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In recent years, modern appliances require high energy density with a burst power supply. Hybrid supercapacitors show high performance based on high energy density without compromising power density and stability over thousands of charge-discharge cycles. In this work, the optimized hybrid electrodes using lanthanum-doped hematite (lanthanum-doped iron oxide) noted as 7.5%La-HMT as a negative electrode and hydrous cobalt phosphate (CoPO) as a battery-type positive electrode have been successfully fabricated

This letter presents a flexible pressure sensor based on silicon nanowires (Si NWs) built by metal-assisted chemical (MAC) etching. The MAC etched NWs, with a height of $30~\mu \text{m}$ and a diameter as small as 200 nm, were post-treated with polydimethylsiloxane to endow the NW sensor with elasticity and high-pressure resistance. The piezoresistance of the Si NWs varies from ${1.03}\times {10}^{{6}}$ to ${5.3}\times {10}^{{4}}$ ohms as the applied pressure changes from 0 to 4.5 kPa, indicating a resistance change rate of about 94%. The Si NW sensor also exhibits a fast response and recovery time as 0.3 s, it is capable of distinguishing pressure changes as low as 0.3kPa, which is way lower than the perceivable range (10-40kPa) of human skin.

This study reports the hydrothermal synthesis and electrochemical performance of Cobalt Tungstate (CoWO4) and Carbon nanotubes and Cobalt Tungstate nanocomposite (CNT-CoWO4) as supercapacitor electrode material. The active materials are directly deposited on carbon cloth substrates to fabricate binder free electrodes which exhibited specific capacitance of 1443 F g-1 and 1486 Fg-1 at 5 mVs−1 scan rate for CoWO4 and CNT-CoWO4 samples, respectively. As a result of increase in potential window (1 V for nanocomposite CNT-CoWO4 as compared to 0.6 V for CoWO4) and higher specific capacitance in three electrode system, CNT-CoWO4 electrode delivers higher energy density than the CoWO4 electrode. A symmetric capacitor is fabricated from CNT-CoWO4 nanocomposite electrodes. The performance of symmetric capacitor, operated within a potential window of 1.5 V, is comparable to the asymmetric devices. Furthermore, the device delivered maximum energy density of 12 W h kg−1 at 432 W kg-1 power density.

In present study, new strategy is employed to build composite nanostructure and asymmetric configuration to enhance the capacitive performance of supercapacitor device. The WO3-MnO2 composite with mesoporous structure is prepared by single-step hydrothermal method and used to gain superior electrochemical performance in asymmetric configuration. A binder-free and additive-less WO3-MnO2 composite electrode exhibits high specific capacitance of 609 F g−1 at a scan rate of 5 mV s−1. The flexible asymmetric supercapacitor device with WO3-MnO2 as a positive electrode and WO3 as a negative electrode demonstrates stable operating potential window of 1.4 V with specific capacitance of 103 F g−1 at a scan rate of 5 mV s−1 and energy density of 24.13 Wh kg−1 at power density of 915 W kg−1. Furthermore, WO3-MnO2//WO3 device exhibits good cycle life with capacity retention of 95% after 2500 cycles and excellent mechanical flexibility. These results reveal the potential of WO3-MnO2 composite electrode for fabrication of high-performance supercapacitors.

In the present work, we analyzed the effect of doping (Bi, Hf, and Nb) on the performance of tungsten oxide (WO3) based supercapacitor. Through substitutional doping, the properties were altered to enhance its electrochemical charge storage performance. The doped samples were tested in different electrolytes (H+, Li+, Na+, Ca2+ and Al3+). The cyclic voltammetry, galvanostatic charge–discharge, and EIS studies were performed to identify the best suitable anode material for the fabrication of asymmetric supercapacitor. Nb:WO3 yielded the highest specific capacitance (Csp) of 782 Fg−1 in Ca electrolyte. An asymmetric device with Nb:WO3 as anode and MnO2 as a cathode using an aqueous Ca ion electrolyte exhibited a high potential window of 2 V and capacitance of 126 Fg−1. The factors responsible for performance of electrode material in different electrolytes were identified through experimental results, theoretical calculations, and relevant simulations. The effect of doping on WO3 crystal structure and electronic properties along with their binding nature/interaction with different electrolyte ions were first postulated through density functional theory (DFT) calculations.

