Publications

自己出力型ZnO/ペロブスカイトヘテロ構造光検出器に及ぼすピロphototronic効果の温度依存性【Powered by NICT】

Single-Crystal CdSe Nanosaws

We report the first successful synthesis and characterization of single-crystal wurtzite CdSe nanoribbons through a simple thermal evaporation process. Asymmetric growth of the nanoribbons occurs, yielding a sawlike shape with sharp teeth on one side. This asymmetric growth is suggested to be induced by the polarization of the c-plane in the wurtzite crystal structure.

Author response for "An ultra-high output self-managed power system based on a multilayer magnetic suspension hybrid nanogenerator for harvesting water wave energy"

From garish to practical: synergetic effects of short-circuiting and charge-trapping for high-entropy energy harvesting

A triboelectric device employing charge-trapping and short-circuiting is developed for high-entropy energy harvesting.

Ultra‐Robust and Hyperelastic Triboelectric Webbing for Self‐Powered Rehabilitation Sensing with Invisible and Embedded Design

Driven by the rapid evolution of flexible electronics, rehabilitation healthcare is shifting toward devices that seamlessly interface with human body. Yet, existing solutions often simply layer flexible sensor units over rigid components, making it difficult to combine high elasticity, mechanical robustness, and true imperceptibility. Here, we are pioneering a super-tough (∼54.7 MPa) and highly stretchable (>400% strain) triboelectric webbing (T-webbing) that overcomes this long-standing trade-off through the synergistic integration of an embedded textured architecture and functional elastic yarns. The T-webbing supports mass customization, exhibits outstanding electrical durability (>100 000 cycles), and enables reliable self-powered sensing capability with tunable mechanical properties for diverse rehabilitation tasks. In a proof-of-concept demonstration, the T-webbing is seamlessly integrated into a machine-learning-enabled lower-limb rehabilitation platform, achieving a motion recognition accuracy of 97.9% while enabling seamless one-click data sharing, intuitive human-machine interaction, and real-time remote guidance. By bridging high mechanical resilience with imperceptible wearability, our study offers a brand-new solution for data-driven, high-compliance, home-based rehabilitation within the Internet-of-Things ecosystem-addressing a pressing clinical need for scalable, patient-friendly solutions.

Recent Progress in Piezo‐Phototronic Effect Enhanced Solar Cells

Abstract For third generation semiconductors, for example, wurtzite ZnO and GaN, a piezopotential will be induced in these non‐centrosymmetric structures through applying a stationery deformation. The synchronous occupancy of semiconductor engineering, piezoelectric property, and optical excitation processes in these materials brings about outstanding device performances, such as promoting carrier creation, transfer, separation, or suppressing carrier recombination. Enormous research interests have been sparked in this emerging field known as the piezo‐phototronic effect. This manuscript reviews the fundamental research progress in enhanced photovoltaic efficiency by this effect, which not only provides a comprehensive coverage of the theoretical and experimental works illustrating the basic physics for understanding the enhanced solar cells when an external mechanical strain is applied, but also gives new insight into designing high‐performance solar cells.

Light-Triggered Pyroelectric Nanogenerator Based on a pn-Junction for Self-Powered Near-Infrared Photosensing

A nanogenerator, as a self-powered system, can operate without an external power supply for energy harvesting, signal processing, and active sensing. Here, near-infrared (NIR) photothermal triggered pyroelectric nanogenerators based on pn-junctions are demonstrated in a p-Si/n-ZnO nanowire (NW) heterostructure for self-powered NIR photosensing. The pyroelectric-polarization potential (pyro-potential) induced within wurtzite ZnO NWs couples with the built-in electric field of the pn-junction. At the moment of turning on or off the NIR illumination, external current flow is induced by the time-varying internal electric field of the pn-heterostructure, which enables a bias-free operation of the photodetectors (PDs). The NIR PD exhibits a high on/off photocurrent ratio up to 107 and a fast photoresponse component with a rise time of 15 μs and a fall time of 21 μs. This work provides an unconventional strategy to achieve active NIR sensing, which may find promising applications in biological imaging, optoelectronic communications, and optothermal detections.

