Pair Of Interdigitated Electrodes Research Articles

The electrohydrodynamic enhancement of heat transfer on interdigitated electrodes by a charge injection pump

Electrohydrodynamic pumps, as a representative type of nonmechanical pump, have received significant research attention due to their inherent advantages of having no moving parts and low power consumption. In particular, the planar charge injection pump has exhibited superior fluid driving performance, making it highly promising for applications in microscale flow driving and chip cooling. A sandwich structure pump with multiple pairs of planar interdigitated electrodes is numerically studied in this paper. The interaction of the flow, thermal, and electric fields is analyzed using the lattice Boltzmann method under different pump configurations, governing parameters, and convection mechanisms. The results reveal that the geometric configurations of the planar interdigitated electrodes have direct effects on the pumping performance and heat transfer rate. Specifically, an optimal configuration is achieved when the width of the collector is twice that of the emitter under two-pair electrode simulation conditions. More interestingly, competition between electric and thermal effects is observed, and the optimal threshold for heat transfer is found at an electric Rayleigh number of T = 300 for the considered cases. Finally, the interaction of the electric and thermal fields induces periodic oscillations. The single-vortex mechanism exhibits the longest oscillation period and inhibits heat transfer, while the multi-vortex mechanism has the shortest oscillation period and enhances heat transfer.

Self-powered wearable electrical stimulation patch with integrated triboelectric nanogenerator for tendinopathy treatment

Tendinopathy is a common musculoskeletal disease for which researchers have proposed various treatments but with limited efficacy. Here, we propose a self-powered wearable electrical stimulation (ES) patch with an integrated triboelectric nanogenerator (TENG) for tendinopathy treatment. The ES patch comprises a freeze-dried PVDF-TrFE/PA6 TENG and a pair of interdigital electrodes (IDTs). The bionically designed ES patch is attached directly to affected tendons. It undergoes deformation and friction during movement and generates pulsed electric output, which is then converted into an electric field via the IDTs to treat tendinopathy. In vitro experiments showed that the self-powered ES patch greatly increased mitochondrial function in degenerative tendon stem/progenitor cells (TSPCs) and promoted tenogenesis. In vivo experiments revealed that the ES patch significantly improved the gait motor function of tendinopathy rats, boosted collagen regeneration, and drastically reduced the degree of tissue inflammatory infiltration and recovery time. Our study demonstrated the great potential of wearable electrical stimulation patches for effectively treating tendinopathy.

Development of a compact impact two-degree-of-freedom linear-rotary piezoelectric motor using one piezoelectric actuator.

A compact impact two-degree-of-freedom linear-rotary piezoelectric motor is proposed using a single actuator. The proposed piezoelectric actuator has a pair of deformation counteracting helical interdigitated electrodes on its outside surface, which can be divided into two parts. When the two parts of the piezoelectric actuator are driving under the same driving voltage signals, the motor can realize independent linear motion. When the two parts of the piezoelectric actuator are driving under the driving voltage signals with opposite duty cycles, the motor can realize independent rotary motion. The fabricated piezoelectric motor can produce a maximum average linear velocity of 1.9 and -2.3 mm/s with a saw-shaped driving signal of 400Vp-p (peak-to-peak driving voltage) at 9kHz. Experiments also show that the fabricated piezoelectric motor can realize a maximum average rotary velocity of 2440 and -2235 mrad/s with a driving signal of 400Vp-p at 9kHz. The maximum load force and torque of the prototype are about 0.4 N and 1.5mNm, respectively. The proposed motor provides a wide driving frequency and realizes high velocity in both linear and rotary motions.

Development of a simultaneous electrorotation device with microwells for monitoring the rotation rates of multiple single cells upon chemical stimulation.

