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Thermophotovoltaic (TPV) systems can be used to harvest thermal energy for thermoelectric conversion with much improved efficiency and power density compared with traditional photovoltaic systems. As the key component, selective emitters (SEs) can re-emit tailored thermal radiation for better matching with the absorption band of TPV cells. However, current designs of the SEs heavily rely on empirical design templates, particularly the metal-insulator-metal (MIM) structure, and lack of considering the overall performance of TPV systems and optimization efficiency. Here, we utilized a deep reinforcement learning (DRL) method to perform a comprehensive design of a 2D square-pattern metamaterial SE, with simultaneous optimization of material selections and structural parameters. In the DRL method, only the database of refractory materials with gradient refraction indexes needs to be prepared in advance, and the whole design roadmap will automatically output the SE with optimal Figure-of-Merit (FoM) efficiently. The optimal SE is composed of a novel material combination of TiO2, Si, and W substrate, with its thickness and structure precisely optimized. Its emissivity spectra match well with the external quantum efficiency curve of the GaSb cell. Consequently, the overall performance of TPV is significantly enhanced with an output power density of 5.78 W/cm2, an energy conversion efficiency of 38.26%, and a corresponding FoM of 2.21, surpassing most existing designs. The underlying physics of optimal SE is explained by the coupling effect of multiple resonance modes. This work advances the practical application potential of TPV systems and paves the way for addressing other multi-physics optimization problems and metamaterial designs. [ABSTRACT FROM AUTHOR]

In the current study, complementary metasurface units with toroidal geometry were fabricated, using the computer numerical control engraving method. The metasurfaces were engraved in copper-coated, FR-4 plates. The produced metasurfaces were electromagnetically characterized in the microwave regime. Furthermore, they were studied regarding their energy harvesting capability, in the microwave range, where they absorb electromagnetic energy. It was found that toroidal structures harvest energy from the incident microwaves and transform it to electric power, through a simple rectification circuit. Moreover, their energy harvesting efficiency was found to be comparable or even superior to those of others reported so far. Therefore, the hereby obtained experimental results evidently show that engraved toroidal metasurfaces could potentially be used as energy harvesters in the microwave regime. [ABSTRACT FROM AUTHOR]

Within the field of elastic metamaterials, topological metamaterials have recently received much attention due to their ability to host topologically robust edge states. Introducing local resonators to these metamaterials also opens the door for many applications such as energy harvesting and reconfigurable metamaterials. However, the interactions between phenomena from local resonance and modulation patterning are currently unknown. This work fills that gap by studying multiple cases of spatially modulated metamaterials with local resonators to reveal the mechanisms behind bandgap formation. Their dispersion relations are determined analytically for infinite chains and validated numerically using eigenvalue analysis. The inverse method is used to determine the imaginary wavenumber components from which each bandgap is characterized by its formation mechanism. The topological nature of the bandgaps is also explored through calculating the Chern number and integrated density of states. The band structures are obtained for various sources of modulation as well as multiple resonator parameters to illustrate how both local resonance and modulation patterning interact together to influence the band structure. Other unique features of these metamaterials are further demonstrated through the mode shapes obtained using the eigenvectors. The results reveal a complex band structure that is highly tunable, and the observations given here can be used to guide designers in choosing resonator parameters and patterning to fit a variety of applications. [ABSTRACT FROM AUTHOR]

Over 2300 years ago, the discovery of tourmaline led to the understanding of pyroelectric properties, which opened new doors to various applications of pyroelectric crystal, such as neutron and x-ray generation, energy harvesting, mass spectrometry, high-voltage sources, and more. In the last two decades, researchers have carried out extensive research and development to select components and materials and innovate the design and construction of the pyroelectric neutron generator (PNG). This manuscript investigates the process and history of the PNG's development. It explains the physics governing pyroelectric crystals and the method of producing neutrons in a comprehensive and straightforward manner. Although PNGs have a lower yield and shorter lifetime compared to other neutron generators, they are still significant for research purposes due to their lack of need for an external high-voltage power supply, lower cost, smaller size, and safety. The main objective of this manuscript is to bring more attention to the research and development of PNGs. In recent years, new methods have been introduced that reduce the amount of neutron flux required for various applications. This has raised hope for the progress of commercial and industrial use of PNGs in the near future. The manuscript mentions some research cases that represent the future perspective of PNG development. Furthermore, the challenges faced by PNGs can be handled more efficiently with the utilization of generative learning algorithms and improvements in the components/mechanisms used for PNG design. [ABSTRACT FROM AUTHOR]

Environmental effects in excitation energy transfer have mostly been modeled by baths of harmonic oscillators, but to what extent such modeling provides a reliable description of actual interactions between molecular systems and environments remains an open issue. We address this issue by investigating fluctuations in the excitation energies of the light harvesting 2 complex using a realistic all-atomistic simulation of the potential energy surface. Our analyses reveal that molecular motions exhibit significant anharmonic features, even for underdamped intramolecular vibrations. In particular, we find that the anharmonicity contributes to the broadening of spectral densities and substantial overlaps between neighboring peaks, which complicates the meaning of mode frequencies constituting a bath model. Thus, we develop a strategy to construct a minimally underdamped harmonic bath that has a clear connection to all-atomistic dynamics by utilizing actual normal modes of molecules but optimizing their frequencies such that the resulting bath model can best reproduce the all-atomistic simulation results. By subtracting the underdamped contribution from the entire fluctuations, we also show that identifying a residual spectral density representing all other contributions with overdamped behavior is possible. We find that this can be fitted well with a well-established analytic form of a spectral density function or, alternatively, modeled as explicit time dependent fluctuations with muti-exponential or power law type correlation functions. We provide an assessment and the implications of these possibilities. The approach presented here can also serve as a general strategy to construct a simplified bath model that can effectively represent the underlying all-atomistic bath dynamics. [ABSTRACT FROM AUTHOR]

