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The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 nm lithium niobate (LiNbO3, LN) thin film remains stable after gamma irradiation from 1 krad to 10 Mrad, which was prepared by piezoresponse force microscopy (PFM). In addition, the changing law of domain wall resistivity is explored through different sample voltages, and it is verified that the irradiated domain wall conductivity is still larger than the domain. This domain wall current (DWC) property can be applied to storage, logic, sensing, and other devices. Based on these, a ferroelectric domain irradiation resistance model is established, which explains the reason at an atomic level. The results open a possibility for exploiting ferroelectric materials as the foundation in the application of space and nuclear fields. [ABSTRACT FROM AUTHOR]

Flexible sensors have been widely studied for use in motion monitoring, human‒machine interactions (HMIs), personalized medicine, and soft intelligent robots. However, their practical application is limited by their low output performance, narrow measuring range, and unidirectional force detection. Here, to achieve flexibility and high performance simultaneously, we developed a flexible wide-range multidimensional force sensor (FWMFS) similar to bones embedded in muscle structures. The adjustable magnetic field endows the FWMFS with multidimensional perception for detecting forces in different directions. The multilayer stacked coils significantly improved the output from the μV to the mV level while ensuring FWMFS miniaturization. The optimized FWMFS exhibited a high voltage sensitivity of 0.227 mV/N (0.5–8.4 N) and 0.047 mV/N (8.4–60 N) in response to normal forces ranging from 0.5 N to 60 N and could detect lateral forces ranging from 0.2–1.1 N and voltage sensitivities of 1.039 mV/N (0.2–0.5 N) and 0.194 mV/N (0.5–1.1 N). In terms of normal force measurements, the FWMFS can monitor finger pressure and sliding trajectories in response to finger taps, as well as measure plantar pressure for assessing human movement. The plantar pressure signals of five human movements collected by the FWMFS were analyzed using the k-nearest neighbors classification algorithm, which achieved a recognition accuracy of 92%. Additionally, an artificial intelligence biometric authentication system is being developed that classifies and recognizes user passwords. Based on the lateral force measurement ability of the FWMFS, the direction of ball movement can be distinguished, and communication systems such as Morse Code can be expanded. This research has significant potential in intelligent sensing and personalized spatial recognition. [ABSTRACT FROM AUTHOR]

As a cutting-edge technology, animal robots based on living organisms are being extensively studied, with potential for diverse applications in the fields of neuroscience, national security, and civil rescue. However, it remains a significant challenge to reliably control the animal robots with the objective of protecting their long-term survival, and this has seriously hindered their practical implementation. To address this issue, this work explored the use of a bio-friendly neurostimulation system that includes integrated stimulation electrodes together with a remote wireless stimulation circuit to control the moving behavior of rat robots. The integrated electrodes were implanted simultaneously in four stimulation sites, including the medial forebrain bundle (MFB) and primary somatosensory cortex, barrel field (S1BF). The control system was able to provide flexibility in adjusting the following four stimulation parameters: waveform, amplitude, frequency, and duration time. The optimized parameters facilitated the successful control of the rat's locomotion, including forward movement and left and right turns. After training for a few cycles, the rat robots could be guided along a designated route to complete the given mission in a maze. Moreover, it was found that the rat robots could survive for more than 20 days with the control system implanted. These findings will ensure the sustained and reliable operation of the rat robots, laying a robust foundation for advances in animal robot regulation technology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 g and 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. [ABSTRACT FROM AUTHOR]

