Comb-shaped Electrodes Research Articles

Acetylene Sensing Characteristics of SnO<sub>2</sub> Nanowires

SnO2 nanowires have been fabricated using thermal evaporation of the mixed powders of SnO2 and active carbon with Au catalysts. The morphology and structure of the prepared nanowires are determined on the basis of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDS), x-ray diffraction (XRD) and transmission electron microscopy (TEM). The comb-shape interdigitating electrode made by MEMS technology is used to auxiliary investigating the gas sensing performance of the synthesized SnO2 nanowires. The SnO2 nanowires have sensing response to acetylene concentration of 1000 ppm under operated temperature of 300°C. The gas sensing mechanism is attributed to the gas adsorption and desorption processes occurring on the surface of the gas sensing material.

In2O3 Nanotower Hydrogen Gas Sensors Based on Both Schottky Junction and Thermoelectronic Emission

Indium oxide (In2O3) tower-shaped nanostructure gas sensors have been fabricated on Cr comb-shaped interdigitating electrodes with relatively narrower interspace of 1.5 μm using thermal evaporation of the mixed powders of In2O3 and active carbon. The Schottky contact between the In2O3 nanotower and the Cr comb-shaped interdigitating electrode forms the Cr/In2O3 nanotower Schottky diode, and the corresponding temperature-dependent I-V characteristics have been measured. The diode exhibits a low Schottky barrier height of 0.45 eV and ideality factor of 2.93 at room temperature. The In2O3 nanotower gas sensors have excellent gas-sensing characteristics to hydrogen concentration ranging from 2 to 1000 ppm at operating temperature of 120–275 °C, such as high response (83 % at 240 °C to 1000 ppm H2), good selectivity (response to H2, CH4, C2H2, and C3H8), and small deviation from the ideal value of power exponent β (0.48578 at 240 °C). The sensors show fine long-term stability during exposure to 1000 ppm H2 under operating temperature of 240 °C in 30 days. Lots of oxygen vacancies and chemisorbed oxygen ions existing in the In2O3 nanotowers according to the x-ray photoelectron spectroscopy (XPS) results, the change of Schottky barrier height in the Cr/In2O3 Schottky junction, and the thermoelectronic emission due to the contact between two In2O3 nanotowers mainly contribute for the H2 sensing mechanism. The growth mechanism of the In2O3 nanotowers can be described to be the Vapor-Solid (VS) process.

Evaluation of distributed-type inorganic electroluminescence devices using comb-shaped electrodes

We deposited comb-shaped metal electrodes with narrow gaps on a glass substrate and succeeded in achieving a high electric field intensity. Using conventional structures, this result could only be achieved by applying transparent electrodes, and in this study, we used a comb-shaped metal (Au) electrode and a comb-shaped indium tin oxide (ITO) electrode. When we measured the luminescence from the opposite side of the comb-shaped electrodes, at 15 V/µm, the luminance in the ITO electrode sample was identical (92–95 cd/m2) to that measured from the side of the comb-shaped electrodes. Conversely, a 111-cd/m2 brightness (a 1.9-fold increase) was observed from the opposite side of the Au electrode. Electrode transmittance was unnecessary when the luminescence was observed from the opposite side of the comb-shaped electrodes, and by using metals such as Au, it was possible to produce a display that did not require transparent electrodes. Finally, we simulated the electric field distribution for the inorganic electroluminescence (EL) using comb-shaped electrodes by semiconductor device simulator Atlas.

フリンジ電界により駆動する静電アクチュエータの動作原理の提案

This paper proposes a novel electrostatic actuator driven by fringe electric field generated between comb-shaped electrodes on a substrate of stator. Ferroelectric teeth of floating mass on the stator are polarized by means of fringe electric field. The mass is laterally moved within the one pitch of the comb-shape electrode thanks to the electrostatic force generated between polarized charge of the tooth and that inside the electrode. Narrow pitch of comb-shaped electrodes is possible, since fluororesin is deposited on the electrode for preventing the discharge between the adjacent electrodes. The narrower pitch increases the electric field even if the applied voltage between two electrodes is rather low, achieving the higher output force. Therefore, the proposed actuator can work at low input voltage. A practical actuator was fabricated, the electrode width and pitch of which were 20 and 80μm, respectively. When the voltage of 300V was applied between the two electrodes, the maximum displacement and force were 20μm and 4mN, respectively. The force per unit area and square of voltage was 0.8N/(kV2·m2), which is not less than those of reported typical capacitive actuators.