This paper explores the emergence of topological interface states in one-dimensional locally resonant lattices incorporating inerters in both nearest neighbor (NN) and beyond-nearest neighbor (BNN) coupling. The investigation focuses on the unique wave propagation characteristics of these lattices, particularly the presence and behavior of interface states. The non-trivial topological behavior due to broken inversion symmetry within the unit cell of the locally resonant lattice is comprehensively investigated in the presence of inerters in NN and BNN coupling. The emerging interface states in the supercell analysis exhibit specific spatial and frequency localization properties due to inerter-based BNN interactions. Additionally, the study demonstrates the ability of inerter elements with weak inertance to control the frequency of interface states while maintaining the fundamental topological properties of the lattice. The identified topological interface states in lattices with BNN coupling present an opportunity for designing diverse devices, such as waveguides, filters, sensors, and energy harvesting systems. Overall, this research enhances our comprehension of topological phenomena in inerter-based locally resonant lattices with BNN interactions and introduces possibilities for creating robust and versatile devices based on topologically protected edge/interface states. [ABSTRACT FROM AUTHOR]

In this paper, a wideband metasurface-loaded (MTS-L) rectenna system is proposed to capture electromagnetic (EM) energy at arbitrary azimuth angles. The radiation patterns of different modes in the original MTS configuration are analyzed using the characteristic mode theory, and potential modes with omnidirectional radiation are screened out. By the arrangement of patches, the roundness performance of the radiation pattern can be ameliorated, and the omnidirectional characteristic is obtained over a wide frequency band. Subsequently, the surface current density of the selected mode is carefully and artificially designed to facilitate probe excitation as well as refrain from introducing complex power-combining networks. A wideband rectifier circuit is designed as the load of the proposed antenna. Eventually, measured results show that it operates from 4.6 to 9.6 GHz with a fractional bandwidth of 70.4%, and the peak system efficiency is 52.2%. The proposed system demonstrates excellent potential for wireless power transmission and EM energy harvesting in indoor environments. [ABSTRACT FROM AUTHOR]

The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices. [ABSTRACT FROM AUTHOR]

Electric-field energy harvesters (EFEHs) have emerged as a promising technology for harnessing the electric field surrounding energized environments. Current research indicates that EFEHs are closely associated with Tribo-Electric Nano-Generators (TENGs). However, the performance of TENGs in energized environments remains unclear. This work aims to evaluate the performance of TENGs in electric-field energy harvesting applications. For this purpose, TENGs of different sizes, operating in single-electrode mode were conceptualized, assembled, and experimentally tested. Each TENG was mounted on a 1.5 HP single-phase induction motor, operating at nominal parameters of 8 A, 230 V, and 50 Hz. In addition, the contact layer was mounted on a linear motor to control kinematic stimuli. The TENGs successfully induced electric fields and provided satisfactory performance to collect electrostatic charges in fairly variable electric fields. Experimental findings disclosed an approximate increase in energy collection ranging from 1.51% to 10.49% when utilizing TENGs compared to simple EFEHs. The observed correlation between power density and electric field highlights TENGs as a more efficient energy source in electrified environments compared to EFEHs, thereby contributing to the ongoing research objectives of the authors.

We use a novel non-equilibrium algorithm to simulate steady-state fluid transport through a two-dimensional (2D) membrane due to a concentration gradient by molecular dynamics (MD) for the first time. We confirm that, as required by the Onsager reciprocal relations in the linear-response regime, the solution flux obtained using this algorithm agrees with the excess solute flux obtained from an established non-equilibrium MD algorithm for pressure-driven flow. In addition, we show that the concentration-gradient-driven solution flux in this regime is quantified far more efficiently by explicitly applying a transmembrane concentration difference using our algorithm than by applying Onsager reciprocity to pressure-driven flow. The simulated fluid fluxes are captured with reasonable quantitative accuracy by our previously derived continuum theory of concentration-gradient-driven fluid transport through a 2D membrane [D. J. Rankin, L. Bocquet, and D. M. Huang, J. Chem. Phys. 151, 044705 (2019)] for a wide range of solution and membrane parameters, even though the simulated pore sizes are only several times the size of the fluid particles. The simulations deviate from the theory for strong solute–membrane interactions relative to thermal energy, for which the theoretical approximations breakdown. Our findings will be beneficial for a molecular-level understanding of fluid transport driven by concentration gradients through membranes made from 2D materials, which have diverse applications in energy harvesting, molecular separations, and biosensing. [ABSTRACT FROM AUTHOR]

Global energy shortage puts stringent demand for energy harvesters capable of transforming external green vibration sources into electrical power. Employing a self-biased magnetoelectric (ME) composite of FeCuNbSiB/Ni/PZT (lead zirconate titanate), a prototype of vibration energy harvester is designed and fabricated. The energy harvester has a circular orbit in which a permanent magnetic cylinder reciprocates once an initial kinetic energy is provided. Upon a vibration signal, like handshaking, movement of the permanent magnetic cylinder causes an alternative magnetic field, which was applied on the ME composite. Via magnetic-force-electrical coupling, the ME composite of FeCuNbSiB/Ni/PZT produces output voltage. Finite element simulation is carried out to reveal the underlying mechanism of the harvester. The analysis shows that a maximum output voltage of 7.63 V can be obtained once an original potential energy is applied for the magnet. In particular, the magnet moves back and forth automatically inside the circular orbit with no need to further apply the energy. The effectiveness of the energy output is experimentally verified. When handshaking the energy harvester, a maximum open-circuit voltage of 5.51 V can be generated. The study offers a solution for power supplying some miniaturized or portable devices, such as small hand set and pedometer. [ABSTRACT FROM AUTHOR]

Energy harvesting textiles have emerged as a promising solution to sustainably power wearable electronics. Textile-based solar cells (SCs) interconnected with on-body electronics have emerged to meet such needs. These technologies are lightweight, flexible, and easy to transport while leveraging the abundant natural sunlight in an eco-friendly way. In this Review, we comprehensively explore the working mechanisms, diverse types, and advanced fabrication strategies of photovoltaic textiles. Furthermore, we provide a detailed analysis of the recent progress made in various types of photovoltaic textiles, emphasizing their electrochemical performance. The focal point of this review centers on smart photovoltaic textiles for wearable electronic applications. Finally, we offer insights and perspectives on potential solutions to overcome the existing limitations of textile-based photovoltaics to promote their industrial commercialization.

