Research Article Issue
Magnetic-field-assisted triboelectric nanogenerator for harvesting multi-directional wave energy
Nano Research 2024, 17 (8): 7144-7152
Published: 02 May 2024
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Ocean wave energy is a significant and promising source of renewable energy. However, the energy harvesting is challenging due to the multi-directional nature of waves. This paper proposes a magnetic-field-assisted triboelectric nanogenerator (MFA-TENG) for harvesting multi-directional wave energy. By incorporating a magnetic field, the planar motion of the pendulum is converted into spatial motion, increasing the triggering of multilayered TENG (M-TENG) and enhancing the output energy of the MFA-TENG. Experimental results demonstrate that the output energy of the MFA-TENG is increased by 73% by utilizing the magnetic field. Moreover, a spring model based on the origami-structured M-TENG is established to analyze the effect of different equivalent stiffnesses on the performance of the M-TENG, aiming to obtain optimal output performance. The results showcase the impressive output performance of the M-TENG, generating outputs of 250 V, 18 μA, and 255 nC. Furthermore, the proposed MFA-TENG effectively harvests multi-directional wave energy under water-wave driven conditions. This study significantly enhances the ability of the MFA-TENG to harvest multi-directional wave energy and presents a promising approach for self-powered marine monitoring in the future.

Research Article Issue
3D interlocked all-textile structured triboelectric pressure sensor for accurately measuring epidermal pulse waves in amphibious environments
Nano Research 2024, 17 (3): 1923-1932
Published: 10 August 2023
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The performance degradation and even damage of the e-textiles caused by sweat, water, or submersion during all-weather health monitoring are the main reasons that e-textiles have not been commercialized and routinized so far. Herein, we developed an amphibious, high-performance, air-permeable, and comfortable all-textile triboelectric sensor for continuous and precise measurement of epidermal pulse waves during full-day activities. Based on the principle of preparing gas by acid-base neutralization reaction, a one-piece preparation process of amphibious conductive yarn (ACY) with densely porous structures is proposed. An innovative three-dimensional (3D) interlocking fabric knitted from ACYs (0.6 mm in diameter) and polytetrafluoroethylene yarns exhibit high sensitivity (0.433 V·kPa−1), wide bandwidth (up to 10 Hz), and stability (> 30,000 cycles). With these benefits, 98.8% agreement was achieved between wrist pulse waves acquired by the sensor and a high-precision laser vibrometer. Furthermore, the polytetrafluoroethylene yarn with good compression resilience provides sufficient mechanical support for the contact separation of the ACYs. Meanwhile, the unique skeletonized design of the 3D interlocking structure can effectively relieve the water pressure on the sensor surface to obtain stable and accurate pulse waves (underwater depth of 5 cm). This achievement represents an important step in improving the practicality of e-textiles and early diagnosis of cardiovascular diseases.

Research Article Issue
Flexo-photocatalysis in centrosymmetric semiconductors
Nano Research 2024, 17 (3): 1173-1181
Published: 01 August 2023
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The separation of photogenerated electron–hole pairs is vitally important for photocatalysis, which can be effectively promoted by polarization field. However, it only manifests in piezoelectric/pyroelectric/ferroelectric materials that have a non-centrosymmetric structure. Here, we demonstrate that the polarization enhanced photocatalysis (with wide spectra from ultraviolet (UV) light to visible light) can be achieved in centrosymmetric semiconductors, such as δ-MnO2 and TiO2 nanosheets integrated nanoflowers, by using the strain-gradient-induced flexoelectric polarization that is always overlooked in polarization-enhanced catalysis. Under ultrasonic and illumination excitation, the organic pollutants (methylene blue (MB), etc.) can be effectively degraded within 30 min with excellent stability and repeatability. Compared with photocatalysis, the flexo-photocatalytic performance of above centrosymmetric semiconductors is substantially increased by 85%. Moreover, the factors related to flexo-photocatalysis such as material morphology, mechanical stimuli source, and adsorption are explored to deeply understand the mechanism of flexo-photocatalysis. This work opens up a way for high-performance photocatalysis in centrosymmetric semiconductors.

