Comb Electrodes Research Articles

De Novo Synthesis of Free-Standing Flexible 2D Intercalated Nanofilm Uniform over Tens of cm2.

Of a variety of intercalated materials, 2D intercalated systems have attracted much attention both as materials per se, and as a platform to study atoms and molecules confined among nanometric layers. High-precision fabrication of such structures has, however, been a difficult task using the conventional top-down and bottom-up approaches. The de novo synthesis of a 3-nm-thick nanofilm intercalating a hydrogen-bonded network between two layers of fullerene molecules is reported here. The two-layered film can be further laminated into a multiply film either in situ or by sequential lamination. The 3 nm film forms uniformly over an area of several tens of cm2 at an air/water interface and can be transferred to either flat or perforated substrates. A free-standing film in air prepared by transfer to a gold comb electrode shows proton conductivity up to 1.4× 10-4 S cm-1 . Electron-dose-dependent reversible bending of a free-standing 6-nm-thick nanofilm hung in a vacuum is observed under electron beam irradiation.

A Novel Technique for Determination of Residual Direct-Current Voltage of Liquid Crystal Cells with Vertical and In-Plane Electric Fields

Generation of residual direct-current (DC) voltage (VrDC) induces serious image sticking of liquid crystal displays (LCDs). In this study, a novel technique to determine the VrDC of LC cells is proposed. We found that the VrDC could be determined from a current-voltage (I-V) curve obtained by the application of triangular voltage. In the case of a vertically aligned twisted nematic (VTN) mode LC cell, where a vertical electric field is applied, the I-V curve shows maximum and minimum current peaks owing to rotation of an LC director, and the VrDC is able to be determined from an average value of the two peaks. On the other hand, in the case of a fringe field switching (FFS) mode LC cell, where an in-plane (lateral) electric field is applied from comb electrodes, the current peaks derived from the rotation of the LC director do not appear. Therefore, we could not adopt the same way with that of the VTN mode LC cell. However, we found that there were two minimum current peaks derived from minimum capacitances of the FFS mode LC cell, and could determine the VrDC by using these two current peaks. The proposed technique would be useful for the evaluation of the VrDC of the LCDs, where the electric field is applied both vertically and laterally.

Chemosensitive Thin Films Active to Ammonia Vapours.

The paper presents various dispersive systems developed for sensing toxic substance—ammonia. Polycarbonate dissolved in methylene chloride was used as a polymer matrix, which was enriched with: multi-walled carbon nanotubes (MWCNs), reduced graphene oxide (rGO) and conductive polymer (polyaniline—PANi). Dispersive systems were applied to the prefabricated substrates with comb electrodes by two methods: spraying and drop-casting, forming an active chemosensitive to ammonia vapours films. The spraying method involved applying the dispersion to the substrate by an aerograph for a specific time, whereas drop-casting involves depositing of the produced dispersive systems using a precision automatic pipette. The electrical responses of the obtained films were examined for nominal concentrations of ammonia vapours. Different types of dispersions with various composition were tested, the relationships between individual compounds and ammonia were analysed and the most promising dispersions were selected. Sensor containing rGO deposited by drop-casting revealed the highest change in the resistance (14.21%).

Human Body Parts Proximity Measurement Using Distributed Tactile Robotic Skin.

Safety in human–machine cooperation is the current challenge in robotics. Safe human–robot interaction requires the development of sensors that detect human presence in the robot’s workspace. Detection of this presence should occur before the physical collision of the robot with the human. Human to robot proximity detection should be very fast, allowing machine elements deceleration to velocities safe for human–machine collision. The paper presents a new, low-cost design of distributed robotic skin, which allows real-time measurements of the human body parts proximity. The main advantages of the proposed solution are low cost of its implementation based on comb electrodes matrix and real-time operation due to fast and simple electronic design. The main contribution is the new idea of measuring the distance to human body parts by measuring the operating frequency of a rectangular signal generator, which depends on the capacity of the open capacitor. This capacitor is formed between the comb electrodes matrix and a reference plate located next to the matrix. The capacitance of the open capacitor changes if a human body part is in vicinity. The application of the developed device can be very wide. For example, in the field of cooperative robots, it can lead to the improvement of human–machine interfaces and increased safety of human–machine cooperation. The proposed construction can help to meet the increasing requirements for cooperative robots.