Here, we described a unique simultaneous electrorotation (ROT) device for monitoring the rotation rate of Jurkat cells via chemical stimulation without fluorescent labeling and an algorithm for estimating cell rotation rates. The device comprised two pairs of interdigitated array electrodes that were stacked orthogonally through a 20 μm-thick insulating layer with rectangular microwells. Four microelectrodes (two were patterned on the bottom of the microwells and the other two on the insulating layer) were arranged on each side of the rectangular microwells. The cells, which were trapped in the microwells, underwent ROT when AC voltages were applied to the four microelectrodes to generate a rotating electric field. These microwells maintained the cells even in fluid flows. Thereafter, the ROT rates of the trapped cells were estimated and monitored during the stimulation. We demonstrated the feasibility of estimating the chemical efficiency of cells by monitoring the ROT rates of the cells. After introducing a Jurkat cell suspension into the device, the cells were subjected to ROT by applying an AC signal. Further, the rotating cells were chemically stimulated by adding an ionomycin (a calcium ionophore)-containing aliquot. The ROT rate of the ionomycin-stimulated cells decreased gradually to 90% of the initial rate after 30 s. The ROT rate was reduced by an increase in membrane capacitance. Thus, our device enabled the simultaneous chemical stimulation-induced monitoring of the alterations in the membrane capacitances of many cells without fluorescent labeling.

Performance improvement in amorphous zinc tin oxide ultraviolet photodetectors using an asymmetric pair of interdigitated electrodes

Solar-blind ultraviolet (UV) photodetectors with an amorphous zinc−tin oxide (a-ZTO) sensing layer have been fabricated on alkali-free glass substrates by a sol-gel method and spin coating technique. The as-prepared a-ZTO semiconductor thin films are highly transparent (>88.5%) in the visible region and exhibit moderate electrical properties at room temperature. The effects of changes in the asymmetry ratio of the line-width of a pair of Al interdigitated electrodes on the photoelectrical characteristics of solution-processed a-ZTO metal−semiconductor−metal (MSM) UV photodetectors was investigated. These photodetector devices had good photosensing properties, and their current-voltage (I–V) characteristic exhibited obvious rectification behavior under UV light illumination when operated at bias voltages of -3 V–3 V. Experimental results showed that the responsivity and specific detectivity of the a-ZTO MSM photodetectors increased with increases in the asymmetry ratio of a pair of Al interdigital electrodes. The a-ZTO MSM UV photodetector operated at 3 V bias voltage had the best responsivity of 7.42 mA/W and the highest specific detectivity of 6.35 × 107 J when the asymmetry ratio of electrodes was 10:1.

Measuring orientation dynamics of carbon fibers by dielectric anisotropy in shear flows

Measuring orientation dynamics of carbon fibers is important for manufacturing high-performance composite materials, however, conventional methods fail to timely and non-destructively measure due to destructive sample preparation or complicated data processing from numerous fibers. Herein, we report a timely and non-destructive method that uses two pairs of interdigital electrodes to record dielectric anisotropy induced by carbon fibers orientation. As a proof-of-concept, orientation dynamics of carbon fibers is successfully characterized, the accuracy of which in measuring the final degree of orientation and dynamic orientation process is evidenced by theoretical calculations and optical observations. Experimental results reveal that increasing the fiber aspect ratios, viscosities of solvents and shear rates, could shorten orientation time or increase the final degree of orientation. Meanwhile, a modified model is proposed to explain orientation dynamics with a maximum error of 4.7%. This method has the potential for measuring the orientation dynamics of carbon fibers in the complex structure during processing.

Continuous electric field modeling of Macro-Fiber Composites for actuation and energy harvesting

This paper presents a new low-order electric field model for Macro-Fiber Composite devices with interdigitated electrodes. Specifically, the paper proposes a continuous electric field model, where the differential form of Gauss's law is used to obtain spatial terms of the electric field, and the integral form of Gauss's law is used to obtain temporal term of the electric field. By neglecting three-dimensional effects, the method of matched asymptotic expansion is employed to obtain the electric field between two pairs of interdigitated electrodes under quasi-electrostatic conditions. By averaging the solution along with the thickness of piezoceramic fibers and expanding it to the device's entire geometry by Fourier series, the low-order model of the electric field between the interdigitated electrodes is obtained. The matched asymptotic expansion and the low-order model agree well with finite element results. Generalized Hamilton's principle is employed to obtain the coupled electromechanical equations of motion for a beam with the Macro-Fiber Composite device. The Euler-Bernoulli assumptions are used to approximate strain distribution. Under current assumptions, equivalent capacitance and electromechanical coupling terms are obtained without using discontinuous functions (e.g., Heaviside or piecewise functions) for electric field terms. The equivalent capacitance is within 2% of the values reported by the manufacturer. Frequency response functions are obtained for the output voltage, tip displacement, and optimum working load of the energy harvester, and the current and the tip displacement for the actuator by assumed modes solution for a cantilever beam. It is shown that the actuator's current is related to the optimum working load of the energy harvester by Ohm's law. In the limited case, the proposed continuous electric field model reduces to the constant electric field model. When the constant electric field model is compared to the continuous electric field model, it is shown that the constant electric field model overpredicts the equivalent capacitance and electromechanical coupling. The relative difference between the two models for equivalent capacitance is around 41%, and for electromechanical coupling is around 22%. These relative differences are in agreement with the empirical correction factors defined in the earlier constant field models.