The application of standing surface acoustic wave (SSAW) tweezers based on backpropagation superposition to achieve precise behavior manipulation of microscale cells and even nanoscale bacteria has been widely studied and industrialized. However, the structure requires multiple transducer components or full channel resonance. It is very challenging to design a simple structure for nano-control by complex acoustic field. In this study, a reflector-interdigital transducer (R-IDT) acoustofluidic device based on unilateral coherence enhancement is proposed to achieve SSAW definition features of periodic particle capture positions. The SAW device based on a unilateral transducer can not only generate leaky-SAW in water-filled microchannel, but also have a contribution of spherical waves in the vibration area of the substrate-liquid interface due to the Huygens-Fresnel diffractive principle. Both of them form a robust time-averaged spatial periodicity in the pressure potential gradient, accurately predicting the lateral spacing of these positions through acoustic patterning methods. Furthermore, a reflector based on Bragg-reflection is used to suppress backward transmitted SAW and enhance forward conducted SAW beams. By using a finite element model, R-IDT structure's amplitude enhances 60.78% compared to single IDT structure. The particle manipulation range of the diffractive acoustic field greatly improves, verified by experimental polystyrene microspheres. Besides, biocompatibility is conformed through red blood cells and Bacillus subtilis. We investigate the overall shift of periodic pressure field that can still occur when the phase changes. This work provides a simpler and low-cost solution for the application of acoustic tweezer in biological cell culture and filtering. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In micron or nano smart sensing systems, piezoelectric cantilever beams are distributed as major components in microsensors, actuators, and energy harvesters. This paper investigates the performance of four cantilever beam devices with "electric-force" conversion based on the inverse piezoelectric effect of lithium niobate (LiNbO3, LN) single-crystal materials. A new compact piezoelectric smart device model is proposed, designed as a single mass block connected by four beams, where devices exhibit smaller lateral errors (0.39–0.41%). The relationship between the displacement characteristics of cantilever beams and driving voltage was researched by applying excitation signals. The results show that the device has the maximum displacement at a first-order intrinsic frequency (fosc = 11.338 kHz), while the displacement shows a good linear relationship (R2 = 0.998) with driving voltage. The square wave signals of the same amplitude have greater "electrical-force" conversion efficiency. The output displacement can reach 12 nm, which is much higher than the output displacement with sinusoidal excitation. In addition, the relative displacement deviation of devices can be maintained within ±1% under multiple cycles of electrical signal loading. The small size, high reliability, and ultra-stability of Si–LN ferroelectric single-crystal cantilever beam devices with lower vibration amplitudes are promising for nanopositioning techniques in microscopy, diagnostics, and high-precision manufacturing applications. [ABSTRACT FROM AUTHOR]

The 0.95K0.42Na0.58Nb0.96Sb0.04O3–0.02BaZrO3–0.03Bi0.5K0.5HfO3 ceramic was fabricated via a conventional solid-state reaction. This ceramic exhibits the diffuse polymorphic phase boundary (PPB) near room temperature. The dielectric, ferroelectric, electromechanical, electrocaloric, and dielectric energy storage properties were studied systemically. The normalized large signal d33* values are approximately 400–600 pm/V at measured temperatures and electric fields, which are larger than or comparable with the values reported in other lead-free compositions. The electrocaloric strength is enhanced at the broad region of PPB provided by the indirect and direct measurements. At low field of 30 kV/cm, the dielectric energy storage is ∼0.12–018 J/cm3 at relative broad temperature range due to the diffuse nature of polymorphic phase boundary. Theoretical simulations reveal that multi-element dopants, such as Sb5+, Hf4+, Zr4+, and Bi3+ ions, could induce the breaking of local structure symmetry in the orthorhombic phase to form the PPB. In addition, the charge distribution may also break the long-range ferroelectric order through the analysis of Bader charge. Our study suggests that the K0.5Na0.5NbO3-based ceramic exhibits improved performance and good thermal stability in piezoelectric, electrocaloric, and dielectric energy storage characteristics in terms of the design of multi-element dopants to form the PPB and it will benefit the promising applications in electronic devices. [ABSTRACT FROM AUTHOR]

In this paper, a novel microwave photonic filter (MPF) based on a single longitudinal mode Brillouin laser achieved by parity time (PT) symmetry mode selection is proposed, and its unparalleled ultra-narrow bandwidth as low as to sub-kHz together with simple and agile tuning performance is experimentally verified. The Brillouin fiber laser ring resonator is cascaded with a PT symmetric system to achieve this MPF. Wherein, the Brillouin laser resonator is excited by a 5 km single mode fiber to generate Brillouin gain, and the PT symmetric system is configured with Polarization Beam Splitter (PBS) and polarization controller (PC) to achieve PT symmetry. Thanks to the significant enhancement of the gain difference between the main mode and the edge mode when the polarization state PT symmetry system breaks, a single mode oscillating Brillouin laser is generated. Through the selective amplification of sideband modulated signals by ultra-narrow linewidth Brillouin single mode laser gain, the MPF with ultra-narrow single passband performance is obtained. By simply tuning the central wavelength of the stimulated Brillouin scattering (SBS) pumped laser to adjust the Brillouin oscillation frequency, the gain position of the Brillouin laser can be shifted, thereby achieving flexible tunability. The experimental results indicate that the MPF proposed in this paper achieves a single pass band narrow to 72 Hz and the side mode rejection ratio of more than 18 dB, with a center frequency tuning range of 0–20 GHz in the testing range of vector network analysis, which means that the MPF possesses ultra high spectral resolution and enormous potential application value in the domain of ultra fine microwave spectrum filtering such as radar imaging and electronic countermeasures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Frequent meteorological disasters pose more and more extensive threats to human life and property. However, the traditional meteorological sensors based on external power supply, for natural disaster monitoring and early warning, are severely limited in remote and unattended areas. Herein, a self‐powered multi‐parameter meteorological sensor (SMPM‐sensor) for various weather monitoring is proposed, which can monitor the weather through the feedback of electrical energy output while collecting natural energy. The designed 360° omnidirectional array structure facilitates efficient collection of all‐weather solar energy and rain energy in different directions and monitoring the light intensity without the influence of solar azimuth. Based on the four‐segmented disc‐shaped structure and the introduced Ecoflex transition layer, the frequency and amplitude of the wind electrical output can be effectively improved. Owing to structure and material optimizations, a good linearity of 0.9746 between the current and the solar illuminance is exhibited, a wide monitoring range of rainfall intensity changes from 0.1 to 11.9 mm min−1, and the linearity between wind speed and voltage frequency can be as high as 0.9986. Therefore, based on excellent sensing performances, good stability, and real‐time characteristic, the fabricated SMPM sensor provides a potential technological strategy for the field of meteorological disaster monitoring. [ABSTRACT FROM AUTHOR]