Gas temperature spatial distribution in air corona discharge with plane comb of metal rod electrodes derived from schlieren images

Gas temperature fields in the air corona discharge with a plane comb electrode system have been determined for the negative and positive polarities of the applied voltage. Highly sensitive schlieren technique used in the study allowed detecting a temperature change in tenths of a degree centigrade at room temperature of the gas flow. The obtained results suggest that the gas in the studied electrode system does not undergo heating at the given range of working parameters.

Fully Electronically Phase Modulation of Millimeter-Wave via Comb Electrodes and Liquid Crystal

This letter presented a nematic liquid crystal (LC) based metal-dielectric-metal structure to fully electronically modulate the reflection phase of electromagnetic waves. The demonstrated structure is composed of a thin LC layer sandwiched between copper comb electrodes and a single slotted reflection array. Based on a proper application of the external electric field, the whole process of nematic LC molecular orientation is controlled. The innovative feeding method can actively prealign and deflect the orientation of LC molecules. Experimental results show that the maximum reflection phase shift is 189.2° at 114.9 GHz. This letter provides a practical way of regulating LC-based terahertz devices. The proposed structure is a potential candidate for the reconfigurable reflectarray antennas.

Design and Analysis of a Hybrid Solar and Vibration Energy Harvester

Abstract The performance of the small-scale stand-alone energy harvesters can be improved by implementing a hybrid energy harvesting technique. This paper aims at presenting the design and characterization of a hybrid energy harvester that can simultaneously harvest energy from mechanical vibration and solar radiation by combining piezoelectric, electromagnetic, electrostatic, and photovoltaic mechanisms. The hybrid device consists of a small high-efficiency solar panel and a bimorph PZT cantilever beam having a cylindrical tip magnet and two sets of capacitors (comb electrodes) attached on two sides of an ASTM 6061 T-6 Aluminum substrate. All the transducing sections of the configuration are interconnected by a smart hybrid electric circuit having a common optimum load resistance, an energy storage, and a microcontroller to generate and store combined power output when subjected to transverse vibration and solar radiation. The initial bias-voltage input required for the electrostatic mechanism is either obtained from the photovoltaic system or taken from the storage through the microcontroller. Results for the maximum power output are obtained at the fundamental resonance frequency of the vibrating cantilever beam. As the hybrid design allows a combined power harvesting method, more power is generated with better conversion efficiency than those obtained by stand-alone mechanisms. In addition to the power calculation, the study includes a stress and fatigue analysis of the cantilever beam using the finite element method to investigate the stress-life criteria of the hybrid structure.

A Comb-Type Capacitive 2-FAL Sensor for Transformer Oil With Improved Sensitivity

A molecularly imprinted polymer (MIP)-based 2-furfuraldehyde (2-FAL, C5H4O2) capacitive sensor with improved sensitivity has been presented. The electrode is shaped into a novel comb structure to increase the fringe field capacitance which is responsible for sensing 2-FAL. The MIP solution sensitive to 2-FAL molecules is prepared using polydimethylsiloxane (PDMS) and is coated on the printed circuit board (PCB) comb electrode. When the sensor is dipped in the transformer oil, the 2-FAL molecules are adsorbed on the template cavity of the MIP. The adsorbed layer of 2-FAL is responsible for the change in capacitance of the sensor. The sensor is tested for six oil samples containing the 2-FAL concentration (0–20-ppm range) and shows a mean sensitivity ( $\mu $ ) of 0.184 pF/ppm with a standard deviation ( $\sigma $ ) 0.022 pF at 1 kHz. The sensor shows a linear result with the coefficient of correlation ( $R^{2}$ ) 0.998, and a maximum nonlinearity is 0.37% at 1 kHz in the 0–20-ppm range. The average repeatability of the sensor is ±0.12% over two weeks. Furthermore, the sensor is connected to a suitably designed electronic circuit based on the instrumentation amplifier for obtaining an electrical signal. The circuit gives an output voltage of 0.35 V/ppm at 1 kHz.

