Search Results (567)

Wearable electronic textiles require flexible, lightweight, and sustainable energy-harvesting platforms. This study presents a proof-of-concept fabric-assisted thermally responsive voltage-generating prototype fabricated from recycled electronic and textile waste. Copper and aluminum current-collector foils recovered from discarded non-functional lithium-ion mobile-phone batteries, together with woven apparel cutting waste composed of 70% cotton, 28% polyester, and 2% elastane, were used as the main device components. The recovered conductive foils were cleaned, dried, and manually integrated into the textile substrate using a weaving and piercing-based approach. Under preliminary human forearm-contact testing, the fabricated prototype generated a maximum RMS open-circuit voltage of 180.75 mV at a body-to-ambient temperature difference of 5.82 K. The prototype also retained 90.73%, 86.88%, 81.33%, and 73.58% of its initial RMS open-circuit voltage after 100 rolling, bending, twisting, and folding cycles, respectively. However, the present study measured open-circuit voltage only, and contributions from contact potential, moisture-assisted galvanic effects, oxide layers, pressure-dependent contact resistance, electrochemical processes, and measurement artefacts cannot be fully excluded. Therefore, the results should be interpreted as preliminary proof-of-concept evidence rather than complete validation of practical thermoelectric power-generation performance. Future work should include controlled Seebeck measurements, direct active-junction temperature monitoring, current and power output, load matching, internal resistance, control samples, repeated trials, and durability testing. Full article

Copper selenide compounds, owing to their excellent electrical transport properties and low thermal conductivity, are promising thermoelectric materials, but their poor mechanical flexibility limits practical applications in flexible devices. Herein, a simple all-electrochemical strategy was developed to fabricate polypyrrole (PPy)/Cu_2−xSe composite thermoelectric films through sequential electropolymerization of pyrrole and electrodeposition of Cu_2−xSe. By optimizing the deposition potential of Cu_2−xSe and pyrrole polymerization time, the thermoelectric performance of the composite films was significantly enhanced. The optimized PPy/Cu_2−xSe composite film achieved a maximum power factor of 174.05 ± 9.87 μW m⁻¹ K⁻², nearly 300 times higher than that of pristine PPy, while maintaining a low thermal conductivity of 0.30 W m⁻¹ K⁻¹. The composite film also exhibited excellent flexibility, retaining 94.77% of its initial power factor after 1000 bending cycles. A flexible thermoelectric device assembled from the composite films delivered a maximum output power of 240.5 nW at ΔT = 50 K. This work provides an effective strategy for developing Cu_2−xSe-based flexible thermoelectric composites. Full article

We study the thermoelectric performance and stationary quantum correlations of a coherent double quantum dot heat engine driven solely by two conventional electronic reservoirs. The role of coherence is isolated by comparing the fully coherent dynamics with those under an energy-conserving pure dephasing channel that does not alter the system energy. Reducing the dephasing strength enhances the particle current, heat current, output power, and thermodynamic efficiency over a broad voltage range. After optimizing the electrochemical load and the dot energy levels, we find that coherence primarily amplifies the attainable power and efficiency without significantly relocating the optimal operating region. Although appreciable interdot coherence already exists at moderate Coulomb interaction, stationary entanglement emerges only when Coulomb blockade sufficiently suppresses the mixed-state contribution from the empty and doubly occupied states. We further construct a transport-based lower bound on the concurrence, providing an experimentally accessible entanglement witness that avoids full state tomography. These findings establish a clear hierarchy among energy filtering, quantum coherence, and Coulomb blockade in a minimal quantum thermoelectric device. Full article

