Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere

High-Performance Flexible Piezoelectric-Assisted Triboelectric Hybrid Nanogenerator via Polydimethylsiloxane-Encapsulated Nanoflower-like ZnO Composite Films for Scavenging Energy from Daily Human Activities

We successfully synthesized flower-like zinc oxide (ZnO) nanoarchitectures by a chemical precipitation method which is a facile, cost-effective, low-temperature, and quick-synthesis process. Furthermore, these nanoarchitectures were used to design an MWCNT (multiwalled carbon nanotube)/ZnO/PDMS (polydimethylsiloxane) composite film-based hybrid nanogenerator (HNG). Here, the ZnO nanoflowers play an important role in enhancing the piezoelectric and triboelectric potentials of HNG, termed as piezoelectric-assisted triboelectric (PAT)-HNG. The ZnO nanoflowers were employed as the piezoelectric material as well as to enhance the surface roughness of PDMS, which can increase the triboelectric performance. Besides, the MWCNTs were also utilized to evenly distribute the ZnO nanoflowers and also to reduce the internal resistance of PAT-HNG. To maximize the electrical output power of the device, the concentration of ZnO and the amount of MWCNTs were changed and the electrical output performance of PAT-HNG was investigated. As a result, an optimized PAT-HNG with MWCNT/ZnO/PDMS composite film was achieved, which consists of ∼4.95 g of PDMS, 4.8 wt % ZnO, and 0.015 g of MWCNT. The electrical output power of the optimized PAT-HNG was employed to drive 20 commercial light-emitting diodes connected in series. To demonstrate the practical applications of PAT-HNG, it was fixed onto a slipper and efficiently harvested the energy from daily human activities. Consequently, the PAT-HNG device exhibited electrical output voltage/current values of ∼75 V/3.2 μA, ∼150 V/8 μA, and ∼400 V/30 μA, while walking, running, and jumping, respectively

Contact-electrification enabled water-resistant triboelectric nanogenerators as demonstrator educational appliances

Triboelectric nanogenerators (TENG) work on the principle of tribo and contact electrification, which is a common phenomenon observed in daily life. TENGs are moving closer to commercialization, particularly for small scale energy harvesting and self-powered sensing. The toys and games industry has attracted a large audience recently with the introduction of digital toys. In this paper we embedded TENGs to power up a toy and operate during its specific application. We have modified two potential electronic demonstrator applications using TENG for lobster toy (LT-TENG) and stress ball (SB-TENG) device. The LT-TENG device generates a maximum electrical response of 60 V/2 µ A, with a power of 55 µ W and power density of 0.065 µ W m ^−2 at a load resistance value of 10 MΩ. Similarly, the SB-TENG device made of aluminum and PDMS as the triboelectric layers generates a maximum electrical output response of 800 V and 4 µ A peak to peak current with an instantaneous power of 6 mW and a power density of 3.5 mW m ^−2 respectively at a load resistance of 10 MΩ. In addition, the layers of the TENGs are packed with polyethylene to maintain the performance of the nanogenerator under harsh environmental conditions, especially with humid environments. The water resistance studies proved that the packed SB-TENG is impervious to water. The LT-TENG device is accompanied by four LEDs, and the device lights up upon actuating the handle. The SB is connected with the measuring instrument to record the quantity of force at which the SB is pressed. The adopted approach paves the way to convert these traditional toys into battery-free electronic designs and its commercialization

Natural silk-composite enabled versatile robust triboelectric nanogenerators for smart applications

Strategies to maximize the surface charge density across triboelectric layers while protecting it from humidity are crucial in employing triboelectric nanogenerators (TENGs) for commercial/real-time applications. Herein, for the first time, we propose the utility of crystalline silk microparticles (SMPs) to improve the surface charge density in materials like polyvinyl alcohol to realise its applicability for TENG devices. Moreover, these SMPs are extracted from discarded Bombyx mori silkworm cocoons by facile, inexpensive, and single-step alkaline-hydrolysis treatment. We examine the performance of these composites with counter-materials composed of waste PTFE plastic cups to show reuse in recycled products. The processing cost of TENG developed from recycled materials is not only low but eco-friendly. The TENG performance as a function of the concentration of SMPs is investigated and compared with the composite's work-function and surface-potentials, with the distance-dependent electric field theoretical model employed to optimize the performance. Consequently, the optimized TENG exhibits maximum output voltage, current, charge, and power density of ∼280 V, 17.3 μA, 32.5 nC, and 14.4 W·m−2, respectively, creating a highly competitive energy harvester that can conform to the rigorous needs of wearables and mobile applications. Furthermore, the fully packaged silicone rubber device protects it from humidity and enables the device utility for practical applications with a soft, comfortable, and skin-friendly interface

