High-Coupled Magnetic-Levitation Hybrid Nanogenerator with Frequency Multiplication Effect for Wireless Water Level Alarm.

Hybrid nanogenerators (HNGs) represent a promising avenue for water energy harvesting, yet their commercial viability faces hurdles such as limited power output, poor coupling, and constrained operational lifespans. Here, a highly coupled triboelectric-electromagnetic magnetic-levitation hybrid nanogenerator (ML-HNG) is introduced that shows great potential for water energy harvesting. The ML-HNG fulfills the challenges of high power output, strong coupling, and long operational lifespans. During the contact-separation process of the triboelectric nanogenerator (TENG), the changing magnetic flux in the electromagnetic generator's coils generates a potential difference between the coils and Cu electrodes. The unique design of the ML-HNG employs a shared coil electrode configuration, which enhances the coupling without adding extra volume. This integration allows the ML-HNG to achieve multi-frequency vibrations and multiple output cycles per external longitudinal movement, a phenomenon known as the frequency multiplication effect. With an average power density of 1.69 W m-3 in water, the ML-HNG provides continuous power for a thermo-hygrometer and can quickly drive a wireless water level alarm system within a minute. This groundbreaking hybrid nanogenerator design holds significant promise for the efficient and consistent harvesting of low-frequency ocean wave energy, marking a substantial advancement in blue energy technology.

Elastic Self-Recovering Hybrid Nanogenerator for Water Wave Energy Harvesting and Marine Environmental Monitoring.

To achieve large-scale development of triboelectric nanogenerators (TENGs) for water wave energy harvesting and powering the colossal sensors widely distributed in the ocean, facile and scalable TENGs with high output are urgently required. Here, an elastic self-recovering hybrid nanogenerator (ES-HNG) is proposed for water wave energy harvesting and marine environmental monitoring. The elastic skeletal support of the ES-HNG is manufactured using three-dimensional (3D) printing technology, which is more conducive to the large-scale integration of the ES-HNG. Moreover, the combination of a TENG and an electromagnetic generator (EMG) optimizes the utilization of device space, leading to enhanced energy harvesting efficiency. Experimental results demonstrate that the TENG achieves a peak power output of 42.68 mW, and the EMG reaches a peak power output of 4.40 mW. Furthermore, various marine environment monitoring sensors, such as a self-powered wireless meteorological monitoring system, a wireless alarm system, and a water quality monitoring pen, have been successfully powered by the sophisticated ES-HNG. This work introduces an ES-HNG for water wave energy harvesting, which demonstrates potential in marine environment monitoring and offers a new solution for the sustainable development of the marine internet of things.

Tactile tribotronic reconfigurable p-n junctions for artificial synapses.

The emulation of biological synapses with learning and memory functions and versatile plasticity is significantly promising for neuromorphic computing systems. Here, a robust and continuously adjustable mechanoplastic semifloating-gate transistor is demonstrated based on an integrated graphene/hexagonal boron nitride/tungsten diselenide van der Waals heterostructure and a triboelectric nanogenerator (TENG). The working states (p-n junction or n+-n junction) can be manipulated and switched under the sophisticated modulation of triboelectric potential derived from mechanical actions, which is attributed to carriers trapping and detrapping in the graphene layer. Furthermore, a reconfigurable artificial synapse is constructed based on such mechanoplastic transistor that can simulate typical synaptic plasticity and implement dynamic control correlations in each response mode by further designing the amplitude and duration. The artificial synapse can work with ultra-low energy consumption at 74.2 fJ per synaptic event and the extended synaptic weights. Under the synergetic effect of the semifloating gate, the synaptic device can enable successive mechanical facilitation/depression, short-/long-term plasticity and learning-experience behavior, exhibiting the mechanical behavior derived synaptic plasticity. Such reconfigurable and mechanoplastic features provide an insight into the applications of energy-efficient and real-time interactive neuromodulation in the future artificial intelligent system beyond von Neumann architecture.

Elastic Kernmantle E-Braids for High-Impact Sports Monitoring.

The kernmantle construction, a kind of braiding structure that is characterized by the kern absorbing most of the stress and the mantle protecting the kern, is widely employed in the field of loading and rescue services, but rarely in flexible electronics. Here, a novel kernmantle electronic braid (E-braid) for high-impact sports monitoring, is proposed. The as-fabricated E-braids not only demonstrate high strength (31 Mpa), customized elasticity, and nice machine washability (>500 washes) but also exhibit excellent electrical stability (>200 000 cycles) during stretching. For demonstration, the E-braids are mounted to different parts of the trampoline for athletes' locomotor behavior monitoring. Furthermore, the E-braids are proved to act as multifarious intelligent sports gear or wearable equipment such as electronic jump rope and respiration monitoring belt. This study expands the kernmantle structure to soft flexible electronics and then accelerates the development of quantitative analysis in modern sports industry and athletes' healthcare.

p-n Junction Based Direct-Current Triboelectric Nanogenerator by Conjunction of Tribovoltaic Effect and Photovoltaic Effect.