Pandit[1] provides a review on the application of magic angle spinning nuclear magnetic resonance (NMR) spectroscopy and related techniques, with which it is possible to access the motion of proteins, pigments, and lipids on sub-nanoseconds to millisecond timescales on very different length scales ranging from solubilized complexes to whole cells. Remarkably, the spectral density includes 50 high-frequency vibrational modes per pigment, besides a low-frequency part characterizing the pigment-protein coupling. Using this technique, excitation energy transfer between the bacteriochlorophyll a pigments of the LH2 complex of purple bacteria is studied. Two important points dealt with in the present Special Topic issue on "Photosynthetic Light-Harvesting and Energy Conversion" are the following: (i) Pigment-protein complexes undergo conformational transitions on many different timescales that include transitions between functionally relevant modes of light harvesting and photoprotection. [Extracted from the article]

A new design of a flexible and compact electrostatic generator with dielectric fluid is presented in this work. The generator utilizes the flow of dielectric fluid between two dielectric films to change the capacitance and converts mechanical energy into electrical energy. We fabricate a dielectric fluid generator (DFG) and build up an experimental setup to investigate the performance of energy harvesting. We use an optimal triangular electromechanical cycle and achieve a maximum energy harvesting power of 1.83 mW with a device that the length of the longest side is 15 cm. The power density is 35.2 μW g−1, and the conversion efficiency is 17.8%. The parameters of the DFG, including the initial voltage, the applied force, and the mechanical loading time, are studied. As a demonstration, we use the DFG to harvest electrical energy from hand tapping to power LEDs. The DFG is flexible and compact, which is promising for harvesting energy from human movements. [ABSTRACT FROM AUTHOR]

An innovative electromagnetic energy harvester was developed using a compact four-ring single-resistor unit cell. To achieve efficient conversion of electromagnetic waves into electricity, we integrated the high-performance Bi2Te3 thermoelectric material onto the load resistor. Remarkably, this unit cell exhibits exceptional energy harvesting capabilities at a frequency of 5.8 GHz while maintaining polarization insensitivity. Through comprehensive analysis, we evaluated the energy harvesting efficiencies, power loss distribution, and current density distribution. Additionally, we investigated the impact of incident power on the unit cell's temperature and energy conversion efficiencies. To enhance energy concentration on the load, we ingeniously designed an "L-shaped" metal through-hole structure within the four-ring single-resistor unit cell. Our results demonstrate that the four-ring single-resistor unit cell achieves an impressive harvesting efficiency of 94.5% at 5.8 GHz, with a thermal conversion efficiency of 43.3 °C/W, an electrical conversion efficiency of 0.23 mV/°C, and an electrical response rate of 9.4 mV/W. Notably, when subjected to a power input of 7 W, the unit cell produces an output voltage of 65.9 mV, and its theoretical maximum output power reaches 180 mW. [ABSTRACT FROM AUTHOR]

To maximize the capabilities of minimally invasive implantable bioelectronic devices, we must deliver large amounts of power to small implants; however, as devices are made smaller, it becomes more difficult to transfer large amounts of power without a wired connection. Indeed, recent work has explored creative wireless power transfer (WPT) approaches to maximize power density [the amount of power transferred divided by receiver footprint area (length × width)]. Here, we analyzed a model for WPT using magnetoelectric (ME) materials that convert an alternating magnetic field into an alternating voltage. With this model, we identify the parameters that impact WPT efficiency and optimize the power density. We find that improvements in adhesion between the laminated ME layers, clamping, and selection of material thicknesses lead to a power density of 3.1 mW/mm2, which is over four times larger than previously reported for mm-sized wireless bioelectronic implants at a depth of 1 cm or more in tissue. This improved power density allows us to deliver 31 and 56 mW to 10 and 27-mm2 ME receivers, respectively. This total power delivery is over five times larger than similarly sized bioelectronic devices powered by radiofrequency electromagnetic waves, inductive coupling, ultrasound, light, capacitive coupling, or previously reported magnetoelectrics. This increased power density opens the door to more power-intensive bioelectronic applications that have previously been inaccessible using mm-sized battery-free devices. [ABSTRACT FROM AUTHOR]

The emergence of new nanoporous materials, based, e.g., on 2D materials, offers new avenues for water filtration and energy. There is, accordingly, a need to investigate the molecular mechanisms at the root of the advanced performances of these systems in terms of nanofluidic and ionic transport. In this work, we introduce a novel unified methodology for Non-Equilibrium classical Molecular Dynamic simulations (NEMD), allowing to apply likewise pressure, chemical potential, and voltage drops across nanoporous membranes and quantifying the resulting observables characterizing confined liquid transport under such external stimuli. We apply the NEMD methodology to study a new type of synthetic Carbon NanoMembranes (CNM), which have recently shown outstanding performances for desalination, keeping high water permeability while maintaining full salt rejection. The high water permeance of CNM, as measured experimentally, is shown to originate in prominent entrance effects associated with negligible friction inside the nanopore. Beyond, our methodology allows us to fully calculate the symmetric transport matrix and the cross-phenomena, such as electro-osmosis, diffusio-osmosis, and streaming currents. In particular, we predict a large diffusio-osmotic current across the CNM pore under a concentration gradient, despite the absence of surface charges. This suggests that CNMs are outstanding candidates as alternative, scalable membranes for osmotic energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper, a broadband metamaterial absorber consisting of the doped silicon substrate and the square array of doped silicon covered by a SU-8 layer is presented. The target structure achieves an average absorption of 94.42% in the studied frequency range (0.5–8 THz). In particular, the structure exceeds 90% absorption in the frequency range of 1.44–8 THz, which is a significant increase in bandwidth relative to reported devices of the same type. Next, the near-perfect absorption of the target structure is verified by the impedance matching principle. Furthermore, through the analysis of the electric field distribution inside the structure, the physical mechanism of its broadband absorption is investigated and explained. Finally, the impact of fluctuations in the incident angle, polarization angle, and structural parameters on the absorption efficiency is examined at length. The analysis shows that the structure has characteristics, such as polarization insensitivity, wide-angle absorption, and good process tolerance. The proposed structure is advantageous for applications in THz shielding, cloaking, sensing, and energy harvesting. [ABSTRACT FROM AUTHOR]