Designing stretchable and skin-conformal self-powered sensors for intelligent sensing and posture recognition is challenging. Here, based on a multi-force mixing and vulcanization process, as well as synergistically piezoelectricity of BaTiO3 and polyacrylonitrile, an all-in-one, stretchable, and self-powered elastomer-based piezo-pressure sensor (ASPS) with high sensitivity is reported. The ASPS presents excellent sensitivity (0.93 V/104 Pa of voltage and 4.92 nA/104 Pa of current at a pressure of 10–200 kPa) and high durability (over 10,000 cycles). Moreover, the ASPS exhibits a wide measurement range, good linearity, rapid response time, and stable frequency response. All components were fabricated using silicone, affording satisfactory skin-conformality for sensing postures. Through cooperation with a homemade circuit and artificial intelligence algorithm, an information processing strategy was proposed to realize intelligent sensing and recognition. The home-made circuit achieves the acquisition and wireless transmission of ASPS signals (transmission distance up to 50 m), and the algorithm realizes the classification and identification of ASPS signals (accuracy up to 99.5%). This study proposes not only a novel fabrication method for developing self-powered sensors, but also a new information processing strategy for intelligent sensing and recognition, which offers significant application potential in human—machine interaction, physiological analysis, and medical research. [ABSTRACT FROM AUTHOR]

The substrate impurities scattering will lead to unstable temperature-sensitive behavior and poor linearity in graphene temperature sensors. And this can be weakened by suspending the graphene structure. Herein, we report a graphene temperature sensing structure, with suspended graphene membranes fabricated on the cavity and non-cavity SiO2/Si substrate, using monolayer, few-layer, and multilayer graphene. The results show that the sensor provides direct electrical readout from temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which results in better sensitivity and wide-range temperature sensing. In addition, monolayer graphene is almost no temperature sensitivity. And the few-layer graphene temperature sensitivity, lower than that of the multilayer graphene cavity structure (3.50%/°C), is 1.07%/°C. This work demonstrates that piezoresistive in suspended graphene membranes can effectively enhance the sensitivity and widen the temperature sensor range in NEMS temperature sensors. [ABSTRACT FROM AUTHOR]

Due to their excellent capabilities to generate and sense ultrasound signals in an efficient and well-controlled way at the microscale, piezoelectric micromechanical ultrasonic transducers (PMUTs) are being widely used in specific systems, such as medical imaging, biometric identification, and acoustic wireless communication systems. The ongoing demand for high-performance and adjustable PMUTs has inspired the idea of manipulating PMUTs by voltage. Here, PMUTs based on AlN thin films protected by a SiO2 layer of 200 nm were fabricated using a standard MEMS process with a resonant frequency of 505.94 kHz, a −6 dB bandwidth (BW) of 6.59 kHz, and an electromechanical coupling coefficient of 0.97%. A modification of 4.08 kHz for the resonant frequency and a bandwidth enlargement of 60.2% could be obtained when a DC bias voltage of −30 to 30 V was applied, corresponding to a maximum resonant frequency sensitivity of 83 Hz/V, which was attributed to the stress on the surface of the piezoelectric film induced by the external DC bias. These findings provide the possibility of receiving ultrasonic signals within a wider frequency range, which will play an important role in underwater three-dimensional imaging and nondestructive testing. [ABSTRACT FROM AUTHOR]

Graphene-based metamaterials have been widely applied in optoelectronic devices, optical modulators, and chemical sensors due to the outstanding tunability and optical response in the terahertz (THz) region. Here, tunable THz metamaterial absorbers based on patterned graphene are designed, fabricated, and modulated. The proposed metamaterial absorbers are constructed by the top layer of patterned graphene arrays and the aluminum (Al) film separated by polyimide (PI). The different THz absorption spectra can be acquired by changing the patterns of graphene. In order to verify the simulation results, a series of tests were conducted by THz time-domain spectrometer (THz-TDS) systems. The proposed absorbers are able to be insensitive to the angle of the incident wave. Besides, chemical doping is applied to turn the Fermi level of graphene and the absorption performance is promoted with the increase of the Fermi level. The experimental results have been demonstrated to have associated resonant peaks with the simulation results. The aim of this paper is to exhibit a systematic study on graphene-based THz metamaterial absorbers, including the simulation and experiments. By comparing the simulation and experimental results, it is useful to clarify the relevant theories and manufacturing processes. The work will provide a further step in the development of high-performance terahertz devices, including tunable absorbers, sensors, and electro-optic switches. [ABSTRACT FROM AUTHOR]