Enhanced Performance of Microarchitectured PTFE-Based Triboelectric Nanogenerator via Simple Thermal Imprinting Lithography for Self-Powered Electronics

Triboelectric nanogenerator (TENG) technology is an emerging field to harvest various kinds of mechanical energies available in our living environment. Nowadays, for industrial and large-scale area applications, developing the TENG with low device processing cost and high electrical output is a major issue to be resolved. Herein, we designed a TENG with low cost by employing the microgrooved architectured (MGA)-poly­(tetrafluoroethylene) (PTFE; Teflon) and aluminum as triboelectric materials with opposite tendencies. Moreover, the MGA-PTFE was fabricated by a single-step, facile, and cost-effective thermal imprinting lithography technique via micropyramidal textured silicon as a master mold, fabricated by a wet-chemical etching method. Therefore, designing the TENG device by following these techniques can definitely reduce its manufacturing cost. Additionally, the electrical output of TENG was enhanced by adjusting the imprinting parameters of MGA-PTFE. Consequently, the MGA-PTFE was optimized at an imprinting pressure and temperature of 5 MPa and 280 °C, respectively. Thus, the TENG with an optimal MGA-PTFE polymer exhibited the highest electrical output. A robustness test of TENG was also performed, and its output power was used to drive light-emitting diodes and portable electronic devices. Finally, the real application of TENG was also examined by employing it as a smart floor and object-falling detector

Enhanced Performance of Microarchitectured PTFE-Based Triboelectric Nanogenerator via Simple Thermal Imprinting Lithography for Self-Powered Electronics

Triboelectric nanogenerator (TENG) technology is an emerging field to harvest various kinds of mechanical energies available in our living environment. Nowadays, for industrial and large-scale area applications, developing the TENG with low device processing cost and high electrical output is a major issue to be resolved. Herein, we designed a TENG with low cost by employing the microgrooved architectured (MGA)-poly­(tetrafluoroethylene) (PTFE; Teflon) and aluminum as triboelectric materials with opposite tendencies. Moreover, the MGA-PTFE was fabricated by a single-step, facile, and cost-effective thermal imprinting lithography technique via micropyramidal textured silicon as a master mold, fabricated by a wet-chemical etching method. Therefore, designing the TENG device by following these techniques can definitely reduce its manufacturing cost. Additionally, the electrical output of TENG was enhanced by adjusting the imprinting parameters of MGA-PTFE. Consequently, the MGA-PTFE was optimized at an imprinting pressure and temperature of 5 MPa and 280 °C, respectively. Thus, the TENG with an optimal MGA-PTFE polymer exhibited the highest electrical output. A robustness test of TENG was also performed, and its output power was used to drive light-emitting diodes and portable electronic devices. Finally, the real application of TENG was also examined by employing it as a smart floor and object-falling detector

Enhanced Performance of Microarchitectured PTFE-Based Triboelectric Nanogenerator via Simple Thermal Imprinting Lithography for Self-Powered Electronics

Triboelectric nanogenerator (TENG) technology is an emerging field to harvest various kinds of mechanical energies available in our living environment. Nowadays, for industrial and large-scale area applications, developing the TENG with low device processing cost and high electrical output is a major issue to be resolved. Herein, we designed a TENG with low cost by employing the microgrooved architectured (MGA)-poly­(tetrafluoroethylene) (PTFE; Teflon) and aluminum as triboelectric materials with opposite tendencies. Moreover, the MGA-PTFE was fabricated by a single-step, facile, and cost-effective thermal imprinting lithography technique via micropyramidal textured silicon as a master mold, fabricated by a wet-chemical etching method. Therefore, designing the TENG device by following these techniques can definitely reduce its manufacturing cost. Additionally, the electrical output of TENG was enhanced by adjusting the imprinting parameters of MGA-PTFE. Consequently, the MGA-PTFE was optimized at an imprinting pressure and temperature of 5 MPa and 280 °C, respectively. Thus, the TENG with an optimal MGA-PTFE polymer exhibited the highest electrical output. A robustness test of TENG was also performed, and its output power was used to drive light-emitting diodes and portable electronic devices. Finally, the real application of TENG was also examined by employing it as a smart floor and object-falling detector

