Biodegradable triboelectric materials for sustainable mechanical energy harvesting

Three-dimensional (3D) hydrogel membranes offer great potential for harvesting osmotic energy from salinity gradients, yet their practical application remains limited by the lack of an autonomous self-healing capability, which is critical for long-term operational stability. Here, we report a self-healing 3D hydrogel membrane engineered via physical metal coordination interactions that enables efficient osmotic energy conversion with autonomous repair functionality. Combined experimental and theoretical investigations reveal that the space-charged 3D network facilitates highly efficient permselective ion transport. Beyond its excellent self-healing capability, the membrane delivers a high power density of 6.35 W m-2 for osmotic energy harvesting from seawater-river water mixing, significantly outperforming most macroscopic porous nanofluidic membranes. This work not only underscores the potential of interconnected 3D hydrogels for high-performance osmotic energy conversion but also provides a practical strategy to achieve durable and sustainable energy harvesting systems.

Recent progress in cellulose-based flexible thermoelectric devices: Materials, designs, mechanisms, and applications.

Investigating the effect of membrane pore size on the permeability of carbon nanotubes in reverse electrodialysis using molecular dynamics simulation.

Singlet fission (SF) provides a promising strategy for surpassing the Shockley-Queisser limit in photovoltaics, thereby enabling high-efficiency, sustainable solar energy harvesting. However, the identification of efficient SF materials is hindered by the limited availability of suitable molecular candidates and the high computational costs associated with conventional quantum-chemical methods for excited states. In this study, we introduce a high-throughput screening framework that integrates a graph neural network (GNN) with multi-level validation to accelerate the discovery of promising SF candidates. Trained on a previously reported FORMED database, the GNN yields highly accurate predictions for SF-relevant excited-state properties, demonstrating a mean absolute error of about 0.1eV for S1, T1, and T2 excitation energies. This capability facilitates the efficient screening of over 20 million molecular structures from both OE62 and QO2Mol databases. Our framework significantly reduces the computational demand associated with time-dependent density functional theory validation and identifies 180 potential SF molecules along with more than 1000 conformers. Subsequent assessments regarding synthetic accessibility, GW approximation and Bethe-Salpeter equation calculations further highlight a subset of experimentally feasible candidates among these SF candidates. The present approach exemplifies an effective, AI-driven strategy for accelerating the discovery of functional materials for sustainable optoelectronic application.

Flexible triboelectric nanogenerators (TENGs) employing polysiloxane/graphene oxide (PS/GO) nanocomposite films were designed to investigate how graphene oxide concentration influences dielectric characteristics and energy harvesting performance. Graphene oxide was prepared using a modified Hummers’ method and incorporated into the polysiloxane matrix at concentrations between 0.01 and 0.1 wt% through a solution-assisted spreading process to obtain uniform flexible films. The presence of GO enhanced interfacial polarization and increased the availability of charge-trapping sites, resulting in improved electrical output. Among all investigated compositions, the sample containing 0.05 wt% GO showed the most efficient triboelectric performance, generating a maximum voltage of 35.2 V and a current of 3.3 μA. Electrical measurements under different external resistances indicated a maximum output power of 54.6 μW at 9 MΩ, corresponding to a power density of 34.1 mW m−2. In addition, the practical applicability of the device was demonstrated through its ability to light multiple LEDs and charge a capacitor under periodic mechanical motion. Overall, the results confirm that optimizing the GO concentration within the polysiloxane matrix is an effective approach to improve the performance of flexible TENGs, offering promising potential for sustainable energy harvesting and self-powered electronic systems.

This work focuses on the development and characterization of flexible triboelectric nanogenerators (TENGs) using low-cost polymers: high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyurethane (PU), and poly (methyl methacrylate) (PMMA). The materials were synthesized into thin films by a solvent casting method. Scanning Electron Microscopy (SEM) showed different surface morphologies, like ductile and brittle natures. Mechanical testing indicated PMMA has higher tensile strength (35 MPa) and better stiffness properties than TPU, which has better flexibility and elastic properties. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of functional groups (C = O and C-O-C) in PMMA and TPU, which are important for charge transfer. X-ray diffraction showed that HDPE had the highest crystalline content (70%) and a large crystallite size (30.17 Å), which explained its effective tribo-negative material. PMMA and TPU had low crystalline materials (<1%), which enhanced any tribo-positive properties. Differential scanning calorimetry (DSC) suggested that a blend of TPU and PMMA had a melting temperature (Tm) of 175.8 °C and even had better thermal stability than TPU or PMMA polymers. A demonstration of the dielectric study illustrates that PMMA had the largest dielectric constant at high frequencies. A 3D-printed model was fabricated for testing the tribo-model (contact-separation), which produced a peak-to-peak voltage output of 155 V in a TPU/PMMA-HDPE TENG. The results show that intentionally combining the polymers and their various mechanical, thermal, and electrical characteristics was able to achieve a TENG that could be efficient, scalable, and low-cost.