Multifunctional, integrated, and reusable operating platforms are highly sought after in biochemical analysis and detection systems. In this study, we demonstrated a novel detachable, reusable acoustic tweezer manipulation platform that is flexible and versatile. The free interchangeability of different detachable microchannel devices on the acoustic tweezer platform was achieved by adding a waveguide layer (glass) and a coupling layer (polydimethylsiloxane (PDMS) polymer film). We designed and demonstrated the detachable multifunctional acoustic tweezer platform with three cell manipulation capabilities. In Demo I, the detachable acoustic tweezer platform is demonstrated to have the capability for parallel processing and enrichment of the sample. In Demo II, the detachable acoustic tweezer platform with capability for precise cell alignment is demonstrated. In Demo III, it was demonstrated that the detachable acoustic tweezer platform has the capability for the separation and purification of cells. Through experiments, our acoustic tweezer platform has good acoustic retention ability, reusability, and stability. More capabilities can be expanded in the future. It provides a simple, economical, and multifunctional reusable operating platform solution for biochemical analysis and detection systems. [ABSTRACT FROM AUTHOR]

Ubiquitous environmental energy has become an important energy source for ensuring long‐lasting operation of unattended monitoring systems. However, several technical bottlenecks remain for achieving improved collection performance of environmental energy. Herein, a transparent composite film comprising micro‐pyramid arrays (mp‐arrays) and a conductive ionic liquid (IL) based on polydimethylsiloxane (PDMS) is innovatively generated as a difunctional layer that acts as an antireflective coating for solar cells and an enhanced triboelectric layer for the raindrop‐harvesting triboelectric nanogenerator (RH‐TENG). The regular mp‐arrays fabricated using the template transfer technology according to the matched refractive index between IL and PDMS effectively inhibit the surface reflection and improve the light trapping ability of solar cells. Owing to a significant increase in transmittance, the power conversion efficiency of the solar cell is enhanced by 10.92% owing to the IL@PDMS coating with mp‐arrays (mp‐IL@PDMS). Further, the conductive IL significantly improves the dielectricity of PDMS film. Due to the improved dielectric constant, increased aspect ratio, and excellent hydrophobicity, the output voltage and current of the RH‐TENG with mp‐IL@PDMS are enhanced by ≈24‐ and 44‐fold, respectively. Overall, this study, which is based on the incorporation of transparent conductive IL, provides a new technical path for efficient multiclimate energy harvesting. [ABSTRACT FROM AUTHOR]

The seeking of resonator with high Q and low insertion loss is attractive for critical sensing scenes based on the surface acoustic wave (SAW). In this work, 128° YX LiNbO3-based SAW resonators were utilized to optimize the output performance through IDT structure parameters. Once the pairs of IDTs, the acoustic aperture, the reflecting grid logarithm, and the gap between IDT and reflector are changed, a better resonance frequency of 224.85 MHz and a high Q of 1364.5 were obtained. All the results demonstrate the structure parameters design is helpful for the performance enhancement with regard to SAW resonators, especially for designing and fabricating high-Q devices. [ABSTRACT FROM AUTHOR]

As a basis for biometric and chemical analysis, issues of how to dilute or concentrate substances such as particles or cells to specific concentrations have long been of interest to researchers. In this study, travelling surface acoustic wave (TSAW)-based devices with three frequencies (99.1, 48.8, 20.4 MHz) have been used to capture the suspended Polystyrene (PS) microspheres of various sizes (5, 20, 40 μm) in sessile droplets, which are controlled by acoustic field-induced fluid vortex (acoustic vortex) and aggregate into clusters or rings with particles. These phenomena can be explained by the interaction of three forces, which are drag force caused by ASF, ARF caused by Leaky-SAW and varying centrifugal force. Eventually, a novel approach of free transition between the particle ring and cluster was approached via modulating the acoustic amplitude of TSAW. By this method, multilayer particles agglomerate with 20 μm wrapped around 40 μm and 20 μm wrapped around 5 μm can be obtained, which provides the possibility to dilute or concentrate the particles to a specific concentration. [ABSTRACT FROM AUTHOR]

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−1 in 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−1 in 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. [ABSTRACT FROM AUTHOR]

