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The safe management of radiation sources and wastes is one of the most important elements in operating nuclear power plants (NPPs). Safe management requires periodically measuring radiation during ...

An upsurge interest in the area of robotic sensors with robustness has been noticed during the past years, owing to human aiding in danger activities leading to even death. Here, a mechanically rob...

Integrating nano- to micro-sized dielectric fillers to elastomer matrices to form dielectric composites is one of the commonly utilized methods to improve the performance of dielectric elastomer actuators (DEAs). Barium titanate (BaTiO3) is among the widely used ferroelectric fillers for this purpose, however, calcium copper titanate CaCu3Ti4O12 (CCTO) has the potential to outperform such conventional fillers. Despite their promising performance, CCTO-based dielectric composites for DEA application are studied to a relatively lower degree. Particularly, the composites are characterized for a comparably small particle loading range, while critical DEA properties such as breakdown strength and nonlinear elasticity are barely addressed in the literature. Thus, in this study, CCTO was paired with polydimethylsiloxane (CH3)3SiO[Si(CH3)2O]nSi(CH3)3 (PDMS), Sylgard 184, to gain a comprehensive understanding of the effects of particle loading and size on the dielectric composite properties important for DEA applications. The dielectric composites’ performance was described through the figures of merit (FOMs) that consider materials’ Young’s modulus, dielectric permittivity, and breakdown strength. The optimum amounts of the ferroelectric filler were determined through the FOMs to maximize composite DEA performance. Lastly, electromechanical testing of the pre-stretched CCTO-composite DEA validated the improved performance over the plain elastomer DEA, with deviations from prediction attributed to the studied composites’ nonlinearity.

Agglomeration is a common occurrence in polymer nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNP) as fillers and usually leads to a reduction of electrical and mechanical properties of the composites. In this paper, we utilize a two-dimensional Monte Carlo percolation model for monofiller and hybrid nanocomposites to examine the effect of CNT agglomeration on electrical and electromechanical behavior of the nanocomposites. We generate microstructures of tunneling network with different agglomerate content, agglomerate morphology (equiaxed to rope-like), and agglomerate filler density to parametrically study the effects of agglomeration on percolation, conductivity and piezoresistivity. Electron tunneling in the network is modeled as the primary mechanism for electrical percolation. Our models indicate that high level of agglomeration leads to a systematic increase of the percolation threshold with a decrease of the conductivity, while low agglomeration level with low filler density within agglomerates improves the percolation and conductivity behavior. The addition of GNP as second filler in hybrid composites leads to an improvement in conductance and piezoresistivity despite the presence of CNT agglomeration.

A triboelectric nanogenerator (TENG) with an ultra-thin thickness of a tribo-dielectric layer (TDL) composed of poly heptadecafluorodecyl methacrylate (PFDMA) is demonstrated. The thickness of the PFDMA, which serves as the TDL, was precisely controlled within a range of 0.5 μm–12 μm through the use of initiated-chemical vapor deposition (i-CVD). The relationship between the TDL thickness and the output characteristics was analyzed by demonstrating the ultra-thin TDL thickness, which is the thinnest thickness polymer TDL ever reported. As the TDL thickness is increased, the short-circuit current (ISC) and the transferred charge (QTR) both increase while the open-circuit voltage (VOC) remains constant. Because a TENG with the ultra-thin TDL shows a different tendency between QTR and the total charge (QTDL) in the TDL, modeling is also carried out to gain a comprehensive understanding of the TDL thickness and output characteristics.

Humidity control is an important environmental concern in storage, transport, and preservation operations in agriculture, food, medical, and other industrial fields. In the present work, we prepared a nanocomposite having flower shaped morphology that consists of metal (Cu) nanoparticles, a metal oxide (ZnO nanorods), and reduced graphene oxide (rGO) with a one-pot synthesis method for the AC conductivity and Humidity sensing response studies at room temperature. The morphology of the nanocomposite was characterized by using XRD, SEM, EDX, and TEM analysis. Conduction in the nanocomposite due to the hopping mechanism was confirmed by studying the power law behavior of its AC conductivity. The nanocomposite shows a maximum sensing response of 97.79% in the range of 11–97% RH, with response and recovery times of 19 s and 42 s, respectively. The nanocomposite shows a low humidity hysteresis and stable humidity sensing ability. The possible humidity sensing mechanism is discussed in detail. Our results show that the nanocomposite having flower shaped morphology is an ideal candidate for building MEMS/NEMS humidity sensors.

The humidity sensing performance of Polyaniline/Water soluble graphene oxide [PWGO] composites have been presented in this work. Various mass ratios of Water soluble graphene oxide [WGO] were mechanically mixed with Polyaniline [PANI] prepared by in-situ polymerization process to form PANI / WGO composites. For the purpose of humidity sensing studies, the samples were structurally characterized by FTIR, Raman, XRD, SEM and TEM techniques and comparatively analyzed. The film of the samples prepared by deposition on ordinary glass substrate using cost effective spin coating technique were tested for their humidity sensing performance in the relative humidity (RH) range of 11–97%. Of the four composites studied, the PWGO-4 composite recorded a good response time of 8 s and a recovery time of 9 s and a very low humidity hysteresis. The mechanism for sensing has been explained on the basis of three sequential steps: chemisorption, physisorption and condensation process. The humidity sensing stability of the composites were tested over a period of 2 months.

The present research work aimed to development of reduced graphene oxide (rGO) and ZnO nanorods based rZN nanocomposite with different molar ratios. This nanocomposite was prepared using a simple, one-step thermal reaction method. The morphology, phase identification and crystalline properties of the nanocomposites were studied using SEM, TEM, SAED and XRD techniques. Further, EDS analysis was used for elemental conformation of the nanocomposite. Films of the nanocomposite were deposited on a substrate by the cost-effective spin coating technique and the resistivity was measured by a Hall measurement system, which shows a decrease in resistivity value. The electrochemical properties studied by measuring the specific capacitance using cyclic voltammetry (CV) and galvanostatic charge–discharge techniques in 3 M KOH solution. These CV studies indicated that the positive synergistic effect of rGO and ZnO nanorods has shown excellent performance. The best results were obtained from the 1:2 ratio of rGO: ZnO, which demonstrated a specific capacitance of 472 F/g, an energy density of 2.62 Wh/kg, and a power density of 32.24 W/kg. These results concluded that rZN nanocomposites are promising electrode materials for supercapacitor applications.

