in the personal mobile app to evaluate the physiological state of individuals. Additionally, the wireless monitoring system can be activated within 10 m, demonstrating the application of PyG sensors in remote data transmission.

Triboelectric nanogenerators (TENGs) have recently drawn much attention in the field of biomechanical energy harvesting and motion monitoring. However, the electrode stretchability and contact-separation model induced complicated packed structure remain a problem that heavily affects output performance during various human movements and requires to be urgently addressed. Here, a single-electrode piezo-triboelectric hybrid nanogenerator (SEP-TENG) integrated with stretchable liquid-metal metal electrodes is reported, which simultaneously achieves outstanding energy harvesting performance and skin-comfort human motion monitoring. A polarized piezoelectric BaTiO3/silicon rubber (SR) composites film is served as the effective negative tribomaterial, benefiting from the improved dielectric constant and piezoelectric charge transfer, the optimized SEP-TENG generates a high peak power density of 5.7 W/m2while contacted with human skin. Besides, owing to the ultralow Young's modulus of the SR encapsulation layer and tribo-piezoelectric hybrid layer, the homogeneous integrated multilayer composite serves no break till a 745% elongation, promoting that the SEP-TENG could effectively harvest biomechanical energy and realize stable power supplying for wearable electronics even under large deformation state. Furthermore, the SEP-TENG could comfortably attach to the finger joints and collect bending energy. This work provides a novel design methodology for a single-electrode TENG to realize omnidirectional biomechanical energy harvesting and motion monitoring.

High-output triboelectric nanogenerators (TENGs) are promising complements of chemical batteries in wearable systems. However, the charge dissipation on tribomaterials in moisture environments remains a challenge impacting the stable energy supply. Herein, asymmetric permittivity manipulation is proposed as a novel strategy to simultaneously improve the output performances and humidity resistance of TENGs. An electrospinning bilayer polycaprolactone (PCL) nanofiber (BPF) composed of outer PCL and inner PCL/CNTs nanofibers which differ widely in permittivity is served as the efficient positive tribomaterial. Benefitting from the increased friction area and dual interfacial polarization in the bilayer dielectric, the transferred charge of the BPF-TENG increases by 740% compared to the PCL gel film-based device, reaching 210 nC at 1Hz. Significantly, a high-speed camera system verifies that the porous hydrophobic PCL nanofiber with a water contact angle of 125 degrees can effectively reduce the accumulation of water droplet on the material surface, contributing to stable output from 20% to 80% relative humidity. The optimized BPF-TENG generates a high peak-to-peak voltage of 2.24kV and a power density of 54W/m2in 80% humidity. Besides, by harvesting biomechanical energy, a 1000 µF capacitor can be charged to 3V and continuously drive electronics to work in wet weather. This strategy can be extended to various commercialized tribo-negative polymers and enables large-scale industrial manufacturing of high-output and humidity-resistant TENGs.

Tuning of magnetic properties by electric field (E-field) has received extensive attentions because it is compact, fast, and energy efficient. Here, multiferroic heterostructures of Fe3O4/Pt/PZN-PT (011) (lead zinc niobate-lead titanate single piezoelectric substrate) were in situ fabricated by atomic layer deposition (ALD) using C10H10Fe and O2as precursors at a low temperature (400 °C) without a subsequent annealing process in H2atmosphere, which is beneficial in combining with traditional silicon-based semiconductor technology. The E-field dependence of the magnetic anisotropy was studied systematically by ferromagnetic resonance spectroscopy with the larger tunable in-plane magnetic anisotropy of 152 Oe and 318 Oe obtained along the [100] and [0–11] axes, corresponding to the largest magnetoelectric coupling coefficient of 31.8 Oe.cm/kV. Also, the tunable out-of-plane magnetic anisotropy of 35 Oe was obtained along the [011] axis. The outstanding E-field tuning magnetism in the Fe3O4/Pt/PZN-PT heterostructures offers significant possibilities for novel multiferroic devices.

Stretchable, skin-conformal, and self-powered wearable pressure sensors have garnered significant attention for use in human joint bending motion monitoring. Here, a piezo-triboelectric pressure sensor (P-TPS) based on triboelectric nanogenerator and piezoelectric nanogenerator is demonstrated. The P-TPS can generate an enhanced electrical output by coupling the dual-mode triboelectrification and piezoelectric effect. The P-TPS shows high sensitivity (voltage = 0.3 V/kPa; current = 4.3 nA/kPa; pressure range = 0–200 kPa), high linearity, and good stability. Furthermore, it demonstrates a wide measurement range (0–800 kPa), table frequency response, and fast response time. Additionally, all components of the P-TPS are fabricated using flexible and stretchable materials, affording satisfactory stretchability and excellent skin conformality. Owing to their ability to self-power, they can be attached to the outside of joints to monitor human joint bending movements in real time. Hence, this study provides a novel method of using a stretchable and skin-conformal piezo-triboelectric nanogenerator with high electrical performance as a self-powered pressure sensor, which offers significant potential in personalized recognition, medical research, and human machine interface.