In the pursuit of non-toxic and high-efficiency perovskite solar cell materials, this study investigates the enhancement of thermoelectric and optoelectronic properties of Zn-doped KSn1-x Zn x I3 (x = 0, 0.25, 0.5, 0.75, 1) perovskites. The study uses first-principles density functional theory (DFT) with the Vienna Ab initio Simulation Package (VASP). Structural analysis confirms a transition from orthorhombic (Pnma) to monoclinic (Pm) phases. All the compositions exhibit thermodynamic, mechanical, and dynamic stability. Electronic properties reveal a robust bandgap range of 1.47-1.96 eV (GGA-PBEsol) and 2.34-3.02 eV (HSE06), positioning these materials as promising candidates for the top cell in a tandem solar cell and UV-optoelectronics. An indirect-to-direct band structure transition occurs at 50% Zn doping, which primarily enhances the stiffness, Pugh's ratio (2.39-2.70), and Poisson's (0.316-0.335) ratio of the lattice for KSn1-x Zn x I3. The elastic modulus (E), shear modulus (G), and bulk modulus (B) in KSn1-x Zn x I3 also significantly increased upon addition of Zn in the compound. These behaviors indicate that although there is better lattice stiffness in the material, there is still very good ductility for making flexible devices. Near-perfect mechanical isotropy has been achieved in KZnI3 with a universal elastic anisotropy factor (A U) of only 0.15. This low level of anisotropic elastic behavior indicates that KZnI3 is unlikely to experience micro- fracture during or after manufacturing. Thermoelectric analysis shows that KSnI3 maintained a high Seebeck coefficient of 230 µV K-1 at low temperature, while KZnI3 showed a 225 µV K-1 Seebeck coefficient at elevated temperature. A high figure of merit (ZT) is achieved by both pristine compounds at high temperature, with values of 1.01 for KSnI3 and 1.27 for KZnI3. Furthermore, for optical properties, a high absorption coefficient of 7.32 × 105 cm-1 is observed by 25% Zn doping at UV-visible range. These findings make Zn-doped KSnI3 perovskite material suitable for efficient, non-toxic, low-cost optoelectronic and thermoelectric devices.

Hydrovoltaic technology generates electricity directly via interactions between nanomaterials and water, demonstrating significant promise for sustainable energy harvesting. However, its widespread application is hindered by insufficient power output and poorly understood underlying mechanisms. Here, we develop a two-dimensional nanofluidic hydrovoltaic device using a MXene/silk nanoparticle composite membrane that leverages ion-electron coupling to enhance electricity generation. Upon deposition of deionized water droplets, an ionization-induced proton gradient generates a maximum open-circuit voltage of 496 mV and a peak short-circuit current of nearly 8 µA. Notably, replacing deionized water with 10-4 M NaCl elevates the output to 593 mV, which is further boosted to 622 mV under infrared irradiation-sufficient to power microelectronic circuits. Mechanism investigations reveal that this enhancement arises from ion-electron Coulomb drag interactions at the solid-liquid interface. This study provides fundamental insights into nanofluidic energy conversion and demonstrates potential applications in self-powered wearable electronics and all-weather energy harvesting systems.

This review seeks to present a comprehensive overview of recent advancements in sustainable energy harvesting technologies, with a focus on photovoltaic (PV), and thermoelectric (TE) systems. It examines the evolution of next-generation PV technologies, such as perovskite and tandem solar cells, which demonstrate remarkable potential for high-efficiency, low-cost energy conversion. In parallel, it explores progress in TE materials, including nanostructured and organic compounds, that have led to enhanced thermoelectric performance and broadened application prospects. The review discusses key challenges related to the scalability, stability, and integration of these systems. Furthermore, it highlights the synergies of combining PV and TE technologies to enhance overall energy-harvesting efficiency. The review concludes by identifying emerging trends and proposing strategic directions for future research to accelerate the development and commercialization of sustainable energy harvesting solutions.