A two degrees of freedom comb capacitive-type accelerometer with low cross-axis sensitivity

In this paper, we report on a SOI-based comb capacitive-type accelerometer that senses acceleration in two lateral directions. The structure of the accelerometer was designed using a proof mass connected by four folded-beam springs, which are compliant to inertial displacement causing by attached acceleration in the two lateral directions. At the same time, the folded-beam springs enabled to suppress cross-talk causing by mechanical coupling from parasitic vibration modes. The differential capacitor sense structure was employed to eliminate common mode effects. The design of gap between comb fingers was also analyzed to find an optimally sensing comb electrode structure. The design of the accelerometer was carried out using the finite element analysis. The fabrication of the device was based on SOI-micromachining. The characteristics of the accelerometer have been investigated by a fully differential capacitive bridge interface using a sub-fF switched-capacitor integrator circuit. The sensitivities of the accelerometer in the two lateral directions were determined to be 6 and 5.5 fF/g, respectively. The cross-axis sensitivities of the accelerometer were less than 5%, which shows that the accelerometer can be used for measuring precisely acceleration in the two lateral directions. The accelerometer operates linearly in the range of investigated acceleration from 0 to 4g. The proposed accelerometer is expected for low-g applications.

A novel capacitive pressure sensor based on non-coplanar comb electrodes

Aiming at the problem of the nonlinearity and cavity leads of traditional capacitive pressure sensors, a non-coplanar comb electrode structure is proposed. The variation of the overlap areas of comb electrodes reflects the change in capacitance, thereby improving the linearity of the sensor. At the same time, the non-coplanar comb electrodes are designed outside the cavity, avoiding the extra fabrication process caused by the electrode leads. Theoretical analysis and finite element simulation analysis based on COMSOL software verified the feasibility of the proposed structure. The prototype sensor chip is successfully fabricated using only three masks based on a SOI wafer and hermetically sealed at 100 kPa. The fabricated sensor chip is tested to a sensitivity of 17aF/Pa and non-linearity error of 1.37% with the pressure ranged from 0 to 30 kPa.

Surface Micro-/Nanotextured Hybrid PEDOT:PSS-Silicon Photovoltaic Cells Employing Kirigami Graphene.

Kirigami graphene allows a two-dimensional material to transform into a three-dimensional structure, which constitutes an effective transparent electrode candidate for photovoltaic (PV) cells having a surface texture. The surface texture of an inverted pyramid was fabricated on a Si substrate using photolithography and wet etching, followed by metal-assisted chemical etching to obtain silicon nanowires on the surface of the inverted pyramid. Kirigami graphene with a cross-pattern array was prepared using photolithography and plasma etching on a copper foil. Then, kirigami graphene was transferred onto hybrid heterojunction PV cells with a poly(ethylene terephthalate)/silicone film. These cells consisted of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the p-type semiconductor, Si(100) as the inorganic n-type semiconductor, and a silver comb electrode on top of PEDOT:PSS. The conductivity of PEDOT:PSS was greatly improved. This improvement was significantly higher than that achieved by the continuous graphene sheet without a pattern. Transmission electron microscopy and Raman spectroscopy results revealed that the greater improvement with kirigami graphene was due to the larger contact area between PEDOT:PSS and graphene. By using two-layer graphene having a kirigami pattern, the power conversion efficiency, under simulated AM1.5G illumination conditions, was significantly augmented by up to 9.8% (from 10.03 to 11.01%).

A Resonant Pressure Sensor Based upon Electrostatically Comb Driven and Piezoresistively Sensed Lateral Resonators.

This study proposes a microfabricated resonant pressure sensor in which a pair of double-ended tuning forks were utilized as resonators where comb electrodes and single-crystal silicon-based piezoresistors were used for electrostatic excitation and piezoresistive detection, respectively. In operations, pressures under measurements deform the pressure-sensitive diaphragm to cause stress variations of two resonators distributed on the central and side positions of the pressure-sensitive diaphragm, where the corresponding changes of the intrinsic resonant frequencies are then captured piezoresistively. The developed resonant pressure sensors were fabricated based on MEMS with open-loop and closed-loop characterizations conducted. Key sensing parameters including quality factors, differential pressure/temperature sensitivities and fitting errors were quantified as higher than 17,000, 48.24 Hz/kPa, 0.15 Hz/°C and better than 0.01% F.S. (140 kpa), respectively. In comparison to previously reported resonant pressure sensors driven by parallel-plate electrodes, the developed sensor in this study is featured with a lower temperature sensitivity and a higher stability.