PH sensitivity of emeraldine salt polyaniline and poly(vinyl butyral) blend

pH sensitivity of emeraldine salt polyaniline (ES-PANI) and poly(vinyl butyral) (PVB) blend film was investigated. This blend film can be used as a pH sensing element in new-type pH sensors to replace traditional instruments based on fragile glass electrodes for pH measurement of water in aquaculture farming. Structural and optical characteristic of PANI were studied by Fourier transform infrared spectroscopy (FTIR) and ultraviolet visible spectroscopy (UV–vis). Electrical characterization of ES-PANI:PVB blend films versus pH was performed with chemiresistors fabricated by micro-lithography. A ES-PANI:PVB layer was drop-coated on comb-shaped platinum electrodes patterned on SiO2/Si substrates. Scanning electron microscope (SEM) and optical microscope were used to investigate morphology of the fabricated platinum electrodes and the coated polymer blend films. I–V measurements of the polymer-coated chemiresistors were performed at very low relative humidity after the polymer films were exposed to pH 1–8. The results showed that logarithm of electrical resistance of the ES-PANI:PVB films increased almost linearly as pH increased from 1 to 8. The initial results showed that the PANI blend-coated chemiresistors can be used as pH sensors for water quality monitoring.

Parallel polymer tandem solar cells containing comb-shaped common electrodes

The poor optical transmittance of common electrodes based on thin metal films in three-terminal parallel tandem solar cells poses a major hindrance to attaining high power conversion efficiency (PCE). High optical transmittance and electrical conductivity of the common electrodes are crucial to achieving high PCE. We report a parallel polymer tandem solar cell that contains a comb-shaped electrode (CSE) based on gold (Au), which provides both high optical transmittance and low electrical resistance. We studied the performance of the tandem cell devices as a function of number of teeth N of the CSEs with tooth dimensions of 50μm (width)×30nm (thickness)×3mm (length). A maximum PCE of 3.72%, which amounts to 85% of the PCE of an ideal tandem cell, was obtained with N=5 in the tandem structure ITO/ZnO/P3HT:PC71BM/PEDOT:PSS+Triton X-100/Au CSE/PEDOT:PSS/PTB7:PC71BM/LiF/Al, where ITO is indium tin oxide, P3HT is regio-regular poly(3-hexylthiophene), PC71BM is [6,6]-phenyl-C71-butyric acid methyl ester, PEDOT:PSS is poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid), Triton X-100 is 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol, and PTB7 is thieno[3,4-b]-thiophene/benzodithiophene. The combination of high optical transmittance and low electrical resistance of the Au CSE and the conductivity-enhanced hole transport layer of PEDOT:PSS+Triton X-100 resulted in a 20% higher PCE than that obtained using conventional common electrodes based on 12nm thick Au films. We analyzed the resistance of the combined anode, which consists of the Au CSE and the PEDOT:PSS+Triton X-100 film, theoretically. The theoretical results enabled us to predict the optimum number of teeth required for the Au CSEs to give the maximum PCE in three-terminal parallel tandem cells, and showed excellent agreement with the experimental results.

Novel active comb-shaped dry electrode for EEG measurement in hairy site.

Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode.

Investigation on edge fringing effect and oxide thickness dependence of inversion current in metal-oxide-semiconductor tunneling diodes with comb-shaped electrodes

A particular edge-dependent inversion current behavior of metal-oxide-semiconductor (MOS) tunneling diodes was investigated utilizing square and comb-shaped electrodes. The inversion tunneling current exhibits the strong dependence on the tooth size of comb-shaped electrodes and oxide thickness. Detailed illustrations of current conduction mechanism are developed by simulation and experimental measurement results. It is found that the electron diffusion current and Schottky barrier height lowering for hole tunneling current both contribute on inversion current conduction. In MOS tunneling photodiode applications, the photoresponse can be improved by decreasing SiO2 thickness and using comb-shaped electrodes with smaller tooth spacing. Meantime, the high and steady photosensitivity can also be approached by introducing HfO2 into dielectric stacks.