Shock Compression of FePt and FePt/Fe3Pt Nanoparticles: Exchange-Coupled Nanocomposite Magnets

The shock‐compression response of partially‐ordered 10–20 nm size FePt and FePt/Fe3Pt nanocomposite particles has been studied in this work. The chemically synthesized and annealed nanoparticle powders were packed into three‐capsule plate‐impact fixtures at ∼45% density and shock consolidated using a gas‐gun at impact velocities of 500 and 750 m/s. The compacts were recovered as disc‐shaped bulk magnets, with up to ∼90% higher density than the initial packing density. Transmission electron microscopy analysis revealed plastic deformation and flow of nanoparticles in the process of void annihilation and densification. High‐resolution imaging revealed complete retention of nano‐size of particles in the dense magnets. Shock compression of the FePt nanoparticles also resulted in an order‐to‐disorder phase transition from fct‐to‐fcc structure. However, annealing at temperatures around 700°C caused complete reversal and formation of ordered fct structure. The resulting magnetic property measurements showed energy product (BH)max up to 14 MGOe and coercivity Hc up to 14.6 kOe, which are higher than the values measured for the starting nanoparticles.

Contact Electrification at the Liquid–Solid Interface

Interfaces between a liquid and a solid (L-S) are the most important surface science in chemistry, catalysis, energy, and even biology. Formation of an electric double layer (EDL) at the L-S interface has been attributed due to the adsorption of a layer of ions at the solid surface, which causes the ions in the liquid to redistribute. Although the existence of a layer of charges on a solid surface is always assumed, the origin of the charges is not extensively explored. Recent studies of contact electrification (CE) between a liquid and a solid suggest that electron transfer plays a dominant role at the initial stage for forming the charge layer at the L-S interface. Here, we review the recent works about electron transfer in liquid-solid CE, including scenerios such as liquid-insulator, liquid-semiconductor, and liquid-metal. Formation of the EDL is revisited considering the existence of electron transfer at the L-S interface. Furthermore, the triboelectric nanogenerator (TENG) technique based on the liquid-solid CE is introduced, which can be used not only for harvesting mechanical energy from a liquid but also as a probe for probing the charge transfer at liquid-solid interfaces.

Mg Doped Perovskite LaNiO₃ Nanofibers as an Efficient Bifunctional Catalyst for Rechargeable Zinc–Air Batteries

Rational design of efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is important for rechargeable zinc–air batteries. Herein, Mg doped perovskite LaNiO3 (LNO) nanofibers (LNMO NFs) were prepared by a facile electrospinning method combined with subsequent calcination. LNMO NFs show a more positive half-wave potential of 0.69 V and a lower overpotential of 0.45 V at a current density of 10 mA cm–2 than those of the pristine LNO NFs. As an air electrode for zinc–air battery, the cell with LaNi0.85Mg0.15O3 NFs catalyst is able to deliver a high specific capacity of 809.9 mAh g–1 at a current density of 5 mA cm–2. It also shows an excellent cycling stability over 110 h at a current density of 10 mA cm–2. DFT calculation results demonstrate that the LNMO surface binds oxygen stronger than LNO, which contributes to enhanced OER activity as observed in our experiments. The results indicate that LNMO NFs are an efficient and durable bifunctional catalyst for zinc–air batteries.

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.

A Bioresorbable Dynamic Pressure Sensor for Cardiovascular Postoperative Care

Bioresorbable electronics that can be absorbed and become part of the organism after their service life are a new trend to avoid secondary invasive surgery. However, the material limitation is a significant challenge. There are fewer biodegradable materials with pressure-sensitive properties. Here, a pressure sensor based on the triboelectric effect between bioabsorbable materials is reported. This effect is available in almost all materials. The bioresorbable triboelectric sensor (BTS) can directly convert ambient pressure changes into electrical signals. This device successfully identifies abnormal vascular occlusion events in large animals (dogs). The service life of the BTS reaches 5 days with a high service efficiency (5.95%). The BTS offers excellent sensitivity (11 mV mmHg-1 ), linearity (R2 = 0.993), and good durability (450 000 cycles). The antibacterial bioresorbable materials (poly(lactic acid)-(chitosan 4%)) for the BTS can achieve 99% sterilization. Triboelectric devices are expected to be applied in postoperative care as bioresorbable electronics.

Alternating the Output of a CdS Nanowire Nanogenerator by a White‐Light‐Stimulated Optoelectronic Effect

The response of a single CdS-nanowire-based nanogenerator to excitation by visible light is investigated. White light reduces the height of the Schottky barrier that existis at the tip nanowire contact, leading to possible barrier breakthrough and a contact-mode change from Schottky to quasi-Ohmic. This work demonstrates the triple coupling among semiconducting, piezoelectric, and optoelectric properties, which may be useful for designing new optopiezotronic devices.