Piezoelectric accelerometers present higher sensitivities and better signal-to-noise ratios in comparison with piezoresistive and capacitive accelerometers. A micro-electromechanical system (MEMS) piezoelectric accelerometer was designed and manufactured with four L-shaped beams covered by Lead Zirconate Titanate (PZT) thin film with $1~\mu \text{m}$ in thickness which was deposited using sol-gel methods. The micro devices, whose size and the optimized PZT distribution were determined by theoretical and simulation analysis, were fabricated on the silicon substrate using PZT films working in the ${d}_{31}$ mode. Different from the conventional vertical crossbeam accelerometers, the designed structure devotes to the larger area piezoelectric film laid on L-shaped supporting beams with higher energy transferring efficiency for sensing. Then the chips of accelerometer were fabricated, and the proposed sensor was packaged on the printed circuit board (PCB). In addition, the microsphere was integrated in the center of the beams. Finally, the properties of the accelerometer were measured by vibration measurement system. The measuring results show that the initial sensitivity of the accelerometer is 28.14mV/g at 500Hz. The proposed piezoelectric accelerometer has high sensitivity and low resonance frequency, and the frequency response on each beam is consistent, providing a new structure for high-performance accelerometer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Traditional accelerometers rely on batteries to provide energy, and the massive use of batteries caused great pressure on the natural environment. In this paper, a self‐powered acceleration sensor is designed. To more easily harvest weak vibration signals and effectively improve the sensitivity, this sensor is built on a magnetic levitation type double helix structure and ZnO‐doped triboelectric film. Experiments indicated that the open‐circuit voltage and short circuit current of the triboelectric nanogenerator (TENG) doped with ZnO are increased by 2.51 times and 2.07 times, respectively. Under shaking table test for simulating machine vibration environment, the sensor's sensitivity reaches 16.31 V (m s−2)−1 and its linearity is 0.993. The sensor power generation is 110 μW and its test range is ≈1–7 m s−2. Also, the sensor can be applied for monitoring human's movement state by installing in a sole. This design provides a new idea for the development of TENG‐based sensors. [ABSTRACT FROM AUTHOR]

Domain wall current (DWC) plays a key role in storage devices, logic devices and sensors due to its high on-off ratio and nano structure size in the era of nanoelectronics technology. In this work, the DWC of single crystal LiNbO3 thin film was studied by piezoresponse force microscope (PFM) and conducting atomic force microscope (c-AFM). We mainly focus on voltage and temperature dependence of DWC which increases with the voltage and temperatures. Based on this research, the packaged DWC temperature sensor is fabricated and applied in wide temperature range. The existence of domain walls makes the current on-off ratio as high as 103 at the voltage of 15 V. Our study shows that DWC has a negative temperature coefficient (NTC) from 140 K to 500 K. The current increases from 3 pA to $57 ~\mu \text{A}$ , which is attributed to the conductivity of switched domain. This work proposes a new type temperature sensor with wide temperature range and high compatibility and sensitivity. In addition, it provides support for harsh environment applications of ferroelectric domain engineering devices. [ABSTRACT FROM AUTHOR]

Charged domain walls (CDWs) have attracted considerable attention owing to their tunable properties related to high-density information storage and nanoelectronics devices. The excellent time endurance of conductivity is a pressing need, which is directly related to the domain stability and boundary conditions. In this study, we propose an effective method to promote the permanent formation of charged domain walls aimed with tip-induced electric fields. The permanent domain structures and CDWs are attributed to the robust stimulus with tip dimensions combined with effective screening conditions. This interesting conductivity near the domain walls is three orders of magnitude higher than the domain inner, and exhibits attractive anti-fatigue properties with the value of ∼60 pA for the duration of more than one month. In addition, the tunable mechanism of CDWs in LiNbO3 thin films is related to carrier gathering near the domain walls for the inclined boundary. These inclined head-to-head domain walls exhibit conductive features only along the negative direction, which can be modulated by the application of a sub-coercive voltage. The results demonstrate the stable manipulation of domain reversal and charged domain walls in LiNbO3 thin films, highlighting them as a critical component, especially for multiple-state logic circuits and potential ferroelectric diode applications in non-volatile memories and nanoelectronics devices. [ABSTRACT FROM AUTHOR]

Domain engineering plays a pivotal role in the development of ferroelectric non-volatile memory devices. In this work, we mainly focus on the domain kinetic in ion-sliced single crystal LiNbO3 thin films under tip-induced electric fields using piezoresponse force microscope (PFM). Polarization reversal takes place when the electric fields are above threshold value (coercive voltage Vc) of films. Besides, the dependence of domain dynamic on pulse duration and amplitude were investigated in detail, and specific local domain reversal (5 μm) was completed by the optimized poling condition. All the results reveal that tip-induced polarization reversal could be an effective way to domain engineering, which gives much more promising prospects regarding to the high density non-volatile ferroelectric memory devices. [ABSTRACT FROM AUTHOR]