Self-assembled and Pd decorated Zn2SnO4/ZnO wire-sheet shape nano-heterostructures networks hydrogen gas sensors

Zn2SnO4/ZnO wire-sheet shape hetero-nanostructures (Zn2SnO4/ZnO HNS) networks gas sensors have been fabricated on Cr comb-shaped interdigitating electrodes with relatively narrower interspace of 1.5µm using thermal evaporation of the mixed powders of ZnO, SnO2 and active carbon with Au catalysts. The self-assembly grown sensors of Zn2SnO4/ZnO HNS networks have excellent gas sensing characteristics to hydrogen concentration ranging from 2 to 1000ppm at operating temperature of 120–300°C. Comparing with Zn2SnO4/ZnO HNS networks sensors, the Pd decorated Zn2SnO4/ZnO HNS (Pd-Zn2SnO4/ZnO HNS) networks sensors exhibit enhanced hydrogen sensing performance such as higher response (74% at 255°C to 1000ppm H2), less response time (15s at 270°C to 1000ppm H2), better selectivity (response to H2, C2H5OH, CH4, C2H2, CO, and C3H8), lower adsorption activation energy (12.72kJ/mol to 1000ppm H2) and smaller deviation from the ideal value of power exponent ß (0.49623 at 255°C). The enhanced sensing properties of the Pd-Zn2SnO4/ZnO HNS can be ascribed to an additional depletion layer at the interface between Pd nanoparticles and Zn2SnO4/ZnO HNS. Both sensors show fine long-term stability during exposure to 2–1000ppm H2 under relatively high operating temperature of 120–300°C in 50 days.

Direct growth of ZnO nanodisk networks with an exposed (0 0 0 1) facet on Au comb-shaped interdigitating electrodes and the enhanced gas-sensing property of polar {0 0 0 1} surfaces

ZnO nanodisk networks were grown directly on Au comb-shaped interdigitating electrodes on SiO2/Si substrate by thermal evaporation of a mixture of ZnCl2 and InCl3·4H2O at 450°C in air. The nanodisk has hexagonal shape with a side length of ∼1.8μm, a diagonal of ∼3.8μm and thickness 64-125nm. It grows mainly along 0 1 1¯ 0 directions, and is enclosed by ±(0001) top and bottom surfaces. The as-prepared ZnO nanodisks having mostly {0001} facets exhibit better gas-sensing performance for NH3, N(C2H5)3 and C2H5OH comparing to ZnO nanorods with 0 1 1¯ 0 facets. The sensor response measured at 300°C are 1.68, 11.84 and 10.19 for NH3, N(C2H5)3 and C2H5OH with concentration 5, 10 and 10ppm, respectively. The enhancement in the gas-sensing properties is mainly attributed to the exposed {0001} facets which provide more active sites for oxygen adsorption and subsequent reaction with the vapor than 1 0 1¯ 0 facets, and therefore improved response. The observation motivates us to further explore new synthetic methods to prepare other metal oxides with a high percentage of reactive facets with potential applications in gas sensors, photocatalysts, solar cells, and optoelectronic devices.

Self-Assembled Alcohol Sensor of In<sub>2</sub>O<sub>3 </sub>Nanorods

In2O3nanorods have been fabricated on Cr comb-shaped interdigitating electrodes using thermal evaporation of the mixed powders of In2O3and active carbon with Au catalysts. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The self-assembly grown sensors of In2O3nanorods have excellent performance in sensor response to alcohol concentration of 500 ppm under operated temperature of 300°C.

