Self-powered Wearable Devices Research Articles

Silk nanoribbon films with enriched silk II structure and enhanced piezoelectricity for self-powered implantable and wearable devices

Piezoelectric biomaterials are intrinsically suitable to convert mechanical energy to electrical output and achieve electricity generation, in vivo/in vitro real-time monitoring, and sensing in biological systems. However, the inability to fabricate piezoelectric bio-materials with excellent piezoelectricity, full biodegradability, and good biocompatibility remains a challenge toward practical applications. As a solution, we present a bio-piezoelectric thin film with macroscopic piezoelectric output, high stability, fast response ability, flexibility, biocompatibility, and biodegradability based on nascent silk nanoribbons (SNRs) with high silk II-type structure. The solvent systems influence the meso/nanostructure and the piezoelectric performance of silk materials. Compared with other silk materials, the SNR fabricated by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation system (T-SNR) maintains higher silk II-type structure and more stable crystalline structure. The T-SNR film possesses electrostriction effect without electrical poling treatment. It presents an apparent piezoelectric constant (d33) of 7.7 pm/V and a piezoelectric voltage coefficient (g33) of 0.58 Vm/N, such values are superior to most reported bio-films. The piezoelectric T-SNR film can realize in vivo/in vitro real-time monitoring, sensing, and self-power ability. With its natural compatibility and degradability, the T-SNR film exhibits the potential for various implantable and wearable applications and may enable the development of fully biodegradable transient electromechanical devices.

Multi-interface Engineering of MXenes for Self-Powered Wearable Devices.

Self-powered wearable devices with integrated energy supply module and sensitive sensors have significantly blossomed for continuous monitoring of human activity and the surrounding environment in healthcare sectors. The emerging of MXene-based materials has brought research upsurge in the fields of energy and electronics, owing to their excellent electrochemical performance, large surface area, superior mechanical performance, and tuneable interfacial properties, where their performance can be further boosted via multi-interface engineering. Herein, a comprehensive review of recent progress in MXenes for self-powered wearable devices is discussed from the aspects of multi-interface engineering. The fundamental properties of MXenes including electronic, mechanical, optical, and thermal characteristics are discussed in detail. Different from previous review works on MXenes, multi-interface engineering of MXenes from termination regulation to surface modification and their impact on the performance of materials and energy storage/conversion devices are summarized. Based on the interfacial manipulation strategies, potential applications of MXene-based self-powered wearable devices are outlined. Finally, proposals and perspectives are provided on the current challenges and future directions in MXene-based self-powered wearable devices. This article is protected by copyright. All rights reserved.

Sodium Niobate Nanowires Embedded PVA-Hydrogel-Based Triboelectric Nanogenerator for Versatile Energy Harvesting and Self-Powered CO Gas Sensor.

The surging demand for sustainable energy solutions and adaptable electronic devices has led to the exploration of alternative and advanced power sources. Triboelectric Nanogenerators (TENGs) stand out as a promising technology for efficient energy harvesting, but research on fully flexible and environmental friendly TENGs still remain limited. In this study, an innovative approach is introduced utilizing an ionic-solution modified conductive hydrogel embedded with piezoelectric sodium niobate nanowires-based Triboelectric Nanogenerator (NW-TENG), offering intrinsic advantages to healthcare and wearable devices. The synthesized NW-TENG, with a 12.5 cm2 surface area, achieves peak output performance, producing ≈840V of voltage and 2.3 µC of charge transfer, respectively. The rectified energy powers up 30 LEDs and a stopwatch; while the NW-TENG efficiently charges capacitors from 1µF to 100 µF, reaching 1V within 4 to 65 s at 6Hz. Integration with prototype carbon monoxide (CO) gas sensortransform the device into a self-powered gas sensory technology. This study provides a comprehensive understanding of nanowire effects on TENG performance, offering insights for designing highly flexible and environmentally friendly TENGs, and extending applications to portable self-powered gas sensors and wearable devices.

