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The complex process of wound healing depends on the coordinated interaction between various immunological and biological systems, which can be aided by technology. This present review provides a broad overview of the medical applications of piezoelectric and triboelectric nanogenerators, focusing on their role in the development of wound healing technology. Based on the finding that the damaged epithelial layer of the wound generates an endogenous bioelectric field to regulate the wound healing process, development of technological device for providing an exogenous electric field has therefore been paid attention. Authors of this review focus on the design and application of piezoelectric and triboelectric materials to manufacture self-powered nanogenerators, and conclude with an outlook on the current challenges and future potential in meeting medical needs and commercialization., Grpahical Abstract

Recently, there has been growing interest in triboelectric nanogenerators (TENGs) that can effectively convert various forms of mechanical energy input into electrical energy. In the present study, a novel Teflon/vitamin B1 powder based triboelectric nanogenerator (TVB-TENG) is proposed. Paper is utilized as a supporting platform for triboelectrification between a commercial Teflon tape and vitamin B1 powder. The measured open-circuit voltage was approximately 340 V. The TVB-TENG can be applied as a humidity sensor and exhibits a linear and reversible response to the relative humidity of the environment. Moreover, the change in relative humidity is also indicated by the change in luminosity of a set of light-emitting diodes (LEDs) integrated in the TVB-TENG system. The TVB-TENG proposed in this study illustrates a cost-effective method for portable power supply and sensing devices.

Based on the conjunction of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) can harvest mechanical energy dispersed in our environment. With the characteristics of simple structure, light weight, broad material availability, low cost, and high efficiency even at low operation frequency, TENG can serve as a promising alternative strategy for meeting the needs of distributed energy for the internet of things and network. The major potential applications of TENG can be summarized as four fields containing micro/nano power sources, self-powered sensors, large-scale blue energy, and direct high-voltage power sources. In this paper, the fundamental physics, output performance enhancement, and applications of TENGs are reviewed to timely summarize the development of TENGs and provide a guideline for future research.

The advances in wearable/flexible electronics have triggered tremendous demands for flexible power sources, where flexible nanogenerators, capable of converting mechanical energy into electricity, demonstrate its great potential. Here, recent progress on flexible nanogenerators for mechanical energy harvesting toward self‐powered systems, including flexible piezoelectric and triboelectric nanogenerator, is reviewed. The emphasis is mainly on the basic working principle, the newly developed materials and structural design as well as associated typical applications for energy harvesting, sensing, and self‐powered systems. In addition, the progress of flexible hybrid nanogenerator in terms of its applications is also highlighted. Finally, the challenges and future perspectives toward flexible self‐powered systems are reviewed.

Throughout the world, wind energy is widely distributed as one of the most universal energy sources in nature, containing a gigantic reserve of renewable and green energy. At present, the main way to capture wind energy is to use an electromagnetic generator (EMG), but this technology has many limitations; notably, energy conversion efficiency is relatively low in irregular environments or when there is only a gentle breeze. A triboelectric nanogenerator (TENG), which is based on the coupling effect of triboelectrification and electrostatic induction, has obvious advantages for mechanical energy conversion in some specific situations. This review focuses on wind energy harvesting by TENG. First, the basic principles of TENG and existing devices’ working modes are introduced. Second, the latest research into wind energy-related TENG is summarized from the perspectives of structure design, self-power sensors and systems. Then, the potential for large-scale application and hybridization with other energy harvesting technologies is discussed. Finally, future trends and remaining challenges are anticipated and proposed.

Flexible electronics with great functional characteristics have proved to be a stepping stone in the field of wearable devices. Amongst all, gesture-sensing techniques have been widely studied for human-machine interfaces. In this paper, we propose a self-powered gesture-sensing system attached to the back of the hands, which has the capability of distinguishing hand gestures by measuring the triboelectric nanogenerator output signal. By attaching the sensor on the back of the hand, we can sense the displacement of tendons to detect the gestures. In addition, humidity resistance and durability of the device were tested and validated. Furthermore, we have established a set of rules to define the relationship between gestures and corresponding English letters. Therefore, the proposed sensor can further serve as an electronic sign language translator by converting gestures into words. Finally, we can integrate this system into gloves to enhance the applicability and utility. Overall, we have developed a real-time self-powered back-of-hand sensing system which can recognize various hand gestures., GRAPHICAL ABSTRACT

