Stepwise gray-scale light-induced electric field gradient for passive and continuous separation of microparticles

This article presents a gray-scale light-induced dielectrophoresis (GS-LIDEP) method that induces the lateral displacements normal to the through-flow for continuous and passive separation of microparticles. In general, DEP force only can affect the particles within very local areas due to the electric field is exponentially decayed by the distance away from the electrodes. Unlike with conventional LIDEP, a broad-ranged electrical field gradient can easily be created by GS pattern illumination, which induces DEP forces with two directions for continuous separation of particles to their specific sub-channels. Candia albicans were effectively guided to the specific outlet with the efficiency of 90% to increase the concentration of the sample below the flow rate of 0.6?μl/min. 2 and 10?μm polystyrene particles can also be passively and well separated using the multi-step GS pattern through positive and negative DEP forces, respectively, under an applied voltage of 36?V_p–p at the frequency of 10?kHz. GS-LIDEP generated a wide-ranged DEP force that is capable of working on the entire area of the microchannel, and thus the mix of particles can be passively and continuously separated toward the opposite directions by the both positive and negative GS-LIDEP forces. This simple, low cost, and flexible separation/manipulation platform could be very promising for many applications, such as in-field detections/pretreatments.     

Genetic synthesis of a fuzzy pulse discriminator in electrical discharge machining

In this paper, a sensor system, called a fuzzy pulse discriminator, is developed to classify various discharge pulses in electrical discharge machining (EDM). The fuzzy rules of the pulse discriminator are obtained based on the features of the gap voltage and gap current between the tool workpiece. The membership functions of the fuzzy pulse discriminator are automatically synthesized by using genetic algorithms. The effectiveness of this approach is verified under different cutting parameters.     

Novel 3D manufacturing method combining microelectrial discharge machining and electrochemical polishing

This paper reports on the potential of microelectrical discharge machining (μEDM) as an innovative method for the fabrication of 3D microdevices. To demonstrate the wide capabilities of μEDM two different microsystems—a microfluidic device for the dispersion of nanoparticles and a star probe for microcoordinate metrology—are presented. To gain optimized process conditions as well as a high surface quality an adequate adaption of the single erosion parameters such as energy, pulse frequency and spark gap has to be carried out and is discussed below. Thus, a surface roughness of R_a?=?80?nm is achieved at the channel bottom. The fabricated stylus elements for the star probe have sphere diameters of 40–200?μm. For further surface quality enhancement a subsequent electrochemical polishing step is investigated. In case of the dispersion micromodule a combined process chain of μEDM-milling and electropolishing has reached a surface improvement above 70%.     

Metal-based piezoelectric microelectromechanical systems scanner composed of Pb(Zr, Ti)O3 thin film on titanium substrate

We have developed a titanium (Ti)-based piezoelectric microelectromechanical systems scanner driven by a Pb(Zr, Ti)O₃ (PZT) thin film for the development of laser scanning displays. The 2-μm-thick PZT thin film was directly deposited on a 50-μm-thick Ti substrate by radio frequency magnetron sputtering. Prior to PZT deposition, the Ti substrate was microfabricated into the shape of a horizontal scanner by wet etching; therefore, we could fabricate a piezoelectric microactuator without using the photolithography process. We confirmed the growth of the polycrystalline PZT film with perovskite structures on the Ti substrate. We achieved an optical scanning angle of 22° at a resonant frequency of 25.4?kHz using a driving voltage of 20?V _pp. These horizontal scanning properties can be applicable for laser displays.     

在微细电火花加工极间放电状态高速采集系统中的DMA技术

为了提高微细电火花加工的脉冲利用率,控制系统要求能对一段时间内的放电状态进行连续采集。通过对待测信号的调理,使采集系统的任务降到只需以微细电火花脉冲电源速率进行采样即可,即速率要求为２ＭＨｚ。然而市场上的板极采集元件不是达不到速度要求,就是速度太高,功能冗余,价格昂贵。为此,笔者采用了ＤＭＡ技术,配合高速Ａ／Ｄ转换器ＡＤＣ－２０８ＭＣ的应用,设计了一个适用于极间放电状态检测的高速采集系统。文中对该     

