Stretchable Nanogenerator Research Articles

Stretchable nanogenerator with micro-nano hierarchical interfaces for self-powered biometric authentication

Stretchable nanogenerator with micro-nano hierarchical interfaces for self-powered biometric authentication

Polarization‐Induced Mechanically Socketed Ultra‐Stretchable and Breathable Textile‐Based Nanogenerator and Pressure Sensor

AbstractTextile‐based wearable triboelectric nanogenerators (TENGs) have emerged as viable power sources for wearable electronics. However, it is still a daunting challenge to realize a high‐performing textile‐based nanogenerator without compromising its intrinsic textile‐like properties, such as stretchability, breathability, and conformability. The above challenge is addressed by fabricating a record high‐performing wearable, breathable and stretchable nanogenerator based on polarization‐induced ultra‐stretchable EVA/Nylon‐11 micro/nano‐fibers (1250%) as the triboelectric positive layer and polarization‐induced ultra‐stretchable EVA/PVDF/BA2CsAgBiBr7 micro/nano‐fibers (1480%) as the triboelectric negative layer. The excellent stretchability, breathability (1.15 Kgm−2d−1) and high energy‐harvesting performance (650 V, 19.5 µAcm−2) are attributed to the mechanically‐socketed structure of the aligned stretchable EVA microfibers with the polarized nanofibers, thus providing a universal framework to fabricate stretchable piezoelectric fibers. Compositional engineering and polarization‐induced surface charges coupled with triboelectric‐induced surface charges enabled enhanced performance compared to other wearable stretchable textile‐based nanogenerators. Additionally, it is utilized as a stretchable self‐powered pressure sensor with an ultra‐wide pressure sensing range (0.05–500 kPa) and high sensitivity (2.5 VkPa−1) even under deformations. To the best of the knowledge, PI‐STENG stands out amongst various stretchable self‐powered pressure sensors in terms of pressure sensing range and stretchability. The PI‐STENG is demonstrated as a machine learning‐enabled intellisensor for workforce safety monitoring.

Emerging Nanogenerators for Rehabilitation Monitoring and Information Interaction

Soft wearable devices with flexibility and stretchability attract thousands of researchers around the world. These devices can be used in health monitoring, intelligent robotic and rehabilitation training system. Emerging nanogenerators (NGs) have been studied extensively for soft wearable devices due to the advantages of easy fabrication, cost-effective, self-powered and high sensitivity in response to mechanics stimulus. Recently, scientists have developed a flexible and stretchable nanogenerator for rehabilitation monitoring and information interaction, which is called FSDM-NG and emphasized in this commentary. The piezoelectric and triboelectric effects of the FSDM-NG have been utilized for different functions, showing some interesting and useful results to be acted as a self-powered limb motion sensor and an interface of information interaction. The purpose of the commentary is to discuss the characteristics and perspectives of NGs as self-powered wearable sensors and information interaction devices in biomedical field.

All 3D Printed Stretchable Piezoelectric Nanogenerator for Self-Powered Sensor Application.

With the rapid development of wearable electronic systems, the need for stretchable nanogenerators becomes increasingly important for autonomous applications such as the Internet-of-Things. Piezoelectric nanogenerators are of interest for their ability to harvest mechanical energy from the environment with its inherent polarization arising from crystal structures or molecular arrangements of the piezoelectric materials. In this work, 3D printing is used to fabricate a stretchable piezoelectric nanogenerator which can serve as a self-powered sensor based on synthesized oxide–polymer composites.

Triboelectric and Piezoelectric Nanogenerators for Future Soft Robots and Machines.

SummaryThe triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are two recently developed technologies for effective harvesting of ambient mechanical energy for the creation of self-powered systems. The advantages of TENGs and PENGs which include large open-circuit output voltage, low cost, ease of fabrication, and high conversion efficiency enable their application as new flexible sensors, wearable devices, soft robotics, and machines. This perspective provides an overview of the current state of the art in triboelectric and piezoelectric devices that are used as self-powered sensors and energy harvesters for soft robots and machines; hybrid approaches that combine the advantages of both mechanisms are also discussed. To improve system performance and efficiency, the potential of providing self-powered soft systems with a degree of multifunctionality is investigated. This includes optical sensing, transparency, self-healing, water resistance, photo-luminescence, or an ability to operate in hostile environments such as low temperature, high humidity, or high strain/stretch. Finally, areas for future research directions are identified.