Electroactive despeckle diffuser using polymer dispersed liquid crystal in-plane switched by interdigitated electrodes

An electroactive despeckle diffuser (EADSD) is demonstrated using a polymer dispersed liquid crystal (PDLC) in-plane switched by two pairs of interdigitated electrodes whose directions are orthogonal. The mechanism underlying speckle suppression involves the time average of different speckle patterns during the exposure time of a detector, wherein the reorientation of LC molecules results in different speckle patterns. The introduction of interdigitated electrodes increases the diversity of the electric field in comparison with a conventional PDLC cell switched by a longitudinal electric field. Experimental results show that this device can reduce speckles more effectively owing to the more diverse electric field. The speckle reduction efficiency is approximately 55% when we drive the EADSD sample fabricated by 60 wt% E7: 40 wt% NOA65 under an exposure power of 6 mW/cm2 by bipolar triangle waveforms applied to the two pairs of interdigitated electrodes with frequencies of 20 Hz and peak voltage values of 150 V, and when the phase delay of the waveforms is 90° or 270°. The EADSD is static and does not require motors to achieve vibration, which make it a superior device for speckle reduction in laser displays.

Measurement of Biomimetic Deposition of Calcium Phosphate in Real Time Using Complex Capacitance

Deposition of minerals, particularly calcium phosphates such as hydroxyapatite, is an important process in the formation of hard tissues such as bone. Herein, a new, affordable, straightforward and nondestructive method based on complex capacitance spectroscopy, an application of electrochemical impedance spectroscopy, is described which allows repeated and real‐time measurements of the same sample throughout the calcium phosphate deposition process. In contrast with end‐point assays which require large numbers of samples to obtain useful time‐course data, this method allows the kinetics of deposition to be measured using a single sample by measuring the impedance of a pair of interdigitated electrodes at a range of frequencies as the layer of mineral is deposited. Changes in the complex capacitance curve over time with deposition can be compared with images of the coating deposited on model substrates, and show different behavior depending on the composition of the coating and the conditions of deposition.

Printed Dielectrophoretic Electrode‐Based Continuous Flow Microfluidic Systems for Particles 3D‐Trapping

AbstractInkjet‐printing is used to fabricate dielectrophoretic electrodes able to trap polystyrene (PS) microparticles as well as model planktonic cells. The possibility of rapid prototyping offered by inkjet‐printing allows the rational design of microchannels with tailored electric field distributions experienced by the suspended particles, which in turn provides a handle to drive them towards target regions. Specifically, this goal is achieved using two facing substrates constituting the bottom and the top walls of the channel, with a pair of interdigitated electrodes previously patterned by inkjet‐printing on each side. Influence of electrode polarization (magnitude and frequency of the input signal) is investigated both theoretically, by modeling the electric field distribution inside the channel, and experimentally using confocal fluorescence microscopy. The printed device is able to sort circulating PS particles as a function of their size, with diameters ranging from 0.5 to 5 µm, as well as to separate planktonic species according to their composition (Alexandrium minutum versus Prorocentrum micans). This work paves the way for the development of large‐area, microstructured dielectrophoretic electrodes able to separate the constituents of samples at flow rates up to 150 µL mn−1.

Avidin-Biotin Technology in Gold Nanoparticle-Decorated Graphene Field Effect Transistors for Detection of Biotinylated Macromolecules with Ultrahigh Sensitivity and Specificity.