A piezoelectric inertia rotary actuator based on asymmetric clamping mechanism

A newly piezoelectric inertia rotary actuator is presented by using asymmetric mechanical structure to produce asymmetric inertia impact force when the symmetric electrical signal is applied to the piezoelectric bimorph Mechanical analysis was derived and simulation model of asymmetric clamping mechanism was established to determine the influence of structural parameters to the output performance. A prototype was developed and a series of experiments were conducted to evaluate the performance in terms of angular displacement, speed, and load characteristic. The experimental results show that the angular displacement of the actuator is approximately proportional to the amplitude of driving voltage, and an angular displacement resolution of 12 µrad is obtained with a square wave of 15 V_p?p at a frequency of 4 Hz. The maximum torque can reach 3.96 N mm at 70 V_p?p applied voltage and 2 Hz driving frequency. The rotary actuator characterized with an asymmetric clamping mechanism will provide new references for the further research on piezoelectric inertia drive mechanism.     

Fuzzy approach to select machining parameters in electrical discharge machining (EDM) and ultrasonic-assisted EDM processes

Condition monitoring of the machining process is very important in today's precision manufacturing, especially in the electrical discharge machining (EDM). This paper introduces a fuzzy-based algorithm for prediction of material removal rate (MRR), tool wear ratio (TWR), and surface roughness (R_z, R_k) in the EDM and ultrasonic-assisted EDM (US/EDM) processes. In this system, discharge current, pulse duration, and ultrasonic vibration of tool are the input variables and outputs are MRR, TWR, R_z, and R_k. The proposed fuzzy model in this study provides a more precise and easy selection of EDM and US/EDM input parameters, respectively for the required MRR, TWR, R_z, and R_k, which leads to better machining conditions and decreases the machining costs. The fuzzy modeling of EDM and US/EDM were able to predict the experimental results with accuracies more than 90%.     

Emission of dispersed‐type inorganic EL devices with frequency‐variable high‐voltage oscillation circuit

Dispersed‐type inorganic electroluminescent (EL) devices composed of a transparent electrode, a phosphor, a dielectric, and a back electrode were prepared under various conditions using a zinc sulfide (ZnS)‐based phosphor. Additionally, a voltage/frequency variable circuit was designed. A compact high‐voltage/frequency variable circuit including three modules for boosting, frequency conversion, and voltage conversion was designed. A 140 V_pp voltage and a frequency in the range of 270 Hz to 2.4 kHz can be controlled by this circuit. The emission has begun to be observed at a voltage about 60 V_pp and a frequency of 400 Hz, at a voltage about 40 V_pp and a frequency of 1.4 kHz, 2.4 kHz, respectively. The emission intensity increased with an increase in frequency; emission with a wavelength of 450 nm was strongly influenced by the frequency. The luminescence and the electrical properties were affected by the preparation conditions including device structures, dispersion of ZnS:Cu, and Cl particles because of the current path generated by defects in the EL cell.     

Biased scan of plasma display panel for data voltage reduction

This paper proposes a method of reducing the data voltage V_d of plasma display panels (PDPs). The proposed biased-scan method uses two separate ground systems: one for the sustain pulse generator (FGND) and the other for the data address and control systems (CHGND). A dc voltage bias, which is applied between CHGND and FGND during the address period, reduces V_d while preventing the undesired glow discharge induced by a scan pulse only. CHGND is connected to FGND for the first sustain pulse of each subfield, which reduces the time lag of address discharge, but it is separated from FGND for the other sustain pulses to increase the margin of the sustain voltage. The proposed method was tested on a 15% Xe 50-in. Full HD (1920 × 1080) single-scan PDP which had a sustain discharge gap of 110 μm. V_d could be reduced by 20 V (30%), and the power consumption of the V_d voltage source decreased by ∼25 W (50%) from that of the conventional method.     