The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO2 have been successfully fabricated on flexible carbon cloth by simple but capable hydrothermal method at different deposition temperatures. The deposition temperature has strong influence on reaction kinetics, which subsequently alters the morphology and electrochemical performance. Among different nanostructured MnO2 thin films, the mesoporous weirds composed thin film obtained at temperature of 453 K exhibits excellent physical and electrochemical features for supercapacitor application. The weirds composed MnO2 thin film exhibits specific surface area of 109 m2 g−1, high specific capacitance of 595 F g−1 with areal capacitance of 4.16 F cm−2 at a scan rate of 5 mV s−1 and high specific energy of 56.32 W h kg−1. In addition to this, MnO2 weirds attain capacity retention of 87 % over 2000 CV cycles, representing better cycling stability. The enhanced electrochemical performance could be ascribed to direct growth of highly porous MnO2 weirds on carbon cloth which provide more pathways for easy diffusion of electrolyte into the interior of electroactive material. The as-fabricated electrode with improved performance could be ascribed as a potential electrode material for energy storage devices.

We present the accurate terahertz spectra of between imitation and cultured pearls using continuous-wave terahertz (CW-THz) spectroscopy. Using Fourier transform infrared (FT-IR) spectroscopy and optical coherence tomography (OCT) measurements, cultured pearls can be distinguished from imitation pearls by observing distinct absorption peaks and discriminative boundaries. The THz absorption spectra up to 0.3 THz obtained from CW-THz spectroscopy show several absorption peaks at specific frequencies with the cultured pearls but no peaks with the imitation pearls, which results from the existence of the nacre polymorph of cultured pearls. Hence, it is expected that the CW-THz system proposed herein will be applicable to fast, nondestructive spectrum analysis including pearl identification.

Supercapacitors have garnered much attention as energy storage devices. In this article review of most popularly studied metal oxide electrode materials are reviewed with the recent developments. The metal oxides in pristine form have not been able to achieve performance characteristics required for practical applications therefore, composite electrode are also studied. The composite electrode works mainly on the synergistic properties of two or more materials which complement each other and consequently perform better than one electrode. Carbon and carbon derivatives are the most popular option for the composite electrodes. The nanostructuring of the electrode materials has a positive effect on the electrode performance. Understanding of charge storage mechanism is important and needs to be considered while working on nanoscale. The review focuses on the charge storage mechanism, composite electrodes and nanostructuring of the electrodes which ultimately result in better supercapacitive performance.

This paper reports heterojunction solar cells consisting of InP nanopillars and aluminum-doped zinc oxide (AZO). The AZO layer sputtered on an InP surface is used not only as a transparent electrode, but also as an excellent rectifying junction with InP. More importantly, the wide-bandgap-AZO functions as a window layer of solar cells, thereby suppressing carrier recombination loss at the AZO-InP heterointerface. The InP nanopillar array reduces the light reflectance and increases the optical path length of the solar cells. The AZO-InP nanopillar-based heterojunction solar cells exhibited an open-circuit voltage, short-circuit current density, fill-factor, and power-conversion efficiency of 0.68 V, 36.8 mA/cm2, 68%, and 17.1%, respectively, under air-mass 1.5 simulated solar illumination (100 mW/cm2).