The strong and specific noncovalent interaction between avidin and biotin is widely exploited in different types of enzyme-linked immunosorbent assay kits, labeled immunosensors, and polymer-based sensing devices for the detection of different biomarkers specific to different diseases such as cancer and influenza. Here, we employed the avidin–biotin technology in a novel gold nanoparticle-decorated graphene field-effect transistor (AuNP-GFET) and demonstrated the specific detection of the biotinylated macromolecules such as biotinylated proteins and nucleotides in the sub-picomolar (pM) range. The AuNP-GFET was constructed by fabricating six pairs of interdigital electrodes on graphene transferred on a SiO2/Si substrate. The sensing performance of AuNP-GFET was characterized by the real-time two-terminal electrical current measurement upon injection of the analyte solution into a silicone pool preattached onto the electrodes. Avidin, a tetrameric biotin-binding protein with strong affinity and specificity, immobilized on AuNP-decorated single-layer graphene, was used as the sensing platform and transduced the electrical signal upon binding to the analyte macromolecules. The sensing capability of the AuNP-GFET was tested with the biotinylated protein A. Sensitivity of the present biosensor was estimated to be ∼0.4 pM. The specificity and applicability of the biosensor were confirmed using both synthetic and real samples. Because the biotin label can retain its binding capability to avidin with strong affinity and specificity even after conjugating with varieties of proteins and nucleotides, the present AuNP-GFET biosensor is expected to promote the research in developing different biosensors.

Enhanced NH3 Sensing Performance of Ti3C2T x Nanosheets Supported By TiO2 Nanoparticles at Room Temperature

Introduction With the rapid development of the chemical industry, the emission of the harmful NH3 has increased significantly, thus the research of high performance NH3 sensors has attracted extensive attention of the researchers [1]. Over the past decades, the emergence of novel materials has brought opportunities for the development of gas sensors. As a representative of another new family of materials, the 2D transition metal carbides, carbonitrides and nitrides (MXenes) have attracted great attention of the researchers in the field of gas sensors due to their unique chemical and physical properties being recently realized [2]. Taking the well-studied Ti3C2T x MXene as an example, it has been proved theoretically and experimentally that the Ti3C2T x has gas sensing properties at room temperature, especially for NH3 [3]. However, its NH3 sensing properties still need to be enhanced. In this work, the gas sensor based on TiO2/Ti3C2T x composite film is fabricated by a simple spraying method and its NH3 sensing properties are investigated at room temperature. Method The 2D Ti3C2T x nanosheets were prepared through etching Al from Ti3AlC2 in diluted HF and Tetramethylammonium hydroxide (TMAOH) solutions [4]. TiO2 nanoparticles in water dispersion were purchased from Sigma-Aldrich. The gas sensors were fabricated by a simple spray method. In brief, 0.4 mL diluted TiO2 nanoparticles solution (5 mg/mL) was sprayed on the polyimide (PI) substrate with seven pairs of Au interdigitated electrodes (electrodes width and distance: 0.2 mm) and dried at 60°C for 10 min for forming the TiO2 film. Then, 1 mL diluted Ti3C2T x nanosheets solution (2 mg/mL) was sprayed on the surface of the TiO2 film for fabricating TiO2-supported Ti3C2T x film gas sensor. For comparison, the gas sensors based on pure TiO2 nanoparticles (0.4 mL) and Ti3C2T x nanosheets (1 mL) were prepared by the same approach. The gas sensing properties of the sensors were tested at different NH3 concentration with 60.8% RH. Results and Conclusions Figure 1a shows the XRD patterns of the three samples, which the diffraction peaks match with the previous reports [5], indicating high purity of the Ti3C2T x and anatase TiO2. From the TEM image of the Ti3C2T x in Fig. 1b, Ti3C2T x is of few-layer nanosheet structure, proving that Ti3C2T x nanosheets is successfully prepared. Figure 1c shows the normalized response-recovery curves of three sensors to 10 ppm NH3. As can be seen, there is no NH3 response for the pure TiO2 sensor, and the responses of the Ti3C2T x and TiO2/Ti3C2T x sensors are about 1.9% and 3.1%, respectively. Compare with Ti3C2T x sensor, the baseline resistance of TiO2/Ti3C2T x sensor is more stable, and the enhanced response of TiO2/Ti3C2T x sensor is 1.63 times than that of pure Ti3C2T x sensor. Fig. 1d shows the good dynamic response-recovery curve of the TiO2/ Ti3C2T x sensor to different concentrations NH3 and the sensor can even respond to NH3 as low as 0.5 ppm. In summary, we rationally designed the gas sensor based on based on TiO2/Ti3C2T x bilayer film for enhancing the NH3 sensing properties of pure 2D Ti3C2T x nanosheets and the results show that the response value and response/recovery speeds of TiO2/Ti3C2T x sensor are evidently improved. Meanwhile, the enhanced NH3 sensing response of the TiO2/Ti3C2T x sensor is explained by the model of self-built electric field (space charge layer) regulation. This work demonstrates that Ti3C2T x nanosheets supported by TiO2 nanoparticles can be used to enhance the NH3 sensing response, which is expected to provide useful reference for the development of high performance Ti3C2T x -based NH3 sensors.