The rapid development of wearable electronics has created a demand for flexible, lightweight, and sustainable power-supply technologies. The persistent temperature difference between the human body and the environment provides a low-grade thermal source for thermoelectric energy harvesting. However, traditional flexible thermoelectric devices still face limited self-supporting capabilities and difficulties in maintaining sufficiently low cold-side temperatures. Here, we designed a passively radiative-cooled thermoelectric film (PRT film) by integrating a PAM/PEDOT:PSS self-supporting thermoelectric composite layer with a polymer metamaterial radiative cooling (PMRC) film. The PAM/PEDOT:PSS layer serves as a self-supporting thermoelectric conversion component for harvesting low-grade heat, while the PMRC film layer acts as a passive cold-side regulator without energy input to lower the cold-side temperature and enhance the temperature gradient. By optimizing the PAM content, the PAM/PEDOT:PSS composite material with 85 wt% PAM achieved the highest power factor of 72.3 μW m⁻¹ K⁻². Under a temperature difference of 39 °C, the optimized PAM/PEDOT:PSS sample provided an open-circuit voltage of 0.47 V, a maximum output power of 1.1 μW, and a power density of 11.2 μW cm⁻². According to the temperature-difference enhancement measured in experiments and the independently obtained load characteristics, the integration of PMRC films is expected to increase the maximum output power from 1.1 to 1.4 μW, with the corresponding power density rising from 11.2 to 14.25 μW cm⁻², representing a 27.2% enhancement. This work demonstrates the feasibility of passive radiative cold-side regulation in enhancing low-level thermoelectric energy harvesting for wearable applications. Full article

Smart buildings increasingly depend on dense, distributed sensing infrastructures to improve energy efficiency, indoor environmental quality and operational flexibility. However, large-scale IoT/WSN deployment is still constrained by wiring effort, battery maintenance and limited access to sensing locations. Energy harvesting (EH) offers a promising approach toward low-maintenance and partly autonomous sensing, but its practical value in building automation depends on more than the output of individual transducers. This article presents a structured review of EH for IoT/WSN and edge-enabled building automation, focusing on smart-building, Building Management System (BMS) and Building Automation and Control System (BACS) contexts. Light-based, thermoelectric, mechanical, RF/wireless-power-transfer and hybrid harvesting technologies are interpreted through a system-oriented chain linking energy sources, power management, storage, communication, adaptive operation, gateways, diagnostics and edge intelligence. The synthesis shows that EH is most promising for low-duty-cycle environmental monitoring, envelope and façade sensing, occupancy and human–building interaction, airflow-related sensing, technical monitoring and retrofit automation. The main challenges concern the transition from device autonomy to sensing-service autonomy, complete-node evaluation under real building conditions, interoperability with supervisory systems and diagnostic interpretation of intermittent operation. Further research is also needed on lifecycle value assessment and safe transferability toward remote, temporary, resilient and closed ecological infrastructure applications. Full article

Organic thermoelectric generators (OTEGs) are promising for wearable low-grade heat harvesting, but their device-level output is often limited by interconnect-induced losses. This study investigates flexible OTEGs based on doped single-walled carbon nanotube (SWCNT) thermoelectric clays and optimizes their interconnect structure. P-type and n-type SWCNT clays were prepared by solution processing using TCNQ and TPP as dopants, respectively, and assembled into a five-pair flexible OTEG. The optimized p-type and n-type clays exhibited Seebeck coefficients of 40.81 and −22.42 μV K⁻¹, respectively. The initial OTEG, in which p-type thermoelectric clay was used as the interconnect, delivered a maximum output power of 16.47 nW at ΔT = 21 K. Replacing this thermoelectric-clay interconnect with a compliant Cu-foil/silver-paste interconnect reduced the internal resistance from approximately 372 Ω to 2 Ω, whereas the open-circuit voltage at ΔT = 21 K increased only modestly from 4.95 to 5.08 mV. Under identical controlled temperature-gradient and load-scanning conditions, the optimized OTEG delivered 3.08 μW at ΔT = 21 K, corresponding to a power density of 356.36 nW cm⁻². Mechanical and wrist-worn tests further indicated the flexibility and practical voltage response of the optimized device. These results demonstrate that interconnect optimization is critical for improving SWCNT-clay-based flexible OTEGs. Full article