Triboelectric nanogenerators (TENGs) have attracted much interest in recent years, due to its effectiveness and low cost for converting high-entropy mechanical energy into electric power. The traditional TENGs generate an alternating current, which requires a rectifier to provide a direct-current (DC) power supply. Herein, a dynamic p-n junction based direct-current triboelectric nanogenerator (DTENG) is demonstrated. When a p-Si wafer is sliding on a n-GaN wafer, carriers are generated at the interface and a DC current is produced along the direction of the built-in electric field, which is called the tribovoltatic effect. Simultaneously, an UV light is illuminated on the p-n junction to enhance the output. The results indicate that the current increases 13 times and the voltage increases 4 times under UV light (365 nm, 28 mW/cm2) irradiation. This work demonstrates the coupling between the tribovoltaic effect and the photovoltaic effect in DTENG semiconductors, promoting further development for energy harvesting in mechanical energy and photon energy.

Alternate-Layered MXene Composite Film-Based Triboelectric Nanogenerator with Enhanced Electrical Performance.

The output power of the triboelectric nanogenerator (TENG) strongly depends on the performance of triboelectric materials, especially microstructures and functional groups of them. In this work, aiming at the excellent triboelectric ability, alternate-layered MXene composite films-based TENG with abundant fluorine groups(-F) through layer-by-layer stacking are designed and fabricated. Benefitting from the uniform intrinsic microstructure and increased dielectric constant, when the amount of the Nb2CTx nanosheets increases to 15 wt%, the TENG based on Nb2CTx/Ti3C2Tx composite nanosheets films achieves the maximum output. The short-circuit current density of 8.06 µA/cm2 and voltage of 34.63 V are 8.4 times and 3.5 times over that of pure Ti3C2Tx films, and 3.3 times and 4.3 times over that of commercial poly(tetrafluoroethylene) (PTFE) films, respectively. Furthermore, the fabricated TENG could be attached to human body to harvest energy from human motions, such as typing, texting, and hand clapping. The results demonstrate that the alternate-layered MXene composite nanosheet films through layer-by-layer stacking possess remarkably triboelectric performance, which broaden the choice of negative triboelectric materials and supply a new choice for high output TENG.

A Polymeric Bilayer Multi-Legged Soft Millirobot with Dual Actuation and Humidity Sensing.

There are numerous works that report wirelessly controlling the locomotion of soft robots through a single actuation method of light or magnetism. However, coupling multiple driving modes to improve the mobility of robots is still in its infancy. Here, we present a soft multi-legged millirobot that can move, climb a slope, swim and detect a signal by near-infrared irradiation (NIR) light or magnetic field dual actuation. Due to the design of the feet structure, our soft millirobot incorporates the advantages of a single actuation mode of light or magnetism. Furthermore, it can execute a compulsory exercise to sense a signal and analyze the ambience fluctuation in a narrow place. This work provides a novel alternative for soft robots to achieve multimode actuation and signal sensing.

Vertically aligned NiS2/CoS2/MoS2 nanosheet array as an efficient and low-cost electrocatalyst for hydrogen evolution reaction in alkaline media.

Recently, the rational design of non-precious metal electrocatalysts for highly efficient hydrogen evolution reaction (HER) in alkaline media has received considerable interests in sustainable and renewable energy researches. Herein, vertically aligned and interconnected NiS2/CoS2/MoS2 nanosheet arrays on Ni foam were prepared by a two-step procedure that conducted by the hydrothermal synthesis of Ni-Co molybdate nanosheet array as the precursor and followed by the vapor phase sulfurization to achieve in situ conversion. Basing on the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations, it can be found that the honeycomb-like structure of the Ni-Co molybdate nanosheet array was well preserved after the sulfurization process. The high-resolution TEM (HRTEM) characterization reveals that the NiS2/CoS2/MoS2 nanosheet array provided abundant well-exposed active edge sites and multiple heterointerfaces towards enhanced alkaline HER performance. Electrochemical studies demonstrated that the ultrathin NiS2/CoS2/MoS2 nanosheets exhibited excellent HER performance with an overpotential of 112 mV at 10 mA cm-2 and a smaller Tafel slope of 59 mV dec-1 in comparison with NiS2/MoS2 (155 mV and 89 mV dec-1) and CoS2/MoS2 (124 mV and 75 mV dec-1) samples by taking the advantage of the well-exposed multiple heterointerfaces. This work presents a facile and reliable synthetic strategy for the rational design of highly efficient electrocatalysts for the HER in alkaline solution based on non-precious metal sulfide nanocomposite.