The heat transfer characteristics of nanofluid play an important role in several industries to optimize their performance with the interaction of dissipative heat. However, in energy harvesting its application is vital. Therefore, the current heat transfer analysis was carried out based on the consequence of viscous and Joule dissipation in favour of the hybrid nanofluid flow over an elongating permeable curved convective thermal surface. Additionally, the external heat source and linear thermal radiation influence the flow phenomena whenever the velocity slip and nanoparticle shape effects associated with Hamilton–Crosser thermal conductivity model are significant. The designed equations relating to the flow phenomena are solved numerically using shooting-based Runge–Kutta fourth techniques followed by the similarity transformations used for the nondimensional form of the system of equations. The role of characterizing factors is deployed via graphs and described briefly. The correlation with the earlier investigation for the numerical outcomes of the rate of energy transport is also reported. The major outcomes of the study reveal that the enhanced curvature parameter along with the particle concentrations within their limit overshoots the velocity profiles further, the external heat source combined with thermal radiation also favors in enhancing fluid temperature. [ABSTRACT FROM AUTHOR]

This paper aims to improve the performance of the piezoelectric buckled beam under low vibration environment using the noncontact magnetic modulation method. Based on the bi-stable buckling beam structure, the magnetic force is introduced to capture more energy. In order to investigate the influence of magnetic force in the process of vibration, the dynamic response of the harvester is analyzed under different magnetic force through numerical simulation and experiment. It is found that the magnetic force has a softening effect on the structure, namely, it could reduce the stiffness of the buckled beam. Therefore, the energy harvester could realize large-amplitude vibration under low-amplitude or low-frequency vibration with the help of magnetic force. The experimental results show that the harvester can realize inter-well vibration only when the vibration acceleration is 3.5 g and the frequency is 15 Hz without the magnetic force. The harvester only needs 2.5 g acceleration or 10 Hz vibration frequency to realize the large-amplitude vibration. While in the case of 12 mm magnetic gap. After the magnetic force is introduced in the harvester, the voltage output under 2.5 g acceleration is increased from 1 to 4 V, and the voltage output at 10 Hz vibration frequency is increased from 0.2 to 2 V. Therefore, the proposed magnetically tuned bi-stable energy harvester can better operate in low frequency and low amplitude environments. [ABSTRACT FROM AUTHOR]

Multiferroic composites of sol-gel synthesized Sodium Bismuth Titanate (Na 0.5 Bi 0.5 TiO 3) and Co–Ti substituted Barium Hexaferrite (BaFe 12-2x Co x Ti x O 19 ; x = 0.0, 0.5, 1.0, 1.5 and 2.0) in the ratio 3:1 was synthesized through ceramic route. Successful formation of R3c rhombohedral and P63 / mmc hexagonal phases corresponding to Na 0.5 Bi 0.5 TiO 3 and BaFe 12-2x Co x Ti x O 19 respectively was confirmed from the XRD and Rietveld refinement pattern. The frequency and temperature dependence of dielectric constant and loss of the composite systems exhibited typical dispersion behaviour which could be understood using the Maxwell-Wagner model. Substituted samples showed enhanced dielectric behaviour where dielectric constant was observed to increase while loss tangent decreased. Using the Universal Jonscher's Power law (JPL), conductivition mechanisms of the composite systems were studied from the ac conductivity behaviour which revealed that the x = 0.0 sample followed Non-overlapping Small Polaron Tunnelling (NSPT) model while the remaining samples followed the Correlated Barrier Hopping (CBH) model. The complex impedance and Nyquist plot analysis showed the enhancement of resistive property in the x ≠ 0 systems. Magnetic hysteresis loop measurements were conducted, and the associated parameters were determined with the assistance of the Law of Approach to Saturation (LAS). Favourable reduction in the magnetic anisotropy was observed indicating the disturbance of magnetic spin structure in the hexaferrite phase. The P-E loops established the novel room temperature multiferroic nature of the composite systems. Significant magnetoelectric coupling was detected at room temperature in all samples, with the x = 0.5 sample exhibiting the highest value of approximately 59.81 mV/cmOe. These desirable properties suggest that the composites may find future device applications as in magnetically tunable energy harvesting devices and self-powered magnetoelectric sensors in the future. [ABSTRACT FROM AUTHOR]

