A wireless, wearable, battery-free multi-sensory system is essential for continuous, non-invasive real-time monitoring of multiple physiological parameters, enabling seamless, discreet healthcare. The main bottleneck in developing such systems lies in achieving low power consumption to enable battery-free operation, while maintaining reliable, high-frequency data acquisition and efficient wireless communication with a skin-impedance-matched antenna within a compact, wearable form factor. To overcome this, we integrate energy-harvesting technologies with high-precision multiple sensors and a flexible, skin-compatible antenna system into a single platform, enabling battery-free operation with efficient data transmission and reception. Our multi-sensory system experimentally demonstrates successful skin-mountable monitoring of ECG, SpO 2 , and temperature at a sampling rate of 70 Hz, with data wirelessly transmitted via Bluetooth Low Energy, all powered by a radio-frequency energy-harvesting antenna. Beyond personal health tracking, this technology also holds great potential for remote patient monitoring in chronic disease management, empowering healthcare providers with continuous access to real-time patient data for timely and uninterrupted data acquisition. Typically, health monitoring systems depend on separate hardware for each physiological signal—such as electrocardiogram, pulse oximetry, and temperature—which requires bulky setups with complex wiring, limiting their practicality for wearable and continuous use. These limitations significantly hinder proactive and long-term monitoring beyond clinical settings. Here, a fully integrated, skin-mountable multisensory patch designed for chest application is demonstrated. The system simultaneously acquires electrocardiogram (ECG), pulse oximetry, and temperature signals, powered sequentially via a battery-free near-field communication (NFC) antenna. Furthermore, high-frequency, noise-free data transmission is achieved through a skin-impedance-matched flexible Bluetooth antenna, ensuring seamless communication without compromising user comfort. This compact, wireless system makes it possible to monitor vital physiological parameters remotely and in real time, helping with early diagnosis, ongoing care, and preventive health tracking outside clinical environments. Fig. | Conceptual illustration of a battery-free, skin-mountable wearable patch. The system enables simultaneous energy harvesting and data transmission through an integrated flexible NFC and Bluetooth antenna. • Integration of Electrocardiogram, pulse oximetry, and temperature sensing into a single flexible and skin-conformal patch for comprehensive physiological monitoring. • Battery-free operation through sequential powering enabled by an embedded NFC antenna for wireless energy harvesting. • Flexible Bluetooth antenna matched to skin impedance for robust and noise-free wireless transmission in real-time. • Optimized system for short-range wireless data transfer (1–10 m), enabling real-time smartphone visualization and cloud connectivity. • Demonstration of consistent signal quality across ECG, SpO₂, and temperature, benchmarked against commercial devices.

Two-dimensional framework membranes (2DFMs) hold great promise for sustainable energy-harvesting technologies, yet their performance is often limited by low electric double-layer (EDL) coverage (ƞEDL) arising from large channels and/or low charge densities. Here, we report an ultrathin ( ~ 50 nm), fully crystalline, ABC-stacked viologen-incorporated 2D polymer membrane (sV2DP) featuring vertically aligned triangular nanochannels (Deff = 1.36 nm) densely decorated with pyridinium sites ( + 22.4 mC m-2). Compared with its non-staggered AA-stacked analogue, sV2DP exhibits a 3.2-fold enhancement in ƞEDL under a 50-fold KCl gradient, combining high anionic selectivity (t- = 0.85) with remarkable selective current density (14.6 kA m-2). Simulations reveal that spirally arranged charges generate a unique "screw-like" anion migration pathway, significantly enhancing transmembrane efficiency relative to non-staggered 2DP analogues. When integrated into micro-aperture osmotic power generators, the sV2DP membrane delivered a peak power density of 243 W m-2 under a 50-fold NaCl gradient, placing it among the highest-performing systems.