Clothing comfort sensing system based on triboelectric and tribological behavior of fabrics

Static electricity accumulated on fabrics often causes discharged discomfort, fire, explosion, and cardiovascular diseases. Meanwhile, the electricity can be harvested and used for self-powered wearable devices. Therefore, it is essential to regulate fabric triboelectricity through studying the relationship between friction coefficients and triboelectric charges. In this paper, a reciprocating tribometer coupled with triboelectric testing instruments is designed to collect in-situ tribological and triboelectric properties for laterally sliding fabric based triboelectric nanogenerators (F-TENGs). In this case, the regulation factors involve motion conditions (including load, frequency, friction angle, etc.), surface components and environments. The results show that faster sliding speed and lower humidity produce higher triboelectric outputs of F-TENGs. Especially, amino groups modified silk shows an extremely strong electron-donating ability and achieves a high triboelectric current of 382.2 nA when paired with polyimide, which is enhanced by 1.67 times compared with silk. Most importantly, the friction coefficient values of F-TENGs show almost the same trend as the triboelectric outputs. Based on this, a sensing system for monitoring comfort level of fabrics is successfully designed through rubbing tested fabrics and observing indicator lamps. This work proposes a tribological approach with valuable insights of the underlying mechanism of triboelectric charging and extended applications.

Engineering self-healable and biodegradable ionic polyurethane with highly tribopositive behavior

According to the development of human-oriented technology, triboelectric nanogenerators (TENGs) present great potential as a power source for self-powered sensors and wearable devices. Advanced next-generation TENGs require not only durability and stable production of electrical energy but also the ability to autonomously self-heal after mechanical damage and biodegradability. Here we report a self-healable, biodegradable, and high performance TENG using engineered ionic polyurethane (IPU). We utilized polycaprolactone-based PU to provide biodegradable properties and introduced imidazolium ionic liquids diol (IL) to facilitate self-healing through ion-dipole interaction. Imidazolium ionic liquid diol also improves triboelectric properties and improves capacitance by forming an electric double layer (EDL), contributing to improved output. These results suggest a high-performance TENG design methodology that can be applied to next-generation soft electronic devices.

Compatible interface based self-charging fiber for wearable electronic

With the rapid development of wearable devices, there is an increasing demand for flexible, eco-friendly, and reliable power sources. The self-charging energy system, which integrates energy collection and storage, has emerged as one of the most promising sustainable energy sources, with an urgent need for its application and implementation. In this work, we proposed a fiber-shaped self-charging system based on supercapacitor (SC) and triboelectric nanogenerator (TENG). For the supercapacitor, a silver-decorated carbon fiber with PEDOT: PSS coated is used as the positive electrode, while carbon nanotube film/Fe2O3/MoS2 serves as the negative electrode. The assembled coaxial structure not only shortens the distance between the positive and negative electrodes, effectively improving charge transfer efficiency, but also ensures the flexibility and mechanical stability of the device. The designed supercapacitor exhibited a capacitance of 213.3 mF cm−2 and demonstrated excellent stability of 92 % retention rate even after 5000 cycles. Moreover, the negative electrode of the supercapacitor also serves as a compatible interface for the TENG, with silicone rubber coating acting as the friction layer, forming a single-electrode structure. This coaxial structure with a compatible interface allows for higher efficiency in charge capture and transfer, doubling the charging efficiency compared to incompatible structures, while also ensuring flexibility, making it more suitable for wearable applications. By weaving the TENG, it exhibits an open-circuit voltage of 150 V, a short-circuit current of 6 μA, and a high power density of 900 mW cm−2. In addition, it can also serve as a self-powered sensor, capable of accurately detecting human motion and current conditions. This research proposes an effective compatible interface architecture promising application prospect for advancing sustainable development of self-powered wearable electronic devices.

High Strength and Toughness Polymeric Triboelectric Materials Enabled by Dense Crystal-Domain Cross-Linking.

Lightweight, easily processed, and durable polymeric materials play a crucial role in wearable sensor devices. However, achieving simultaneously high strength and toughness remains a challenge. This study addresses this by utilizing an ion-specific effect to control crystalline domains, enabling the fabrication of a polymeric triboelectric material with tunable mechanical properties. The dense crystal-domain cross-linking enhances energy dissipation, resulting in a material boasting both high tensile strength (58.0 MPa) and toughness (198.8 MJ m-3), alongside a remarkable 416.7% fracture elongation and 545.0 MPa modulus. Leveraging these properties, the material is successfully integrated into wearable self-powered devices, enabling real-time feedback on human joint movement. This work presents a valuable strategy for overcoming the strength-toughness trade-off in polymeric materials, paving the way for their enhanced applicability and broader use in diverse sensing applications.