Renewable energy sources, such as wind, tide, solar cells, etc, are the primary research areas that deliver enormous amounts of energy for our daily usage and minimize the dependency upon fossil fuel. Paralley, harnessing ambient energy from our surroundings must be prioritized for small powered systems. Nanogenerators, which use waste energy to generate electricity, are based on such concepts. We refer to these nanogenerators as energy harvesters. The purpose of energy harvesters is not to outcompete traditional renewable energy sources. It aims to reduce reliance on primary energy sources and enhance decentralized energy production. Energy storage is another area that needs to be explored for quickly storing the generated energy. Supercapacitor is a familiar device with a unique quick charging and discharging feature. Encouraging advancements in energy storage and harvesting technologies directly supports the efficient and comprehensive use of sustainable energy. Yet, self-optimization from independent energy harvesting and storage devices is challenging to overcome. It includes instability, insufficient energy output, and reliance on an external power source, preventing their direct application and future development. Coincidentally, integrating energy harvesters and storage devices can address these challenges, which demand their inherent action. This review intends to offer a complete overview of supercapacitor-based integrated energy harvester and storage systems and identify opportunities and directions for future research in this subject. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel S-scheme NiO/PbBiO 2 Br composites are synthesized through a hybrid approach combining hydrothermal and photodeposition methods. • NiO/PbBiO 2 Br composites demonstrate dual energy harvesting capabilities from solar and vibration sources. • A synergistic effect between piezocatalysis and photocatalysis is observed in NiO/PbBiO 2 Br. • NiO/PbBiO 2 Br exhibits significantly increased photoactivity in RhB degradation. • Enhanced charge separation efficiency is achieved in NiO/PbBiO 2 Br via an S-scheme mechanism. The fabrication of an S-scheme heterojunction demonstrates as an efficient strategy for achieving efficient charge separation and enhancing catalytic activity of piezocatalysts. In this study, a new S-scheme heterojunction was fabricated on the PbBiO 2 Br surface through the photo-deposition of NiO nanoparticles. It was then employed in the piezoelectric catalytic degradation of Rhodamine B (RhB). The results demonstrate that the NiO/PbBiO 2 Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO 2 Br synthesized after 2 h of irradiation, achieving a RhB degradation rate of 3.11 h−1, which is 12.4 times higher than that of pure PbBiO 2 Br. Simultaneous exposure to visible light and ultrasound further increases in the RhB degradation rate, reaching 4.60 h−1, highlighting the synergistic effect of light and piezoelectricity in the NiO/PbBiO 2 Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO 2 Br heterojunction was undertaken through electrochemical analyses, theoretical calculations, and in-situ X-ray photoelectron spectroscopy analysis. The outcomes reveal that p-type semiconductor NiO and n -type semiconductor PbBiO 2 Br possess matching band structures, establishing an S-scheme heterojunction structure at their interface. Under the combined effects of band bending, interface electric fields, and Coulomb attraction, electrons and holes migrate and accumulate on the conduction band of PbBiO 2 Br and valence band of NiO, respectively, thereby achieving effective spatial separation of charge carriers. The catalyst's synergistic photo-piezoelectric catalysis effect can be ascribed to its role in promoting the generation and separation of charge carriers under both light irradiation and the piezoelectric field. The results of this investigation offer valuable insights into the development and production of catalytic materials that exhibit outstanding performance through the synergy of piezocatalysis and photocatalysis. [ABSTRACT FROM AUTHOR]

The exploration of energy harvesting encompasses a wide array of sources, with a specific focus on recovering mechanical and magnetic energy from overlooked outlets, driving current research endeavours. In this study, we developed highly flexible Magneto-Mechano-Electric (MME) harvesters by combining poly(vinylidene fluoride) (PVDF)/barium calcium zirconium titanate (BCT-BZT) composite films with metglas. The flexible piezoelectric polymer-ceramic composite films were fabricated using a solvent casting technique. The high piezoelectric BCT-BZT fillers were synthesized through a sol-gel reaction route. A thorough analysis was carried out on these composites to evaluate their structural, functional, microstructural, and dielectric properties. The composite film loaded with 20 wt% BCT-BZT filler achieved a 78 % β-phase with a significant enhancement in the dielectric properties, resulting in a high permittivity∼40 and low dielectric loss. Employing these films, we engineered nanogenerators capable of converting mechanical energy into electrical energy, yielding an output voltage of 11 V. Thereafter, to harvest mechanical and stray magnetic fields, we developed a MME generator comprising a magnetic Metglas layer and PVDF-BCT-BZT composite and achieved an output voltage of 3.3 V with a power density of 85 μW/m2 when subjected to an AC magnetic field of 5 Oe. Furthermore, the MME generator has demonstrated the ability to charge various capacitors showcasing its potential for usage in self-powered, non-contact, and implantable devices. [ABSTRACT FROM AUTHOR]

In the energy harvesting field, it is critical to efficiently convert ambient vibrations into usable electrical energy, especially under conditions characterized by low amplitude and random excitations. This study introduces a novel hybrid bistable piezoelectric energy harvester (HBPEH) designed to optimize energy conversion in challenging environmental conditions. The HBPEH features a unique piezoelectric cantilever beam integrated with a dynamic amplifier at the fixed end, significantly enhancing both rotational and lateral displacements of the beam. This innovation lowers the threshold for snap-through events, crucial for maximizing energy transfer in bistable systems, and enables superior energy harvesting capabilities. Furthermore, the HBPEH demonstrates significantly higher power outputs when subjected to excitation intensities beyond critical levels, outperforming conventional energy harvesters. Extensive numerical and theoretical analyses confirm that the HBPEH offers a promising solution for applications hindered by suboptimal energy conversion rates. Its ability to operate effectively under diverse and unpredictable excitation conditions underscores the HBPEH's robustness and superiority in advanced energy harvesting scenarios. The design improvements introduced in this study highlight the potential of the HBPEH to transform energy harvesting approaches. By addressing the limitations of traditional harvesters, the HBPEH provides enhanced efficiency and reliability, making it suitable for a broader range of practical applications in variable environmental conditions. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators, known as TENGs, offer great potential as versatile energy harvesting devices. In recent years, there has been a rise in TENG designs that prioritize compatibility with sustainable biomaterials, leading to new possibilities in green technology. The novelty of this work lies in its pioneering exploration of utilizing sustainable biomaterials, particularly coconut husk, within the field of Tribo-electric nanogenerators (TENGs). This study focuses on evaluating and characterizing coconut husk as TENG material considering factors such as rotational speed, vane count, and coarseness, all of which influence the output potential of the B-TENG. The BTENG model employed in this research operates on a rotational sliding mode, featuring a biobased material layer of coconut husk, a layer of PTFE, and copper as electrodes. The B-TENG has a diameter of 100 mm with varying vane configurations (3-vane, 4-vane, and 5-vane). The sliding mode demonstrated impressive versatility, yielding output voltages spanning from 0.73 V to 4.0 V across rotational speeds of 200 RPM to 1400 RPM. Remarkably, the 5-vane fine-grained coconut husks achieved a maximum power of 121.10 mW at 10 Ohm and a power density of 3.84 mW/cm². This research carries global significance, contributing to the advancement of energy harvesting technology. Its applications range from harnessing the motion of human bodies to rotating machineries in any industry. [ABSTRACT FROM AUTHOR]