Tribovoltaic nanogenerator (TVNG), as an emerging energy harvesting technology, is capable of converting environmental mechanical energy into direct-current electrical energy, thus attracting widespread attention. However, most of the perovskites prepared for TVNG are lead-containing, and the mechanism of the photo-enhanced output performance of TVNG is also unclear. Herein, the all-inorganic lead-free perovskite CsBi3I10 was introduced and a rolling-mode TVNG based on a Cu/CsBi3I10 dynamic Schottky junction was constructed. Under AM 1.5G illumination, the open-circuit voltage and short-circuit current of the TVNG reach 0.46V and 15.5µA, respectively, representing increases of 230% and 250% compared to those in the dark state. Moreover, a nonlinear photo-enhancement effect was observed, that is, the output signal of the device under dynamic light conditions exceeds the sum of the signals under dynamic dark and static light conditions. By characterizing the surface potential of the material via KPFM and combiningthe electron-cloud potential-well model of contact electrification, a possible theory based on the dual-electric-field model is proposed to elucidate the nonlinear photo-enhancement effect. This study provides insights into the co-harvesting of mechanical and light energy as well as the exploration of the microscopic mechanism of TVNGs, thereby broadening the application scope of perovskite materials and devices.

An ion-selective membrane with diode-like properties is a prerequisite for directional ion transport and efficient osmotic power conversion. However, in conventional nanofluidic systems, rectification rapidly deteriorates under high ionic strengths due to severe Debye length screening, which critically limits performance in realistic salinity environments. Here, we report a high-performance mesoscale ionic diode based on a single conical mesochannel selectively modified with a thin porous MXene layer, forming a well-defined porous subnano-on-meso architecture (p-MXene@MC). The pore-engineered MXene simultaneously provides high surface charge while maintaining continuous, low-resistance ion transport pathways, thereby enabling strong rectification even under high ionic strengths. As a result, the p-MXene@MC exhibits a rectification ratio of 7.7-fold at 1m KCl, and delivers a maximum osmotic power of 697 pW under a 1000-fold KCl gradient, outperforming earlier single-channel osmotic power generators. When protons serve as charge carriers, ultrafast transport within the hydrated porous MXene framework further boosts the power output to ∼1001 pW. The enhanced rectification and energy conversion performance by porous MXene is supported by our simulations based on the Poisson-Nernst-Planck and Navier-Stokes models. This work offers a generalizable strategy for overcoming electrostatic screening and transport limitations in mesoscale channels, paving the way toward practical nanofluidic energy harvesting technologies.

Liquid-solid triboelectric nanogenerators (LS-TENGs) based on contact electrification and electrostatic induction effect havegarnered significantattention as apromisingrenewable energy harvesting technology. So far, the LS-TENGs still have relatively low charge density. Here, we developed a tubular structure LS-TENG with high charge density by employing a self-assembled fluoroalkyl layer and grounding water. It was found that the transferred charge of the tubular structure LS-TENG can be enhanced by grounding water, which is likely attributed to the grounded water acquiring more charges from the ground to effectively shield the dielectric surface charges. Then, applying fluorinated modification on silica (SiO2) surface to enhance surface contact electrification, the tubular LS-TENG generated a high transferred charge of 1.96 µC (charge density of 2.16 mC m-2), superior to previous LS-TENGs based on contact electrification. The electrical output performance of the tubular LS-TENGs can be precisely regulated by adjusting the motion frequency, swing angle, and liquid properties. Finally, the tubular LS-TENGs successfully realized the parallel connection of multiple devices and powered a hygrothermometer, which exhibits great potential in low-frequency mechanical energy harvesting and self-powered system applications.