Wearable All-Fabric Hybrid Energy Harvester to Simultaneously Harvest Radiofrequency and Triboelectric Energy.

Distributed micro-energy harvesting devices offer the flexibility, sustainability, and multi-scenario applicability that will be critical to wearable electronic products in the Internet of Things. The radiofrequency and triboelectric (RF-TE) hybrid energy harvester (HEH) concept and prototype is presented for the first time, to simultaneously capture the energy from ambient electromagnetic waves and biological motions. The proposed hybrid energy harvesting system consists of a wearable rectenna, a triboelectric nanogenerator (TENG), and a power management circuit (PMC). Among them, the all-fabric rectenna exhibits good impedance matching characteristics in the ISM frequency. The flexible TENG unit can generate a maximum power density of 0.024µWcm-2. The designed multifunctional fabric-based PMC can considerably enhance the controllability of harvested hybrid energy. Additionally, a normalizable fabric circuit board quasi surface mount technology (FCB-SMT) is proposed to integrate all modules on the same fabric substrate in one step, making the entire system superior mechanical robustness. The proposed wearable fabric-based RF-TE hybrid energy harvester is capable of successfully driving consumer electronics (such as sensors, watches, etc.). It provides a new energy solution strategy for self-powered wearable electronic devices and is anticipated to encourage the efficient utilization of renewable energy.

Enhancing self-powered wearable device performance: ZIF-8/rGO hybrid nanostructures for extended operation and electrochemical glucose detection

The growing demand for wearable devices designed for continuous monitoring necessitates an extended power supply, prompting the development of self-powered sensing devices capable of prolonged operation. Multifunctional materials have become a prime focus for self-powered systems. One such material is ZIF-8, a porous crystalline metal–organic framework (MOF) that holds promise for non-enzymatic glucose detection due to its expansive surface area, functional sites, electrocatalytic activity, and biocompatibility. Our research details the successful synthesis of ZIF-8 and a composite consisting of ZIF-8 and reduced graphene oxide (rGO). We extensively investigated the structural, elemental, and morphological attributes of these materials using various characterization techniques. Our examination of glucose detection involved cyclic voltammetry and amperometry studies. The hybrid electrode, benefiting from the synergistic interplay between ZIF-8 and rGO, exhibited an exceptional sensitivity of 5047.18 μA mM−1 cm−2 and a detection limit of 0.3 μM, spanning the range of 0.005 mM to 5 mM. Furthermore, we explored these materials' potential in the supercapacitance realm. The ZIF-8/rGO hybrid electrode demonstrated an impressive specific capacitance of 287F/g at a current density of 1 Ag−1, displaying pseudocapacitive behaviour. A proof-of-concept prototype device, utilizing ZIF-8/rGO, was fabricated and investigated for its potential in wearable glucose sensing. The device yielded satisfactory results, showcasing its capability as a self-powered wearable sensor. In general, ZIF-8/rGO hybrid nanostructure emerged as a promising candidate for supercapacitor and electrochemical glucose detection applications.

Estimation of Kinetic Energy Harvesting Potential for Self-Powered Wearable IoT Devices With 67 000 Participants From the UK Biobank

Estimation of Kinetic Energy Harvesting Potential for Self-Powered Wearable IoT Devices With 67 000 Participants From the UK Biobank

Improved Energy Harvesting Ability of Single-Layer Binary Fiber Nanocomposite Membrane for Multifunctional Wearable Hybrid Piezoelectric and Triboelectric Nanogenerator and Self-Powered Sensors.