Sodium dodecylbenzenesulfonate (SDBS) is widely used as an efficient detergent in various fields. It is also used to remove radioactive atoms including Cs ions, and as a result, Cs-bound SDBS are generated during a nuclear decontamination process. A silica-based adsorbent with mesopores was prepared and surface-functionalized with amine groups to have a positively-charged pocket for SDBS with electrostatic attraction. The removal of SDBS using such an adsorbent was investigated under various conditions. The removal of high SDBS concentration (more than 2000 ppm) was successfully carried out using both a mesoporous structure and electrostatic attraction. The effects of the initial SDBS concentration, the concentration of adsorbent, the SDBS adsorption time, and the pH in the adsorption of SDBS with the mesoporous silica-based adsorbent were investigated in detail. In addition, the adsorption of Cs ion-bound SDBS was investigated for a practical decontamination process, implying that the adsorbent did not remove Cs ions together with SDBS.

In the present research paper, enhancement in humidity sensing properties of copper ferrite (CF) by mechano chemical mixing it with yttrium oxide (Y2O3) to form copper ferrite-yttrium oxide (CFYO) nanocomposite is discussed. The nanocomposite was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. Appearance of characteristic bands of both CF and Y2O3 with slight shifts in the FTIR spectrum of the composite indicating interaction between them and formation of the composite confirmed. Enhancement in active sites for water adsorption in the composite due to the presence of Y2O3 confirmed from both XRD and SEM studies. Increased agglomeration of nano sized particles and improved crystallinity of the composite as compared to those of CF confirmed from TEM studies and SAED patterns. The resistive type humidity sensing behaviour of CF and CFYO composite were studied and comparatively analyzed. The composite showed maximum sensing response of 4895 as against 110 of CF in the range 11%–97% RH. The response and recovery times of the composite were found to be 9 s and 23 s respectively while those of CF were 60 s and 90 s respectively. The CFYO sample showed stable sensing ability with a low humidity hysteresis. The sensing mechanism is discussed on the basis of chemisorption, physisorption and capillary condensation processes.

In the present work, we prepared magnesium ferrite/molybdenum trioxide (MFMO) nanocomposite using mechano chemical mixing method for humidity sensor at room temperature. Enhancement in active sites for water adsorption in the composite due to the presence of MoO3 confirmed from X-ray diffraction (XRD) studies. Change in grain size distribution and increase in intergranular pores in the composite favouring water adsorption confirmed from its scanning electron microscopy (SEM) image. Increased agglomeration of nano sized particles and improved crystallinity of the composite confirmed from Transmission electron microscopy (TEM) studies and selected area electron diffraction (SAED) pattern. The composite showed maximum sensing response of 4902 as against 183 of MF in the range 11%–97% RH. The response and recovery times of the composite were found to be 45 s and 74 s respectively while those of MF 225 s and 364 s respectively. The nanocomposite sample showed stable humidity sensing ability and a low humidity hysteresis. Molybdenum trioxide plays a major role in enhancing the humidity sensing performance of MFMO composite at room temperature. The sensing mechanism discussed on the basis of chemisorptions, physisorption and capillary condensation processes.

The absolute necessary for measuring temperature with large accuracy and with a wide range in various industrial sectors increases the need for researcher to choose a suitable material, which is useful especially in bio-medical applications, food packaging and air conditioning system. A slight deviation of temperature creates a lot of problems which cannot be controlled rapidly. Hence, the temperature sensor needs to have the properties of high sensitivity, fast response, low cost, high volume production, and high reliability. Considering the essentialities of the temperature measurement almost in all types of industrial sectors, the sensing materials used for fabricating the sensors should have flexibility for both temperature and pressure sensing ability. In this aspect, conducting polymers have an efficient candidate for temperature sensor. As the conducting polymers are fabricated by the incorporation of conducting filler in polymers, the resistivity of such materials is very sensitive to temperature for which response to the signal very fast. The high accuracy measurement as well as wide measurement scale can only be achieved by conducting polymer based sensors which are more stable at high temperature. However, the sensitivity and selectivity of nanostructure conducting polymer-based sensors still needs a lot of enhancement. In the present review, fabrication of conducting polymers and their importance as temperature sensors have been discussed.

This paper suggests an estimation method for ship’s hydrodynamic coefficients, which is based on the system identification method that calculates an optimum value in a mathematical way. For the purpose of modelling existing ships, this study collects real ship sea trial data as benchmarks. Prior to the optimization, a sensitivity analysis is carried out for easy and effective optimization. The simulation results using optimized coefficients agree well with corresponding benchmarks. Following this, with various trim and draught conditions, this study suggests new estimation formulas that concern all trim and draught conditions. Simulation results applying the estimation formulas are satisfactory in regard to a corresponding benchmark, compared to a result obtained by using an existing regression formula.

Mixed metal chalcogenide nanoarchitectures have been attracting enormous attention as battery-type electrodes for hybrid supercapacitors (HSCs) owing to their enhanced electrochemical (EC) performance. Despite having high electrical conductivity and good EC properties, tellurium has not been fully utilized in metal chalcogenide electrodes as much as sulfur and selenium. Herein, a facile strategy for the fabrication of nickel and iron (NiFe) mixed metal telluride hierarchical nanorods (MMT HNRs) on nickel foam (NF) is proposed. Furthermore, conductive silver (Ag) is decorated on MMT HNRs (AMMT HNRs) to improve the conducting channels, thereby EC performance. Benefitting from the combined advantages of electroactive NiFe mixed metal, conductive tellurium and Ag, and hierarchical nanorod-like nanomorphology, the AMMT HNR electrode has delivered high areal capacity (1.1 mAh cm-2). Finally, the AMMT based HSC with activated carbon coated NF (AC/NF) as a negative electrode exhibited the highest areal capacitance (1176.5 mF cm-2) with high areal energy density (0.669 mWh cm-2) and power density (64 mW cm-2). Moreover, the HSC device has maintained good cycling stability (86% capacity retention) even after 5000 cycles. New findings of this study definitely shed light on the development of telluride-based mixed metal chalcogenide supercapacitors.