With the evolution of power electronic system to miniaturization and integration, dielectric capacitors are extensively studied in electric power systems such as electron beam and direction energy weapons owing to outstanding energy storage density and low loss. In this work, Pb0.97La0.02ZrO3 (PLZ) films were deposited on LaNiO3 (LNO)/Pt and LNO electrodes using sol-gel method, respectively. High spontaneous polarization (Ps ~ 91.3 μC cm−2) and low remanent polarization (Pr ~ 7.3 μC cm−2) can be obtained from PLZ/LNO/Pt/TiO2/SiO2/Si with energy storage density up to 25.4 J cm−3, which could be explained by good ohmic contact between films and composite electrodes. Besides, recoverable energy storage of films exhibits outstanding temperature stability (25.9–25.3 J cm−3) over -60 - 20 °C. These results suggest that LNO/Pt composite electrodes can be used to optimize PLZ films properties, which could be considered as a valid way for developing wide temperature range energy-storage capacitors. Highlights: High quality PbLaZrO3(PLZ) films could be obtained by LaNiO3 (LNO)/Pt electrode owing to good ohmic contact and lattice matching between films and composite electrode. High spontaneous polarization (Ps ~ 91.3 μC cm−2) and low remanent polarization (Pr ~ 7.3 μC cm−2) can be obtained in PLZ/LNO/Pt/TiO2/SiO2/Si. Excellent energy storage could be obtained in PLZ films within wide temperature range (−60–200 °C). Especially, recoverable energy storage of films exhibits outstanding temperature endurance (25.9–25.3 J cm−3) over −60–20 °C. [ABSTRACT FROM AUTHOR]

Collecting energy from body movements to supply power for equipment is an important method to rapidly develop wearable intelligent equipment. This method places high requirements, such as being lightweight and stable, on a nanogenerator. Herein, a bioinspired helical triboelectric nanogenerator (BH‐TENG) that realizes energy acquisition through the intensity and frequency of body movement is designed based on the helical structure of DNA. The helical structure facilitates more contact areas and provides increased stability to complete the power generation process than the simple structure with planar electrodes and functional layers in the same volume. It is found that when the frequency is 4 Hz and the impact load is 50 N, the output current reaches 17 µA and the voltage reaches 300 V with a charge transfer capacity of 371 nC. When the BH‐TENG is fitted in the sole of a shoe, it can light 120 LEDs when a subject is walking. After simple rectification output and capacitance matching, the BH‐TENG is verified to work independently and stably for 20 min to provide power for small digital thermometer. The above experiments show the advantages of the BH‐TENG in acquiring body motion energy. [ABSTRACT FROM AUTHOR]

SrRuO/BiFeO/SrRuO thin-film capacitors were fabricated to investigate the role of mobile oxygen vacancies in a switchable photovoltaic (PV) effect that depends on ferroelectric domain orientations. Normally, the flowing direction of the stabilized photocurrent is opposite to ferroelectric polarization orientation. However, an abnormal overshoot of initial positive transient photocurrent parallel to the ferroelectric polarization could be observed under light illumination for a poled BiFeO thin film with the polarization pointing to the bottom electrode. Moreover, the photocurrent has a strong response with respect to voltage poling time and relaxation time after poling, which seems to be correlated with time-dependent migration of oxygen vacancies and concurrent charge trapping effect. Our results not only reveal the scenario how oxygen-vacancy migration and charge trapping effect affect the switchable PV effect, besides ferroelectric polarization, but also are helpful for the understanding and designing of new switchable photoelectric devices. [ABSTRACT FROM AUTHOR]

We demonstrated a BiFeO3single-crystalline thin film, which was deposited on a (100) SrTiO3single-crystal substrate by using a pulse laser deposition technology. The as-grown domain structure was investigated by piezoresponse force microscopy, which possesses two preferential downward <111> orientations in an angle of 71°. We have found that the abnormal out of plane stripe domain patterns match with the in-plane domains. According to schematic diagrams and quantitative equations, we explained that the coupling between the out of plane and in-plane domains arise from the buckling effect, which can open a new way to reconstruct the real polarization vectors. [ABSTRACT FROM AUTHOR]