A novel multiple-axis MEMS gyroscope-accelerometer with decoupling frames

PurposeTechnological capabilities of manufacturing microelectromechanical system (MEMS) gyroscopes are still insufficient if compared to manufacturing high-efficient gyroscopes and accelerometers. This creates weaknesses in their mechanical structure and restrictions in the measurement accuracy, stability and reliability of MEMS gyroscopes and accelerometers. This paper aims to develop a new architectural solutions for optimization of MEMS gyroscopes and accelerometers and propose a multi-axis MEMS inertial module combining the functions of gyroscope and accelerometer.Design/methodology/approachThe finite element modeling (FEM) and the modal analysis in FEM are used for sensing, drive and control electrode capacitances of the multi-axis MEMS inertial module with the proposed new architecture. The description is given to its step-by-step process of manufacturing. Algorithms are developed to detect its angular rates and linear acceleration along three Cartesian axes.FindingsExperimental results are obtained for eigenfrequencies and capacitances of sensing, drive and control electrodes for 50 manufactured prototypes of the silicon electromechanical sensor (SES). For 42 SES prototypes, a good match is observed between the calculated and simulated capacitance values of comb electrodes. Thus, the mean-square deviation is not over 20 per cent. The maximum difference between the calculated and simulated eigenfrequencies in the drive channel of 11 SES prototypes is not over 3 per cent. The same difference is detected for eigenfrequencies in the first sensing channel of 17 SES prototypes.Originality/valueThis study shows a way to design and optimize the structure and theoretical background for the development of the MEMS inertial module combining the functions of gyroscope and accelerometer. The obtained results will improve and expand the manufacturing technology of MEMS gyroscopes and accelerometers.

Low sunlight concentration properties of InAs ultrahigh-density quantum-dot solar cells

InAs ultrahigh-density quantum-dot (UHD-QD) solar cells with type-I GaAs or type-II GaAsSb capping layers were fabricated by molecular beam epitaxy. The solar cell properties of these UHD-QD cells were measured as a function of quasi-sunlight concentration (QX) and were compared with that of the GaAs reference cell. For UHD-QD cells, the reduction of fill factor at high QX was suppressed by the low resistance of those cells, despite the wide separation width of 500 μm between comb electrodes. The open circuit voltage increased logarithmically with increasing QX, and the diode ideal factor was especially close to 1 for the type-II UHD-QD cell. These results could be mainly explained by carrier separation and lateral carrier transport through the UHD-QD layer. As a result, power conversion efficiency of UHD-QD cells increased with increasing QX and exceeded that of GaAs reference cell at over 4 suns in QX.

Design of capacitance based on interdigitated electrode for BioMEMS sensor application

In this paper present, an electrostatic actuation mechanism based on the interdigitated electrode for the Biomedical Micro Electro Mechanical Systems (Bio-MEMS) sensors was mainly used for sensing or actuation in analytical and different detection applications. One of the main things interdigitated electrode (IDE) for capacitance derived from multiple electrode pairs has been connected in parallel with wide proof mass, folded spring beam attached as anchor in the sensor construction. The total capacitance was a sum of capacitance contributed by neighbouring electrodes. Hence the opposite walls of comb electrodes in the overlapping region form a parallel plate capacitor and contribute a capacitance C easily analyzed with fringe capacitance can be estimated to analytically difficult one. However, the nearly accurate way to estimate for the fringe capacitance is by using the finite element method (FEM). The major importance of the geometric dimensions on interdigitated electrode sensors are studied with an analytical model. The design of capacitive based IDE sensors are simulated and demonstrated on visualizing of the electrical properties by COMSOL Multiphysics software.

A power-density-enhanced MEMS electrostatic energy harvester with symmetrized high-aspect ratio comb electrodes

In this paper, we experimentally demonstrate a new approach to improve the output power of electrostatic energy harvester with an electret skin. A symmetric three-ports comb-electrode mechanism is used to reduce the binding electrostatic force, thereby allowing a smooth mechanical motion of the suspended electrodes of a high-aspect ratio in a small acceleration range. Given the same device footprint, two energy harvesters having different aspect ratios are prepared to compare the power generation performances. The output power is increased 6.4 times by increasing the aspect-ratio from the 7.1 to 33.3. At the same time, the volumetric power density is also improved from 62.5 μW cm−3 to 270.2 μW cm−3. These results suggest a possibility to further enhance the aspect ratio to shorten the charge time of a large storage capacitor for autonomous internet of things wireless sensor node.