Supercapacitor (SC) electrodes fabricated with the combination of carbon nanotubes (CNTs) and metal oxides are showing remarkable advancements in the electrochemical properties. Herein, NiO decorated CNT/ZnO core-shell hybrid nanocomposites (CNT/ZnO/NiO HNCs) are facilely synthesized by a two-step solution-based technique for the utilization in hybrid supercapacitors. Benefitting from the synergistic advantages of three materials, the CNT/ZnO/NiO HNCs based electrode has evinced superior areal capacity of ~67 µAh cm−2 at a current density of 3 mA cm−2 with an exceptional cycling stability of 112% even after 3000 cycles of continuous operation. Highly conductive CNTs and electrochemically active ZnO contribute to the performance enhancement. Moreover, the decoration of NiO on the surface of CNT/ZnO core-shell increases the electro active sites and stimulates the faster redox reactions which play a vital role in augmenting the electrochemical properties. Making the use of high areal capacity and ultra-long stability, a hybrid supercapacitor (HSC) was assembled with CNT/ZnO/NiO HNCs coated nickel foam (CNT/ZnO/NiO HNCs/NF) as positive electrode and CNTs coated NF as negative electrode. The fabricated HSC delivered an areal capacitance of 287 mF cm−2 with high areal energy density (67 µWh cm−2) and power density (16.25 mW cm−2). The combination of battery type CNT/ZnO/NiO HNCs/NF and EDLC type CNT/NF helped in holding the capacity for a long period of time. Thus, the systematic assembly of CNTs and ZnO along with the NiO decoration enlarges the application window with its high rate electrochemical properties.

The environmental pollution issues caused by plastic-based polymers have become serious concerns over the past few decades. Accordingly, the need for using green and ecofriendly polymers in triboelectric nanogenerators (TENGs) is gradually increasing. In this research, the glycerol paper-based sodium lauroyl glutamate (SLG)-TENG with an antibacterial effect and also water and oil solubility has been successfully developed by a facile vacuum filtration method. Silver nanowire (AgNW) and carbon nanotube (CNT) layers were deposited by casting their respective dispersions in isopropyl alcohol (IPA) on SLG. During the fabrication process, concentrations of CNTs and AgNWs were varied from 0.35 to 0.5 wt % for CNTs, and from 0.05 to 0.3 wt % for AgNWs to determine the optimal concentration. From the electrical output measurements, it was observed that the CNT-based SLG-TENG showed a high open-circuit voltage (Voc) and short-circuit current (Isc) at 0.425 wt % while the AgNW-based SLG-TENG showed enhanced electrical properties at 0.15 wt %. A detailed explanation for the existence of the optimal point for CNTs and AgNW-based SLG-TENG is given by using the results of ultraviolet–visible spectroscopy and energy dispersive spectroscopy. Furthermore, the antibacterial effect has been strongly proven from the consequences of bacteria cultivation on SLG. Due to these peculiar properties of SLG-TENG, we have tested its applicability as a skin-attachable sensor, writing sensor, water leakage sensor, and humidity sensor and discussed its results with supporting videos. This work gives new insights into the simple design of biodegradable and antibacterial TENG-based wearable sensors in real life.

Wind is a great sustainable energy source for harvesting due to its abundant characteristic. Typically, large space, loud noise, and heavy equipment are essential for a general wind power plant and it is solely operated by big-scale wind. However, wind energy can be efficiently harvested by utilizing the triboelectric nanogenerator due to its abundance, ubiquity, and environmentally friendliness. Furthermore, a few previously reported wind-driven triboelectric nanogenerators, which have the bulk fluttering layer by wind, still show difficulty in generating electricity under the conditions of weak wind because of the static friction arisen from the inherent structure. In this case, the output performance is deteriorated as well as the generator cannot operate completely. In this work, a wind-driven triboelectric nanogenerator (wind-TENG) based on the fluttering of the PTFE strips is proposed to solve the aforementioned problems. At the minimum operating wind pressure of 0.05 MPa, this wind-driven TENG delivers the open-circuit voltage of 3.5 V, short-circuit current of 300 nA, and the associated output power density of 0.64 mW/m2 at the external load resistance of 5 MΩ. Such conditions can be used to light up seven LEDs. Moreover, this wind-TENG has been utilized as a direction sensor which can sense the direction at which the wind is applied. This work thus provides the potential application of the wind-TENG as both self-driven electronics and a self-powered sensor system for detecting the direction under environmental wind.

Agglomeration is a common occurrence in polymer nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNP) as fillers and usually leads to a reduction of electrical and mechanical properties of the composites. While the conductive nanocomposites exhibit remarkable electromechanical properties and have potential applications in sensing and actuation, their performance mainly depends on the polymer matrix and the dispersed nanofillers. In this paper, we use a two-dimensional Monte Carlo percolation model for monofiller and hybrid nanocomposites to examine the effect of CNT agglomeration, GNP geometry, CNT-to-GNP volume ratio and polymer matrix properties on the strain sensing behavior of the nanocomposites. We generate microstructures of tunneling network with different size, aspect ratio, alignment and content of GNP fillers. Agglomeration parameters such as agglomerate content, morphology (equiaxed to rope-like), and agglomerate filler density are also modelled to generate realistic microstructure. The Poisson's ratio and the tunneling barrier height of the polymer matrix are also parametrized. Our results indicate that high level of agglomeration leads to a systematic decrease of piezoresistivity, while low agglomeration level with low filler density within agglomerates improves the electromechanical behavior. The addition of GNP as second filler to the CNT composites leads to a better piezoresistive behavior of the nanocomposites. Increasing the content, aspect ratio and size of the GNP also leads to an improvement of the piezoresistivity. GNPs uniformly aligned in the direction of electrical conductivity measurements lead to a significantly higher piezoresistive behavior, up to 6 times greater than that of nanocomposites based on only CNT. Higher values of the polymer matrix Poisson's ratio lead to an improved piezoresistivity.