Polymer-Based Functional Cantilevers Integrated with Interdigitated Electrode Arrays-A Novel Platform for Cardiac Sensing.

Heart related ailments are some of the most common causes for death in the world, and some of the causes are cardiac toxicity due to drugs. Several platforms have been developed in this regard over the years that can measure electrical or mechanical behavior of cardiomyocytes. In this study, we have demonstrated a biomedical device that can simultaneously measure electrophysiology and contraction force of cardiomyocytes. This dual-function device is composed of a photosensitive polymer-based cantilever, with a pair of metal-based interdigitated electrodes on its surface, such that the cantilever can measure the contraction force of cardiomyocytes and the electrodes can measure the impedance between cells and substrate. The cantilever is patterned with microgrooves so that the cardiomyocytes can align to the cantilever in order to make a higher cantilever deflection in response to contraction force. Preliminary experimental results have identified the potential for use in the drug-induced cardiac toxicity tests, and further optimization is desirable to extend the technique to various bio-sensor areas.

Performances of surface plasmon enhanced MgZnO ultraviolet photodetector based on parallel effect

The responsivity of surface plasmon (SP) modified metal–semiconductor-metal ultraviolet photodetectors (PDs) was increased from 1.15 × 10−3 to 2.5 × 10−3 A/W by varying the number of interdigitated electrode pairs. MgZnO films with Pt nanoparticles (NPs) having a grain size of 6.26 nm in a 25-pair interdigitated electrode arrangement showed improved responsivity and signal to noise ratio in comparison with the bare MgZnO PD. This improvement was attributed to both the enhanced conductivity and increased absorption resulting from the near-field enhancement of the SP. Parallel effect physical simulation results were in reasonable agreement with our experimental results.

A flexible piezoresistive sensor with highly elastic weave pattern for motion detection

A flexible high-sensitive piezoresistive sensor using conductive and highly elastic woven fabric has been fabricated for detecting human motion. Different from the previously reported pressure-strain sensors, the present sensing system is prepared based on the elastic weave between conductive warp and weft yarns on a pair of interdigital electrodes, and encapsulated by PDMS elastomer. This new sensing module exhibits the comparable sensing performance with conventional strain sensor, including the ratio of compressed resistance to initial value, sensitivity, hysteresis and repeatability. The pressure-resistance relationships of various conductive weave patterns and contact area between electrodes and conductive yarns have been systematically investigated. It was found that plain woven fabric displays an inverse proportion decline of resistance with the increase of compression pressure, the similar trends was noted for the parameters of weft density, contact area of weave and electrode, and laying angles of them. Demonstrations of such sensing modules in detecting finger pressing, bending and contraction of human abdomen from breathing were performed and clear and effective signals were output for corresponding actions.

A Hand-Held Point-of-Care Biosensor Device for Detection of Multiple Cancer and Cardiac Disease Biomarkers Using Interdigitated Capacitive Arrays.