The increasing development of ingestible medical devices for gastrointestinal diagnostics, drug delivery, and physiological monitoring has created a growing demand for reliable and long-lasting power sources. Conventional batteries limit device lifetime, increase capsule size, and raise safety concerns, making biomechanical energy harvesting from gastrointestinal motility a promising alternative for self-powered ingestible systems. This review aims to provide a comprehensive overview of biomechanical energy harvesting from gastrointestinal mechanical activity for powering ingestible biomedical devices, with emphasis on energy sources, transduction mechanisms, materials, system integration, limitations, and future research directions. Recent literature on gastrointestinal biomechanics and energy harvesting technologies was analyzed, focusing on major transduction mechanisms such as piezoelectric, triboelectric, and electromagnetic generators. The review also evaluates material selection, device architectures, encapsulation strategies, and power management circuits from a system-level integration perspective. Piezoelectric, triboelectric, and electromagnetic energy harvesters demonstrate the ability to convert low-frequency gastrointestinal mechanical energy into electrical energy suitable for ultra-low-power biomedical devices. Hybrid energy harvesting systems improve energy reliability and output performance. However, several challenges remain, including low energy density, variability in gastrointestinal mechanical forces, miniaturization constraints, material durability, electrical conversion losses, and lack of standardized testing protocols. Biomechanical energy harvesting has significant potential to enable battery-free ingestible biomedical devices. Future developments in hybrid energy systems, ultra-low-power electronics, biodegradable materials, and adaptive power management are expected to support the development of fully autonomous self-powered ingestible medical devices.

Assistive mobility technologies have become increasingly important in improving the quality of life for individuals with disabilities. However, individuals with dual sensory loss, including visual and hearing impairments, continue to face major challenges in safe navigation and environmental awareness. Traditional mobility aids such as white canes and guide dogs provide only limited support because they cannot identify dynamic obstacles or hazardous environmental conditions in real time. This research proposes “SenseStep: AI-Integrated Smart Assistive Footwear for Dual Sensory Loss Individuals,” an intelligent wearable assistive system that combines artificial intelligence, embedded sensors, and wireless communication technologies to improve mobility assistance and user safety. The proposed system integrates ultrasonic sensors, flame sensors, and water sensors to detect nearby obstacles and environmental hazards. A camera module combined with a YOLO-based deep learning model performs real-time object recognition and distance estimation. The collected sensor and vision data are processed by a microcontroller to generate structured vibration-based feedback and optional Braille output, enabling communication without relying on visual or auditory cues. The system also includes a wireless communication module for sending emergency alerts and location updates to caregivers during hazardous situations. In addition, piezoelectric energy harvesting technology is integrated to improve battery efficiency by converting walking pressure into electrical energy. Experimental testing demonstrated an overall detection accuracy of 92%, with obstacle detection accuracy of 94%, hazard detection accuracy of 90%, and object recognition accuracy of 93%. The proposed system significantly improves safety, accessibility, and independence for individuals with dual sensory impairments by providing an intelligent, reliable, and energy-efficient assistive mobility solution Keywords— Artificial Intelligence; Smart Footwear; YOLO; Assistive Technology; Embedded Systems; Object Detection

A review of energy harvesting technologies for railway systems: principles, applications and challenges

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

ABSTRACT The growing demand for autonomous, sustainable, and delocalized power sources for low-power-consuming electronic devices is driving a significant research effort on energy harvesting technologies. Among these, micro-thermoelectric generators (µTEGs) emerge as an appealing solution because of the abundance of residual latent heat sources. This paper proposes an approach to combine high-performance thermoelectric oxides with Si-based µTEGs, leveraging the miniaturization and high-density integration of CMOS-like technologies. The approach is applied to the integration of niobium-doped strontium titanate (Nb:STO) thin films on Si-based planar µTEG structures. The Nb:STO-based µTEG achieves a specific power density Γ = 0.36 nW·cm−2·K−2 under controlled temperature gradients, which is below state-of-the-art performance probably due to lower electrical conductivity from polycrystalline growth. When the chips were tested under realistic operating conditions – placed on a hot surface at 175°C – a maximum power output of p = 0.07 nW was obtained. Nonetheless, by implementing a technological solution for thermal dissipation, the temperature gradient across the thermoelectric material improved by a factor of 110, resulting in a significantly higher extracted power of p = 7.75 nW.