The dynamic electromechanical coupling behavior of composite materials is highly dependent on external excitation frequency. While degradable biomolecular materials typically exhibit lower piezoelectric coefficients compared to ceramics, neglecting their frequency‐dependent performance in the design of piezoelectric devices further leads to less efficient utilization of their piezoelectric properties. This oversight greatly hinders the practical application of these materials. To address this, a novel fractional derivation (FD) theory‐assisted model is introduced to reversely design the glycine‐polyvinyl alcohol (PVA) thin films for versatile enhanced bio‐applications. An electromechanical coupling model incorporating FD theory is developed to learn the relationships between FD parameters, film dimensions, and dynamic electromechanical properties. This model accurately predicts the electromechanical performance of the films across a wide frequency range, validated by both finite element simulations and experimental results. This therefore allows to establish key design principles for piezoelectric thin film in bioenergy harvesting and sensing, by tailoring thin film parameters to enhance the piezoelectric performance at specific stimuli frequencies. Demonstrations of glycine‐PVA film devices guided by this model reveal excellent performance in ultrasonic energy harvesting and carotid artery bio‐signal sensing. This study provides a robust theoretical framework for designing and optimizing biodegradable piezoelectric materials for various practical applications. [ABSTRACT FROM AUTHOR]

The next‐generation bionics and, more specifically, wearable and implantable bioelectronics require wireless, battery‐free, long‐term operation and seamless bio‐integration. Design considerations, materials choice, and implementation of efficient architectures have become crucial for the fabrication and deployment of wireless devices, especially if they are flexible or soft. Wireless power and data transfer represent key elements for the development of robust, efficient, and reliable systems for health monitoring, advanced disease diagnosis and treatment, personalized medicine. Here, the recent advances in materials and technologies used for wireless energy sourcing and telemetry in bio‐integrated flexible bionic and bioelectronic systems are reviewed. The study tackles different challenges related to mechanical compliance, low thickness, small footprint, biocompatibility, biodegradability, and in vivo implementation. The work also delves into the main figures of merit that are mostly adopted to quantify the wireless power/data transfer performances. Lastly, the pivotal applications of wearable and implantable wireless bionics/bioelectronics are summarized, such as electrical stimulation/recording, real‐time monitoring of physiological parameters, light delivery trough optical interfaces, electromechanical stimulation via ultrasounds, highlighting their potential for future implementation and the challenges related to their commercialization. [ABSTRACT FROM AUTHOR]

Droplet‐based electricity generators (DEGs) have emerged as innovative devices capable of transducing the kinetic energy of falling water droplets into electrical power, thereby presenting a promising solution for ambient energy harvesting. For effective application, DEGs must exhibit transparency and flexibility to facilitate aesthetic integration and optical/mechanical adaptability for utilization on natural objects and wearable devices. In this study, a hydrogel‐based DEG (Hy‐DEG) designed is proposed to be seamlessly integrated into everyday environments without compromising design or functionality. With the intrinsic characteristics of hydrogel, the Hy‐DEG exhibits superior optical transmittance (≈99%) and stretchability (≈70% of its original length), generating the electrical output performance of ≈45 V of voltage, 15 µA of current, and 42 µW of maximum peak power, with single droplet impact. This capability of the Hy‐DEG can operate electronic devices for environmental monitoring while maintaining seamless integration with commonly encountered surfaces. In this context, this study elucidates the characteristics of hydrogel bestowing novel functionalities upon the DEG, expanding the potential for energy harvesting in residential and commercial contexts. The implications of this research extend beyond conventional energy generation, fostering the development of self‐powered, transparent, and flexible devices. [ABSTRACT FROM AUTHOR]

With the development of wireless communication technology, the number of devices accessing the communication network is increasing. This paper addresses critical issues such as low spectrum resource utilization and the energy constraints of devices. The investigation focuses on the system performance of the shared relay Cognitive Radio Non-Orthogonal Multiple Access (CR-NOMA) network based on Simultaneous Wireless Information and Power Transfer (SWIPT) network model. Unlike the existing CR-NOMA model in which the secondary network user do not participate in the transmission of information from the primary network, we consider the secondary network near user as shared relay. The shared relay utilizes SWIPT technology to harvest energy using a nonlinear energy harvesting model. Additionally, the shared relay assists in transmitting information from the primary network base station to primary user, as well as from the secondary network base station to far user of the secondary network. Subsequently, we conduct a series of simulations to analyze the effects of Signal-to-Noise Ratio (SNR), power distribution factor, interference threshold, and time-switching (TS) factor on system performance. Furthermore, we compare and analyze the performance of our proposed network model against CR-NOMA network across three dimensions: outage probability, throughput, and energy efficiency. Our results demonstrate that the proposed network model exhibits superior outage performance and enhances user throughput compared to the CR-NOMA network. Additionally, it demonstrates improved energy efficiency compared to the shared relay CR-NOMA network, leading to an overall improvement in network performance. [ABSTRACT FROM AUTHOR]

The development of triboelectric nanogenerators (TENGs) using sustainable materials addresses the global electronic waste issue. This research focuses on fabricating a TENG device with biodegradable polylactic acid (PLA) as the tribopositive material and polytetrafluoroethylene (PTFE) as the tribonegative material. ZnFe2O4 nanoparticles are incorporated into the PLA matrix to enhance surface charge density and synthesised via a simple combustion method. PLA-ZnFe2O4 composite films were prepared by solvent casting with varying nanofiller content (0.25, 0.45, 0.65, and 0.85 g). Prepared composites were characterised by Powder X-ray Diffraction (PXRD) for crystalline nature and phase purity, Fourier Transform Infrared Spectroscopy (FTIR) for vibrational analysis, and Scanning Electron Microscopy (SEM) for surface morphology. The inclusion of ZnFe2O4 nanoparticles improves TENG output performance, with a maximum output voltage of 18.4 V and a current of 1.57 µA observed for a PLA (poly(lactic acid)) composite with 39.39% nanoparticle content. Electrical studies on the optimised device show successful charging of various capacitors and powering 20 LEDs and a calculator. Body movements like walking and jumping were also tested to measure voltage and current outputs. These findings highlight new possibilities for developing smart, self-powered electronic devices. [ABSTRACT FROM AUTHOR]