While wearable self-powered electronic devices have shown promising improvements, substantial challenges persist in enhancing their electrical output and structural performance. In this work, a working mechanism involving simultaneous piezoelectric and triboelectric conversion within a monolayer-structured membrane is proposed. Single-layer binary fiber nanocomposite membranes (SBFNMs) (PVDF/CNTX@PAN/CNTX, DPCPCX) with two distinct interpenetrating nanocomposite fibers were created through co-electrospinning, incorporating multiwalled carbon nanotubes (CNTs) into polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN), respectively. The resulting membrane demonstrated an exceptional synergistic effect of piezoelectricity and triboelectricity along with a high machine-to-electric conversion capability. The addition of CNTs increased the PVDF β-phase and the PAN planar zigzag conformation. As a result, the DPCPC0.5-SBFNMs-based piezoelectric nanogenerator exhibited excellent electrical output (187 V, 8.0 μA, and 1.52 W m-2), maintaining an exceptionally high level of output voltage compared with other piezoelectric nanogenerators. It successfully illuminated 50 commercial light-emitting diodes simultaneously. The output voltage of DPCPC0.5-SBFNMs was 5.1 and 4.6 times higher than that of PAN or PVDF single-fiber membranes, respectively. Furthermore, the peak voltage of DPCPC0.5-SBFNMs exceeded that of co-electrospinning PVDF/CNT1.0@PAN (DPCP1.0) and PVDF@PAN/CNT1.0 (DPPC1.0) by 20 and 10 V, respectively. The piezoelectric sensor made of DPCPC0.5-SBFNMs accurately sensed human movement, ranging from tiny to large, and demonstrated utility as an alarm in medical treatment, fire fighting, and monitoring. Endogenous triboelectricity is proposed in SBFNM piezoelectric materials, enhancing electromechanical conversion and electrical output capacity, thereby promising a wide application potential in self-powered wearable electronic devices.

Self-Powered Photodetector Based on Ag/CH3NH3PbI3/C Asymmetric Dual-Terminal Device.

CH3NH3PbI3 is capable of exhibiting a superior photoresponse to visible light, but its self-powered devices are typically formed through p-n junctions. In this study, we fabricated a Ag/CH3NH3PbI3/C dual-terminal asymmetric electrode device using a single CH3NH3PbI3 perovskite micro/nanowire, enabling both the photoresponse and self-powered characteristics of CH3NH3PbI3 to visible light. Compared with traditional p-n junction devices, this simple device demonstrates enhanced interface photovoltaic effects by optimizing the combination of the Ag electrode with CH3NH3PbI3, resulting in superior self-powered characteristics. Under low bias voltage, the device achieves a significant on/off ratio of 103, with superior sensitivity and responsivity as well as a maximum rectification ratio of about 12. The photogenerated voltage and current reach approximately 0.8 V and 2 nA, respectively. This simple, compact, and self-powered asymmetric device exhibits great potential for applications in self-powered optoelectronics and wearable devices. This research provides a promising approach for recognizing and utilizing surface state effects in single nanoscale structures.

3D-printed wearable BaTiO3/PDMS piezoelectric nanogenerator for self-powered body movement sensing

Flexible piezoelectric nanogenerators (PENGs) used in body movement real-time monitoring are of great interest for their wide application potential such as in the field of smart healthcare. In this work, a self-powered BaTiO3/Polydimethylsiloxane (PDMS) PENG for body movement sensing was successfully fabricated by extrusion 3D printing. Matrix system composed of different ratios of PDMS was selected based on the rheological property of materials. Experimental investigations were conducted to examine the impact of printing pressure and speed on the linewidth. Subsequently, the extrusion parameters for nanogenerators were determined based on the printed linewidth. The composite showed good ferroelectric property. After polarization, the nanogenerators exhibited an improvement in output performance of up to 55.2%. Additionally, the device demonstrated a good linear relationship between voltage and tapped force test by an electromechanical vibrator. Successful detection of body or muscle movement signals was achieved when the nanogenerator was mounted on the human finger, throat, or foot using a wearable sock, highlighting its potential for applications in self-powered wearable devices for smart healthcare.

Piezoelectric nanogenerators for self-powered wearable and implantable bioelectronic devices.