Research Article Issue
Flexoelectricity-enhanced photovoltaic effect in trapezoid-shaped NaNbO3 nanotube array composites
Nano Research 2023, 16 (9): 11914-11924
Published: 27 July 2023
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In this work, we successfully prepared vertically aligned NaNbO3 nanotube (NN-NT) with trapezoidal shapes, in which the orthorhombic and monoclinic phases coexisted. According to the structure analysis, the NN-NT/epoxy composite film had excellent flexoelectric properties due to the lattice distortion caused by defects and irregular shape. The flexoelectric effect is the greatest in the vertical direction in the flexible NN-NT/epoxy composite film, and the flexoelectric coefficient ( μ12) is 2.77 × 10−8 C·m−1, which is approximately 5-fold higher than that of the pure epoxy film. The photovoltaic current of the NN-NT/epoxy composite film increased from 39.9 to 71.8 nA·cm−2 in the direction of spontaneous polarization when the sample was bent upward due to the flexoelectricity-enhanced photovoltaic (FPV) effect. The flexoelectric effect of the NN-NT/epoxy composite film could modulate the photovoltaic response by increasing it by 80% or reducing it to 65% of the original value. This work provides a new idea for further exploration in efficient and lossless ferroelectric memory devices.

Research Article Issue
A drawstring triboelectric nanogenerator with modular electrodes for harvesting wave energy
Nano Research 2023, 16 (8): 10931-10937
Published: 19 June 2023
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The development and utilization of marine blue energy has become the focus of current research. A drawstring triboelectric nanogenerator with modular electrodes (DS-TENG) is proposed to harvest wave energy. Motion displacement and water wave adaptability are improved by using the drawstring structure in the DS-TENG. Furthermore, the modular electrode design is applied to improve the durability and replaceability of the generation units. The rationality of the structure is verified by theoretical analysis, and performance experiments on the fundamental output, displacement and frequency, durability and application are carried out. The DS-TENG can achieve output performance of 98.03 nC, 3.63 μA, 238.50 V and 923.92 µW at 150 mm and 1.0 Hz. In addition, the performance drops by 6.11% after 110,000 cycles for DS-TENG durability. This paper will provide reference for the design of TENG that adapts to a wide range of wave heights.

Research Article Issue
Enhanced performance of triboelectric mechanical motion sensor via continuous charge supplement and adaptive signal processing
Nano Research 2023, 16 (7): 10263-10271
Published: 03 June 2023
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The development of automation industry is inseparable from the progress of sensing technology. As a promising self-powered sensing technology, the durability and stability of triboelectric sensor (TES) have always been inevitable challenges. Herein, a continuous charge supplement (CCS) strategy and an adaptive signal processing (ASP) method are proposed to improve the lifetime and robustness of TES. The CCS uses low friction brushes to increase the surface charge density of the dielectric, ensuring the reliability of sensing. A triboelectric mechanical motion sensor (TMMS) with CCS is designed, and its electrical signal is hardly attenuated after 1.5 million cycles after reasonable parameter optimization, which is unprecedented in linear TESs. After that, the dynamic characteristics of the CCS-TMMS are analyzed with error rates of less than 1% and 2% for displacement and velocity, respectively, and a signal-to-noise ratio of more than 35 dB. Also, the ASP used a signal conditioning circuit for impedance matching and analog-to-digital conversion to achieve a stable output of digital signals, while the integrated design and manufacture of each hardware module is achieved. Finally, an intelligent logistics transmission system (ILTS) capable of wirelessly monitoring multiple motion parameters is developed. This work is expected to contribute to automation industries such as smart factories and unmanned warehousing.