In Internet of Things (IoT) era, electronic textiles (E-textiles), which combine various functional devices on a fabric, have attracted attention. Among various components for E-textiles, the human-machine interface device, for example, a keyboard, is one of the most important parts. The triboelectric nanogenerator (TENG) can be a powerful sensing component for the interface device due to its cost-effectiveness, design flexibility and self-powered operation. Previous studies reported fabric-based sensor devices with TENG, but as yet, no device that harnesses commercial compatibility with the textile industry has been reported. It is timely to explore a low-cost TENG-based keyboard made completely of commercial fabric for early commercialization. This paper proposes a TENG-based wearable keyboard that uses only cheap commercial fabrics. Each cell in the proposed keyboard generates electrical signals according to an external touch without any power supply. After an appropriate filtering process, the proposed keyboard can detect a key stroke without any ambiguity. We verify the keyboard operation by typing a word and playing music. The material dependency of the proposed keyboard is experimentally validated with various material pairs. Finally, the endurance of the proposed keyboard against folding, repeated touches and washing is experimentally confirmed for actual applications in a real environment.

In the present work, we reported the preparation of ZnO/PANI/RGO ternary nanocomposite by physical blending method and its photocatalytic efficiency of degradation of methyl orange under solar light. The samples were characterized by XRD, FTIR and UV–Vis spectroscopy. Optical band gap was calculated using Tauc plot for ZnO, PANI and RGO. The photocatalytic studies were evaluated using Methyl Orange with a degradation rate of 99% in 50 min. It is observed that photocatalytic efficiency enhanced by PANI (wt%). The PANI has the ability to create more charge carriers and delay the recombination process. The kinetic studies fitted to pseudo first order reaction. The nanocomposite acts as a promising photocatalyst for the removal of organic pollutants from water.

Cellulose is one of the emerging materials as a natural polymer. In this work, cellulose nanofiber is utilized as a dielectric layer in triboelectric nanogenerator. To retain the flexibility of the fabricated paper, Ag nanowires layer is employed for electrode material and counter triboelectric layer simultaneously. This triboelectric nanogenerator is fabricated by a filtration process with different cellulose nanofiber and Ag nanowire condition. This triboelectric nanogenerator operates by contacting and separating of only two same bilayer paper consisting of cellulose nanofiber and Ag nanowire. Cellulose nanofiber and Ag nanowires layer acting as not only triboelectric layer and counter-triboelectric layer but substrate and electrode respectively. The case of cellulose nanofiber solution homogenized with 20 passes in 1000 bar and Ag nanowire with 0.1 wt% solution shows the optimal peak corresponding to 21 V of open-circuit voltage and 2.5 µA of short-circuit current. The maximum power output represents the value of 693 mW/m2 for a 10 MΩ external resistance. Fabricated device is dispersed and completely dissolved in deionized water by using sonicator for 30 min and returns to original ingredient without producing any pollutant. This nanogenerator plays roles of not only harvesting ambient energy but folding sensor, humidity sensor, and e-paper-like device due to the paper-like characteristics and nano-porous of cellulose nanofiber and Ag nanowires.

Green energy techniques, such as harvesting wind energy, is gaining great attention as they can provide environmental-friendly and renewable power sources in this era of energy crisis. Here, we report a triboelectric nanogenerator (TENG) which harvest mechanical energy driven by wind that works as a sustainable power source as well as a self-powered wind speed sensor. By adopting a novel method that employs the rolling motion of polymer beads, which serve as freestanding layers, under the wind speed of 20 m/s, the TENG delivered output voltage up to 17.8 V, output current of 5.3 µA, and a corresponding output power density of 1.36 mW/cm2. The correlation between electrical outputs, wind velocity, width of electrode is systematically investigated. Furthermore, the fabricated device is able to generate an electrical energy regardless of the direction of the wind, and it works well even for long term in the surrounding environment. Additionally, the device is small in size and comparatively flat in its structure, further enhancing potential of its application, such as self-powered wind speed sensor, as an effective portable power source that is readily available to be used in our daily life.

Irrecoverable data destruction on a mobile device is important to prevent unintentional data disclosure. In this regard, transient electronics, a form of electronics that can be made to disappear or can be destroyed in a controllable manner, has been actively researched. To erase data completely, irreversible reactions such as physical or chemical destruction have been used. However, these techniques either require external voltage or destroy a memory device so that it cannot be reused. Here, we demonstrate a novel self-powered data-erasing method for nanoscale flash memory devices which uses triboelectricity via a kill switch, which consists of a nylon pad connected to a gate electrode of the flash memory. Through a one-time touch of the kill switch by a finger wearing a polytetrafluoroethylene (PTFE) glove, data stored in flash memory is set to the ‘1′ state on the chip scale simultaneously with low-level triboelectricity, allowing the memory to be reused afterward. Moreover, the memory can be permanently destroyed by a single touch of the kill switch with a finger without a glove that generates high-level triboelectricity. These erase methods provide a rapid and convenient means of self-powered irrecoverable data erasing in the era of the Internet of Things (IoT).

To harvest ambient mechanical energy, a triboelectric nanogenerator is actively researched as a sustainable energy source. One of the advantages of the triboelectric nanogenerator is the almost exclusive use of widely available materials that can be manufactured at a low cost. For example, silica, composed of silicon and oxygen, not only can play a role as a triboelectric material but is abundant everywhere in the earth’s crust. Here, we report a triboelectric nanogenerator using three types of silica powder as a freestanding dielectric layer: sand, silicon, and silicon dioxide. Among them, the triboelectric nanogenerator with silicon dioxide powder and polytetrafluoroethylene film produces the highest electrical output power. The instantaneous peak power density is 0.3 mW/m2, achieved by shaking the triboelectric nanogenerator by hand. Five serially connected commercial light emitting diodes are simultaneously turned on by persons with a hand. The proposed triboelectric nanogenerator can be utilized as a useful electric power generator in Third World due to its low-cost and widely available component materials.