Abstract: Triboelectric nanogenerators (TENGs) have rapidly developed into a transformative energy harvesting technology, enabling self-powered, sustainable electronic systems. This review offers the first comprehensive, multidisciplinary perspective that connects the physics of triboelectric charge transfer with material innovation, device engineering, and real-world applications. We systematically categorize and measure the triboelectric series across a wide range of materials, including polymers, 2D materials, MOFs, perovskites, cellulose, and biodegradable frameworks, using experimentally validated methods. In addition to traditional approaches, this work highlights emerging strategies such as machine learning-guided material discovery, 3D printing, and advanced structural engineering to improve charge retention, durability, and power output. Unlike existing reviews, it uniquely combines theory and application insights, presents diverse uses from biomedical sensing and environmental monitoring to underwater communication and mechanoluminescence, and outlines a forward-looking plan for sustainable energy harvesting. This comprehensive synthesis serves as an essential resource for researchers and technologists designing next-generation TENGs and multifunctional self-powered devices.

Investigation of the ion-electron hybrid thermoelectric properties of ultra-low carbon fiber-reinforced metakaolin-based geopolymer for sustainable energy harvesting building materials

ABSTRACT Moisture‐enabled electricity generation technology offers a new paradigm for sustainable energy harvesting, but its practical applications are still limited by issues such as low output power and insufficient long‐term stability. In this paper, an asymmetric sandwich‐structured hydrogel moist–electric generator (SSHMEG) with an ion concentration gradient is designed and constructed. Through dynamic exchange with moisture in ambient humidity, a stable ion diffusion direction is established inside the device, thereby achieving durable and efficient moisture‐enabled electricity generation performance. The SSHMEG achieves an open‐circuit voltage as high as 1.15 V and a short‐circuit current density of 2350 μA cm −2 at 90% relative humidity (RH), along with excellent long‐term stability (maintaining &gt; 1.05 V continuously for 20 days). Featuring high integrability to meet the output requirements of electronic devices, the SSHMEG is highly sensitive to humidity and internal resistance changes (e.g., respiration and stretching), enabling its application as a self‐powered respiration/strain sensor. Combined with deep learning, the strain sensor based on SSHMEG realizes gesture recognition with 100% accuracy. Through the collaborative innovation of the material–structure mechanism, this work paves a new path for the next‐generation high‐performance, multi‐functional, and self‐powered MEG systems.

ABSTRACT The environmental effects of fossil fuel consumption have continued to promote research in other energy sources that are more eco-friendly and can be sustained in the long run. One of the promising energy harvesting methods is plant-based energy harvesting, which has been considered a potential approach in developing energy harvesting systems for low-power applications, such as precision agriculture, environmental monitoring, and IoT sensor networks. The present research aimed to evaluate the potential of long-term energy harvesting using an Aloe vera plant, considering its health and the biocompatibility of electrodes. There was a challenge when uncoated zinc (Zn) and copper (Cu) electrodes emitted toxic ions (Zn2+ and Cu2+) that initiated foliar desiccation, tissue necrosis, and physiological degradation. Graphite-coated electrodes were henceforth brought in as biocompatible alternatives for reducing ion leakage while maintaining electrical conductivity. A commercially used wound-healing agent was also applied at sites of electrode insertion to facilitate tissue conservation. The health of the plants and energy harvesting were monitored over a period of 7 days. The results of this research have shown that material modification and application of a wound-healing agent have a positive effect on plant health without compromising energy harvesting.

Amid growing concerns about ecological sustainability, piezoelectric nanogenerators (PENGs) are a popular alternative for harvesting clean energy from ambient mechanical movements. Nonetheless, the fundamental unpredictability of mechanical inputs limits their effective use in energizing devices that necessitate uninterrupted functionality. In response to this limitation, we present a piezoelectric-driven self-charging supercapacitor (PSCSC) that effectively harvests and stores electrical energy concurrently. A flexible porous poly(vinylidene fluoride) (PVDF) nanogenerator film was synthesized through the incorporation of 3 wt % BaSnO3-rGO nanoparticles that resulted in ∼95% β-phase stabilization of PVDF. The film demonstrates an enhanced piezoelectric performance, producing ∼52 V and 2.1 μA current when subjected to low-pressure stimulation (∼15.8 kPa). A PSCSC was fabricated utilizing BaSnO3-rGO coated nickel foam as electrodes, porous 3 wt % BaSnO3-rGO PVDF/BaSnO3-rGO film as a piezo-separator, and a PVA-KOH gel functioning as a solid electrolyte. The PSCSC demonstrates self-charging capabilities without the need for a rectifier, achieving ∼429 mV in just 180 s under dynamic finger imparting and can effectively power electronic devices like LEDs, calculators, and watches. A sustainable energy harvesting and storage strategy is presented in this work, paving the way for the use of autonomous power sources for portable devices.