Prototype of energy harvesting door handles using polymer nanocomposite

Here in, we report on a prototype for energy harvesting from door handles for harnessing mechanical energy used during the opening and closure operation of doors. Three different morphologies of zinc oxide (ZnO) nanoforms namely ZnO nanorods (ZnO R), ZnO nanocrystallite (ZnO P) and ZnO nanoneedles (ZnO W) are blended at an optimum concentration of 10% with polydimethyl siloxane (PDMS) polymer. The frictional, triboelectric and converse piezoresponse of these films were studied using derived modes of atomic force microscopy. Three different structures of devices were fabricated by spin-coating, solution casting and tape casting techniques. Dispersion filler, graphite oxide (GO) nanosheets are added to the composite with superior electrical property. The device with solution casting was tested for various mechanical inputs, with and without external resistive loads connected. The device yielded an output voltage of 6.25 V on each approach-release operation. The device shows a power density of 0.73 µW/cm2 during an impact of 5 N. A laboratory prototype of door handle energy harvester was prepared on a comb electrode by tape casting the polymer nanocomposite recipe of PDMS + 10% ZnO W + 10% GO and generated a power density of 0.17 nW/cm2 by charging a 1F commercial capacitor.

Operational Features of MEMS with an Even Number of Electrodes

The results of investigations on the influence of the nonparallelism of electrodes on electromechanical interactions in imbalanced Micro Electro Mechanical Systems (MEMS) with comb electrode structures in the modes with a controllable voltage and charge are presented. The formulas for the calculation of the potential energy, electrostatic force, critical voltage, critical charge, and the magnitude of critical displacement of a movable electrode under different inclinations of the electrodes, which are necessary for the MEMS design, taking into account their real design features, are derived. It was stated that increasing the mutual inclination and the number of electrodes reduces the modulation depth of the capacitance Cmax/Cmin of the imbalanced capacitors with nonparallel electrodes, which can significantly limit the achievable modulation depth of the capacitance of tunable MEMS, especially when there are a large number of electrodes. It is revealed that in imbalanced MEMS, in the case of controllable voltage, when increasing the relative inclination of the electrodes, the electrostatic attraction force between charged electrodes decreases and the magnitudes of the critical voltage and displacement increase. Increasing the number of electrodes of an imbalanced capacitor will lead to a decrease in the range of the controllable displacement of the movable electrodes and the magnitude of the critical voltage. It is stated that under an invariable charge and nonparallel electrodes in imbalanced MEMS with a comb electrode structure a pull-in effect appears. When increasing the relative inclination of the electrodes, the electrostatic attraction force between the charged electrodes increases and the quantities of the critical charge and displacement decrease. When increasing the number of electrodes in imbalanced MEMS with a comb electrode structure in the invariable charge mode, the value of the critical displacement decreases monotonically and the magnitude of the critical charge rises.

Liquid-crystal-integrated metadevice: towards active multifunctional terahertz wave manipulations.

Active terahertz elements with multifunction are highly expected in security screening, nondestructive evaluation, and wireless communications. Here, we propose an innovative terahertz metadevice that exhibits distinguishing functions for transmitted and reflected waves. The device is composed of a thin liquid crystal layer sandwiched by Au comb electrodes and a dual-ring resonator array. For transmission mode, the metadevice manifests the electromagnetically induced transparency analog. For reflection mode, it works as a perfect absorber. The comb electrodes actuate the in-plane switching of liquid crystals, making the metadevice actively tuned. 60GHz frequency tuning of an electromagnetically induced transparency analog and 15% modulation depth of the absorption are demonstrated. Such modulations can be realized in the millisecond scale. The in-plane switching driving mode avoids the electrode connections among separate resonators, thus freeing the design of the metadevice. The proposed work may pave a bright road towards various active multifunctional terahertz apparatuses.

Bacteria Sensors Based on Interdigitated Silicon Nanowires Electrodes

The detection of pathogenic bacteria in food, water and air is an important issue because of its critical impact on public health, especially with the emergence of multi-resistant bacteria. Standard microbiological methods of bacterial culture impose deadlines that can slow down the establishment of means of protocols against contaminations. In this context, a strategy is to develop ultrasensitive sensors based on silicon nanowires networks for rapid detection of bacteria. Indeed, the nanowires have a large contact surface allowing preferential interactions with the bacteria. Resistors based on silicon nanowires used as bacteria sensors are fabricated using conventional silicon technologies. The nanowires are obtained by the VLS (Liquid Solid Vapor) method using gold as catalyst and the interdigited comb electrodes are made of high doped polycrystalline silicon. The bacteria are preferentially attached to the nanowire network (fig. 1a and b). The electrical characterization of the the devices shows that the current through the resistors increases significantly due to the presence of bacteria (fig. 1c). The results show the potential use of the resistors, with the nanowires as sensitive units, for the detection of bacteria. Figure 1