A triboelectric nanogenerator (TENG) is an energy harvester which converts ambient mechanical energy into electrical energy. A disk-based rotational TENG converts rotational mechanical energy into electrical energy with advantages over a vertical contact-separation based TENG. Since the disk-based TENG operates in grating-based sliding mode, its electrical output is advantageous in terms of prolonged continuous energy harvesting. However, rotational mechanical energy is less abundant than linear mechanical energy in typical environments. In this work, a new disk-based TENG which converts linear mechanical energy into electrical energy through the use of a gear system (linear-to-rotational TENG, LR-TENG) was fabricated as an experimental device. A TENG based on a vertical contact-separation mode (V-TENG), composed of identical triboelectric materials, was also fabricated as a control device. Here, it is experimentally demonstrated that the electrical output of the LR-TENG was superior to that of the V-TENG at the same magnitude of applied force and at an identical level of applied mechanical energy, as the surface charge density of the LR-TENG is much greater than that of the V-TENG. The LR-TENG can effectively provide power to numerous small electronic devices. Examples include charging a commercial capacitor and lighting commercial LEDs.

Wind based triboelectric generators (W-TEGs) have been actively studied because of their clean, sustainable, and semi-permanent operation. However, the charge transfer characteristics of W-TEGs have not been clearly understood so far. In this work, a multi-directional W-TEG with a single stack structure, which stably collects wind energy blowing from all directions, was demonstrated. The proposed W-TEG is composed of two metal electrodes at the top and the bottom with an intercalated polymer membrane, which is driven to alternately flip and flop between both metal electrodes by an external wind. The overall shape is square, and the polymer membrane is supported by spacers at 4 corners. Structural parameters such as the thickness of the polymer membrane, the length or width of the square device, and the height of the spacers were optimized to investigate the relation between wind frequency and the amount of transferred charge. The analyzed data were supported by numerical simulations. By providing in-depth understanding this study can contribute to the development of W-TEGs.

Multi-gate transistors, such as double-gate, tri-gate and gate-all-around transistors are the most advanced Si transistor structure today. Here, a genuine double-gate transistor with a graphene channel is experimentally demonstrated. The top and bottom gates of the double-gate graphene field-effect transistor (DG GFET) are electrically connected so that the conductivity of the graphene channel can be modulated simultaneously by both the top and bottom gate. A single-gate graphene field-effect transistor (SG GFET) with only the top gate is also fabricated as a control device. For systematical analysis, the transfer characteristics of both GFETs were measured and compared. Whereas the maximum transconductance of the SG GFET was 17.1 μS/μm, that of the DG GFET was 25.7 μS/μm, which is approximately a 50% enhancement. The enhancement of the transconductance was reproduced and comprehensively explained by a physics-based compact model for GFETs. The investigation of the enhanced transfer characteristics of the DG GFET in this work shows the possibility of a multi-gate architecture for high-performance graphene transistor technology.

We prepared shape-controllable, sodium alginate-based hydrogels containing various particles inside the hydrogels. Centrifugal injection method was employed to obtain smaller sized gels, compared t...

A triboelectric nanogenerator (TENG) is a promising type of energy harvester which converts ambient mechanical energy into electrical energy efficiently as part of the effort to overcome the energy depletion issue. To enhance the electrical output of the TENGs, the surface morphology is intentionally created on the surface of a friction layer of these harvesters. In this work, the shape dependency of the geometric morphology of a TENG, in terms of the electrical output, force sensitivity, and durability, is investigated by measurements and simulations with the aid of ANSYS. A well-ordered pillar-shaped and dome-shaped nanostructure was created on polydimethylsiloxane (PDMS), which is commonly used as a friction layer in TENGs. It was found here that the TENG with dome-shaped PDMS (DP-TENG) showed greater force sensitivity than the TENG with pillar-shaped PDMS (PP-TENG). However, the PP-TENG was found to be more durable than the DP-TENG. These results stem from the fact that the dome-shaped nanostructure will deform more easily than the pillar-shaped nanostructure. This study suggests a guideline for the structural engineering of the surface morphology of the friction layer with the consideration of the geometric shape to maximize the important properties of the TENGs.

Constantly operated systems such as traffic and security systems that continually maintain the operation are continuously consuming tremendous energy as a standby power. The triboelectric nanogenerator (TENG) is a suitable alternative as the sustainable energy source of these systems because the TENG can be utilized as the energy source of these systems by generating the electricity from the wasted energy around the systems. The paint is an attractive material for the TENG because the paint is commonly utilized and the contact frequently occurs on the surface coated by the paint. Herein, the paint based TENG (PBT) is developed with the facile spray deposition to harvest this wasted mechanical energy generated from the paint coated surface due to the contact. The electrical outputs of the PBT are investigated and recorded maximum increased output of 280%. Furthermore, the applicability of the PBT is demonstrated by adopting the various materials for fabrication and the PBT shows great stability. Finally, intrusion detection system (IDS) and camouflaged keypad (CKP) are implemented as applications, respectively. The violation of traffic-norm at the stop line is successfully detected with the IDS, which is indicating the strong possibility for the traffic system. The CKP successfully replaces the keypad of the conventional keyboard with the guaranteeing high personal security during the login process. Considering good compatibility of the PBT, it can be expected to apply in the smart traffic system as well as advanced security system in near future.

With the rapidly increasing number of older people in our societies, fall detection is becoming more important: Older adults may fall at home when they are alone and they may not be found in time for them to get help. In addition, a fall itself can cause serious injuries such as lacerations, fractures and hematomas. Although many previous studies have been reported on various fall detection technologies based on wearable sensors, the inconvenience of wearing them is problematic. Vision or ambient based methods may be alternatives, but high cost and complex installation process limit applicable areas. We propose a cost-effective, ambient-based fall detection system based on a pressure sensing triboelectric nanogenerator (TENG) array. Apart from simple observation of output signal waveforms according to different actions, key technologies, including appropriate filtering and distinguishing between falls and daily activities, are demonstrated with data acquisition from 48 daily activities and 48 falls by eight participants. The proposed system achieves a classification accuracy of 95.75% in identifying actual falls. Due to its low cost, easy installation and notable accuracy, the proposed system can be immediately applied to smart homes and smart hospitals to prevent additional injuries caused by falls.