In this study, a novel piezoelectric energy harvester (PEH) based on the array composite spherical particle chain was constructed and explored in detail through simulation and experimental verification. The power test of the PEH based on array composite particle chains in the self-powered system was realized. Firstly, the model of PEH based on the composite spherical particle chain was constructed to theoretically realize the collection, transformation, and storage of impact energy, and the advantages of a composite particle chain in the field of piezoelectric energy harvesting were verified. Secondly, an experimental system was established to test the performance of the PEH, including the stability of the system under a continuous impact load, the power adjustment under different resistances, and the influence of the number of particle chains on the energy harvesting efficiency. Finally, a self-powered supply system was established with the PEH composed of three composite particle chains to realize the power supply of the microelectronic components. This paper presents a method of collecting impact energy based on particle chain structure, and lays an experimental foundation for the application of a composite particle chain in the field of piezoelectric energy harvesting.

Paper electronics offer an environmentally sustainable option for flexible and wearable systems and perfectly fit the available printing technologies for high manufacturing efficiency. As the heart of energy‐consuming devices, paper‐based batteries are required to be compatible with printing processes with high fidelity. Herein, hydrogel reinforced cellulose paper (HCP) is designed to serve as the separator and solid electrolyte for paper batteries. The HCP can sustain higher strain than pristine papers and are biodegradable in natural environment within four weeks. Zinc‐metal (Ni and Mn) batteries printed on the HCP present remarkable volumetric energy density of ≈26 mWh cm–3, and also demonstrate the feature of cuttability and compatibility with flexible circuits and devices. As a result, self‐powered electronic system could be constructed by integrating printed paper batteries with solar cells and light‐emitting diodes. The result highlights the feasibility of hydrogel reinforced paper for ubiquitous flexible and eco‐friendly electronics., Hydrogel reinforced cellulose paper presents enhanced mechanical and conductivity properties that make them suitable as the separator and quasi‐solid electrolyte for paper batteries. The printed zinc batteries (Mn–Zn and Ni–Zn) are flexible, cuttable, and potentially integrable with other paper electronics.

How can rural communities achieve economic and technological revitalization? Technologies can widen economic and social divides between rural and urban communities. Developments in the Internet of Things (IoT) and clean energy technologies provide an opportunity to lessen this gap. How can the IoT better serve rural areas? IoT devices have been battery-powered and communicate through existing networks. Such devices can be difficult to deploy in rural areas because of the maintenance burden of primary cell batteries and poor network infrastructure. Solar energy harvesting and LoRa (long range) modulation are emerging IoT methods that can surpass limitations in rural reliability for the IoT. The Fleet Tracker is a distributed solar-powered GPS tracking system that uniquely uses both of these techniques, acting as a proof of concept for improved reliability in the IoT. How do rural electric cooperatives impact the energy transition in the United States? Rural electric cooperatives support the energy transition through projects that revitalize local economies and lower members’ utility bills. These include energy efficiency upgrades and community solar. These projects demonstrate that global movements must find connections to local communities. Rural electric cooperatives act as a bridge between the global goal of mitigating climate change and local economic needs.

The development of polymer-based devices has attracted much attention due to their miniaturization, flexibility, lightweight and sustainable power sources with high efficiency in the field of wearable/portable electronics, and energy system. In this work, we proposed a polyvinylidene fluoride (PVDF)-based composite matrix for both energy harvesting and energy storage applications. The physicochemical characterizations, such as X-ray diffraction, laser Raman, and field-emission scanning electron microscopy (FE-SEM) analyses, were performed for the electrospun PVDF/sodium niobate and PVDF/reduced graphene oxide composite film. The electrospun PVDF/sodium niobate nanofibrous mat has been utilized for the energy harvester which shows an open circuit voltage of 40 V (peak to peak) at an applied compressive force of 40 N. The PVDF/reduced graphene oxide composite film acts as the electrode for the symmetric supercapacitor (SSC) device fabrication and investigated for their supercapacitive properties. Finally, the self-charging system has been assembled using PVDF/sodium niobate (energy harvester), and PVDF/reduced graphene oxide SSC (energy storage) and the self-charging capability is investigated. The proposed self-charging system can create a pathway for the all-polymer based composite high-performance self-charging system.