A flower-like CoS2/MoS2 heteronanosheet array as an active and stable electrocatalyst toward the hydrogen evolution reaction in alkaline media.

CoS2/MoS2 heteronanosheet arrays (HNSAs) with vertically aligned flower-like architectures are fabricated through in situ topotactic sulfurization of CoMoO4 nanosheet array (NSA) precursors on conductive Ni foam. CoMoO4 NSAs are prepared by a self-template hydrothermal method without using any hard template and surfactant. Benefiting from a 3D flower-like architecture constituted by ultrathin nanosheets with abundant exposed heterointerfaces as highly active sites and predesigned void spaces, the as-synthesized CoS2/MoS2 HNSAs exhibit an excellent hydrogen evolution reaction (HER) performance with a low overpotential of 50 mV at 10 mA cm-2, and a small Tafel slope of 76 mV dec-1 in 1.0 M KOH, which outperforms most previously reported CoS2 and MoS2 based electrocatalysts with compositional or morphological similarity. This work demonstrates the great potential in developing high-efficiency and earth-abundant electrocatalysts for alkaline HER through heterointerface engineering and morphological design by utilizing transition metal molybdate as a promising platform.

Nitrogen-Doped Porous Carbon Nanosheets Strongly Coupled with Mo2C Nanoparticles for Efficient Electrocatalytic Hydrogen Evolution.

Exploring earth-abundant and noble metal-free catalysts for water electrolysis is pivotal in renewable hydrogen production. Herein, a highly active electrocatalyst of nitrogen-doped porous carbon nanosheets coupled with Mo2C nanoparticles (Mo2C/NPC) was synthesized by a novel method with high BET surface area of 1380 m2 g-1 using KOH to activate carbon composite materials. The KOH plays a key role in etching out MoS2 to produce Mo precursor; simultaneously, it corrodes carbon to form porous structure and produce reducing gas such as H2 and CO. The resulting Mo2C/NPC hybrid demonstrated superior HER activity in acid solution, with the overpotential of 166 mV at current density of 10 mA cm-2, onset overpotential of 93 mV, Tafel slope of 68 mV dec-1, and remarkable long-term cycling stability. The present strategy may provide a promising strategy to fabricate other metal carbide/carbon hybrids for energy conversion and storage.

Self-Healable, Stretchable, Transparent Triboelectric Nanogenerators as Soft Power Sources.

Despite the rapid advancements of soft electronics, developing compatible energy devices will be the next challenge for their viable applications. Here, we report an energy-harnessing triboelectric nanogenerator (TENG) as a soft electrical power source, which is simultaneously self-healable, stretchable, and transparent. The nanogenerator features a thin-film configuration with buckled Ag nanowires/poly(3,4-ethylenedioxythiophene) composite electrode sandwiched in room-temperature self-healable poly(dimethylsiloxane) (PDMS) elastomers. Dynamic imine bonds are introduced in PDMS networks for repairing mechanical damages (94% efficiency), while the mechanical recovery of the elastomer is imparted to the buckled electrode for electrical healing. By adjusting the buckling wavelength of the electrode, the stretchability and transparency of the soft TENG can be tuned. A TENG (∼50% stretchabitliy, ∼73% transmittance) can recover the electricity genearation (100% healing efficiency) even after accidental cutting. Finally, the conversion of biomechanical energies into electricity (∼100 V, 327 mW/m2) is demonstrated by a skin-like soft TENG. Considering all these merits, this work suggests a potentially promising approach for next-generation soft power sources.

Magnetic-Induced-Piezopotential Gated MoS2 Field-Effect Transistor at Room Temperature.

Utilizing magnetic field directly modulating/turning the charge carrier transport behavior of field-effect transistor (FET) at ambient conditions is an enormous challenge in the field of micro-nanoelectronics. Here, a new type of magnetic-induced-piezopotential gated field-effect-transistor (MIPG-FET) base on laminate composites is proposed, which consists of Terfenol-D, a ferroelectric single crystal (PMNPT), and MoS2 flake. When applying an external magnetic field to the MIPG-FET, the piezopotential of PMNPT triggered by magnetostriction of the Terfenol-D can serve as the gate voltage to effectively modulate/control the carrier transport process and the corresponding drain current at room temperature. Considering the two polarization states of PMNPT, the drain current is diminished from 9.56 to 2.9 µA in the Pup state under a magnetic field of 33 mT, and increases from 1.41 to 4.93 µA in the Pdown state under a magnetic field of 42 mT and at a drain voltage of 3 V. The current on/off ratios in these states are 330% and 432%, respectively. This work provides a novel noncontact coupling method among magnetism, piezoelectricity, and semiconductor properties, which may have extremely important applications in magnetic sensors, memory and logic devices, micro-electromechanical systems, and human-machine interfacing.