This paper presents a hand-held point-of-care device that incorporates a lab-on-a-chip module with interdigitated capacitive biosensors for label-free detection of multiple cancer and cardiovascular disease biomarkers. The developed prototype is comprised of a cartridge incorporating capacitive biodetection sensors, a sensitive capacitive readout electronics enclosed in a hand-held unit, and data analysis software calculating the concentration of biomarkers using previously stored reference database. The capacitive biodetection sensors are made of interdigitated circular electrodes, which are preactivated with single (for detecting one biomarker) or multiple specific antibodies (for detecting multiple disease biomarkers). Detection principle of capacitive biosensor is based on measuring the level of capacitance change between interdigitated electrode pairs induced by the change in dielectric constant due to affinity-based electron exchange in between antibodies/antigens and electrodes. The more antibody-antigens binding occurs, the more capacitance change is measured due to the change in dielectric constant of the capacitance media. The device uses preactivated ready-to-use cartridges embedded with capacitive biosensors with shelf-life of three months under optimal conditions, and is capable of onsite diagnosis and can report the result in less than 30 min. The device is verified with real patient blood samples for six different disease biomarkers.

Controlling responsivity depends on change of interdigital electrodes in planar MgZnO UV photodetectors

In this work, the responsivity-controlled high performance UV photodetectors fabricated from MgZnO films was investigated with an emphasis on the effect of varying the number of interdigitated electrode pairs. The responsivity of MgZnO photodetectors was optimized by increasing the number of interdigital electrode pairs at a given bias. The result is due to the parallel structure of the interdigital electrodes and the depletion width of the Schottky junctions. This demonstrates a straightforward way of tailoring the responsivity of UV photodetectors for practical applications.

Screen-printing Bi2S3 nanowires on silk fabrics for a flexible optical switch

The development of textile-based wearable devices has been a hot research topic in recent years. However, a fabric-supported optical switch has never been reported. Herein, a pair of interdigital silver electrodes and hydrothermally synthesized Bi2S3 nanowires (NWs) were screen-printed successively onto silk fabric to construct a silk fabric-based flexible optical switch. The device showed irradiation power-dependent light-on currents and was able to respond to blue, green and red light. A fast response/recovery time of less than 2 ms could be achieved. After 120 cycles of distortion or bending, the light-on current remained as high as >85%. Bi2S3 NW films with different patterns could be printed on top of the devices without significantly affecting their performance. It was also demonstrated that the system could be utilized to trigger the rotation of an electrical fan. This work may provide a facile approach for the preparation of a silk fabric-based optical switch for wearable electronics.

Paper-based printed impedance sensors for water sorption and humidity analysis

The hygroscopic nature of cellulose-based materials poses a challenge in utilising paper for printed electronics. Adsorbed moisture strongly modulates the conductive and dielectric properties of paper. While affecting the function of printed electronic elements, this behaviour is beneficial for low-cost humidity sensing. Here we describe a simple, sensitive paper-based sensor with a pair of inkjet-printed interdigitated electrodes for analysing water sorption of cellulose over a wide range of relative humidity from 10% to 90%. Impedance spectroscopy between 100 Hz and 1 MHz reveals the humidity-dependent electrical properties of paper. We show in particular that measurements at 1 MHz provide reliable information about the water adsorption and desorption of paper. In contrast, testing at frequencies below 200 kHz is dominated by ionic electrode polarisation, masking the water sorption kinetics of the sensor. Transient adsorption follows nearly an exponential function, while desorption is described by a stretched exponential law. At equilibrated conditions, the effective paper permittivity measured during adsorption and desorption is characterised by a Guggenheim–Anderson–de Boer sorption isotherm which allows for a quantitative evaluation of the sorption hysteresis. Our means of sensing provides a simple and practical method of recording and analysing simultaneously conductivity and permittivity as well as wetting and drying of moist paper.

CO sensing characteristics of In-doped ZnO semiconductor nanoparticles

Abstract A study on the CO sensing characteristics of In-doped ZnO semiconductor nanoparticles (IZO NPs) prepared by a modified sol–gel technique is reported. The morphological and microstructural features of IZO NPs with various dopant concentrations (1 at.%, 2 at.%, 3 at.%, and 5 at.% In) were investigated by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The influence of indium doping on defect characteristics of ZnO was also investigated by photoluminescence (PL). A thick film of IZO NPs was deposited by screen printing on an alumina substrate provided with a pair of Pt interdigitated electrodes to fabricate a simple conductometric sensor platform. The as fabricated In-doped ZnO sensors showed enhanced sensitivity to CO gas with respect to pure ZnO one. Sensors with low dopant loading (1 at.% and 2 at.% In) were found to be more sensitive with shorter response and recovery times than those with high dopant loading.