In this paper, a wireless implantable sensor prototype with subcutaneous solar energy harvesting is proposed. To evaluate the performance of a flexible solar panel under skin, ex-vivo experiments are conducted under natural sunlight and artificial light sources. The results show that the solar panel covered by a 3 mm thick porcine flap can output tens of microWatts to a few milliWatts depending on the light conditions. The subcutaneous solar energy harvester is tested on different body parts, which suggests the optimal position for the harvester to implant is between neck and shoulder. A wireless implantable system powered by the subcutaneous energy harvester is presented, which consists of a power management circuit, a temperature sensor, and a Bluetooth low energy module. An application is developed for data visualization on mobile devices, which can be a gateway for future IoT-based healthcare applications. The entire device is embedded in a transparent silicone housing (38 mm $\times$ 32 mm $\times$ 4 mm), including a 7 mAh rechargeable battery for energy storage. The average power consumption of the implants is about $30~\mu \text{W}$ in a 10 min operation cycle. With the subcutaneous solar energy harvester, the self-powered operation of the implantable sensor prototype is demonstrated by long-term experimental results. Two worst-case scenarios (no exposure to light and battery depletion) are considered with ex-vivo experiment simulations.

Wearable devices for health monitoring and fitness management have foreseen a rapidly expanding market, especially those for noninvasive and continuous measurements with real-time display that provide practical convenience and eliminated safety/infection risks. Herein, a self-powered and fully integrated smartwatch that consists of flexible photovoltaic cells and rechargeable batteries in the forms of a "watch strap", electrochemical glucose sensors, customized circuits, and display units integrated into a "dial" platform is successfully fabricated for real-time and continuous monitoring of sweat glucose levels. The functionality of the smartwatch, including sweat glucose sensing, signal processing, and display, can be supported with the harvested/converted solar energy without external charging devices. The Zn-MnO2 batteries serve as intermediate energy storage units and the utilization of aqueous electrolytes eliminated safety concerns for batteries, which is critical for wearable devices. Such a wearable system in a smartwatch fashion realizes integration of energy modules with self-powered capability, electrochemical sensors for noninvasive glucose monitoring, and in situ and real-time signal processing/display in a single platform for the first time. The as-fabricated fully integrated and self-powered smartwatch also provides a promising protocol for statistical study and clinical investigation to reveal correlations between sweat compositions and human body dynamics.

A novel self-powered system was constructed to in situ remove nitrate and Cr(VI) from synthetic groundwater and achieve river sediment remediation simultaneously. The sediment organic matter in an anodic chamber was used as a carbon source to provide self-powered energy to reduce the cathode&rsquo, s contaminants. With the acceptance of protons and electrons, nitrate and Cr(VI) were transformed into nitrite and Cr(III), respectively. In a 72 h test with both nitrate and Cr(VI) present, nitrate was removed at a rate of 70.96 mg/m3&middot, h and Cr(VI) at a rate of 8.95 mg/m3&middot, h. When a phosphate buffer was used in the test, their removal rates were changed to 140.83 mg/m3&middot, h and 8.33 mg/m3&middot, h, respectively. The results showed that the self-powered system could achieve the simultaneous reduction of nitrate and Cr(VI), although the presence of Cr(VI) hindered nitrate reduction. This system could realize simultaneous in situ groundwater and sediment remediation, with no need for additional energy or materials.

Piezoelectric energy conversion that generate electric energy from ambient mechanical and vibrational movements is promising energy harvesting technology because it can use more accessible energy resources than other renewable natural energy. In particular, flexible and stretchable piezoelectric energy harvesters which can harvest the tiny biomechanical motions inside human body into electricity properly facilitate not only the self-powered energy system for flexible and wearable electronics but also sensitive piezoelectric sensors for motion detectors and in vivo diagnosis kits. Since the piezoelectric ZnO nanowires (NWs)-based energy harvesters (nanogenerators) were proposed in 2006, many researchers have attempted the nanogenerator by using the various fabrication process such as nanowire growth, electrospinning, and transfer techniques with piezoelectric materials including polyvinylidene fluoride (PVDF) polymer and perovskite ceramics. In 2012, the composite-based nanogenerators were developed using simple, low-cost, and scalable methods to overcome the significant issues with previously-reported energy harvester, such as insufficient output performance and size limitation. This review paper provides a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system with development history, power performance, and applications.

Accepted: 2011-10-14, 資料番号: SA1005129000

A built-in method of on-chip solar battery in a CMOS LSI is proposed. The proposed solar battery can be formed using conventional CMOS process technology. It can generate a high voltage of 0.6-0.83 V by a series connection structure of two types of p-n junction diodes formed with the CMOS circuit simultaneously on the LSI chip. The generated voltage is sufficient to drive the conventional CMOS circuit without modi. cation. The test chip was produced experimentally using conventional 0.35 mu m CMOS technology, and the drive performance of the on-chip solar battery was evaluated. The conversion efficiency of the proposed solar battery was 2.6%. The area of the solar battery required for power consumption was 6.1 mm(2)/mu W in the case of the 2000lx illumination.