The utilization of salt concentration gradients as a renewable energy source represents a pivotal solution to the energy crisis. However, it is a persistent challenge to fabricate high‐performance ion permeable membranes with excellent ion permselectivity. In this work, hydrogen‐bonded organic framework (HOF) is in situ growth on anodic aluminum oxide (AAO) via chemical‐binding and solution‐processing strategy. The hydrogen bonding and π–π interactions forming the porous structure and the internal unprotonated carboxyl groups endow the HOF with superior cation selectivity and ion permeability. Furthermore, benefiting from the remarkable asymmetry of the prepared nanofluidic membrane arising from structure and charge of AAO and HOF, the HOF/AAO presents outstanding ion current rectification (ICR) characteristic, which can eliminate the ion concentration polarization (ICP) and power loss. Therefore, an impressive output power density with 500‐fold NaCl gradient is achieved as 75.2 W m−2 using the as‐prepared HOF/AAO, which is superior to most of reported membranes (7.0–40.0 W m−2). To show the critical role of HOF, 2D and 3D MOF with the same monomers are also synthesized, achieving decreased power densities of 36.2 and 58.3 W m−2 respectively. The present work provides a novel strategy to develop high‐performance nanofluidic ICR membranes for osmotic energy harvesting. [ABSTRACT FROM AUTHOR]

Harvesting low‐grade waste heat into electrical energy is recognized as a promising solution for sustainable energy supply. In parallel, thermotropic smart windows have emerged as an efficient way to reduce building energy consumption. It is posit that thermotropic smart windows with inherent thermoelectric property may offer unique advantages for practical applications. Herein, the preparation and characterization of a series of ionic hydrogels that exhibit temperature‐sensitive phase transition behavior is reported, which are suitable for both thermotropic smart windows and thermoelectric generators. Notably, the lower critical solution temperature (LCST) of this ionic hydrogels can be feasibly modulated, and the thermoteopic phase transition also induces a sharp increase in their Seebeck coefficient, reaching up to 39.03 mV K−1 with a power factor (PFi) value up to 0.838 mW m−1 K−2. A prototype dual functional thermotropic smart window that simultaneously works as an ionic thermoelectric generator is further demonstrated, achieving both efficient phase transition driven by solar heat at ≈26 °C and an energy density up to 250 mJ m−2. This study offers new opportunity for the development of smart materials that can bridge the gap between thermal comfort and energy sustainability for energy harvesting and smart building applicat. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) micro‐nano droplets show the superiority in reducing the high surface tension applicable in conductive inks for flexible electronics. However, the dynamic surface makes LM droplets susceptible to be oxidized, facing challenges in storage and applications. Herein, a bifunctional groups cross‐linking strategy is adopted to encapsulate LM droplets into a robust shell. During sonicating LM in carboxymethyl chitosan (CMCS) solution with bifunctional groups (i.e., carboxyl and amino groups), a robust interface shell is constructed by anchoring effect, thereby providing high chemical stability (>7d). When directionally freezing‐drying LM dispersions, aerogel with Janus architecture is produced driven by the gravity of LM droplets. Due to the unique heterogeneous structure, the resultant aerogel exhibits a selective multifunctional response toward directional bending. In addition, owing to the gradient distribution of CMCS within aerogel, moisture electricity generator can be built with a high output voltage of 460 mV. Thus, this bifunctional groups cross‐linking strategy not only improves the chemical stability of LM micro‐nano droplets, but also renders a new method for producing multifunctional aerogel with energy harvesting and selective directional recognition, and applicable in smart sensors and power supplying devices. [ABSTRACT FROM AUTHOR]

The rapid development of the Internet of Things has led to numerous functional electronic devices, making it a significant challenge to provide power for these distributed devices. Triboelectric self‐power technology is ideal for smart devices due to its material diversity and high energy efficiency. However, traditional triboelectric materials have weak electrostatic induction due to their low dielectric constant. Additionally, the thermionic emission effect reduces their electric output in high temperatures, limiting their applications. This study designes a thermally robust aramid triboelectric material with a high dielectric constant through heat‐induced cross‐linking heterogeneous interface engineering. This novel material not only achieves high triboelectric output but also maintains high performance across a wide temperature range. The heat‐induced cross‐linking process enhances the interaction between aramid nanofibers and Al2O3 nanosheets, significantly improving the electrical performance, and flame retardance of the material, and the relative dielectric constant increases 16‐fold. The triboelectric nanogenerator constructed with this material achieves a power density of 3.97 W m−2, and maintains high triboelectric output at 260 °C. Finally, a self‐powered detection system collects high‐temperature gas energy and drives sensors is designed. This research presents a novel strategy for high‐performance triboelectric materials, showing significant potential for self‐powered devices. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) hold immense potential as sustainable energy sources, with waste materials serving as promising materials for their fabrication. Nearly 270 million tons of waste is produced yearly, most of which remains unrecycled. TENGs can utilize this wide range of waste to convert mechanical energy to electrical energy while providing a solution for the global issue of plastic waste. On the other hand, the enormous demand for wearable electronics and the Internet of Things (IoT) trigger the development of self‐reliant energy sources. Currently, TENGs are one of the preferred choices as they are easy to design and generate high output. In this regard, TENGs are promising for utilizing waste materials, particularly for self‐powered or energy‐autonomous applications. This review focuses on utilizing waste materials from diverse sources, including biowaste, household waste, medical, laboratory, pharmaceutical, textile, electronic waste (e‐waste), and automotive waste for TENG development. Different waste materials are detailed for their potential as materials for TENGs, their availability, and recycling methods. The review also highlights the applications of TENGs fabricated from waste materials. Finally, the challenges, limitations, and future perspectives of using waste materials for TENG fabrication are discussed to motivate further advances. [ABSTRACT FROM AUTHOR]