A low frequency tunable hybrid generator

A serious of experimental tests on a commercial brass reinforced PZ bimorph cantilever of the type 5H4E were carried out in a vibration laboratory using a Labview of NI make as instrumentation and control system. Originally the bender acted as a tunable PZ generator, using perforated steel shims as a proof mass. The generator was converted to a hybrid generator by adding ring magnets to its other surface and making them working as part of an electromagnetic generator in addition of being a proof mass. Two arrangement of the electromagnetic generator were investigated at a frequency of (33) Hz which is the resonance frequency at max power of the original PZ generator. By using a shaker the cantilever was vibrated and set into acceleration of (0.25) g rms during all stages as this value was considered to be available and acceptable in balanced large rotating machines in industry. The hybrid generator produced (187) μW for max power, (14.8) V_rms for max OCV, and (8.26) V_rms for max on load voltage for the PZ part, while the electromagnetic part produced max (70) V_rms, (490) μW for arrangement (1) and (34) V_rms, (116) μW for arrangement (2) on no load condition and at the same frequency. The experimental results obtained from the electromagnetic generator are acceptable compared with theory.     

Electrical and photoelectrical characterizations of isotype GaAs15P85/GaP heterojunctions prepared by liquid phase epitaxy

The present work deals with the electrical and optoelectronic characterizations of the isotype GaAs₁₅P₈₅/GaP devices prepared by liquid phase epitaxy. The electrical properties of the fabricated junction were studied by analyzing its current–voltage (I–V) characteristics, capacitance–voltage (C–V) characteristics in the dark at different temperatures in the range of 300–450 K. The analysis of dark current–voltage (I–V) characteristics at different temperatures were presented in order to elucidate the conduction mechanism and to evaluate the important device parameters. The predominant charge transport mechanism in these devices was found to be thermionic emission in the depletion layer and over the barrier of GaAs₁₅P₈₅/GaP heterojunction at forward bias voltage. From the capacitance–voltage, measurements at high frequency (1 MHz) information can be obtained about the carrier concentration, the diffusion potential, the barrier height of GaAs₁₅P₈₅/GaP heterojunction. The current–voltage characteristics of the GaAs₁₅P₈₅/GaP heterojunction under different illumination intensities were studied. The power low dependence of the reverse current voltage is characterized by space charge limited conduction, SCLC dominated by exponential trap distribution at the higher reverse voltage region.     

Flexible color LCD panel driven by low‐voltage‐operation organic TFT

Abstract— A flexible color LCD panel driven by organic TFTs (OTFTs) was successfully demonstrated. A pentacene OTFT with an anodized Ta₂O₅ gate insulator, which can be operated at low voltage, was developed. In order to improve the electrical performance of the OTFT, the gate insulator was surface treated by processes such as O₂ plasma, UV light irradiation, and hexamethyldisilane treatments. The fabricated OTFT exhibited a mobility of 0.3 cm²/V‐sec and a current on/off ratio of 10⁷ with a low operating drain voltage of ?5 V. A fast‐response‐time flexible ferroelectric LCD, which contains polymer networks and walls, was integrated with the OTFTs by using a lamination and a printing technique. As a result, color images were achieved on the fabricated panel by using a field‐sequential‐color method at a low driving voltage of less than 15 V_pp.     

MONITOR AND CONTROL OF DISCHARGE ENERGY DURING EDMING

A pulse energy at 100MHz is verified to be able to determine the normal and abnormal discharge during electrical discharge machining (EDMing). A band pass filter is designed to detect the energy at this frequency, and can verify which discharge pulses are normal and abnormal, respectively. A field programmable gate array (FPGA) is used to implement the discharge detection circuit, including detection of the time of ignition (T_d) and discharge high‐energy. Function analysis is used to design the proportional (P) T_d controller to allow the bounded variation of reference input and the feedback signals. Energy of about 100MHz can be maintained within a specified pulse width by regulating the position of the electrode, including a slight regulation and jump motion. The rate of erosion during the roughing and finishing of a die‐sinking EDM is confirmed to demonstrate the improvements obtained by the EDMing.     