In this study, InGaN-based green light-emitting diodes (LEDs) with a graded-superlattice (GSL) layer inserted between the 3 µm thick n-type GaN and the multiple quantum wells (MQWs) were studied numerically and experimentally. The simulated results indicate that the use of GSL inserting layer consisting of 12-stacked InGaN/GaN layers leads to the enhancement of electron injection into the MQWs resulting in the increase of radiative recombination rate, suppressing the electron overflow to the p-GaN side. The photoluminescence and output power of the GSL LEDs show a 73.5 and 42.5%, respectively, in a comparison with the reference LEDs that has no inserting layer. This improvement with the GSL LEDs indicates that the GSL insertion layer acts not only as a stress-relaxing buffer layer releasing the residual stress in MQWs, but also as an electron cooler enhancing the electron capture rate in MQWs.

Presently, significant attention has been paid towards the rational synthesis of nanostructured anode and cathode electrode materials for assembling high-performance supercapacitors. Despite significant progress being achieved in designing cathode electrode materials, anode electrode materials with high capacitance are hardly investigated. In the present article, a tungsten oxide (WO3) thin film is prepared on a flexible stainless steel substrate by a wet chemical method and used as an anode electrode to fabricate a flexible asymmetric supercapacitor (ASC). An electrochemical investigation of the WO3 thin film shows a maximum specific capacitance of 530 F g−1 at 1 mA cm−2 in a potential window of 0 to −0.8 V in 1 M Na2SO4 electrolyte. In addition, a highly energetic, flexible ASC device is assembled using a WO3 thin film as an anode, a MnO2 thin film as a cathode and polymer gel as an electrolyte. The as-assembled MnO2//WO3 ASC device exhibited a stable electrochemical potential window of 1.8 V and better cycling stability. What's more, the flexible MnO2//WO3 ASC device achieves a high specific capacitance of 115 F g−1 with an acceptable specific energy of 52 W h kg−1 at a current density of 3 mA. Hence, the proposed flexible MnO2//WO3 ASC device creates one more option for anode materials to develop flexible energy storage devices.

Metal sulfides have received well deserved attention due to their excellent electrical conductivity and thermal stability, as compared to metal oxides, allowing them to achieve a high capacitance and energy density for portable energy storage devices. In this study, the preparation of highly porous nano-flames composed of nickel sulfide (NiS) thin film on a cost effective, flexible stainless steel substrate through a trouble free, inexpensive and simple chemical bath deposition (CBD) method is reported. The prepared nano-flames composed of a NiS thin film demonstrates the excellent electrochemical features with a maximum specific capacitance (Cs) of 750.6 F g−1 at a scan rate of 5 mV s−1 in a three electrode system. Furthermore, the portable symmetric flexible solid state supercapacitor (FSS-SC) and electrochemical supercapacitor (SC) are fabricated and tested. In comparison with the symmetric electrochemical SC, the symmetric FSS-SC shows an excellent electrochemical performance with a high Cs of 104 F g−1 at 5 mV s−1 with a good electrochemical stability of 85.3% over 3000 CV cycles. This study constitutes the first comparison of symmetric FSS-SCs and electrochemical SCs formed with NiS nano-flames. Such an impressive symmetric FSS-SC is predicted to be an exceptionally promising candidate for energy storage systems.

In the present investigation, the applicability of Fe2O3 and CuO thin films as anode and cathode electrodes respectively in supercapacitors has been systematically studied. Fe2O3 and CuO thin films are synthesized by simple and cost effective chemical methods and further more all-solid-state symmetric (Fe2O3/Fe2O3, CuO/CuO) and asymmetric (CuO//Fe2O3) supercapacitor devices are fabricated. The electrochemical properties (cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (ESR), etc.) of these devices are studied using two electrodes system. The asymmetric supercapacitor shows improved performance with maximum operating potential window of 2.0 V and specific capacitance of 79 F g−1 at 2 mA cm−2 current density. The maximum energy density and power density of 23 W h kg−1 and 19 kW kg−1 are obtained for asymmetric supercapacitor. In addition, the asymmetric supercapacitor demonstrates the excellent flexibility with capability retention of 89% over bending at an angle of 180°.