Characteristics of distributed-type inorganic electroluminescence panels with comb-shaped electrodes

We deposited comb electrodes with narrow gaps between the teeth on a glass substrate, thus realizing a high electric field intensity that cannot be achieved with conventional structures. Au electrodes are deposited to form a comb shape and then spin-coated with a phosphor layer obtained by mixing ZnS phosphor particles with resins in a certain ratio. An AC voltage was applied to the gaps between the teeth of the comb electrode to emit light, from which the luminance was measured for different electric field intensities. The luminance was not affected by the transmittance of the electrodes themselves when measured from the phosphor layer side. Therefore, it may be possible to produce a display that does not require transparent electrodes by using the phosphor layer side of a device with comb electrodes made of metals, such as Au, for the display.

Analysis on Magnetic Images of Solar Cell by Laser-SQUID Microscope

We have developed a laser-superconducting quantum interference device (laser-SQUID) microscope based on a scanning SQUID probe microscope with a laser excitation system. This microscope can image the local magnetic field distributions detected by the SQUID above a semiconducting sample, which is caused by the photocurrent from the laser excitation spot. In this study, we analyzed the laser-SQUID microscope images of a polycrystalline silicon solar cell equipped with comb-shaped top electrodes. Moreover, these images were obtained by using not only a sample-scanning mode but also a probe-scanning mode. In the sample-scanning mode, the images correspond to the changes of the magnetic field intensity against the positional changes of the laser spot over the sample. On the other hand, in the probe-scanning mode, the images correspond to the magnetic field distribution around a laser spot excited at a fixed position on the sample. Those results indicated that the photocurrent mainly reached the electrode neighbor to the laser spot, and diffused from the electrode to all the other electrodes. Due to the current flow along the electrodes, the image taken by the sample-scanning mode showed the gradually inclined background magnetic signal.

Design, fabrication and application of an SOI-based resonant electric field microsensor with coplanar comb-shaped electrodes

This paper presents a highly sensitive resonant electric field microsensor based on silicon on insulator (SOI) technology. To improve the electric field coupling effect, the microsensor uses coplanar shutter electrodes and sense electrodes. To obtain higher conversion gain, both electrodes adopt novel comb-shaped structures. A finite element method (FEM) was used to simulate and optimize the structures of the comb-shaped electrodes. The sensitivity model of the microsensor was analyzed by the conversion gain of the vibration-amplitude-to-charge variation. The resolution of the microsensor is approximately 40 V m−1 with an uncertainty of 1% for the dc field, while the resolution is better than 10 V m−1 for the 50 Hz ac field. The microsensors were packaged and assembled to form an electric field probe to measure the atmospheric electric field. The test results showed that the probe precisely detected the occurrence of thunderstorms, and the plotted data agreed well with those of the conventional electric field mill.

High-density poly(hexyl methacrylate) brushes offering a surface for near-zero azimuthal anchoring of liquid crystals at room temperature

High-density poly(hexyl methacrylate) (PHMA) brushes offered a near-zero azimuthal anchoring surface for nematic liquid crystals (NLCs) at room temperature. NLCs in a cell with PHMA-grafted substrates aligned along comb-shaped electrodes after a light push. The LC cell was driven at a threshold voltage five times lower than that of a conventional cell.

In situ growth of ZnO nanowires on Zn comb-shaped interdigitating electrodes and their photosensitive and gas-sensing characteristics

ZnO nanowires were grown in situ on Zn comb-shaped interdigitating electrodes by using a simple hydrothermal reaction of metallic Zn with Na2C2O4 in solution at 140°C. ZnO nanowires were bridged across the trenched electrodes. In this process, the “pick and place” method of nanowire integration was avoided. The self-assembly grown ZnO nanowires had excellent performance as a sensor to ultraviolet (UV) light, NH3 and N(C2H5)3. The Voutput value was about 0.6V in air, under UV illumination, however, it increased to 1.3V. The sensitivities at 260°C were 1.3 and 1.4 when the concentrations of NH3 and N(C2H5)3 gas were 0.5 and 0.9ppm, respectively. The performance of this kind of sensors could be further improved by increasing the quantity of the Zn electrodes.

Frequency-controlled deflection of spatial solitons in nematic liquid crystals

We demonstrate frequency-controlled angular steering of light-induced solitary waveguides using dual frequency nematic liquid crystals. Specially designed comb-shaped electrodes allow the maximization of the in-plane electro-optic angular deviation of the soliton Poynting vector, modulating the resulting walk-off up to an overall deflection of 13° when the frequency of the applied voltage goes from 1 to 100 kHz.