The research investigates the structural, elastic and mechanical characteristics of lead-free cubic CsGeF3 perovskite under density functional theory (DFT) through combined Quantum Espresso and Thermo_PW computational techniques. The researchers conducted three exchange-correlation functional tests (PZ, PBE, and WC) to determine lattice parameter optimization, elastic constant computation and mechanical stability assessment. The research showed that optimized lattice constants achieved results which closely aligned with existing theoretical data. The material's mechanical stability is demonstrated by its predicted elastic constants which require cubic crystal structures to maintain structural integrity. The evaluation of material’s mechanical properties used Young's, Shear modulus, and Bulk moduli, Poisson's and Pugh's ratio, machinability index, Vickers hardness test and anisotropy factor measurement. The study found that CsGeF3 can withstand compression while displaying ductile behaviour in certain operational situations. The comprehensive study shows that CsGeF3 functions as a lead-free perovskite which shows potential in optoelectronic devices and solar energy harvesting technologies.

Road piezoelectric energy harvesting technology has been widely studied and applied. However, after long-term use, the piezoelectric ceramics inside the harvester will be broken, which seriously affects the use of the piezoelectric system. A reliable recycling process can be adopted to reuse the transducer. Therefore, this study focuses on the feasibility of field application of road piezoelectric energy harvester after recycling. The loading test of road piezoelectric energy harvester based on recycled ceramics was carried out to explore the influence of different recycling conditions on the output characteristics of the piezoelectric harvester. The experimental results show that the sintering temperature should be increased slightly during the recycling process, and the optimal window temperature is 1285 °C. The electrical output performance of the recycled ceramics prepared at the sintering temperature is stable. The electrical response of the piezoelectric harvester based on the recycled ceramics at different vehicle speeds is tested by field experiments. Finally, the economy of the recycling technology is discussed. The results show that the comprehensive cost of recycling technology in road piezoelectric industrialization is reduced by 12.11%. The recycling technology of piezoelectric harvester can provide a new idea of technology application for the back-end operation and maintenance of road piezoelectric system, solve the problems of electronic waste treatment while reducing the comprehensive cost, and produce inestimable social and economic benefits in the field of environmental protection.

ABSTRACT Digitalization and emerging technologies are increasing the demand for wireless sensing and the Internet of Things (IoT), which provide opportunities for autonomous sources of electricity in the form of energy harvesting systems. This paper focuses on the challenges in hybrid piezoelectric‐electromagnetic kinetic energy harvesting systems that deliver output power at milliwatt levels, sufficient for current IoT electronics. The main task in the employment of energy harvesting technology for industrial applications is transitioning from laboratory test samples to industrial‐scale prototype deployment, with emphasis on sensitivity and uncertainty analyses of energy harvesting parameters. This paper analyses this problem using a single‐degree‐of‐freedom model for a hybrid piezoelectric‐electromagnetic kinetic energy harvester, where the effect of uncertainty in design and material input parameters on harvested power outputs is examined. Industrial application uncertainties, including manufacturing and geometric tolerances, uncertainties in material parameters, and fluctuations in ambient input parameters, are assessed and analyzed using the Saltelli method. Key findings highlight the amplification of uncertainties, with mechanical damping identified as the most influential parameter of harvested power. By investigating piezoelectric and electromagnetic coupling factors, this study provides actionable insights for optimizing hybrid energy harvesters and adjusting coupling parameters for maximal output power generation.

Integrated charge excitation triboelectric nanogenerator for all weather wave energy harvesting.

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.

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.