Precisely sized separation of multiple particles based on the dielectrophoresis gradient in the z-direction

We present a new 3D dielectrophoresis-field-flow fraction (DEP-FFF) concept to achieve precise separation of multiple particles by using AC DEP force gradient in the z-direction. The interlaced electrode array was placed at the upstream of the microchannel, which not only focused the particles into a single particle stream to be at the same starting position for further separation, but also increased the spacing between each particle by the retard effect to reduce particle–particle aggregation. An inclined electrode was also designed in back of the focusing component to continuously and precisely separate different sizes of microparticles. Different magnitudes of DEP force are induced at different positions in the z-direction of the DEP gate, which causes different penetration times and positions of particles along the inclined DEP gate. 2, 3, 4, and 6?μm polystyrene beads were precisely sized fractionation to be four particle streams based on their different threshold DEP velocities that were induced by the field gradient in the z-direction when a voltage of 6.5?V_p–p was applied at a flow rate of 0.6?μl/min. Finally, Candida albicans were also sized separated to be three populations for demonstrating the feasibility of this platform in biological applications. The results showed that a high resolution sized fractionation (only 25% size difference) of multiple particles can be achieved in this DEP-based microfluidic device by applying a single AC electrical signal.     

Selective position of individual cells without lysis on a circular window array using dielectrophoresis in a microfluidic device

We trapped individual cells between two circular windows using negative dielectrophoretic (DEP) force and then sequentially trapped them inside circular windows by positive DEP force without electrical lysis in a microfluidic device. Three parameters, (1) the transmembrane potential that determines the lysis of a cell, (2) individual cell size that affects the trapped position accuracy of the cell, and (3) the Clausius–Mossotti (CM) factor that decides the trapped efficiency of the cell, were characterized experimentally and numerically in this sequential cell trapping technique. In this characterization, we confirmed that the swap rate of applied voltage frequency, size similarity between the cell and circular window, and instantaneous change rate of Re(f _CM) as a function of frequency were important factors in determining the selective position of individual cells without lysis. Our results provide useful suggestions for designing the structure of microfluidic DEP devices and optimizing variables required to manipulate individual cell trapping using both negative and positive DEP forces.     

A novel gate driver circuit for depletion‐mode a‐IGZO TFTs

In this paper, a novel gate driver circuit, which can achieve high reliability for depletion mode in a‐InGaZnO thin‐film transistors (TFTs), was proposed. To prevent the leakage current paths for Q node effectively, the new driving method was proposed by adopting the negative gate‐to‐source voltage (V_GS) value for pull‐down units. The results showed all the V_OUT voltage waveforms were maintained at VGH voltage despite depletion‐mode operation. The proposed circuit could also obtain stable V_OUT voltage when the threshold voltage for all TFTs was changed from ?6.5 to +11.5 V. Therefore, the circuit can achieve high reliability regardless of threshold voltage value for a‐IGZO TFTs. In addition, the output characteristics and total power consumption were shown for the alternating current (AC)–driven and direct current (DC)–driven methods based on 120‐Hz full‐HD graphics (1920 × 1080) display panel. The results showed that the AC‐driven method could achieve improved V_OUT characteristics compared with DC‐driven method since the leakage current path for Q node can be completely eliminated. Although power consumption of the AC‐driven method can be slightly increased compared with the DC‐driven method for enhancement mode, consumption can be lower when the operation has depletion‐mode characteristics by preventing a leakage current path for pull‐down units. Consequently, the proposed gate driver circuit can overcome the problems caused by the characteristics of a‐IGZO TFTs.     

Fabrication of aluminium doped zinc oxide piezoelectric thin film on a silicon substrate for piezoelectric MEMS energy harvesters