It is a great challenge to detect in-situ high-frequency vibration signals for extreme environment applications. A highly sensitive and robust vibration sensor is desired. Among the many piezoelectric materials, single-crystal lithium niobate (LiNbO3) could be a good candidate to meet the demand. In this work, a novel type of micro-electro-mechanical system (MEMS) vibration sensor based on a single crystalline LiNbO3 thin film is demonstrated. Firstly, the four-cantilever-beam MEMS vibration sensor was designed and optimized with the parametric method. The structural dependence on the intrinsic frequency and maximum stress was obtained. Then, the vibration sensor was fabricated using standard MEMS processes. The practical intrinsic frequency of the as-presented vibration sensor was 5.175 kHz, which was close to the calculated and simulated frequency. The dynamic performance of the vibration sensor was tested on a vibration platform after the packaging of the printed circuit board. The effect of acceleration was investigated, and it was observed that the output charge was proportional to the amplitude of the acceleration. As the loading acceleration amplitude is 10 g and the frequency is in the range of 20 to 2400 Hz, the output charge amplitude basically remains stable for the frequency range from 100 Hz to 1400 Hz, but there is a dramatic decrease around 1400 to 2200 Hz, and then it increases significantly. This should be attributed to the significant variation of the damping coefficient near 1800 Hz. Meanwhile, the effect of the temperature on the output was studied. The results show the nearly linear dependence of the output charge on the temperature. The presented MEMS vibration sensors were endowed with a high output performance, linear dependence and stable sensitivity, and could find potential applications for the detection of wide-band high-frequency vibration. [ABSTRACT FROM AUTHOR]

(Pb,La)(Zr,Ti)O antiferroelectric 1.4 μm-thick films have been prepared on Pt (111)/Ti/SiO/Si(100) substrates by sol-gel process. The structures and dielectric properties of the antiferroelectric thick films were investigated. The films displayed pure perovskite structure with (100)-preferred orientation. The surface of the films was smooth, compact and uniform. The antiferroelectric (AFE) characterization have been demonstrated by P (polarization)-E (electric field) and C(capacitance)-V (DC bias) curves. The AFE-ferroelectric (FE) and FE-to-paraelectric (PE) phase transition were also investigated as coupling functions of temperature and direct current electric field. With the applied field increased, the temperature of AFE-to-FE phase transition decreased and the FE-to-PE phase shifted to high temperature. The AFE-to-FE phase transition was adjustable by direct current electric field. (Pb,La) (Zr,Ti) O antiferroelectric films have broad application prospects in microelectromechanical systems because of the phase transition. [ABSTRACT FROM AUTHOR]

(Pb, La)(Zr, Ti)O antiferroelectric thick films with (100)-preferred orientation were fabricated on Pt(111)/Ti/SiO/Si(100) substrates via a sol-gel method. The electric-field-induced antiferroelectric (AFE) to ferroelectric (FE) phase transition characteristics were studied by C (capacitance)-E (electric field) measurements at different temperature. The films were in AFE state under 0 kV/cm below 122 °C, and the switching field values decreased, with increasing temperature. The films were in FE state between 122 and 135 °C, and when the temperature above 135 °C, the films were in PE state. The temperature-dependent dielectric parameters were deconvoluted using a Gaussian fit multi-peaks showed that two typical phase transitions were discovered. The first peak is the AFE-to-FE phase transition and the second peak is the FE-to-PE phase transition which has been verified by C-E tests. [ABSTRACT FROM AUTHOR]

An integration technology for wafer-level LiNbO3 single-crystal thin film on Si has been achieved. The optimized spin-coating speed of PI (polyimide) adhesive is 3500 rad/min. According to Fourier infrared analysis of the chemical state of the film baked under different conditions, a high-quality PI film that can be used for wafer-level bonding is obtained. A high bonding strength of 11.38 MPa is obtained by a tensile machine. The bonding interface is uniform, completed and non-porous. After the PI adhesive bonding process, the LiNbO3 single-crystal was lapped by chemical mechanical polishing. The thickness of the 100 mm diameter LiNbO3 can be decreased from 500 to 10 μm without generating serious cracks. A defect-free and tight bonding interface was confirmed by scanning electron microscopy. X-ray diffraction results show that the prepared LiNbO3 single-crystal thin film has a highly crystalline quality. Heterogeneous integration of LiNbO3 single-crystal thin film on Si is of great significance to the fabrication of MEMS devices for in-situ measurement of space-sensing signals. [ABSTRACT FROM AUTHOR]

Graphene nanostructures are widely perceived as a promising material for fundamental components; their high-performance electronic properties offer the potential for the construction of graphene nanoelectronics. Numerous researchers have paid attention to the fabrication of graphene nanostructures, based on both top-down and bottom-up approaches. However, there are still some unavoidable challenges, such as smooth edges, uniform films without folds, and accurate dimension and location control. In this work, a direct writing method was reported for the in-situ preparation of a high-resolution graphene nanostructure of controllable size (the minimum feature size is about 15 nm), which combines the advantages of e-beam lithography and copper-catalyzed growth. By using the Fourier infrared absorption test, we found that the hydrogen and oxygen elements were disappearing due to knock-on displacement and the radiolysis effect. The graphene crystal is also formed via diffusion and the local heating effect between the e-beam and copper substrate, based on the Raman spectra test. This simple process for the in-situ synthesis of graphene nanostructures has many promising potential applications, including offering a way to make nanoelectrodes, NEMS cantilever resonant structures, nanophotonic devices and so on. [ABSTRACT FROM AUTHOR]