One of the recent innovations in the field of personalized healthcare is the piezoelectric nanogenerators (PENGs) for various clinical applications, including self-powered sensors, drug delivery, tissue regeneration etc. Such innovations are perceived to potentially address some of the unmet clinical needs, e.g., limited life-span of implantable biomedical devices (e.g., pacemaker) and replacement related complications. To this end, the generation of green energy from biomechanical sources for wearable and implantable bioelectronic devices gained considerable attention in the scientific community. In this perspective, this article provides a comprehensive state-of-the-art review on the recent developments in the processing, applications and associated concerns of piezoelectric materials (synthetic/biological) for personalized healthcare applications. In particular, this review briefly discusses the concepts of piezoelectric energy harvesting, piezoelectric materials (ceramics, polymers, nature-inspired), and the various applications of piezoelectric nanogenerators, such as, self-powered sensors, self-powered pacemakers, deep brain stimulators etc. Important distinction has been made in terms of the potential clinical applications of PENGs, either as wearable or implantable bioelectronic devices. While discussing the potential applications as implantable devices, the biocompatibility of the several hybrid devices using large animal models is summarized. This review closes with the futuristic vision of integrating data science approaches in developmental pipeline of PENGs as well as clinical translation of the next generation PENGs. STATEMENT OF SIGNIFICANCE: Piezoelectric nanogenerators (PENGs) hold great promise for transforming personalized healthcare through self-powered sensors, drug delivery systems, and tissue regeneration. The limited battery life of implantable devices like pacemakers presents a significant challenge, leading to complications from repititive surgeries. To address such a critical issue, researchers are focusing on generating green energy from biomechanical sources to power wearable and implantable bioelectronic devices. This comprehensive review critically examines the latest advancements in synthetic and nature-inspired piezoelectric materials for PENGs in personalized healthcare. Moreover, it discusses the potential of piezoelectric materials and data science approaches to enhance the efficiency and reliability of personalized healthcare devices for clinical applications.

Low-Temperature Centimeter-Scale Growth of Layered 2D SnS for Piezoelectric Kirigami Devices.

Tin monosulfide (SnS) is a promising piezoelectric material with an intrinsically layered structure, making it attractive for self-powered wearable and stretchable devices. However, for practical application purposes, it is essential to improve the output and manufacturing compatibility of SnS-based piezoelectric devices by exploring their large-area synthesis principle. In this study, we report the chemical vapor deposition (CVD) growth of centimeter-scale two-dimensional (2D) SnS layers at temperatures as low as 200 °C, allowing compatibility with processing a range of polymeric substrates. The intrinsic piezoelectricity of 2D SnS layers directly grown on polyamides (PIs) was confirmed by piezoelectric force microscopy (PFM) phase maps and force-current corroborative measurements. Furthermore, the structural robustness of the centimeter-scale 2D SnS layers/PIs allowed for engraving complicated kirigami patterns on them. The kirigami-patterned 2D SnS layer devices exhibited intriguing strain-tolerant piezoelectricity, which was employed in detecting human body motions and generating photocurrents irrespective of strain rate variations. These results establish the great promise of 2D SnS layers for practically relevant large-scale device technologies with coupled electrical and mechanical properties.

High-output triboelectric nanogenerator based on L-cystine/nylon composite nanofiber for human bio-mechanical energy harvesting

Thanks to the characteristics of lightweight and high-efficiency in low-frequency, triboelectric nanogenerator (TENG) is considered a highly promising technology to effectively harvest human mechanical energy. However, the low output of wearable TENG significantly limits its application in self-powered wearable electronic systems. Herein, we propose a high-output multilayer-structured triboelectric nanogenerator (HM-TENG) fabricated by nylon/L-cystine composite nanofiber film (NCNF), which can efficiently harvest various human bio-mechanical energy. Based on the excellent positive triboelectric performance of L-cystine and the corresponding preparation process research, the fabricated TENG by NCNF with 8 w% L-cystine achieves several times the output performance of TENG with pure nylon nanofiber. Besides, the fabricated HM-TENG obtain a high power density of 11.52 W/m2, which is 5–500 folds higher than previous related research work. Importantly, relied on the designed power management circuit and the installation of a foot mounted HM-TENG, various self-powered wearable electronic devices constructed by harvesting human bio-mechanical energy have been successfully demonstrated. Our research not only provides a novel method for developing high-output TENG but also offers a important solution for the design of self-powered electronic devices.