Thin film piezoelectric materials play an essential role in micro electro mechanical system (MEMS) energy harvesting due to its low power requirement and high available energy densities. Non-ferroelectric piezoelectric materials such as ZnO and AlN are highly silicon compatible making it suitable for MEMS energy harvesters in self-powered microsystems. This work primarily describe the design, simulation and fabrication of aluminium doped zinc oxide (AZO) cantilever beam deposited on <100> silicon substrate. AZO was chosen due its high piezoelectric coupling coefficient, ease of deposition and excellent bonding with silicon substrate. Doping of ZnO with Al has improved the electrical properties, conductivity and thermal stability. The proposed design operates in transversal mode (d ₃₁ mode) which was structured as a parallel plated capacitor using Si/Al/AZO/Al layers. The highlight of this work is the successful design and fabrication of Al/AZO/Al on <100> silicon as the substrate to make the device CMOS compatible for electronic functionality integration. Design and finite element modeling was conducted using COMSOL? software to estimate the resonance frequency. RF Magnetron sputtering was chosen as the deposition method for aluminium and AZO. Material characterization was performed using X-ray diffraction and field emission scanning electron microscopy to evaluate the piezoelectric qualities, surface morphology and the cross section. The fabricated energy harvester generated 1.61?V open circuit output voltage at 7.77?MHz resonance frequency. The experimental results agreed with the simulation results. The measured output voltage is sufficient for low power wireless sensor nodes as an alternative power sources to traditional chemical batteries.     

An optimal design method for minimization of common voltage distortion in large‐sized and high‐resolution liquid crystal displays

This paper proposes an optimal design method that minimizes the common voltage (V_COM) distortion for large‐sized and high‐resolution liquid crystal displays (LCDs). Three design methods are examined using different architectures of the panel and circuit to compensate for the V_COM distortion. The proposed design method adopts a panel architecture that compensates for the V_COM distortion simultaneously at the top and bottom of the panel using a dual compensation circuit. It is implemented using a 27‐in. quad high‐definition LCD, and its V_COM distortion is further minimized by optimizing the compensation ratio of the dual compensation circuit. In addition, the minimized V_COM distortion is evaluated by measuring the horizontal crosstalk of the implemented panel according to the decrease in the charging time of the subpixel. As the charging time decreases from 11.6 to 7.8 μs, the measured crosstalk level varies from 0.10% to 1.06%, respectively, meeting the goal of less than 2%. Therefore, the proposed design method is suitable for large‐sized and high‐resolution LCDs requiring low V_COM distortion.     

Development of a methodology for the extraction of BSIM3v3.2.2 parameters of Ge-channel MOSFETs and estimation of analog circuit performance

We have developed an algorithm which utilizes model equations for MOSFETs to extract BSIM3v3.2.2 MOSFET model parameters of Ge-channel transistors. The model represents the entire transfer characteristics from sub-threshold to strong inversion regions and the output characteristics from linear to saturation regions thus capturing all the operating bias conditions of gate to source voltage V_GS and drain to source voltage V_DS. For extraction of various BSIM parameters, the model equations are fitted with reported experimental characteristics, and some with TCAD simulation data of Ge MOSFETs for various geometrical dimensions over a wide range of bias conditions. The algorithm used for extracting BSIM3V3.2.2 parameters by fitting BSIM3v3.2.2 model equations with experimental or simulation data is written in MATLAB code. The extracted BSIM model parameters are employed in ADS circuit simulator to reproduce the transfer characteristics of Ge MOSFETs with the same channel length and channel width of 80 nm for both high and low body bias conditions. The characteristics obtained from ADS match well with those obtained from TCAD simulation using SILVACOATLAS thereby ensuring the accuracy of our extraction methodology. The extracted set of BSIM3V3.2.2 parameters is used to generate transfer and output characteristics of Ge channel pMOSFETs at channel length of 70 nm. The extracted value of threshold voltage, bulk mobility and saturation velocity are −0.2 V, 0.18 m²/V.s and 1.2 × 10⁶ m/s, respectively. Our study reveals that various device parameters such as transconductance, intrinsic voltage gain, and cut-off frequency show a maximum value of 677 μS/μm, 2.7, and 63 GHz, respectively.

     

Artificial neural network models for the prediction of surface roughness in electrical discharge machining

In the present paper Artificial Neural Networks (ANNs) models are proposed for the prediction of surface roughness in Electrical Discharge Machining (EDM). For this purpose two well-known programs, namely Matlab^® with associated toolboxes, as well as Netlab^®, were emplo- yed. Training of the models was performed with data from an extensive series of EDM experiments on steel grades; the proposed models use the pulse current, the pulse duration, and the processed material as input parameters. The reported results indicate that the proposed ANNs models can satisfactorily predict the surface roughness in EDM. Moreover, they can be considered as valuable tools for the process planning for EDMachining.