In situ measurements of sensing signals in space platforms requires that the micro-electro-mechanical system (MEMS) sensors be located directly at the point to be measured and in contact with the subject to be measured. Traditional radiation-tolerant silicon-based MEMS sensors cannot acquire spatial signals directly. Compared to silicon-based structures, LiNbO3 single crystalline has wide application prospects in the aerospace field owing to its excellent corrosion resistance, low-temperature resistance and radiation resistance. In our work, 4-inch LiNbO3 and LiNbO3/Cr/Au wafers are fabricated to silicon substrate by means of a polyimide bonding method, respectively. The low-temperature bonding process (≤ 100 °C) is also useful for heterostructure to avoid wafer fragmentation results from a coefficient of thermal expansion (CTE) mismatch. The hydrophilic polyimide surfaces result from the increasing of -OH groups were acquired based on contact angle and X-ray photoelectron spectroscopy characterizations. A tight and defect-free bonding interface was confirmed by scanning electron microscopy. More importantly, benefiting from low-temperature tolerance and radiation-hardened properties of polyimide material, the bonding strength of the heterostructure based on oxygen plasma activation achieved 6.582 MPa and 3.339 MPa corresponding to room temperature and ultra-low temperature (≈ −263.15 °C), which meets the bonding strength requirements of aerospace applications. [ABSTRACT FROM AUTHOR]

The microcantilevers based on the antiferroelectric (AFE) (Pb0.97La0.02)(Zr0.95Ti0.05)O3 (PLZT) thick films were fabricated by bulk silicon micromachining process. The conspicuous electrostrictive strain properties with phase transition of the AFE PLZT films induced by electric field were investigated. The resonant vibration velocity and tip deflection on a 650-\mum-long cantilever were up to 6767 mm/s and 45.7 \mum, under the square wave excitation with the voltage of 40 V, matched to the AFE-ferroelectric phase transition electric field of 210 kV/cm. The ratio of induced tip displacement and cantilever length per unit voltage [d(\delta)/L/dV] was proposed to show the mutation response ability. In addition, the new AFE PLZT microcantilevers exhibited superior value of 10.77/kV, further higher than the traditional ones. Extensive application requirements for microdevices would be met in various fields of microelectromechanical systems. [ABSTRACT FROM PUBLISHER]

As a new energy harvesting strategy, triboelectric nanogenerators which have a broad application prospect in collecting environmental energy, human body mechanical energy, and supplying power for low‐power electronic devices, have attracted extensive attention. However, technology challenges still exist in the stretchability for the preparation of some high‐performance triboelectric materials. In this work, a new strategy for nonmetallic nylon‐modified triboelectric nanogenerators (NM‐TENGs) is reported. Nylon is introduced as a high performance friction material to enhance the output performance of the stretchable TENG. The uniform matrix reduces the difficulty of heterogeneous integration and enhances the structural strength. The open‐circuit voltage (VOC) and short‐circuit current (ISC) of NM‐TENG can reach up to 1.17 kV and 138 µA, respectively. The instantaneous power density reaches 11.2 W m−2 and the rectified output can directly light ≈480 LEDs. The transferred charge density is ≈100 µC m−2 in one cycle when charging the capacitor. In addition, a low‐power electronic clock can be driven directly by the rectified signal without additional circuits. NM‐TENG also has high enough strain rate and can be attached to the human body for energy harvesting effectively. This work provides a new idea for fabrication of stretchable TENGs and demonstrates their potential application. [ABSTRACT FROM AUTHOR]

As a promising functional material, ferroelectric Pb(ZrxTi1−x)O3 (PZT) are widely used in many optical and electronic devices. Remarkably, as the film thickness decreases, the materials' properties deviate gradually from those of solid materials. In this work, multilayered PZT thin films with different thicknesses are fabricated by Sol-Gel technique. The thickness effect on its microstructure, ferroelectric, and optical properties has been studied. It is found that the surface quality and the crystalline structure vary with the film thickness. Moreover, the increasing film thickness results in a significant increase in remnant polarization, due to the interfacial layer effect. Meanwhile, the dielectric loss and tunability are strongly dependent on thickness. In terms of optical properties, the refractive index of PZT films increase with the increasing thickness, and the photorefractive effect are also influenced by the thickness, which could all be related to the film density and photovoltaic effect. Besides, the band gap decreases as the film thickness increases. This work is significant for the application of PZT thin film in optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]