Metal/bacteria cellulose nanofiber bilayer membranes for high-performance hydrovoltaic electric power generation

Hydrovoltaic devices that produce electricity from water represent a promising solution for green energy harvesting. Hydrovoltaic power generators based on various emerging nanostructured materials have shown great potential in water-enabled electricity generation. However, the development of high-performance and practical hydrovoltaic devices remains limited because of low electric power generation, high cost of precursor materials, and complicated fabrication processes. In this study, we developed a novel metal-coated bacteria cellulose nanofiber bilayer membrane (MBCBM) for high-performance hydrovoltaic power-generation devices. The top side of the MBCBM has metal-bacteria cellulose (BC) nanofibers that serve as a conducting electrode for fast charge carrier collection, whereas the bottom side has BC nanofibers that serve as hydrovoltaic materials for high efficient energy generation. A Schottky barrier was incorporated into the hydrovoltaic device, which enhanced the electric power output. Experiments revealed that the optimized single-MBCBM based hydrovoltaic device generated a maximum voltage of 0.935 V, current of 7.51 mA, and power output of 6.07 mW with a 50 μl electrolyte solution. The hybrid membrane and device design concept is expected to effectively utilize practical sustainable and clean energy sources for Internet of Things (IoT) devices and self-powered wearable devices in next-generation electronics.

Multilayered Functional Triboelectric Polymers for Self-Powered Wearable Applications: A Review.

Multifunctional wearable devices detect electric signals responsive to various biological stimuli and monitor present body motions or conditions, necessitating flexible materials with high sensitivity and sustainable operation. Although various dielectric polymers have been utilized in self-powered wearable applications in response to multiple external stimuli, their intrinsic limitations hinder further device performance enhancement. Because triboelectric devices comprising dielectric polymers are based on triboelectrification and electrostatic induction, multilayer-stacking structures of dielectric polymers enable significant improvements in device performance owing to enhanced interfacial polarization through dissimilar permittivity and conductivity between each layer, resulting in self-powered high-performance wearable devices. Moreover, novel triboelectric polymers with unique chemical structures or nano-additives can control interfacial polarization, allowing wearable devices to respond to multiple external stimuli. This review summarizes the recent insights into multilayered functional triboelectric polymers, including their fundamental dielectric principles and diverse applications.

Experimental feasibility investigation on wearability of cloth-type electronic devices composed of functional polyvinylidene difluoride (PVDF) fibers

In the fabrication of fabric-type electronic devices, especially mobile wearable devices, various electrical functions such as sensing, actuation, and energy harvesting can be realized using complex fibrous electrical components and the associated techniques such as weaving and wiring. This study introduces a hybrid cloth-type electronic device composed of PVDF and ordinary fiber yarns. Moreover, experimental protocols for evaluating the electrical performances of cloth-type electronic devices are used to check the feasibility of the proposed wearable electronic device. The magnitude of the generated voltage signal depending on the weaving pattern and types of functional fibers under impact loading were experimentally investigated, and the most appropriate weaving pattern was suggested. To check the serviceability of the proposed cloth-type wearable device, its performance was tested under various hygrothermal environmental conditions. After conducting several electro-mechanical tests and a washing test, the proposed hybrid cloth-type electronic device was found to have adequate potential for use in self-powered wearable electronic devices.

Energy harvesting for self-powered wearable device applications

The universal energy demand and pollution have prompted research scientists to explore other energy harvesting technologies that can generate energy from the natural resource environment, mainly due to the use of conventional energy sources. Energy harvester can be extracted and to convert into useful electric energy. The piezoelectric energy harvester is an excellent method of extracting mechanical energy due to its high electric and mechanical combination and piezoelectric harvester coefficient to compare electro-static, electro-magnetic, and triboelectric transitions. Therefore, the harvesting of piezoelectric energy is highly appreciated by the scientific community. Energy harvesters can be used to convert electrical energy into strong vibrations, which can be to store and used on a variety of ultra-low power electronic devices. With the advent of a various variety of wearable digital devices and fitness tracking devices, the piezoelectric generator suitable for portable and wearable electronic power source is one of the most interesting.