Boosting Light Harvesting in Perovskite Solar Cells by Biomimetic Inverted Hemispherical Architectured Polymer Layer with High Haze Factor as an Antireflective Layer

Biomimetic microarchitectured polymer layers, such as inverted hemispherical architectured (IHSA)-polydimethylsiloxane (PDMS) and hemispherical architectured (HSA)-PDMS layers, were prepared by a simple and cost-effective soft-imprinting lithography method via a hexagonal close-packed polystyrene microsphere array/silicon mold. The IHSA-PDMS/glass possessed superior antireflection (AR) characteristics with the highest/lowest average transmittance/reflectance (<i>T</i>_avg/<i>R</i>_avg) values of approximately 89.2%/6.4% compared to the HSA-PDMS/glass, flat-PDMS/glass, and bare glass (<i>T</i>_avg/<i>R</i>_avg ∼88.8%/7.5%, 87.5%/7.9%, and 87.3%/8.8%, respectively). In addition, the IHSA-PDMS/glass also exhibited a relatively strong light-scattering property with the higher average haze ratio (<i>H</i>_avg) of ∼38% than those of the bare glass, flat-PDMS/glass, and HSA-PDMS/glass (i.e., <i>H</i>_avg ≈ 1.1, 1.7, and 34.2%, respectively). At last, to demonstrate the practical feasibility under light control of the solar cells, the IHSA-PDMS was laminated onto the glass substrates of perovskite solar cells (PSCs) as an AR layer, and their device performances were explored. Consequently, the short-circuit current density of the PSCs integrated with the IHSA-PDMS AR layer was improved by ∼17% when compared with the device without AR layer, resulting in the power conversion efficiency (PCE) up to 19%. Therefore, the IHSA-PDMS is expected to be applied as an AR layer for solar cells to enhance their light absorption as well as the PCE

Effect of calcination temperature on cobalt substituted cadmium ferrite nanoparticles

The Cd0.9Co0.1Fe2O4 nanoparticles are synthesized using chemical co-precipitation method. The as-prepared samples are calcinated at 300 and 600 degrees C for 2 h. The thermal effects on structural, morphological and magnetic properties are reported. The X-ray diffraction data confirm the formation of single-phase cubic spinel structure. The Surface morphology and compositional features are studied using SEM with EDX and TEM measurements. The Magnetic properties of samples are evaluated using vibrating sample magnetometer. The magnetic properties, like saturation magnetization and coercivity are increases with increasing calcination temperature. The enhancement is attributed to the transition from a multi-domain to a single-domain nature. From the FTIR spectra, it is confirmed that the vibrations of tetrahedral and octahedral complexes corresponds to absorption bands at 590 cm(-1) (nu(1)) and 460 cm(-1) (nu(2)) respectively. The particle size enhances significantly with increasing the calcinated temperature.ope

Natural silk-composite enabled versatile robust triboelectric nanogenerators for smart applications

Strategies to maximize the surface charge density across triboelectric layers while protecting it from humidity are crucial in employing triboelectric nanogenerators (TENGs) for commercial/real-time applications. Herein, for the first time, we propose the utility of crystalline silk microparticles (SMPs) to improve the surface charge density in materials like polyvinyl alcohol to realise its applicability for TENG devices. Moreover, these SMPs are extracted from discarded Bombyx mori silkworm cocoons by facile, inexpensive, and single-step alkaline-hydrolysis treatment. We examine the performance of these composites with counter-materials composed of waste PTFE plastic cups to show reuse in recycled products. The processing cost of TENG developed from recycled materials is not only low but eco-friendly. The TENG performance as a function of the concentration of SMPs is investigated and compared with the composite's work-function and surface-potentials, with the distance-dependent electric field theoretical model employed to optimize the performance. Consequently, the optimized TENG exhibits maximum output voltage, current, charge, and power density of ∼280 V, 17.3 μA, 32.5 nC, and 14.4 W·m−2, respectively, creating a highly competitive energy harvester that can conform to the rigorous needs of wearables and mobile applications. Furthermore, the fully packaged silicone rubber device protects it from humidity and enables the device utility for practical applications with a soft, comfortable, and skin-friendly interface