To enhance the energy density and power performance of supercapacitors, the rational design and synthesis of active electrode materials with hierarchical mesoporous structure is highly desired. In the present work, fabrication of high-performance hierarchical mesoporous WO

Zinc oxide (ZnO) nanorod-based ultraviolet (UV) detectors have high responsivity at room temperature due to carrier generation assisted by the depletion region formed by oxygen adsorbed on the surface of nanorods. As such, the amount of oxygen adsorbed on the ZnO nanorod surface and the number of electron-hole pairs that reaches the depletion region on the surface can change the response of the detector. In this paper, the transient responses of metal-semiconductor-metal ZnO nanorod-based UV detectors based on a quasi-symmetric Wheatstone bridge configuration were investigated. Responsivity, defined as the ratio of the Wheatstone bridge detector output current to the total power of the UV light incident on the active area of the detector, as high as 54 A/W was obtained in some of these UV detectors at 30 °C. It was found that the responsivity and the temperature effects on the UV response of the Wheatstone bridge ZnO nanorod UV detectors can be tailored by the difference in the diameters and lengths of the rods grown in the two quadrants.

The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO

To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices.

Mac(metal assisted chemical) etching is a simple, low-cost and anisotropic etching method to make Si NWs (silicon nanowires). In this method, smaller surface area is damaged co mpared to dry etching process, either. Mac etching uses a combination of an oxide removal acid (e.g. HF), an oxidant (e.g. 6 6 ) with a noble metal (e.g. Au, Ag, Pt, etc.) as the catalyst. Typically, the Si beneath the nobl e metal is etched faster than the Si w ithout noble metal coverage by electron transfer mechanism at the noble metal /solution and the noble metal/Si interface. While Mac etching to build Si NWs, unwanted etching occurs in the bulk silicon layer resulting from excess hole diffusion caused by the increase in hole concentration at the nearby metal layers. In this study, we explored the ratio of oxidant to oxide removal acid in the Mac etching solution that is most effective in etching the Si underneath the noble metal layer suppressing the unwanted etching. At the optimized ratio, Si NWs were fabr icated at a faster rate with good uniformity Keywords: Metal assisted chemical etching, silicon nanowires, etching rate

III-V compound semiconductors seem to be the ideal materials for photovoltaic devices because they exhibit fast carrier velocity. III-V compound semiconductors, however, are unfavorable materials to be commercialized on large scale photovoltaic devices because of their high material cost. The textured surface shows the potential to increase the performance of solar cells because of the properties such as high absorption and longer light path length. These properties can overcome the disadvantage of the III-V compound semiconductors through thin thickness use when producing solar cells. In this study, we demonstrate that textured surfaces on InP formed by nano-sphere lithography and plasma etching process can enhance the absorption effectively in comparison with planar surface. The power conversion efficiency of InP solar cells using the textured InP and the aluminum doped zinc oxide was achieved up to 8%.

Recent studies have shown that zinc oxide (ZnO)-based ultraviolet (UV) photodetectors have better sensitivity and can be fabricated cheaply and compactly. To know whether the responsivity of these types of UV photodetectors can be improved by manipulating the dimension of the electrodes and length of the nanorods, we investigated the dependence of dark current and responsivity of the metal-semiconductor-metal (MSM)-type ZnO detector on those factors. The MSM ZnO nanorods based detector was designed compactly by arranging the interdigitated electrodes in a square form resembling a Wheatstone bridge where ZnO nanorods with diameters ranging from 20 to 70 nm were prepared by hydrolysis method. The crystallinity and surface morphology of the rods determined using X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively, are also discussed here. We observed that the responsivity of the detector measured for a UV wavelength of 365 nm depends on the spacing between electrodes, width of the electrode, and length of the nanorod.