Core-Shell-Yarn-Based Triboelectric Nanogenerator Textiles as Power Cloths.

Although textile-based triboelectric nanogenerators (TENGs) are highly promising because they scavenge energy from their working environment to sustainably power wearable/mobile electronics, the challenge of simultaneously possessing the qualities of cloth remains. In this work, we propose a strategy for TENG textiles as power cloths in which core-shell yarns with core conductive fibers as the electrode and artificial polymer fibers or natural fibrous materials tightly twined around core conductive fibers are applied as the building blocks. The resulting TENG textiles are comfortable, flexible, and fashionable, and their production processes are compatible with industrial, large-scale textile manufacturing. More importantly, the comfortable TENG textiles demonstrate excellent washability and tailorability and can be fully applied in further garment processing. TENG textiles worn under the arm or foot have also been demonstrated to scavenge various types of energy from human motion, such as patting, walking, and running. All of these merits of proposed TENG textiles for clothing uses suggest their great potentials for viable applications in wearable electronics or smart textiles in the near future.

On-Skin Triboelectric Nanogenerator and Self-Powered Sensor with Ultrathin Thickness and High Stretchability.

Researchers have devoted a lot of efforts on pursuing light weight and high flexibility for the wearable electronics, which also requires the related energy harvesting devices to have ultrathin thickness and high stretchability. Hence, an elastic triboelectric nanogenerator (TENG) is proposed that can serve as the second skin on human body. The total thickness of this TENG is about 102 µm and the device can work durably under a strain of 100%. The carbon grease is painted on the surface of elastomer film to work as stretchable electrode and thus the fine geometry control of the electrode can be achieved. This elastic TENG can even work on the human fingers without disturbing body movement. The open-circuit voltage and short-circuit current from the device with a contact area of 9 cm2 can reach 115 V and 3 µA, respectively. Two kinds of self-powered sensor systems with optimized identification strategies are also designed to demonstrate the application possibility of this elastic TENG. The superior characteristics of ultrathin thickness, high stretchability, and fine geometry control of this TENG can promote many potential applications in the field of wearable self-powered sensory system, electronics skin, artificial muscles, and soft robotics.

Self-Powered Random Number Generator Based on Coupled Triboelectric and Electrostatic Induction Effects at the Liquid-Dielectric Interface.

Modern cryptography increasingly employs random numbers generated from physical sources in lieu of conventional software-based pseudorandom numbers, primarily owing to the great demand of unpredictable, indecipherable cryptographic keys from true random numbers for information security. Thus, far, the sole demonstration of true random numbers has been generated through thermal noise and/or quantum effects, which suffers from expensive and complex equipment. In this paper, we demonstrate a method for self-powered creation of true random numbers by using triboelectric technology to collect random signals from nature. This random number generator based on coupled triboelectric and electrostatic induction effects at the liquid-dielectric interface includes an elaborately designed triboelectric generator (TENG) with an irregular grating structure, an electronic-optical device, and an optical-electronic device. The random characteristics of raindrops are harvested through TENG and consequently transformed and converted by electronic-optical device and an optical-electronic device with a nonlinear characteristic. The cooperation of the mechanical, electrical, and optical signals ensures that the generator possesses complex nonlinear input-output behavior and contributes to increased randomness. The random number sequences are deduced from final electrical signals received by an optical-electronic device using a familiar algorithm. These obtained random number sequences exhibit good statistical characteristics, unpredictability, and unrepeatability. Our study supplies a simple, practical, and effective method to generate true random numbers, which can be widely used in cryptographic protocols, digital signatures, authentication, identification, and other information security fields.

Raman study of 2D anatase TiO2 nanosheets.