Among the many types of wasted energy around us, mechanical energy has been considered to have a considerable amount of potential to be scavenged due to its abundance and ubiquity in our lives. To convert ambient mechanical energy into electrical energy efficiently, the triboelectric nanogenerator (TENG) has been intensively studied. Polydimethylsiloxane (PDMS), due to its superior mechanical and electrical properties, has commonly been selected as a friction layer in TENGs. Herein, it is newly discovered that the output power of a fabricated TENG is highly correlated with the Young's modulus of PDMS. An enhancement of the output power is achieved by the optimization of the PDMS mixture ratio. In addition, to improve the output power of the TENG further, a well-ordered microstructure was directly created on the surface of the PDMS by means of ultrafast laser irradiation. Direct patterning to create the surface morphology on the PDMS surface with the aid of laser irradiation is more efficient than conventional surface modification techniques such as replication and a few microfabrication steps. Compared to a control TENG using bare PDMS, an increase in the output power of more than twofold is achieved by an experimental TENG using patterned PDMS with a laser power of 29 mW. The TENG utilizing the patterned PDMS achieves a maximum output power density level of 107.3 μW/cm2.

Ambient mechanical energy, which is abundant in the living environment, is a promising energy harvesting source. This technology can provide an eco-friendly and sustainable form of energy. Here, a novel solution-processed aluminum coating (SC) method to create an electrode, consisting of sandpaper, is demonstrated for a triboelectric nanogenerator (TENG). The proposed SC method harnesses the strong adhesion of Al to the target substrate, with conformal deposition of Al following a pre-existing nano-to-micro surface morphology, and offering good thickness controllability without discontinuities, and the ability to coat an Al film in a manner unrestricted by the size or type of substrate. The fabricated TENG using the SC method is capable of serving as an energy supplier and can be commercialized for the Internet of Things (IoT) due to its high output power and low-cost.

본 연구에서는 2005년부터 2007년 사이에 중국 공업지대에서 Ozone Monitoring Instrument (OMI) 센서에서 관측한 이산화황 값의 증가에 따른 Total Ozone Mapping Spectrometer (OMI-TOMS)와 Differential Optical Absorption Spectrometer (OMI-DOAS) 오존전량 값의 차이를 위성자료를 이용하여 비교를 수행하였다. 중국 공업지대에서는 Planetary boundary layer (PBL)내의 이산화황을 나타내는 PBL SO2 자료가 사용되었다. 중국 공업지대에서 PBL내의 이산화황 농도 증가에 대하여 두 오존 값의 차이가 증가하는 경향성(R (Correlation coefficient) = 0.36)이 나타났다. 이산화황 이외에 두 오존 산출 알고리즘에 모두 영향을 미칠 수 있는 에어로솔 광학 두께(AOD; Aerosol Optical Depth)가 증가하는 경우 이산화황과 두 오존 값의 차이 사이의 회귀식의 기울기(1.83 ≤ slope ≤ 2.36)가 비슷하게 유지되는 경향이 나타났다. 이는 다양한 AOD 조건에서도 이산화황이 두 오존 값의 차이를 증가시키는 관계가 나타나는 경향은 거의 비슷하게 유지되는 것으로 생각된다. 중국 공업지대에서 PBL내에 존재하는 이산화황과 화산 폭발에 의하여 고층(Middle troposphere (TRM), Upper troposphere and Stratosphere (STL))에서 존재하는 이산화황의 농도가 1 DU 증가하는 경우 두 오존 값의 차이는 각각 1.6 DU, 3.9 DU, 4.9 DU로 계산되었다. 고층(TRM, STL)의 이산화황과 저층(PBL)의 이산화황이 증가하는 경우 두 오존 값의 차이가 다르게 나타나는 것은 이산화황이 존재하는 고도에 따라서 두 오존 값의 차이에 미치는 영향이 다름을 의미한다. 이는 OMI-TOMS 오존을 산출하는데 사용되는 파장영역(317.5 nm)에서 행성경계층에서 이산화황에 의해 흡수되는 복사휘도의 감소된 민감도에 의한 것으로 생각된다.

A rotating-disk-based triboelectric nanogenerator (TENG) generating electrical energy from wind usually includes a propeller. TENGs are widely used because their high frequency of rotation allows them to generate a relatively high output current. Deep analysis of the gas flow in a TENG is essential to improve its energy conversion efficiency. However, previous studies have isolated the propeller and the TENG as separate entities that harvest wind energy and generate electrical energy, respectively. Most studies focused on each entity because considering both the dynamics and the TENG operation together is an intricate process. This paper introduces a dynamic analysis of the gas flow by dividing it into four vertical and horizontal directions and carrying out a COMSOL simulation to verify the pressure on the propeller and the flow of the gas. The electrical outputs are measured while varying the height and angle of the inlet and the number of wings on the propeller. After optimization, the P-TENG generated a high output power density of 283.95 mW/m2, which can light up 205 light-emitting diodes and drive a commercial small electronic appliance. In addition, optimizing the P-TENG through a variety of analyses allowed it to provide sustainable power to a self-powered wireless sensor system.

Thermal energy is generated from all equipment during operation. Likewise, thermal energy exists everywhere and dissipates uselessly. It is necessary to transform thermal energy into renewable electrical energy by utilizing materials and devices exhibiting unique features of thermal properties. Shape memory alloys (SMAs) consisting of a compound of nickel (Ni) and titanium (Ti), operate based on unique thermomechanical properties, such as shape memory effect (SME) and superelastic effect (SE). Due to these two effects, SMAs are possible to be deformed and recovered by external heat. One-dimensional SMA wire (SW) can effectively harvest wasted thermal energy by the phase change in SMA from a wrinkled state to a straight state in order to generate continuously rotating energy with two sheaves. In this paper, we propose a thermally-driven SMA-wire based hybrid generator (SW-HG), including a disk-TENG and thermoelectric generator (TEG) which lead to generate a high voltage and large current, respectively. In addition, the operation principle of rotating by the deformation and the recovery of the SW at the phase-change temperature are systematically investigated as well as analyzed using two theoretical models. The unique thermomechanical behavior of the SW-HG is applied to commercial vehicles using output signals for the real-time temperature monitoring inside the engine room. Considering these unique features of SW, the SW-HG is expected to be dependable devices for IoT applications as well as can effectively convert surrounding wasted heat energy into reusable electrical energy in real life.