Humidity sensors based on ZnO nanorods (NRs) have been developed using a Wheatstone bride (WB) configuration, where the ZnO NRs were selectively grown onto the one quadrant of the WB circuit. It turns out that the WB-based sensor possesses superior performances in terms of response and recovery time, and thermal stability in comparison with conventional types of resistive sensors. Thus, the WB sensor exhibits a fast response and recovery time (~1 s), and temperature-invariant behaviors over a broad range of temperatures up to 180 °C, which is likely because of the self-calibrating and error correction capabilities of the WB circuit itself.

This paper describes a method of detecting organic compounds in water using an ultraviolet LED (280 nm) spectroscopy system and a photodetector. The LED spectroscopy system showed a high correlation between the concentration of the prepared potassium hydrogen phthalate and that calculated by multiple linear regression, indicating an adjusted coefficient of determination ranging from 0.953–0.993. In addition, a comparison between the performance of the spectroscopy system and the total organic carbon analyzer indicated that the difference in concentration was small. Based on the close correlation between the spectroscopy and photodetector absorbance values, organic measurement with a photodetector could be configured for monitoring.

Field-controllable pentacene-semiconductor-based strain sensors were fabricated with hybrid gate dielectrics using polyvinyl phenol (PVP) and high-k inorganic tantalum pentoxide (Ta2O5) onto polyethylene naphthalate films. The Ta2O5 gate-dielectric layer combined with a thin PVP layer to form very smooth and hydrophobic surfaces turns out to improve the molecular structures of pentacene films significantly. The PVP-Ta2O5 hybrid-gate-dielectric films exhibit a high dielectric constant of 19.27 and a leakage-current density of as low as 100 nA/cm2 . The sensors employing a thin-film-transistor-like Wheatstone bridge configuration able to operate at reduced voltage (~ 4 V) show good device characteristics with a field-effect mobility of 1.89 cm2/V · s and a threshold voltage of -0.5 V. The strain sensor characterized with bending at 45° with respect to the bridge bias direction with different bending radii of 50-, 40-, 30-, 20-, and 8-mm displays output signals improved in linearity in a low range of operating voltages.

Variations in concentrations of ions in biological systems can be important events in the onset of a physiological disorder. In an episode of myocardial ischemia, acidosis and elevation of potassium ion concentration has been observed in the extra-cellular matrix of the myocardium. As a spectrum of markers, they can help detect onset of ischemia as well as infarctions. In this study, Flexible Organic Ion-Sensitive Field-Effect Transistors (ISFETs) have been characterized to detect Ischemia-like variations in pH and potassium ion concentration. Detection capabilities, of the sensors, have been shown as pure chemical concentration to current signal transduction of the ISFET. Independent of peripheral amplifier-converter circuits, they are standalone sensors. The sensors have been evaluated for their sensitivity and signal resolution. Calibration expression, following a thermo-electric model for device operation, represents an explicit relations between transistor drain current and ion concentrations. Signal conditioning, by normalization, has been attempted to make the calibration expression explicit in ion-concentration. Finally a reliable detection strategy, in differential mode, is proposed for a reference electrode free device.

Postannealing effects on pentacene thin film transistors (TFTs) are discussed correlating the pentacene film morphology, the crystalline polymorph, and the electronic transport. The bulk phase thermally induced in pentacene during postannealing treatment is found to be another main cause detrimental to the carrier transport of TFTs. In addition, it turns out that encapsulation of the TFTs using polyvinyl alcohol helps to improve the thermal stability by retarding the onset of the bulk phase in pentacene.

Determination of Organic compound concentration in water – is an imperative key to the control of water quality since it provide important information on pollution control of water supply. This work propose an optical sensor system where the organic compound concentration in water is determined using LED light(280nm). The absorbance was quantified according to the high, low and fine concentration of organic compound by means of linear regression modeling.