High-Yield Fabrication of Graphene Chemiresistors With Dielectrophoresis

We demonstrate a simple, low-cost, but effective approach to deposit graphene on silicon wafers with dielectrophoresis. With a comb-shaped electrode design, graphene sheets can be actively captured between electrodes. Dielectrophoresis proves effective in depositing a large-scale array of graphene on desired locations. The deposition of semiconducting single-walled carbon nanotubes (s-SWNTs) with the same approach is also studied to compare the two forms of carbon-based nanomaterials. The graphene deposition has a lower success rate (approximately 62%) than s-SWNTs (100%) to cover the comb fingers due to the 2-D sheet structure and larger dimensions of the material. The assembled graphene sheets can successfully bridge over the electrode gap to create functional, ready-to-use electronic devices. The dielectrophoretically deposited graphene is used as the semiconducting material in a liquid-gated field-effect transistor, and it demonstrates p-type characteristics with holes as the majority charge carriers. When used in two-terminal chemiresistors, the deposited graphene demonstrates high sensitivity toward pH values in liquid. The resistance of graphene is inversely proportional to the pH value of the solution in the range of 5-9 with the pH sensitivity of 17.5 Ω/decade. The high-precision, high-yield deposition provides a practical approach for the fabrication of future graphene electronic devices and sensors.

Optimized Electrode Geometry for an Improved Impedance Based Macroporous Silicon Bacteria Detector

This paper reports the optimization of electrode geometry on macroporous silicon biosensor for improved bacteria detection. Macroporous silicon of 8 μm thickness and 55% porosity has been fabricated on a 10-20 Ω-cm wafer using hydrofluoric acid and dimethyl sulfoxide. The electrode configurations selected for optimization are coplanar rectangular types with simple two-electrode, interdigitated comb finger-like electrode, and a combination of simple electrode and comb-shaped electrode designs. With these configurations, 14 different patterns have been generated with varying lengths and spacing within the technological constraints of low cost screen printing method of electrode fabrication with a wide range of effective exposed area from 0.04 to 0.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> by techniques from design of experiments. The sensitivity toward bacteria detection for all the patterns has been estimated by computation of an area utilization factor (AUF) which has been defined as the ratio of the effective area occupied by the captured bacteria to the effective exposed area available for capture. From the AUF values, eight patterns have been selected which are above a lower cut-off threshold for experimentation with E.coli O157 in the range of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CFU/ml to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> CFU/ml. It has been observed that the pattern with the highest AUF is capable of detecting 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CFU/ml E.coli O157 with a sensitivity of 11% without any pre-concentration which was not possible in the earlier reports of macroporous silicon.

Electric impedance sensing in cell-substrates for rapid and selective multipotential differentiation capacity monitoring of human mesenchymal stem cells

Biosensor systems which enable impedance measurements on adherent cell layers under label-free conditions are considered powerful tools for monitoring specific biological characteristics. A radio frequency identification-based sensor platform was adopted to characterize cultivation and differentiation of human bone marrow-derived multipotent stem cells (bmMSC) over periods of up to several days and weeks. Electric cell-substrate impedance sensing was achieved through fabrication of sensitive elements onto glass substrates which comprised two comb-shaped interdigitated gold electrodes covering an area of 1.8mm×2mm. The sensing systems were placed into the wells of a 6-well tissue culture plate, stacked onto a reader unit and could thus be handled and operated under sterile conditions. Continuous measurements were carried out with a sinusoidal voltage of 35mV at a frequency of 10kHz.After seeding of human bmMSC, this sensor was able to trace significant impedance changes contingent upon cell spreading and adhesion. The re-usable system was further proven suitable for live examination of cell-substrate attachment or continuous cell monitoring up to several weeks. Induction of either osteogenic or adipogenic differentiation could be validated in bmMSC cultures within a few days, in contrast to state-of-the-art protocols, which require several weeks of cultivation time. In the context of medical cell production in a GMP-compliant process, the here presented interdigitated electric microsensor technology allows the documentation of MSC quality in a fast, efficient and reliable fashion.