Combining with an artificial intelligence and 5G technologies, the new era of Internet of Things (IoT) has been emerging. Hence, a human-machine interface (HMI) is becoming indispensable in IoT. However, conventional HMIs are suffering from limitations like, the requirement of power sources and structure-complexity. As a solution, triboelectric nanogenerator (TENG) based HMI can be considered as an attractive alternative due to the self-powered operation of TENG. Herein, we suggest the self-powered triboelectricity-based touchpad (TTP) which combines with artificial intelligence consisting of TENG array (49 pixels) constructed on thin, transparent, and flexible substrate, as well as this TTP works based on two major kinds of TENG mechanisms in tapping and sliding modes. The tracing ability of the TTP is demonstrated with high accuracy. Furthermore, the TTP recognizes the digit patterns from ‘0’ to ‘9’ with classification accuracy of 93.6%, 92.2%, and 91.8% at the bending angles of 0°, 119°, and 165° through the pre-trained neural network. With the remarkable applicability of the next-generation HMI in IoT, the TTP is implemented as the smart calculator by using graphical user interface modeling. Considering its good compatibility, it can be expected to be a promising HMI in near future with practical IoT towards artificial intelligence.

Many decentralized communities like rural communities of developing countries and remote communities, suffer from a scarcity of adequate water treatment because there is insufficient capital to construct relevant facilities, no experts to handle the required chemicals, insufficient electricity to operate them. Herein, we report a fully self-powered electro-coagulation (SPEC) system for de-centralized water treatment. For this, a triboelectric nanogenerator harvests ambient wind energy to provide the needed power. A simple electro-coagulation unit, composed of a simple pair of electrodes, successfully removes dissolved colloidal pollutants from water, while coagulating and precipitating pollutants, without any use of chemicals or an external power supply. The SPEC system removes 90% of algae and 97% of organic dye with self-powered treatment for 72 h. Due to its easy operation, and its low cost arising from its inherently simple structure, requirement for much smaller-scale facilities and low operating cost, the SPEC system could become a powerful candidate for appropriate water treatment in many regions lacking centralized water treatment.

A triboelectric nanogenerator (TENG) offers improved output power for enhanced performance and throughput at a low cost as a type of practical energy harvester. In this work, a novel method which enhances the output power with the aid of a nano-to-micro morphology and which reduces the fabrication cost via the simple process of the glass transition of a polystyrene (PS) substrate is introduced. The glass transition of the PS quickly produces the nano-to-micro morphology within 1 min with only a heating process in an air environment. The pristine PS substrate was crumpled in a uniaxial or biaxial direction when heated to a temperature of 170 °C. Thus, the throughput is notably increased without the use of complicated fabrication processes or high-level equipment. The power enhancement effects of the proposed TENG were characterized. Under the optimized condition, the fabricated nanogenerator showed a fourfold increase in both the open-circuit voltage and short-circuit current due to the fourfold enhancement of the surface charge density arising from the crumpled structure compared to a control device without a nano-to-micro structure on the PS substrate. In this case, 160 serially connected light-emitting diodes (LEDs) were successfully illuminated with the optimized device, which was 2 cm by 2 cm in size.

The plasmonic coupling, the enhanced electromagnetic field occurring through a uniform and small separation between metallic particles, is required for better application to localized surface plasmon resonance. Graphene has been studied as a good spacer candidate because of its precise controllability at subnanoscale. Here, the enhancement of plasmonic coupling among metallic nanoparticles (NPs) uniformly spread out on both sides of a graphene spacer is experimentally and simulatively investigated. Additionally, the post-evaporated flat structure is rippled along one direction to reduce the separation between nanoparticles. As the amount of rippling increases, the enhancement factor (EF) of the plasmonic coupling increases almost linearly or quadratically depending on the size of nanoparticles. Such a highly rippled nanostructure is believed to not only increase the plasmonic coupling in either side of the spacer but lead to a higher density of “hot spots” through the spacer gap also. The observed EFs of a structure with the MLG spacer are consistent with the simulation results obtained from the classical electrodynamics. On the other hand, the SLG case appears to be inconsistent with such a classical approach, indicating that the plasmon tunneling through the thin barrier is prevalent in the case of the SLG spacer.

The performance of a triboelectric nanogenerator (TENG) was effectively enhanced by forming nanostructures at the contacting interface. The contacting interface usually consists of metal and polymer surface, but the formation of nanostructures have only been actively studied for the polymer so far. In this work, a simple and effective route to forming nanostructures on the metal surface is proposed, using a water-assisted oxidation (WAO) process. The one-step WAO process requires only hot water without any complicated equipment and treatment. Using the WAO process, densely packed micro and nanostructures were successfully formed on three target metal surfaces: aluminum, copper, and zinc. The output power of the TENG was enhanced after the nanostructure formation because of the increased contact area. The influence of the process conditions on the nanostructure morphology was additionally analyzed to maximize the output power. The simple and low-cost WAO process is advantageous in terms of practicality.

The anisotropic wetting characteristics of scalloped nanogrooves (SNGs) were investigated for the first time. SNGs with various scallop edge angles were fabricated by Bosch deep reactive ion etching (DRIE). The wetting properties of the nanopatterned surfaces were studied in dynamic and static regimes. The anisotropic wettability of the SNGs was successfully employed to control fluid flows in microfluidic channels.

Future space exploration requires easy-to-transport, easy-to-build and deployable space habitats. One of the biggest threats faced by the habitat structures is the impact damage caused by micrometeoroid orbital debris (MMOD) traveling at high velocities of few km/s. This work presents fabrication and testing of hybrid nanocomposites with carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) as fillers in a flexible epoxy matrix, that are proposed to be used for sensing the impact damage by MMOD on inflatable space structures. CNTs and GNPs are chosen as fillers owing to their excellent electrical properties and piezoresistivity. A hypervelocity impact is conducted on the nanocomposite sensors to study their functionality in the space environment. The results prove that the piezoresistive nanocomposites can be utilized as a part of damage detection system, which would not only detect the impact damage caused by MMOD of 3 mm diameter traveling at 7 km/s but also discern its location and depth within the inflatable structural layers.

