Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors

This reprint is a collection of the Special Issue "Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors" published in Nanomaterials, which includes one editorial, six novel research articles and four review articles, showcasing the very recent advances in energy-harvesting and self-powered sensing technologies. With its broad coverage of innovations in transducing/sensing mechanisms, material and structural designs, system integration and applications, as well as the timely reviews of the progress in energy harvesting and self-powered sensing technologies, this reprint could give readers an excellent overview of the challenges, opportunities, advancements and development trends of this rapidly evolving field

Advanced Energy Harvesting Technologies

Energy harvesting is the conversion of unused or wasted energy in the ambient environment into useful electrical energy. It can be used to power small electronic systems such as wireless sensors and is beginning to enable the widespread and maintenance-free deployment of Internet of Things (IoT) technology. This Special Issue is a collection of the latest developments in both fundamental research and system-level integration. This Special Issue features two review papers, covering two of the hottest research topics in the area of energy harvesting: 3D-printed energy harvesting and triboelectric nanogenerators (TENGs). These papers provide a comprehensive survey of their respective research area, highlight the advantages of the technologies and point out challenges in future development. They are must-read papers for those who are active in these areas. This Special Issue also includes ten research papers covering a wide range of energy-harvesting techniques, including electromagnetic and piezoelectric wideband vibration, wind, current-carrying conductors, thermoelectric and solar energy harvesting, etc. Not only are the foundations of these novel energy-harvesting techniques investigated, but the numerical models, power-conditioning circuitry and real-world applications of these novel energy harvesting techniques are also presented

Nanogenerators in Korea

Fossil fuels leaded the 21st century industrial revolution but caused some critical problems such as exhaustion of resources and global warming. Also, current power plants require too much high cost and long time for establishment and facilities to provide electricity. Thus, developing new power production systems with environmental friendliness and low-cost is critical global needs. There are some emerging energy harvesting technologies such as thermoelectric, piezoelectric, and triboelectric nanogenerators, which have great advantages on eco-friendly low-cost materials, simple fabrication, and various operating sources. Since the introduction of various energy harvesting technologies, many novel designs and applications as power suppliers and physical sensors in the world have been demonstrated based on their unique advantages. In this Special Issue, we would like to address and share basic approaches, new designs, and industrial applications related to thermoelectric, piezoelectric, and triboelectric devices which are on-going in Korea. With this Special Issue, we aim to promote fundamental understanding and to find novel ways to achieve industrial product manufacturing for energy harvesters

Study of systems powered by triboelectric generators for bioengineering applications

Treballs Finals de Grau d'Enginyeria Biomèdica. Facultat de Medicina i Ciències de la Salut. Universitat de Barcelona. Curs: 2020-2021. Director: Pere Lluís Miribel Català. Co-director: Manel Puig i Vida

Advanced Materials and Technologies in Nanogenerators

This reprint discusses the various applications, new materials, and evolution in the field of nanogenerators. This lays the foundation for the popularization of their broad applications in energy science, environmental protection, wearable electronics, self-powered sensors, medical science, robotics, and artificial intelligence

Magnetic Bistability for a Wider Bandwidth in Vibro-Impact Triboelectric Energy Harvesters

Mechanical energy from vibrations is widespread in the ambient environment. It may be harvested efficiently using triboelectric generators. Nevertheless, a harvester’s effectiveness is restricted because of the limited bandwidth. To this end, this paper presents a comprehensive theoretical and experimental investigation of a variable frequency energy harvester, which integrates a vibro-impact triboelectric-based harvester and magnetic nonlinearity to increase the operation bandwidth and improve the efficiency of conventional triboelectric harvesters. A cantilever beam with a tip magnet was aligned with another fixed magnet at the same polarity to induce a nonlinear magnetic repulsive force. A triboelectric harvester was integrated into the system by utilizing the lower surface of the tip magnet to serve as the top electrode of the harvester, while the bottom electrode with an attached polydimethylsiloxane insulator was placed underneath. Numerical simulations were performed to examine the impact of the potential wells formed by the magnets. The structure’s static and dynamic behaviors at varying excitation levels, separation distance, and surface charge density are all discussed. In order to develop a variable frequency system with a wide bandwidth, the system’s natural frequency varies by changing the distance between the two magnets to reduce or magnify the magnetic force to achieve monostable or bistable oscillations. When the system is excited by vibrations, the beams vibrate, which causes an impact between the triboelectric layers. An alternating electrical signal is generated from a periodic contact-separation motion between the harvester’s electrodes. Our theoretical findings were experimentally validated. The findings of this study have the potential to pave the way for the development of an effective energy harvester that is capable of scavenging energy from ambient vibrations across a broad range of excitation frequencies. The frequency bandwidth was found to increase by 120% at threshold distance compared to the conventional energy harvester. Nonlinear impact-driven triboelectric energy harvesters can effectively broaden the operational frequency bandwidth and enhance the harvested energy