The last years have seen the increasing development of innovative railway pantographs based on smart materials and equipped with monitoring features based on wireless sensor nodes. In this scenario, one of the most important challenges is the power supply of pantograph sensors. Energy harvesting systems have been proposed for powering monitoring sensors in a variety of applications, including railway pantographs. These systems convert ambient energy sources into electrical energy. The use of energy harvesting systems coupled with storage devices, such as rechargeable batteries or supercapacitors, can be a very promising solution for making the sensors self-powered, thus avoiding the drawbacks associated with supplying from the main grid or disposable batteries. In this paper, the operating principles of the main technologies used for energy harvesting in railway pantographs are described in detail, together with some examples of laboratory prototypes and commercial devices. The proposed analysis focuses on the perspectives and challenges of various energy harvesting technologies and can help select the most suitable technology for the development of innovative sensorized pantographs.

Micro and nanostructured liquid–solid (LS) interfaces have emerged as a crucial platform for advancing self-powered sensing and energy harvesting technologies, particularly in liquid–solid triboelectric nanogenerators (LS-TENGs). Compared with conventional solid–solid systems, LS interfaces offer reduced mechanical wear, improved durability, and unique interfacial charge dynamics. This review provides a comprehensive overview of recent progress in understanding LS interfacial charge-generation mechanisms and in engineering micro and nanostructured surfaces to enhance triboelectric performance. The transition from classical electric double layer (EDL) theory to Wang’s hybrid EDL model is discussed to clarify the dominant role of direct electron transfer during liquid–solid contact electrification. The effects of nonpolar oils, superlubric liquid layers, and asymmetric electrolytes on interfacial charge regulation are systematically summarized. Furthermore, recent advances in microstructured LS interfaces-including bioinspired surfaces, tip-array architectures, photoresponsive microstructures, and wettability-engineered designs are reviewed in terms of their influence on contact dynamics and charge stability. At the nanoscale, electrospun nanofibers, nanoparticle-decorated polymers, nanowires, metallic nanotube arrays, and laser-induced graphene are highlighted as effective strategies to amplify surface area, local electric fields, and multifunctionality. Finally, emerging applications in energy harvesting, chemical, and biological sensing are discussed. This review elucidates structure-interface-function relationships at LS interfaces and provides design guidelines for next-generation self-powered sensing and energy-harvesting platforms.

As the paradigm of modern medicine shifts toward prevention and management, the importance of implantable electronics for real-time physiological monitoring and therapeutic intervention has surged, yet the mechanical mismatch between conventional rigid devices and soft tissues poses significant challenges regarding inflammation and long-term performance. Consequently, this review hierarchically analyzes advanced semiconductor integration strategies for flexible and stretchable implantable systems, utilizing Silicon Nanomembrane (SiNM) technology as a core building block to achieve mechanical compliance while maintaining CMOS compatibility. We systematically examine flexible substrate processing and patterning techniques, including laser-induced graphene (LIG) and printing methods, and place special emphasis on conformal encapsulation strategies using inorganic/organic multilayer thin films to ensure miniaturization and reliability in harsh biological environments. Furthermore, the review covers system-level integration issues, including hierarchical wireless communication strategies tailored to implantation depth and hybrid energy harvesting technologies for battery-free operation, ultimately proposing that the organic integration of these elements is essential for realizing next-generation "Fully Autonomous Bio-integrated Systems".

Organic thin-film thermoelectric generators (TEGs) hold great promise as flexible and wearable energy harvesters. However, their broader application is hindered by the difficulty of establishing a temperature gradient within the thin film when using planar heat sources. Here, we introduce pseudo-transverse TEGs (pT-TEGs), an architecture employing an elastic substrate with two thermal conductivities, enabling the orthogonal conversion of longitudinal heat flux into lateral thermovoltage by mimicking the transverse thermoelectric effect. This design circumvents the limitations of conventional thin-film TEGs, such as the need for three-dimensional deformation to form a temperature gradient, allowing efficient thermal energy harvesting from planar heat sources while preserving a two-dimensional form factor. Furthermore, the fully solution-processed and modular pT-TEGs exhibit excellent mechanical flexibility and high scalability. We believe that this approach offers a practical platform for the realization of genuine two-dimensional TEGs and will contribute to the advancement of flexible and wearable energy harvesting technologies.