Magnetic and Electrical Characterizations of Half‐Metallic Fe₃O₄ Nanowires

The magnetic properties of magnetite (Fe3O4) nanowires are investigated by means of electron holography, which deduces the magnetic information from the phase shift of electrons. The magnetic flux is parallel to the longitudinal axis of the nanowires (see figure). Observations on the magnetization distribution reveal the possibility of regulating the spin current with the half-metallic nanowires, owing to the controlled magnetization distribution in the 1D form.

An Integrated Solar Panel with a Triboelectric Nanogenerator Array for Synergistic Harvesting of Raindrop and Solar Energy

The triboelectric nanogenerator (TENG) is regarded as an effective strategy for harvesting energy from raindrops, and is a complementary solution with solar cells to achieve all-weather energy harvesting and sustainable energy supply. However, due to the irregularity of natural rainfalls in the volume, frequency, density, and location, designing high-efficiency raindrop TENG (R-TENG) arrays faces great challenges. In this work, a highly transparent, large-area, and high-efficiency R-TENG array with rational material choice, electrode structure, and array distribution is developed for efficiently harvesting irregular raindrop energy. The problem of electrical signal cancellation among adjacent raindrops can be fully avoided, as viewed from the high-resolution space-time analyses of high-speed camera and electrical signal characteristics. With the rationally designed electrode instead of multiple complex electrodes, all charges can be exported by the R-TENG array in a simulated irregular raindrop scenario. Moreover, it is demonstrated that the R-TENG possesses higher average power density (40.80 mW m-2 ) than that of the solar cell (37.03 mW m-2 ) in rainy condition. Additionally, a self-powered wireless light-intensity-monitoring system is demonstrated for real-time and all-day weather monitoring. This work provides useful guidance for designing high-efficiency TENG arrays integrated with solar panels for harvesting irregular raindrop energy and solar energy.

Electrocatalytic oxygen evolution reaction for energy conversion and storage: A comprehensive review

Water oxidation or oxygen evolution reaction (OER) electrocatalysis got much attention in the last few years because of its prime role in water splitting, rechargeable metal-air batteries and fuel cells. Therefore, the development of efficient, abundant and economical catalysts for water oxidation reaction is one of the main subjects of present study in renewable energies. This review article summarizes the very recent efforts in the field of OER electrocatalysis along with the faced challenges. The solutions to these challenges also outline with appropriate examples of scientific literatures. Significantly, the present review will provide the standards to evaluate the activity and stability for heterogeneous OER catalysts. It will clearly summarize the future directions and applications, especially the combination of sustainable energy utilization (like triboelectric nanogenerator) with water splitting. The providing study will help to explore and develop better catalysts and units for practical applications and will offer basic understanding of OER process along with the standard parameters to evaluate the performance.

Actively Perceiving and Responsive Soft Robots Enabled by Self‐Powered, Highly Extensible, and Highly Sensitive Triboelectric Proximity‐ and Pressure‐Sensing Skins

Abstract Robots that can move, feel, and respond like organisms will bring revolutionary impact to today's technologies. Soft robots with organism‐like adaptive bodies have shown great potential in vast robot–human and robot–environment applications. Developing skin‐like sensory devices allows them to naturally sense and interact with environment. Also, it would be better if the capabilities to feel can be active, like real skin. However, challenges in the complicated structures, incompatible moduli, poor stretchability and sensitivity, large driving voltage, and power dissipation hinder applicability of conventional technologies. Here, various actively perceivable and responsive soft robots are enabled by self‐powered active triboelectric robotic skins (tribo‐skins) that simultaneously possess excellent stretchability and excellent sensitivity in the low‐pressure regime. The tribo‐skins can actively sense proximity, contact, and pressure to external stimuli via self‐generating electricity. The driving energy comes from a natural triboelectrification effect involving the cooperation of contact electrification and electrostatic induction. The perfect integration of the tribo‐skins and soft actuators enables soft robots to perform various actively sensing and interactive tasks including actively perceiving their muscle motions, working states, textile's dampness, and even subtle human physiological signals. Moreover, the self‐generating signals can drive optoelectronic devices for visual communication and be processed for diverse sophisticated uses.

Triboelectrification Induced UV Emission from Gas Plasmon