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

Editorial for the Special Issue on Nanogenerators in Korea

Nanogenerator-based technologies have found outstanding accomplishments in energy harvesting applications over the past two decades [...

Mechanical Conversion and Transmission Systems for Controlling Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) are a promising renewable energy technology. Many applications have been successfully demonstrated, such as self-powered Internet-of-Things sensors and many wearables, and those portable power source devices are useful in daily life due to their light weight, cost effectiveness, and high power conversion. To boost TENG performance, many researchers are working to modulate the surface morphology of the triboelectric layer through surface-engineering, surface modification, material selection, etc. Although triboelectric material can obtain a high charge density, achieving high output performance that is predictable and uniform requires mechanical energy conversion systems (MECSs), and their development remains a huge challenge. Many previous works did not provide an MECS or introduced only a simple mechanical system to support the TENG integration system device. However, these kinds of designs cannot boost the output performance or control the output frequency waveform. Currently, some MECS designs use transmission conversion components such as gear-trains, cam-noses, spiral springs, flywheels, or governors that can provide the step-up, controllable, predictable, and uniform output performance required for TENGs to be suitable for daily applications. In this review, we briefly introduce various MECS designs for regulating the output performance of TENGs. First, we provide an overview of simple machines that can be used when designing MECSs and introduce the basic working principles of TENGs. The following sections review MECSs with gear-based, cam-based, flywheel-based, and multiple-stage designs and show how the MECS structure can be used to regulate the input flow for the energy harvester. Last, we present a perspective and outline for a full system design protocol to correlate MECS designs with future TENG applications

Plasmonic Coupling in Three-Dimensional Au Nanoparticle Assemblies Fabricated by Anodic Aluminum Oxide Templates

We investigated optical properties of three-dimensional (3D) assemblies of Au nanoparticles (NPs), which were fabricated by dewetting of thin Au layers on anodic aluminum oxides (AAO). The NP assembly had hexagonal array of repeated multiparticle structures, which consisted of six trimers on the AAO surface and one large NP in the AAO pore (pore-NP). We performed finite-difference time-domain simulation to explain the optical response of the NP assemblies and compared the calculation results with experimental data. Such complementary studies clearly revealed how the plasmonic coupling between the constituent NPs influenced the spectral response of our NP assemblies. In particular, comparison of the assemblies with and without pore-NPs suggested that strong plasmonic coupling between trimers and pore-NP significantly affected the spectra and the field distribution of the NP assemblies. Plasmonic multi-NP assemblies could provide us new platforms to realize novel optoelectronic devices

Structural color and near-infrared tunability of ruthenium-coated anodic aluminum oxide by atomic layer deposition

Here, we systematically investigate optical behaviors of ruthenium (Ru)-coated nanoporous anodic aluminum oxide (AAO) nanoarchitectures in the visible and near-Infrared (NIR) regions, where they are fabricated by an atomic layer deposition (ALD) process. Depending on the Ru thickness and the AAO dimensions, the Ru nanoarchitectures could be completely changed (tubular-type or wire-type Ru nanostructures), and the corresponding optical properties are critically affected. Brilliant structural colors are found from the Ru-coated AAO nanostructures, in which the color display covers the full visible range. Beyond the visible region, we also examine the optical behaviors of Ru-coated AAO nanostructures in the NIR region. © 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.1

Recent progress towards smart transportation systems using triboelectric nanogenerators

The field of transportation plays a crucial role in the development of society. It is vital to establish a smart transportation system to increase the convenience and security of human life. The incorporation of artificial intelligence and the internet of things into the traffic system has facilitated the emergence of innovative technologies like autonomous vehicles or unmanned aerial vehicles, which contribute to the reduction of traffic accidents and the liberation of human driving time. However, this improvement involves the use of multiple sensor devices that need external power sources. As a result, pollution occurs, as do increases in manufacturing costs. Therefore, the quest to develop sustainable energy remains a formidable obstacle. Triboelectric nanogenerators (TENGs) have emerged as a possible solution for addressing this problem owing to their exceptional performance and simple design. This article explores the use of TENG-based self-power sensors and their potential applications in the field of transportation. Furthermore, the data collected for this study might aid readers in enhancing their comprehension of the benefits linked to the use of these technologies to promote their creative ability

Stretchable and Flexible Snake Skin Patterned Electrodes for Wearable Electronics Inspired by Kirigami Structure

Abstract Herein, snake‐skin‐patterned electrodes, with high versatility and excellent biocompatibility, are developed by combining the Kirigami structure and biomimicry. The snake‐skin electrode has excellent stretchability owing to the integration of the Kirigami structure and patterning. The snake skin patterns are optimized through finite element analysis (FEA) simulations to determine the most stretchable pattern structure. Based on the FEA results, we fabricated the optimal pattern on a polyurethane (PU) substrate by sputtering the AgPdCu alloy target. Even at high strains of 30% and 50%, the electrode exhibits much better stretchability compared with the electrode without the snake skin pattern. The best stretchable electrode exhibits a resistance change (ΔR) of less than 1.5 when it is severely stretched at up to 50% strain. Additionally, the dynamic stretching fatigue test, reveals that it exhibits stable conductivity, thus proving the effectiveness of using snake‐skin pattern for stretchable electrodes. The bending, rolling, folding and twisting tests confirm that the electrode has outstanding flexibility, too. A wearable temperature sensor with a snake‐skin‐patterned electrode exhibits stable and highly sensitive temperature sensing properties. In addition, light emitting diodes connected to the stretchable electrode exhibits stable brightness despite severe deformation of the electrodes

Self-Assembled Three-Dimensional Nanocrown Array

Although an ordered nanoplasmonic probe array will have a huge impact on light harvesting, selective frequency response (<i>i.e.</i>, nanoantenna), and quantitative molecular/cellular imaging, the realization of such an array is still limited by conventional techniques due to the serial processing or resolution limit by light diffraction. Here, we demonstrate a thermodynamically driven, self-assembled three-dimensional nanocrown array that consists of a core and six satellite gold nanoparticles (GNPs). Our ordered nanoprobe array is fabricated over a large area by thermal dewetting of thin gold film on hexagonally ordered porous anodic alumina (PAA). During thermal dewetting, the structural order of the PAA template dictates the periodic arrangement of gold nanoparticles, rendering the array of gold nanocrown. Because of its tunable size (<i>i.e.</i>, 50 nm core and 20 nm satellite GNPs), arrangement, and periodicity, the nanocrown array shows multiple optical resonance frequencies at visible wavelengths as well as angle-dependent optical properties

Magnetic Force Enhanced Sustainability and Power of Cam-Based Triboelectric Nanogenerator

Since the first invention of triboelectric nanogenerators (TENGs) in 2012, many mechanical systems have been applied to operate TENGs, but mechanical contact losses such as friction and noise are still big obstacles for improving their output performance and sustainability. Here, we report on a magnet-assembled cam-based TENG (MC-TENG), which has enhanced output power and sustainability by utilizing the non-contact repulsive force between the magnets. We investigate the theoretical and experimental dynamic behaviors of MC-TENGs according to the effects of the contact modes, contact and separation times, and contact forces (i.e., pushing and repulsive forces). We suggest an optimized arrangement of magnets for the highest output performance, in which the charging time of the capacitor was 2.59 times faster than in a mechanical cam-based TENG (C-TENG). Finally, we design and demonstrate a MC-TENG-based windmill system to effectively harvest low-speed wind energy, ~4 m/s, which produces very low torque. Thus, it is expected that our frictionless MC-TENG system will provide a sustainable solution for effectively harvesting a broadband of wasted mechanical energies