Electronic skin (E-skin) with tactile sensing characteristics has presented great potential in disease diagnosis and health assessment; however, the imperfect combination of ultra-flexibility and high-sensitivity have restricted its widespread application. Here, we report a contact-separation triboelectric-nanogenerator (CS-TENG) consisting of ultra-flexible micro-frustum-array polydimethylsiloxane (mf-PDMS) film and Cu electrodes as the basic friction units, which can achieve self-powered weak physiological signal monitoring with great comfort. The CS-TENG uses elastic mf-PDMS as both the major body and the friction layer to realize ultra-flexible and conformal contact with irregular human skin. By exploring the microelectromechanical system (MEMS) preparation process, a uniform and controllable mf-arrays structure was fabricated to utilize both the normal and shear stresses, thereby increasing friction and enhancing device sensitivity. The CS-TENG displays high sensitivity (5.67 V/105Pa), good linearity (R2 = 0.99 of voltage), high stability (more than 80000 cycles), and fast response time (60 ms). With these outstanding characteristics, the CS-TENG can sense subtle changes in wrist pulse under various physiological conditions, which can also be easily arranged into a 1 × 3 array to mimic the three-fingered pulse-taking in traditional Chinese medicine. This work provides a new way to prepare ultra-flexible and high-sensitive TENG as E-skin and demonstrates its potential application.

In recent years, as the world has been warming, frequent natural disasters are posing a great threat to humans. By combining 5G technology with the Internet of Things (IoT) concept and increasing the placement of wireless sensor networks, disaster-prone points can be closely monitored. However, regular replacement of the traditional chemical batteries for devices that are a part of the developing IoT remains a significant challenge, especially in remote areas. In this article, we propose and report a hybrid energy harvester used in wind energy harvesting. The device consists of a rotating body and a sliding body. The electromagnetic generators (EMGs) in the rotating body and the triboelectric nanogenerators (TENGs) on the sliding body form the entirety of the power generating mechanism, and all generated units are completely sealed in the device box, which is isolated from the harsh environment. This paper not only systematically studies the influence of dielectric material types and sizes on the output performance of TENGs, but also studies the output performance of this device under different wind speeds. The results show that when the wind speed is not less than 4 m/s, the energy harvester can convert wind energy into electricity. The output performance of TENGs and EMGs increases with increasing wind speed, and the voltages of the TENG and the EMG are 416 V and 63.2 V at the 15 m/s wind speed, respectively. When the wind speed is 9 m/s, the maximum output power of TENG and EMG are 0.36 mW and 18.6 mW, respectively. The device can charge a capacitor of 1000 μF to 19.8 V in 30s. By supplying power to electronic devices and wireless monitoring systems including temperature sensors and humidity sensors, it is shown that the creation and implementation of such an energy harvester is practical and has a significant impact on promoting the development of IoT. Meanwhile, it can be used as a self-powered sensor to detected wind speed by analyzing the frequency of TENG output voltage.

Highly skin-conformal wearable tactile sensors with high sensitivity and wide measurement range are promising for physiological signal monitoring, personalized recognition and human-machine interaction. In this paper, we report a hybrid piezoelectric-triboelectric sensor (HPTS) primarily composed of polarized micro-frustum-arrays structure lead-zirconate-titanate and polydimethylsiloxane (PZT&PDMS) composite film (m-PZT&PDMS) and m-Cu film, which can simultaneously generate the coupling of piezoelectric effect and triboelectrification by the contact-separation working mode. Combining the hybrid effect, micro-frustum-arrays structure and high piezoelectric constant material, the HPTS presents excellent sensitivity and wide measurement range. The HPTS can reach a sensitivity of 15.43 V/kPa when triboelectric effect performs in the pressure of 0 kPa–100 kPa, and 18.96 V/kPa when both the piezoelectric and triboelectric effects work in the pressure range of 100 kPa–800 kPa. In addition, the HPTS is largely based on the PZT&PDMS film being directly in contact with the skin, showing excellent skin-conformal characteristic. It also demonstrates good linearity, fast response time and high stability. These characteristics are attractive for sensing radial artery wave, monitoring the slide and touch of a finger, and detecting the strong pressure of limb movement. Hence, this work provides a new strategy by applying a highly skin-conformal piezoelectric-enhanced triboelectric nanogenerator with high sensitivity and wide measurement range as a wearable tactile sensor, exhibiting immense potential in medical research, personalized recognition and human-machine interaction.

Flexible and wearable technology, a large trend in recent electronic technology revolution, proposes an urgent demand for the similarly flexible and wearable power supply. Hence a fully flexible and stretchable piezoelectric-enhanced triboelectric nanogenerator fabric (P-TNGF) possessing high output performance, good air permeability and excellent reliability is proposed in this work for human-body movement energy exploiting. Three consecutive energy conversion processes consisting of two triboelectrification processes and one piezoelectric electrification process exist at three different stages of a work period of P-TNGF, which contributes to harvest ambient energy maximally. By the optimization design of uninterrupted energy harvesting in overall process, a maximum open-circuit voltage and short-circuit current of P-TNGF can reach 600 V and 17 μA, respectively, and a maximum output power of 1.11 W/m2is obtained experimentally under 20MΩ load. Moreover, the operating capability of P-TNGF in various conditions, such as different stimulation frequency and external contact materials is investigated experimentally, showing excellent reliability and availability. Prepared samples are attached to different human-body parts, such as foot and joints, to demonstrate its wearability and biomechanical energy harvesting capability. Processed by rectification circuit, alternating current generated from P-TNGF are charged into several capacitors with various capacitances, which can be utilized to drive commercial electronic devices. The proposed P-TNGF has great significance for the further development of flexible and wearable technology.