Applications of nanogenerators for biomedical engineering and healthcare systems

The dream of human beings for long living has stimulated the rapid development of biomedical and healthcare equipment. However, conventional biomedical and healthcare devices have shortcomings such as short service life, large equipment size, and high potential safety hazards. Indeed, the power supply for conventional implantable device remains predominantly batteries. The emerging nanogenerators, which harvest micro/nanomechanical energy and thermal energy from human beings and convert into electrical energy, provide an ideal solution for self‐powering of biomedical devices. The combination of nanogenerators and biomedicine has been accelerating the development of self‐powered biomedical equipment. This article first introduces the operating principle of nanogenerators and then reviews the progress of nanogenerators in biomedical applications, including power supply, smart sensing, and effective treatment. Besides, the microbial disinfection and biodegradation performances of nanogenerators have been updated. Next, the protection devices have been discussed such as face mask with air filtering function together with real‐time monitoring of human health from the respiration and heat emission. Besides, the nanogenerator devices have been categorized by the types of mechanical energy from human beings, such as the body movement, tissue and organ activities, energy from chemical reactions, and gravitational potential energy. Eventually, the challenges and future opportunities in the applications of nanogenerators are delivered in the conclusive remarks. The combination of nanogenerator and biomedicine have been accelerating the development of self‐powered biomedical devices, which show a bright future in biomedicine and healthcare such as smart sensing, and therapy

TRIBOELECTRIC DEVICES FOR POWER GENERATION AND SELF-POWERED SENSING APPLICATIONS

Ph.DDOCTOR OF PHILOSOPH

Optimisation of Triboelectric Nanogenerator performance in vertical contact-separation mode

Triboelectric nanogenerator (TENG) is one of the most promising energy harvesters – a technology that uses repeated or reciprocating contact of suitably chosen materials to generate charge via the triboelectric effect (TE) and utilizes this as usable voltage and current. TENGs are attractive as they can continuously generate charge over a wide range of operating conditions and have several valuable advantages such as light weight, simple structure, low cost and high efficiency. Therefore, TENGs have been explored in a wide range of applications, including self-powered wearable electronics, powering electronics and even for harvesting ocean wave/wind energy. One of the major limitations of TENGs is their low power output (usually <500 W/m2). This thesis focuses of a few specific approaches to optimising TENG output performance. This thesis begins by presenting a solution to this challenge by optimizing a low permittivity substrate beneath the tribo-contact layer. The open circuit voltage is found to increase by a factor of 1.3 in moving from PET to the lower permittivity PTFE. TENG performance is also believed to depend on contact force, but the origin of the dependence had not previously been explored. Herein, we show that this behaviour results from a contact force dependent real contact area Ar as governed by surface roughness. The open circuit voltage Voc, short circuit current Isc and Ar for a TENG were found to increase with contact force/pressure. Critically, Voc and Isc saturate at the same contact pressure as Ar suggesting that electrical output follows the same evolution as Ar. Assuming that tribo charges can only transfer across the interface at areas of real contact, it follows that an increasing Ar with contact pressure should produce a corresponding increase in the electrical output. These results underline the importance of accounting for real contact area in TENG design, as well as the distinction between real and nominal contact area in tribo-charge density definition. High-performance ferroelectricassisted TENGs (Fe-TENGs) are developed using electrospun fibrous surfaces based on P(VDFTrFE) with dispersed BaTiO3 (BTO) nanofillers in either cubic (CBTO) or tetragonal (TBTO) form in this thesis. TENGs with three types of tribo-negative surface were investigated and output increased progressively. Critically, P(VDF-TrFE)/TBTO produced higher output than P(VDFTrFE)/ CBTO even though permittivity is nearly identical. Thus, it is shown that BTO fillers boost output, not just by increasing permittivity, but also by enhancing the crystallinity and amount of the β-phase (as TBTO produced a more crystalline β-phase present in greater amounts)

Electrostatic Discharge

As we enter the nanoelectronics era, electrostatic discharge (ESD) phenomena is an important issue for everything from micro-electronics to nanostructures. This book provides insight into the operation and design of micro-gaps and nanogenerators with chapters on low capacitance ESD design in advanced technologies, electrical breakdown in micro-gaps, nanogenerators from ESD, and theoretical prediction and optimization of triboelectric nanogenerators. The information contained herein will prove useful for for engineers and scientists that have an interest in ESD physics and design