High-performance stretchable PZT particles/Cu@Ag branch nanofibers composite piezoelectric nanogenerator for self-powered body motion monitoring

The development of stretchable nanogenerators has attracted intensive attentions for their promising applications in wearable electronics recently. Here, a newly high-performance stretchable PZT particles/Cu@Ag branch nanofibers (BNFs) nanocomposite piezoelectric generator (NCPG) is reported. The uniform mixture of PZT particles and Cu@Ag BNFs is blended into silicone rubber matrix that exhibits remarkably piezoelectric, mechanical and electrical characteristics. Owing to the similar molding method and the identical elastic matrix, the piezoelectric layer and the electrode layers could be completely integrated into stretchable NCPG based on all-in-one structure, which reveals high output performances (Vpeak–peak ≈ 61 V, Ipeak–peak ≈ 1.1 μA, 22.36 μw cm−3). The generated electricity is utilized to directly light five green emitting diodes (LEDs) and to drive a digital thermometer after stored in capacitor under the mechanical tensile strain stimulation. Moreover, the stretchable NCPG could act as a self-powered body motion sensor for distinguishing the bending angles and frequencies of the knee joint. This work provides a novel design idea for stretchable nanogenerators and shows great potential applications in artificial intelligence, medical diagnosis and movement entertainment.

A bionic stretchable nanogenerator for underwater sensing and energy harvesting

Soft wearable electronics for underwater applications are of interest, but depend on the development of a waterproof, long-term sustainable power source. In this work, we report a bionic stretchable nanogenerator for underwater energy harvesting that mimics the structure of ion channels on the cytomembrane of electrocyte in an electric eel. Combining the effects of triboelectrification caused by flowing liquid and principles of electrostatic induction, the bionic stretchable nanogenerator can harvest mechanical energy from human motion underwater and output an open-circuit voltage over 10 V. Underwater applications of a bionic stretchable nanogenerator have also been demonstrated, such as human body multi-position motion monitoring and an undersea rescue system. The advantages of excellent flexibility, stretchability, outstanding tensile fatigue resistance (over 50,000 times) and underwater performance make the bionic stretchable nanogenerator a promising sustainable power source for the soft wearable electronics used underwater.

Deposition Time and Annealing Effects of ZnO Seed Layer on Enhancing Vertical Alignment of Piezoelectric ZnO Nanowires

Well aligned crystalline zinc oxide (ZnO) nanowires (NWs) on ZnO/Au/Ti/Si substrates were grown by so-called “hydrothermal synthesis”. ZnO seed layers with different thicknesses ranging from 5 to 100 nm, achieved by controlling the deposition time, were prepared by radio-frequency sputtering, followed by a post-annealing treatment in air at 400 °C. The effects of deposition time and annealing treatment of ZnO seed layers on the subsequent growth of ZnO NWs were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The experimental results reveal that the quality and growth behaviors of ZnO NWs are strongly dependent on both the thickness and the heat treatment of the ZnO seed layers. This work is an optimization step of an easy, cost-effective, and industrially scalable process flow recently developed for the fabrication of a high performance, nanocomposite-based stretchable nanogenerator (SNG) on polydimethylsiloxane (PDMS) substrate. The morphological improvement of hydrothermally grown ZnO NWs may therefore lead to higher performance SNGs for the targeted application of mechanical energy harvesting, in order to supply flexible and wearable electronics.

Organic/Inorganic Hybrid Stretchable Piezoelectric Nanogenerators for Self‐Powered Wearable Electronics

AbstractPiezoelectric nanocomposite‐based nanogenerators are gaining extensive attention as energy harvesters and self‐powered tactile sensors for their applications in wearable electronics and personal healthcare. Herein, a facile, cost‐effective, and industrially scalable process flow is reported for the fabrication of high performance mechanically robust nanocomposite‐based stretchable nanogenerator (SNG) on polydimethylsiloxane substrate. The inorganic/organic nanocomposite piezoelectric energy harvesting devices are realized by encapsulating the ZnO nanowires in a parylene C polymer matrix. The suggested fabrication process flow is implemented to fabricate SNG on flexible bank cards. The SNG devices exhibit excellent performances with a high open‐circuit voltage ≈10 V, short‐circuit current density ≈0.11 µA cm−2, and peak power ≈3 µW under a vertical compressive force using a mechanical shaker. The obtained electricity from the SNG devices is used to drive electronic devices such as liquid crystal displays without employing any storage unit, implying the device significance in the field of consumer electronics. Besides, commercially available energy harvesting modules are used to store the generated electrical energy in capacitors. Furthermore, the SNG device can be adopted as self‐powered wearable tactile sensor for detecting slight body movements, which shows its potential applications in autonomous wearable electronics.