Nearly two-thirds of global energy is lost as waste heat. Thermoelectric materials enable the direct conversion of heat into electricity, offering a promising recovery strategy. However, many high-performance systems rely on toxic or scarce elements such as Pb and Te, limiting sustainability. This review compares transport mechanisms in bulk and thin-film thermoelectrics, highlights environmentally benign material alternatives and fabrication routes, and discusses key challenges and future opportunities for sustainable energy applications. To provide a comprehensive overview of tellurium- and Pb-free bulk thermoelectrics, recent developments are summarized in a comprehensive table detailing material composition, peak zT values, temperature differences (ΔK), efficiencies (η), power output (P_out) (or maximum power density (P_max)), and device geometries. Full article

With the rapid advancement of the IoT society and growing awareness of environmental issues, thermoelectric conversion technology—which directly converts waste heat into electricity—is gaining attention as a self-powered, autonomous power source capable of driving countless devices. While currently mainstream metal-based inorganic thermoelectric materials demonstrate high performance, their high rigidity and brittleness, as well as their frequent inclusion of toxic heavy metals, have limited their application in biological systems and on curved surfaces. As a next-generation alternative, single-walled carbon nanotubes (SWCNTs)—which possess excellent flexibility, electrical conductivity, and mechanical strength while being low in toxicity—are garnering significant attention. However, n-type SWCNT materials, which are essential for thermoelectric module fabrication, have faced two major barriers to practical application: low atmospheric stability (they easily revert to p-type upon exposure to atmospheric oxygen and moisture) and thermoelectric performance that falls short of inorganic materials. This review comprehensively outlines the latest composite approaches designed to overcome these critical challenges and achieve both extreme atmospheric stability and high thermoelectric performance in n-type SWCNT materials, along with the flexibility required to withstand severe deformation. Three main strategies are discussed. The first is the organic/polymer approach, which involves doping with organic small molecules that control the LUMO level or bicyclic organic superbases with strong electron-donating properties, as well as polymer coating, to achieve long-term stable n-type characteristics and high power output even in air or under severe high-temperature conditions. The second is the inorganic hybrid strategy, which involves nanoscale compositing with inorganic materials such as Bi₂Te₃ and Cu₂O; this reduces thermal conductivity through phonon scattering via interface control, while the inorganic layer physically blocks oxygen to ensure long-term atmospheric stability. The third approach involves ultra-long-term stabilization techniques, such as bulk encapsulation using cationic or gemini surfactants, and environmentally friendly aqueous processes utilizing natural amino acids. Furthermore, we discuss the latest developments in imparting practical-level toughness (flexibility) capable of withstanding thousands of bending cycles and high tensile stress through the introduction of dynamic covalent network polymers and elastomers. The conformal flexible thermoelectric power generation modules created through the integration of composite optimization, low-environmental-impact processes, and doping techniques will serve as a crucial foundational technology for realizing a sustainable next-generation electronics society, including future wearable devices, artificial skin, and smart sensor networks. Full article

Pentagonal NiAs₂ is a low-symmetry two-dimensional material relevant to nanoelectronic and thermoelectric applications, but its low lattice thermal conductivity (κ) may limit heat dissipation in device-related scenarios. In this work, the strain-dependent lattice thermal transport of monolayer penta-NiAs₂ is investigated using first-principles calculations combined with the phonon Boltzmann transport equation. The lattice thermal conductivity increases monotonically with tensile strain. Mode-resolved analysis shows that this enhancement mainly originates from the selective reinforcement of the out-of-plane acoustic ZA branch, rather than from a uniform increase in all phonon branches. Tensile strain weakens low-frequency anharmonicity, suppresses phonon scattering, and prolongs the ZA phonon lifetime. Meanwhile, the modified ZA dispersion increases its group velocity, further enhancing its contribution to heat transport. The reduced group velocities of the TA, LA, and most optical branches further limit their contributions to thermal conductivity. The results reveal a ZA-phonon-mediated mechanism for strain-enhanced thermal transport in penta-NiAs₂ and provide guidance for tuning phonon transport in pentagonal two-dimensional materials. Full article