Herein, we present for the first time a spectroscopic study of two-dimensional (2D) anatase TiO2 nanosheets. Previous publications demonstrated that Raman spectroscopy was mostly employed to characterize the TiO2 nanoparticle size and the phase transition of amorphous-anatase and anatase-rutile. In this study, TiO2 nanosheets were characterized by XRD, AFM and Raman spectroscopy, which demonstrated a shift toward higher frequency and broadening in the full width at half maximum of the characteristic Eg mode by decreasing the thickness of anatase TiO2 with a 2D nanostructure. In contrast to the study of TiO2 nanoparticles, the Raman vibrations can be attributed to phonon confinement in 2D TiO2 nanosheets which can be employed to characterize the thickness of TiO2 nanosheets. In order to effectively identify the thickness of the 2D TiO2 nanostructure, we established a reliable method for the examination by characterizing the shifts of the Eg mode.

Nanopillar Arrayed Triboelectric Nanogenerator as a Self-Powered Sensitive Sensor for a Sleep Monitoring System.

A flexible and low-cost triboelectric nanogenerator (TENG) based on a patterned aluminum-plastic film and an entrapped cantilever spring leaf is developed as a self-powered sensitive triboelectric sensor for sleep-body movement monitoring. The working mechanism and the impact factors of electric output performance were systematically investigated and elaborated. Due to the patterned nanostructures of the recently designed TENG, both the output voltage and current are greatly enhanced, and thereby the sensitivity of the device is significantly improved. The self-powered and sensitive device has been demonstrated as a smart body motion sensor of sleep monitoring for diagnosis of sleep disorders due to its high sensitivity and excellent stability. This work may promote the application of self-powered TENGs for healthcare and be helpful for the development of real-time mobile healthcare services and smart external portable electronics.

Piezo-phototronic effect enhanced UV photodetector based on CuI/ZnO double-shell grown on flexible copper microwire.

In this work, we present a facile, low-cost, and effective approach to fabricate the UV photodetector with a CuI/ZnO double-shell nanostructure which was grown on common copper microwire. The enhanced performances of Cu/CuI/ZnO core/double-shell microwire photodetector resulted from the formation of heterojunction. Benefiting from the piezo-phototronic effect, the presentation of piezocharges can lower the barrier height and facilitate the charge transport across heterojunction. The photosensing abilities of the Cu/CuI/ZnO core/double-shell microwire detector are investigated under different UV light densities and strain conditions. We demonstrate the I-V characteristic of the as-prepared core/double-shell device; it is quite sensitive to applied strain, which indicates that the piezo-phototronic effect plays an essential role in facilitating charge carrier transport across the CuI/ZnO heterojunction, then the performance of the device is further boosted under external strain.

Triboelectric Nanogenerator as a Self-Powered Communication Unit for Processing and Transmitting Information.

In this paper, we demonstrate an application of a triboelectric nanogenerator (TENG) as a self-powered communication unit. An elaborately designed TENG is used to translate a series of environmental triggering signals into binary digital signals and drives an electronic-optical device to transmit binary digital data in real-time without an external power supply. The elaborately designed TENG is built in a membrane structure that can effectively drive the electronic-optical device in a bandwidth from 1.30 to 1.65 kHz. Two typical communication modes (amplitude-shift keying and frequency-shift keying) are realized through the resonant response of TENG to different frequencies, and two digital signals, i.e., "1001" and "0110", are successfully transmitted and received through this system, respectively. Hence, in this study, a simple but efficient method for directly transmitting ambient vibration to the receiver as a digital signal is established using an elaborately designed TENG and an optical communication technique. This type of the communication system, as well as the implementation method presented, exhibits great potential for applications in the smart city, smart home, password authentication, and so on.

Flexible Self-Powered GaN Ultraviolet Photoswitch with Piezo-Phototronic Effect Enhanced On/Off Ratio.

Flexible self-powered sensing is urgently needed for wearable, portable, sustainable, maintenance-free and long-term applications. Here, we developed a flexible and self-powered GaN membrane-based ultraviolet (UV) photoswitch with high on/off ratio and excellent sensitivity. Even without any power supply, the driving force of UV photogenerated carriers can be well boosted by the combination of both built-in electric field and piezoelectric polarization field. The asymmetric metal-semiconductor-metal structure has been elaborately utilized to enhance the carrier separation and transport for highly sensitive UV photoresponse. Its UV on/off ratio and detection sensitivity reach to 4.67 × 10(5) and 1.78 × 10(12) cm·Hz(0.5) W(1-), respectively. Due to its excellent mechanical flexibility, the piezoelectric polarization field in GaN membrane can be easily tuned/controlled based on piezo-phototronic effect. Under 1% strain, a stronger and broader depletion region can be obtained to further enhance UV on/off ratio up to 154%. As a result, our research can not only provide a deep understanding of local electric field effects on self-powered optoelectronic detection, but also promote the development of self-powered flexible optoelectronic devices and integrated systems.