Ultra-Stretchable Piezoelectric Nanogenerators via Large-Scale Aligned Fractal Inspired Micro/Nanofibers.

Stretchable nanogenerators that directly generate electricity are promising for a wide range of applications in wearable electronics. However, the stretchability of the devices has been a long-standing challenge. Here we present a newly-designed ultra-stretchable nanogenerator based on fractal-inspired piezoelectric nanofibers and liquid metal electrodes that can withstand strain as large as 200%. The large-scale fractal poly(vinylidene fluoride) (PVDF) micro/nanofibers are fabricated by combination of helix electrohydrodynamic printing (HE-Printing) and buckling-driven self-assembly. HE-Printing exploits “whipping/buckling” instability of electrospinning to deposit serpentine fibers with diverse geometries in a programmable, accurately positioned, and individually-controlled manner. Self-organized buckling utilizes the driven force from the prestrained elastomer to assemble serpentine fibers into ultra-stretchable fractal inspired architecture. The nanogenerator with embedded fractal PVDF fibers and liquid-metal microelectrodes demonstrates high stretchability (>200%) and electricity (currents >200 nA), it can harvest energy from all directions by arbitrary mechanical motion, and the rectified output has been applied to charge the commercial capacitor and drive LEDs, which enables wearable electronics applications in sensing and energy harvesting.

A Stretchable Nanogenerator with Electric/Light Dual‐Mode Energy Conversion

As an alternative technology, stretchable electronics attract long‐lasting attention. A newly‐designed stretchable nanogenerator with unique dual‐mode energy conversion is reported. The ability of converting the input mechanical stimuli to either electric or light output is achieved by monolithically integrating a transparent single‐electrode triboelectric nanogenerator (S‐TENG) with a ZnS based mechanoluminescence (ML) composite. This stretchable device with versatile functions promotes the development of the smart systems to efficiently and diversely utilize ubiquitous mechanical energy and demonstrates great potential for artificial e‐skins.

High performance triboelectric nanogenerators with aligned carbon nanotubes.

As the essential element of a triboelectric nanogenerator (TENG), friction layers play key roles that determine the device performance, which can be enhanced by material selection and surface modification. In this work, we have embedded aligned carbon nanotubes (CNTs) on the polydimethylsiloxane (PDMS) surface as the effective dielectric layer to donate electrons. This layer not only increases the electron generation for the output, but also shows notable stretchability. The length and the properties of the aligned CNTs can be controlled precisely. Using the 40 μm CNT as an example, the fabricated CNT-PDMS TENG shows an output voltage of 150 V and a current density of 60 mA m-2, which are 250% and 300% enhancement compared to the TENG using directly doped PDMS/multiwall carbon nanotubes, respectively. The maximum power density of this TENG reaches 4.62 W m-2 at an external load of 30 MΩ. The TENG has demonstrated superior stability during cyclic measurement of over 12 000 cycles. Besides, the aligned CNT-PDMS film shows superhydrophobicity (154°) and good sheet resistance of 280 Ω sq-1. This stretchable aligned CNT-PDMS film can be universally utilized as a positive triboelectric layer pairing with polymeric materials such as polyethylene terephthalate, polyimide, PDMS and polytetrafluoroethylene for TENGs. This work provides an effective method of structure design for flexible and stretchable nanogenerators.

Transparent flexible stretchable piezoelectric and triboelectric nanogenerators for powering portable electronics

Transparent flexible and stretchable nanogenerators (NGs) that harvest various types of mechanical energy exhibit a great potential for powering low-power portable devices and self-powered electronic systems. Integration of transparency, flexibility and stretchability to NGs has gained a lot of interest for realizing the energy harvesting systems in practical life. Flexible piezoelectric nanostructures, which can generate electrical signal when mechanically deformed, are the most promising candidates for piezoelectric NGs, which offer sufficient power to drive portable electronics and cardiac pacemakers. Moreover, triboelectric NGs enlighten a new technique to harvest mechanical energies with high conversion efficiency. This review highlights the recent research progress of transparent and flexible ZnO nanorods/nanowires, two-dimensional ZnO nanosheets, stretchable micro-patterned P(VDF-TrFE) polymer, ZnSnO3 nanocubes-based piezoelectric NGs along with graphene and hydrophobic sponge structure-based triboelectric NGs, and their potential applications in powering portable electronics are summarized and presented. Finally, the power generation under different modes of pressure/friction such as vertical compressive, bending, contact-separation and stretching are collected and the involved future challenges are discussed in terms of device configuration and efficiency.