With the rapid development of commercial aerospace, emerging applications such as satellite constellations, space-based communications, and orbital computing platforms have significantly increased the demand for efficient and reliable spacecraft power systems. Abundant exploitable energy exists in the space environment, including Air Mass Zero (AM0) solar radiation, spacecraft surface temperature gradients, ambient electromagnetic radiation, and radioisotope thermal energy, making multi-source energy harvesting a promising approach for improving satellite energy autonomy and system redundancy. This paper reviews the following four key space energy harvesting technologies: photovoltaic power generation, radio frequency (RF) energy harvesting, thermoelectric energy harvesting, and radioisotope thermoelectric generators (RTGs). The impacts of harsh space environmental factors on device performance and reliability are analyzed, and the applicability of different technologies in low Earth orbit (LEO), geostationary orbit (GEO), and deep-space missions is discussed. Furthermore, a multi-source self-powered satellite energy architecture integrating energy harvesting, energy storage, and power management is proposed. Finally, the major challenges and future development trends of satellite energy harvesting systems are summarized. Full article

The increasing demand for materials with enhanced properties and high-performance devices has driven substantial research into nanomanufacturing, particularly using carbon nanotubes (CNTs), because of their exceptional properties and high sensitivity to chemical doping. In this way, this work summarizes nanomanufacturing methods for CNT-based devices developed in Brazil, covering the complete cycle from nanocomposite production to functional device assembly across cellulosic, polymeric, and metallic matrix systems. For cellulosic matrices, vacuum filtration enables the production of buckypaper, which is subsequently assembled into chemiresistive, thermoresistive, and thermoelectric devices. For polymeric matrices, 3D printing combined with surface functionalization techniques (spray coating, inverted immersion, and direct immersion) produces piezoresistive robotic sensors, metal-free thermal sensors, and biomedical scaffolds for tissue engineering. For metallic matrices, electrodeposition can produce Cu-CNT-coated aluminum comparable to traditional copper power transmission cables, while arc welding produces stainless steel composites with properties comparable to commercial high-grade steels. These devices have commercial and industrial applications, with low-cost and scalable production methods in comparison with conventional materials. Characterization results demonstrate that CNT integration into diverse matrices successfully bridges nanoscale properties to macroscopic functional devices. Current challenges include uniform CNT dispersion and structural defect control, laboratory to industry scale transition, and long-term device stability under environmental conditions. Future perspectives encompass lab-on-chip systems, wearable devices, 3D-printed smart structures, Internet of Things integration, and machine learning-enhanced analytics. Full article

A significant amount of mechanical and thermal energy is lost when typing on a laptop keyboard. To address this, hybrid energy harvesters must increase the generated power density and mitigate energy fluctuation issues. This paper explores the potential enhancement of energy harvesting by combining thermoelectric and piezoelectric effects within a multilayered structure integrated into a laptop keyboard button. Through numerical simulation, the study assesses how these two behaviors can synergistically increase the power density generated by the hybrid device. The focus is on optimizing energy efficiency by harnessing the heat losses from integrated circuits and the mechanical stresses due to the act of typing. The point is to refine the design of such a system to maximize the conversion of ambient energy into electricity. The findings indicate that the hybrid structure combining both piezoelectric and thermoelectric effects, effectively captures energy from a laptop keyboard, producing a substantial amount of electricity. This investigation shows that the generator can produce up to 2.07 mW of power using PU-40%PZT as piezoelectric material and an additional 71.93 μW through the PEDOT: PSS as thermoelectric material from a single keystroke when pressed and heated. This study underscores the potential for improving energy-harvesting efficiency in laptop keyboards, contributing to more sustainable and energy-efficient electronic devices. Full article