Advances in smart sensors, miniaturization, and related technologies leading to the emergence of smart fabrics are prerequisites to the construction of a point-of-care (POC) system for continuous health monitoring and illness prevention. Low manufacturing cost, light weight, portability and flexibility are among the requirements for smart sensors when embedded into smart fabrics. Organic semiconductor technology has recently been envisioned to meet these requirements, and to encourage the development of organic semiconductor based sensors because of its low process temperature and potential for very low cost manufacturing. In this paper, we present flexible sensors based on an organic semiconductor capable of measuring physiological parameters such as strain and temperature, adopting pentacene thin film transistors (TFTs) and Wheatstone bridge structures. It is expected that these sensors, integrated into textile structures, will enable real time POC monitoring of a patient's respiration rate, skin temperature, body heat flow and body temperature at an early stage.

This paper presents the design, fabrication, and experimental results of a 1 : 4 monolithic power distribution network for Ku-band array antenna applications. The network integrated on a high-resistivity silicon (HRS) substrate surface stabilized by polysilicon consists of three Wilkinson power dividers, four dc blocking filters, and four coplanar waveguide (CPW)-to-microstrip (MS) transitions. Each output ports are fed with a barium-strontium-titanate phase shifter. It is found that the introduction of the polysilicon layer between the oxide and HRS reduces RF losses significantly, which will enable the monolithic integration of high-power controller modules onto silicon because of the existence of the oxide layer, preventing any degradation of RF performances. The individual components show insertion losses ranging from 0.4 to 2.6 dB at 15 GHz, and the interconnecting CPW lines result in a loss of 0.064 dB/mm. This network was successfully integrated with MS patch antennas monolithically, showing good performance of 32-dB return loss at 14.85 GHz, and 10/spl deg/ beam-steering capability.

Design and experimental results of a surface acoustic wave (SAW) microsensor with polymer microfluidic cell for the sensing and identification of liquids is presented in this paper. This microsensor, which is a part of a smart tongue–nose system, uses a horizontally polarized SAW (SH-SAW) for the detection and identification of liquids. The SH-SAW microsensors are fabricated on 36°-rotated Y-cut X-propagating LiTaO3 (36YX.LT) substrate. This design consists of a dual-delay-line configuration in which one line is free and other one is metallized and shielded. Polymer microfluidic cells were designed and fabricated on top of it using a microstereolithography system to avoid dielectric loading of the IDTs by liquid which leads to unwanted dielectric sensitivity to the sensor. Due to the high electromechanical coupling of the 36YX.LT substrate, it could detect differences in electrical properties and hence distinguish different liquids. It is clear from these results that the microsensor based on 36YX.LT is an effective liquid identification system for the electronic tongue application.

An improved design for a distributed micro-electromechanical system phase shifter, periodically loaded with polymer bridges, is presented in this note. The phase shifter, fabricated on a quartz substrate, is capable of continuous change in phase up to about 90° (at 15 GHz) with a maximum actuation voltage of 20 V. Modifications in the present design include the use of a dielectric layer to prevent breakdown as well as to reduce the actuation voltage requirement, and a reduction in the bridge height and thickness. It has been shown that polymer materials by themselves can reduce the actuation voltage due to their low Young's modulus.

A lift-off process for direct photolithographic top-contact organic thin-film transistors (TFTs) has been developed using a bilayer of polyvinyl alcohol and SU8. Top-contact pentacene TFTs fabricated by this method, with a fixed channel width of 300 μm but different channel lengths varying from 10 to 80 μm, exhibited mobility values in the range of 0.01-0.03 cm2/V·s with the average of 0.021 ± 0.007 cm2/V·s. It is expected that the adoption of SU8 with a high aspect ratio enables the easy fabrication of submicrometer channel devices, giving rise to improved carrier transport characteristics.

In this paper, we illustrate an innovative detection method integrating hybrid sensors for motorized wheelchairs. By recognizing its surrounding circumstance, it can prevent accidents as well as provide convenience for users. Its sensors are designed to sense obstacles so that the technology is able to control motors to avoid collision or turning over. Using the 8 infrared distance sensors detect 360° of an obstacle. In addition, the controlling of motor’s speed based on the distance can avoid obstacle collision safely.