Polar 2D materials hold the emerging functionalities such as ferro‐, piezo‐, and pyro‐electric properties. On account of infrared‐active low bandgap and polar nature at reduced dimensionality, they served as an ideal choice of pyroelectric material. It can cover up a diverse range of applications, such as waste thermal energy harvesting, IR imaging, photodetector, temperature sensors, and several catalytic processes due to the abundance of dynamic thermal fluxes. Recently, 2D pyroelectric materials have manifested a substantial role in thermal energy harvesting. Consequently, it is realized that there are plenty of scopes available to diversify its applicability. Thus, the challenges are spotlighted in this perspective to envision the desired 2D pyroelectric materials to achieve the effective thermal energy harvesting, sensing, and catalytic efficacy. Particularly, the emphasis is given to elucidate the role of spontaneous polarization in 2D materials to ascertain the giant pyroelectricity. [ABSTRACT FROM AUTHOR]

In this work, we propose elastic metamaterials with phase discontinuities to steer the propagation of near-source bulk waves in a semi-infinite elastic medium. Our design exploits an array of embedded subwavelength resonators with tailored masses to attain a complete phase shift spanning 0−2π. This phase control allows for diverse wave functionalities, such as directional refraction and energy focusing. Through the use of dispersion diagrams and the generalized Snell's law, along with a multiple scattering formulation, we analytically demonstrate the effectiveness of our design in achieving the desired wavefront manipulation. The proposed design has the potential to advance the field of guiding elastic waves using metamaterials and find practical applications in areas such as isolating ground-borne vibrations in densely urbanized regions and energy harvesting. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

In this paper, an inertial amplifier and a quasi-zero stiffness system are combined to propose an energy harvesting system that can change the dynamic mass of the system. By adjusting the inertial amplifier, it is possible to change the distribution of its chaotic region and the effective range of energy collection. The kinetic equations of the system with an inertial amplifier under a combination of multiple harmonic excitations are developed. Based on this, the system was simulated and tested and the Lyapunov exponent, the RMS value of the induced voltage and the coexisting basins of attraction were plotted. Subsequently, the best optimization solution to improve the energy harvesting efficiency of the system was identified. In addition, the system was tested for impulse excitation based on the given coexisting basins of attraction. The simulation results show that the inertial amplifier can effectively improve the range of the energy harvesting region and the distribution of the chaotic region in the system ground under ultra-low-frequency vibration. The initiation of impulse excitation can change the energy harvesting performance of the system to a great extent. [ABSTRACT FROM AUTHOR]

The perovskite materials are broadly incorporated into optoelectronic devices due to a number of advantages. Their rapid technological progress is related to the relatively simple fabrication process, low production cost and high efficiency. Significant improvement is made in the light emitting, detection performance and device design especially operating in the visible and near‐infrared regions. This review presents the status and possible future development of the perovskite devices such as solar cells, photodetectors, and light‐emitting diodes. The fundamental properties of perovskite materials related to their effective device applications are summarized. Since the development of the perovskite technology is mainly driven by the revolutionary evolution of the semiconductor perovskite solar cell as a robust candidate for next‐generation solar energy harvesting, this topic is considered first. The device engineering of various perovskite photodetector structures, including perovskite quantum dot photodetectors, is then discussed in detail. Their performance is compared with the current commercial photodetectors available on the global market together with their challenges. Finally, the considerable progress in the fabrication of the perovskite light‐emitting diodes with external quantum efficiency exceeding 20% is presented. The paper is completed in an attempt to determine the development of perovskite optoelectronic devices in the future. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have been widely used to harness various forms of mechanical energy for conversion to electrical energy. However, the contentious challenge in characterising TENGs is the lack of standard protocols for assessing mechanical‐to‐electrical energy conversion processes. Herein, macroscopic signal analysis is used to identify three key charging events within triboelectric signals: charge induction (CI), contact electrification (CE), and electrostatic discharge (ESD). By considering two phases of motion during contact‐separation (approach and departure of the contact materials), CI arising from the motion of bound surface charge (varying electric field) between opposing contact materials is shown to dominate the measured displacement current signal, rather than the process of CE itself. Furthermore, the conventional signal (i. e. voltage, current, charge) interpretation of CE and CI during approach and departure phases is re‐assessed, to indicate that the sudden spike of current often observed immediately prior to contact (or after separation) arises from polarity inverting electrostatic discharge (ESD). This aspect of the measured triboelectric effect, which is often ignored, is crucial for the design of TENGs and hence, techniques to enhance the understanding and control over the stochastic occurrence of ESDs is explored. The methods proposed for the deconvolution of the macroscopic signal components of TENGs, and mitigation of ESD occurrences, will allow for precise quantification of the associated charging events. The applications of this study will template the design and development of future super‐TENGs with optimised energy conversion capabilities. [ABSTRACT FROM AUTHOR]

Luminescent materials require systems that exhibit both dual‐state emission (DSE) and aggregation‐induced emission (AIE) to overcome the limitation of aggregation‐caused quenching (ACQ). Herein, a molecular assembler capable of crafting nanowires that exhibit programmable fluorescence across a broad spectrum of colors in a precisely quantized manner is reported. Because it is a starburst dendritic box made of PAMAM dendrimer (P), controller (C) molecules, and motor (M) molecules, the assembler is called PCM. Here, Nile red is chosen as C and placed into the hollow core of the dendrimer; a double ratchet motor (DRM) is chosen as M and is connected to the N‐terminals of the PAMAM dendrimer. While aqueous dispersed PCM assemblers have broad fluorescence bands beyond 300 nm, their crafted nanowires produce quantized cyan‐green, yellow, and orange‐red light emission in the spectra. These PCM assemblers are shown to hold long‐term memory, rapid switching, and energy harvesting by modulating photonic bandgaps, causing a longer redshift in the solid phase. The DSE of PCM can yield versatile photonics applications like bioimaging and energy harvesting. As PCM nanowires can modulate photonic bandgaps to cause a longer redshift, PCM fluorophores hold promise for drug delivery and cell separation like infrared‐sensitive operations. [ABSTRACT FROM AUTHOR]