Abstract Triboelectric nanogenerators (TENGs) hold great potential for sustainable ocean-wave energy harvesting; however, the directional randomness, low frequencies of natural ocean waves severely hinder stable and efficient energy capture. To overcome these challenges, we propose a novel cylindrical low-frequency TENG (CLF-TENG) specifically designed to address the intrinsic limitations of the marine environment. Inspired by the mechanical principle of a traditional bamboo-copter, the device employs a face-ratchet–driven-ring overrunning (one-way) clutch that converts the axial reciprocating motion of a helical screw into unidirectional and continuous disc rotation, thereby transforming irregular wave excitation into stable mechanical motion. Furthermore, polyester foam with a three-dimensional volume effect is incorporated into the ternary-dielectric TENG disc to enable simultaneous surface and bulk charge storage, effectively enhancing charge density and boosting overall electrical output. Under an excitation frequency of 0.1 Hz, the CLF-TENG achieved an electrical output with an open-circuit voltage of 891.54 V and a short-circuit current of 24.05 mA, successfully powering miniaturized marine electronic devices and thereby exhibiting excellent adaptability to low-frequency ocean wave environments. This study advances the practical application of TENGs in complex ocean conditions and provides a promising pathway toward self-powered marine energy systems.

ABSTRACT Developing environment‐friendly processes for producing semiconductor thin films is essential for the development of sustainable optoelectronic and energy harvesting technologies. In this study, films of Fe‐doped zinc oxide (ZnO) were synthesized for the first time using neem ( Azadirachta indica ) leaf extract as a reducing agent, spin coated, and annealed at 200°C and 500°C, for Fe concentrations of 0–20 at.%. Additionally, this method of synthesis avoids the use of toxic chemicals and is a cost and energy efficient alternative to conventional vacuum deposition methods. X‐ray diffraction (XRD) shows that all compositions contain wurtzite ZnO with (002) preferred orientation, and that Fe incorporation leads to a systematic decrease in the crystallite size, and an increase in internal stress, with a higher annealing temperature promoting grain growth and a partial relaxation of the strain. UV–vis spectroscopy shows that all films have high transparency in the visible range, and that Fe doping leads to a red shift of the absorption edge, due to defect states and associated microstrain which results in a narrowing of the band gap. Results of photoluminescence (PL) spectroscopy indicate that Fe doping suppresses the near band edge UV emission and enhances the broad visible deep‐level bands. This indicates that the density of defects, related to oxygen and cations, increases as a result of Fe doping, which is dependent on the concentration of the dopant and the annealing temperature. The optimized Fe:ZnO films containing intermediate amounts of Fe that were annealed at 500°C show that under mechanical stimulation, films were able to generate multiple volt outputs due to the appropriate balance between the piezoelectric response as a result of the orientation of the internal stresses along with the crystallographic defects. Such a result creates a clear structure–property–function relationship with neem‐assisted Fe‐doped ZnO‐thin films, confirming neem‐assisted Fe‐doped ZnO films are promising as eco‐friendly active layers in transparent, flexible nanogenerators and self‐powered sensors. Recent findings also reveal that eco‐friendly ZnO systems exhibit competitive photocatalytic and sensing performance, and continue to prove their technological importance.

Exploring the electronic, optical, and thermoelectric properties of novel CsLaMTe3 (M = Cd, Zn) materials for sustainable energy harvesting

High-performance piezoelectric nanogenerator based on PVDF/2D layered Mo₃AlC₂ composites for sustainable energy harvesting applications

Harnessing the synergistic effects of green-synthesized Sn2ZnO₄ nanoparticles in biodegradable PVA nanocomposites for high-output triboelectric nanogenerators enabling sustainable energy harvesting