This paper presents a constant-temperature, single-heat-source continuous-flow PCR (CF-PCR) microdevice that achieves stable thermal control for denaturation, annealing, and extension on a single platform. Key innovations include: (1) a metal-powder/PDMS thermal conduction block with trapezoidal geometry that generates a programmable temperature gradient and tunable residence times under one heat source; and (2) a thermoelectric cooler (TEC)-based Peltier system that creates distinct high- and low-temperature zones by co-optimizing the hot/cold side temperature difference, spacer material (92% alumina), and input voltage (3.6 V). A self-pressurized gas-diffusion micropump, enabled by a capillary quartz tube at the outlet, drives continuous sample flow without external actuation. The platform features three configurations: an on-chip zoned-heating design, an off-chip coiled-tube setup, and a battery-powered handheld system (727 g, 6 W, ~4 h runtime). Using CNC-machined and thermally bonded PMMA microchips with BSA passivation, the on-chip device achieves ~80% amplification efficiency relative to commercial instruments for H7N9 and pGEM-3Zf(+); the off-chip version reaches ~75%. The portable system yields HPV and RUBV amplification intensities comparable to benchtop devices. This approach provides a practical, scalable solution for “sample-in–answer-out” nucleic acid testing in point-of-care settings. Full article

There has been a rising trend for recovering waste heat, especially after the invention of new types of semiconductors. Among all available utilization options, thermoelectric generation (TEG) systems are promising for recovering waste heat. Thermoelectric devices are environment-friendly, operate silently, and are suitable for low- to high-power applications. This review paper presents a comprehensive study of TEGs, starting with the current problem, state of the art, advantages, disadvantages, generation and related principles, and applications, and covers different arrangements (individual and combined) and working fluids. Furthermore, this article systematically covered various experimental and numerical studies, including optimization, offering insights into heat exchanger configurations, working fluids, and performance parameters. Here, an effort is made to describe the contributions of individual/coupled TEG systems. As a coupled system, the individual TEG system is used with other systems like solar, distillation, solar pond, etc., for cogeneration and enhanced efficiency. The thermal/system parameters of individual/coupled systems are thoroughly discussed, and their impact on efficiency and power generation is illustrated. It was found that the design of the heat exchanger configuration varies from plate type to an efficient liquid-based electricity generation system in these TEG systems. The working fluid inside the fluid loop of a thermoelectric generation system varies from simple fluids to nanofluids. The current state of thermoelectric generation technology is facing challenges in module materials, equipment cost optimization, and commercialization. The progressive TEG generation capabilities have improved with recent advancements in these areas. The power densities are increasing from 0.5 to 1.2 W/cm² in earlier standalone TEGs to 2.5–4.8 W/cm² in recent optimized hybrid configurations, and overall system efficiencies are rising from an average of 5.2% (standalone) to 18.7% in coupled solar-TEG or waste heat recovery systems. The reported maximum ZT values are also improved from ~1.2 to 2.1–2.8 in next-generation materials. Liquid-based heat exchangers in conjunction with nanofluids are the most efficient way to maximize temperature gradient coefficient (0.75–0.92) and minimize parasitic losses. While flexible, ionic, and hybrid next-generation material platforms are still in the early phases of development (TRL 3–5), liquid-based heat exchanger systems improved with nanofluids are closest to commercialization (Technology Readiness Level, TRL 6–8). Therefore, further research in these areas is required to mitigate these challenges. Finally, the recent developments in the thermoelectric generation field and future research direction are briefly discussed. Full article

Industrial waste heat recovery is an important approach for improving energy utilization efficiency and reducing environmental impacts. Thermoelectric devices can directly convert waste heat into electricity, but their practical application is limited by relatively low output power. Active water cooling can enhance the power generation performance of thermoelectric devices, but the pumping power may reduce the net output power. In this study, a water-cooling thermoelectric device is investigated under constant heat input conditions using three-dimensional numerical simulations and a semi-analytical prediction model. The effects of cooling water inlet temperature and flow rate on the thermal response, electrical output, heat transfer behavior, and net output power are systematically analyzed. The results show that increasing the cooling water flow rate increases the gross electrical power but also increases pumping power, resulting in an optimal flow rate of approximately 3 m/s to maximize the net output power. At inlet temperatures of 24 °C, 28 °C, and 32 °C, the maximum net output powers are 51.46 W, 49.89 W, and 48.68 W, respectively. A prediction model for cooling water input conditions is further developed based on energy balance and convective heat transfer correlations, and the predicted velocities agree with the numerical results with relative errors below 2%. Full article