Open Access Letter Issue
Rational TENG arrays as a panel for harvesting large-scale raindrop energy
iEnergy 2023, 2 (2): 93-99
Published: 01 June 2023
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Raindrops contain abundant renewable energy including both kinetic energy and electrostatic energy, and how to effectively harvest it becomes a hot research topic. Recently, a triboelectric nanogenerator (TENG) using liquid–solid contact electrification has been demonstrated for achieving an ultra-high instantaneous power output. However, when harvesting the energy from the dense raindrops instead of a single droplet, a more rational structure to eliminate the mutual influence of individual generation units is needed for maximize the output. In this work, a “solar panel-like” bridge array generators (BAGs) is proposed. By adopting array lower electrodes (ALE) and bridge reflux structure (BRS), BAGs could minimize the sharp drop in the peak power output for large-scale energy harvesting devices. When the area of the raindrop energy harvesting device is 15 × 15 cm2, the peak power output of BAGs reached 200 W/m2, which is remarkable for paving a potential industrial approach for effective harvesting raindrop energy at a large scale.

Open Access Research Highlights Issue
Scaling up blue energy harvesting: Transitioning from single generators to multiple generators
iEnergy 2023, 2 (2): 91
Published: 01 June 2023
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Research Article Issue
Ambipolar tribotronic transistor of MoTe2
Nano Research 2023, 16 (9): 11907-11913
Published: 30 May 2023
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Two-dimensional (2D) tribotronic devices have been successfully involved in electromechanical modulation for channel conductance and applied in intelligent sensing system, touch screen, and logic gates. Ambipolar transistors and corresponding complementary inverters based on one type of semiconductors are highly promising due to the facile fabrication process and readily tunable polarity. Here, we demonstrate an ambipolar tribotronic transistor of molybdenum ditelluride (MoTe2), which shows typical ambipolar transport properties modulated by triboelectric potential. It is comprised of a MoTe2 transistor and a lateral sliding triboelectric nanogenerator (TENG). The induced triboelectric potential by Maxwell’s displacement current (a driving force for TENG) can readily modulate the transport properties of both electrons and holes in MoTe2 channel and effectively drive the transistor. High performance tribotronic properties have been achieved, including low cutoff current below 1 pA·μm−1 and high current on/off ratio of ~ 103 for holes and electrons dominated transports. The working mechanism on how to achieve tribotronic ambipolarity is discussed in detail. A complementary tribotronic inverter based on single flake of MoTe2 is also demonstrated with low power consumption and high stability. This work presents an active approach to efficiently modulate semiconductor devices and logic circuits based on 2D materials through external mechanical signal, which has great potential in human–machine interaction, intelligent sensor, and other wearable devices.

Review Article Issue
Bionic iontronics based on nano-confined structures
Nano Research 2023, 16 (9): 11718-11730
Published: 06 May 2023
Abstract PDF (9.8 MB) Collect

The Moore’s law in silicone-based electronics is reaching its limit and the energy efficiency of the most sophisticated electronics to mimic the iontronic logic circuit in single-celled organisms is still inferior to their natural counterpart. Unlike electronics, iontronics is widely present in nature, and provides the fundamentals for many life activities through the transmission and conversion of information and energy via ions.

Moreover, as nanotechnology and fabrication processes continue to advance, highly efficient iontronics could be enabled by creation of asymmetry from nano-confined unipolar ion transport through various nanohierarchical structures of materials. The introduction of bionic design and nanostructures has made it possible for ions to demonstrate numerous anomalous behaviours and entirely new mechanisms, which are governed by complex interfacial interactions. In this review, we discuss the origins, development, mechanism, and applications of bionic iontronics and analyze the unique benefits as well as the practicality of iontronics from a variety of perspectives. Iontronics, as an emerging field of research with innumerable challenges and opportunities for exploring the theory and applications of ions as transport carriers, promises to provide new insights in many subjects covering energy and sensing, etc., and establishes a new paradigm in investigating the ionic-electric signal transduction interface for futuristic iontronic logic circuit and neuromorphic computing.

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