The sensitivity of the electronic properties of carbon nanotubes to gases, chemicals, temperature, and mechanical strain enables their use as fillers in nanocomposites for sensing applications. In this paper, the authors develop a low-cost and scalable process based on inkjet printing technology to fabricate printed flexible sensors used for strain and damage detection. A well-dispersed conductive water-based ink is fabricated with functionalized multiwall carbon nanotubes (MWCNT) and deposited onto paper and Kapton substrates to obtain a sheet resistance as low as 500 Ω/sq with about 30 printed layers. The number of printed layers, the direction of the electrical resistance measurement, and the type of substrate have clear effects on the sensor's electrical performances related to the detection of mechanical strain and impact damage. This work demonstrates the effectiveness of the printed sensors for micrometeoroid and orbital debris (MMOD) impact damage detection through hypervelocity testing.

Ever-rising skyscrapers and the growing number of densely populated large cities face an increased danger from earthquakes. To lessen the risk of this natural disaster, critical facilities must be equipped by a reliable warning system. However, conventional sensors which detect the velocity and acceleration of the seismic vibrations, consumes an external power, which cannot be placed in many buildings due to limitations in electricity supply. In this work, a self-powered seismic sensor is fabricated using the three-dimensional printing technology. The proposed device can be operated based on the triboelectricity, which converts an external mechanical energy into an electrical energy. The proposed device exhibits an exceptional behavior of a friction-free due to its sophisticated designed structure with a levitating oscillator. The fundamental parameters representing the device performance are systematically analyzed with various operation mode. Water-assisted oxidized Al electrodes allow full-contact with the polytetrafluoroethylene triboelectric oscillator film, subsequently, produce the highest values of output parameter as follows; an open-circuit voltage of 29.44 V, a short-circuit current of 204 nA, and a peak power density of 2.501 mW/m2 at a load resistance of 50 MΩ. Frequency reversibility is also demonstrated from the frequency response of the short-circuit current during the operation in lateral-contact mode. Because of inherently friction-free characteristics of the proposed device, this device shows high sensitivity, low sensing limit, and long residual signal, which is experimentally verified. In order to test the sensing ability of the device, artificial seismic vibrations are applied with vertical forces of 4 N and 2.4 N. An alert software program displays the sensing ability of the device with the signals over 1 V, which is the threshold voltage. The stability of the device in humid conditions and its durability for 3100 s in the output voltage measurement represent the possibility of this device as a reliable sensor. Due to the simple three-dimensional printing technology and its inherently friction-free characteristics, the proposed device can be employed as a self-powered sensor capable of warning about dangerous earthquake disasters.

We investigate the effects of aerosol peak height (APH) and various parameters on the air mass factor (AMF) for SO2 retrieval. Increasing aerosol optical depth (AOD) leads to multiple scattering within the planetary boundary layer (PBL) and an increase in PBL SO2 AMF. However, under high AOD conditions, aerosol shielding effects dominate, which causes the PBL SO2 AMF to decrease with increasing AOD. The height of the SO2 layer and the APH are found to significantly influence the PBL SO2 AMF under high AOD conditions. When the SO2 and aerosol layers are of the same height, aerosol multiple scattering occurs dominantly within the PBL, which leads to an increase in the PBL SO2 AMF. When the APH is greater than the SO2 layer height, aerosol shielding effects dominate, which decreases the PBL SO2 AMF. When the SO2 and aerosol layers are of the same height under low AOD and solar zenith angle (SZA) conditions, increased surface reflectance is found to significantly increase the PBL SO2 AMF. However, high AOD dominates the surface reflectance contribution to PBL SO2 AMF. Under high SZA conditions, Rayleigh scattering contributes to a reduction in the light path length and PBL SO2 AMF. For volcanic SO2 AMF, high SZA enhances the light path length within the volcanic SO2 layer, as well as the volcanic SO2 AMF, because of the negligible photon loss by Rayleigh scattering at high altitudes. High aerosol loading and an APH that is greater than the SO2 peak height lead to aerosol shielding effects, which reduce the volcanic SO2 AMF. The SO2 AMF errors are also quantified as a function of uncertainty in the input data of AOD, APH, and surface reflectance. The SO2 AMF sensitivities and error analysis provided here can be used to develop effective error reduction strategies for satellite-based SO2 retrievals.

Energy conversion cannot be sufficiently achieved from a single output device having a single input. Energy conversion efficiency and output power of triboelectric nanogenerator (TENG) can be enhanced by increasing the contact area or the number of devices. Especially, combining two or more of the four operational mode (contact-separation, lateral sliding, single electrode, freestanding) of triboelectric nanogenerator would be more efficient to harvest mechanical energy than with singleharvesting mode. In this paper, a hybrid coaxial triboelectric nanogenerator (HC-TENG) can generate electrical output from dual outputs. This HC-TENG consists of a disk-TENG and LS-TENG so that a large current can be harvested from the rotating movement of disk-TENG at a high frequency input and an additional output can be generated from the LS-TENG by adding one axis. The structure of device with one axis was inspired by the structure of crank engine, which can convert linear motion into rotational motion. When applying the structure of HC-TENG to an application, the input-output efficiency was calculated by using the rotational kinetic energy formula with the value of 16.66%. Moreover, the efficiency of HC-TENG was verified by comparing experimental values with theoretical calculations for the presence of the dual outputs. This combination of multiple TENGs can be adopted for enhancing efficiency from every ambient rotational movement in real life.

Energy harvesting technology, which collects natural energy and converts it into electrical energy, is a very important technology for the future energy industry. Solar cells are one of the most popular energy harvesting devices due to their high power and cost-effectiveness; however, because solar cells are highly influenced by weather conditions, they are not suitable for continuously generating electricity. In this paper we propose a new unified harvesting module (UHM), which is thin and lightweight, to harvest natural energy sources in various weather conditions. The UHM consists of two triboelectric nanogenerators (TENG), a transparent one for harvesting energy from raindrop impacts and one for harvesting wind energy, and a solar cell. This device can turn on 62 LEDs in real time without any energy storage device. Additionally, the UHM can be used as a self-powered weather sensor to detect rain drops, sunlight, and wind speed based on its electrical output. From this, the weather monitoring platform was subsequently demonstrated for use on a smart farm using a data acquisition system and LabVIEW software. This work proposes a new generator for not only harvesting natural energy, but also for broadening its application to the Internet of Things by developing practical usage of energy harvesting technology systems.