Showing papers in "Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems in 2016"

Nonlinear bending vibration of a rotating nanobeam based on nonlocal Eringen's theory using differential quadrature method

Abstract: This study investigates the small scale effect on the nonlinear bending vibration of a rotating cantilever and propped cantilever nanobeam. The nanobeam is modeled as an Euler---Bernoulli beam theory with von Karman geometric nonlinearity. The axial forces are also included in the model as the true spatial variation due to the rotation. Hamilton's principle is used to derive the governing equation and boundary conditions for the Euler---Bernoulli beam based on Eringen's nonlocal elasticity theory. The differential quadrature method as an efficient and accurate numerical tool in conjunction with a direct iterative method is adopted to obtain the nonlinear vibration frequencies of nanobeam. The effect of nonlocal small---scale, angular speed, hub radius and nonlinear amplitude of rotary nanobeam is discussed.

Modeling of mechanical resonators used for nanocrystalline materials characterization and disease diagnosis of HIVs

Abstract: The modeling and performance of mechanical resonators used for mass detection of bio-cells, nanocrystalline materials characterization, and disease diagnosis of human immune-viruses (HIVs) are investigated. To simulate the real behavior of these mechanical resonators, a novel distributed-parameter model based on Euler---Bernoulli beam theory is developed. This model is equipped with a micromechanical model and an atomic lattice model to capture the inhomogeneity nature of the material microstructure. Compared with lumped-parameter model predictions, the results show that this developed model best fits with the real behavior of the mechanical resonators when detecting the mass of vaccinia virus. In terms of material characterization, the developed model gives very good estimations for the densities and Young's moduli of the grain boundary of both the nanocrystalline silicon and nanocrystalline diamond. For disease diagnosis, it is shown that the number of human immune-deficiency virus particles in a liquid sample can be easily detected when using the proposed model. The results also show that the developed model is beneficial and can be used to design mechanical resonators made of nanocrystalline materials with the ability to control the resonators' sizes and the material structure.

Design and performance evaluation of a novel robotic catheter system for vascular interventional surgery

Abstract: Vascular interventional surgery (VIS) is an effective treatment method for vascular diseases However, there are many problems in traditional VIS, such as surgeons are radiated by X-ray, the lack of well skilled surgeons, the security of the surgery will be reduced due to the Surgeons' fatigue, high risk of the surgery To solve these problems, a robotic catheter system is needed to protect the surgeons and enhance the safety of the surgery In this paper, a novel robotic catheter system with master---slave structure for VIS has been developed This system is designed with the consideration of the operation method in traditional VIS, which allows the surgeon to operate a real catheter on the master side, then the surgeon make full use of the natural catheter manipulation experience and skills obtained in conventional catheter operation The salve manipulator operates the catheter insert into the blood vessel with following the operation of the surgeon, and the operating force of the salve manipulator is detected On the master side, a novel damper-based magnetorheological (MR) fluid is designed to realize the force feedback, which is also used to reappear the operation force from the salve manipulator The damper connected directly with real catheter is a piston structure using the MR fluid to realize the force feedback It can transmit the feedback force to surgeon's hand through the operating catheter connected with damper, which seems that the surgeon operates the catheter beside the patient The operating transparency of the developed system has been enhanced The mechanism of the developed system has been introduced in detail Performance evaluation experiments for the developed robotic catheter system have been done The experimental results indicated that the developed robotic catheter system is fit for VIS

Novel nano polymeric system containing biosynthesized core shell silver/silica nanoparticles for functionalization of cellulosic based material

Abstract: An innovative strategy for functional finishing of cellulosic based materials is based on the incorporation of a thin layer of surface modifying systems (SMS) in the form of stimuli-sensitive nanogels containing combining metal nanoparticles and silica. The silver---silica core---shell nanoparticles (NPs) were synthesized by simple one pot chemical method. Silica/silver nanoparticles have been synthesized using low concentration of dextran as reducing and stabilizing agent and using ascorbic acid as antioxidant agent. The core---shell NPs were characterized for their structural, morphological, compositional and optical behaviour using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Stimuli-responsive nanogel was prepared by copolymerization of poly(N-isopropylacrylamide) with pullulan, results in a nanogel that is responsive to both temperature and pH, the nano-particulate hydrogel of poly-NiPAAm-pullulan copolymer was synthesized using surfactant-free emulsion method. The prepared nano-particles were used during the preparation steps of the pullulan nanogel to obtain nanogel/combining metal/silica NPs to produce a composite materials. The nanoparticle size in dry (collapsed) state is estimated at 250 nm by SEM and TEM, and effect of temperature and pH on gel-nanoparticles was investigated by DLS and UV---vis spectrophotometry. The incorporation of the nanoparticles to cellulosic material was done by a simple pad dry-cure procedure from aqueous nanoparticle dispersion that contained a cross-linking agent. This application method provided sufficient integrity to coating by maintaining the responsiveness of surface modifying system. The stimuli responsiveness of modified cellulosic materials has been confirmed in terms of regulating its water uptake in dependence of pH and temperature.

Direct joining of a laser-ablated metal surface and polymers by precise injection molding

Abstract: The joining of metal and polymer surfaces is a promising technology to reduce the total weight of parts and to improve interface reliability. In this study, a micro square grid (200 μm × 200 μm) was fabricated on an aluminum surface using laser ablation. Molten glass-reinforced poly(butylene terephthalate), poly(styrene) and acrylonitrile---butadiene---styrene were introduced to the micro square grids by a precise injection molding machine. The maximum load tensile test was used as a measure of the joining strength between aluminum and the polymer. The tensile strength tests assisted in the differentiation of three modes of separation: interface-peeling, cohesive failure and matrix fracture. The maximum load increased with the effective joined area where interface-peeling was observed. The maximum load ceased at a certain effective joined area, and matrix fracture occurred. Cohesive failure was observed where the effective joined area was smaller than the area for which matrix fracture was observed, and the joined strength was larger than that observed for interface-peeling. The maximum stress, which was calculated by dividing cross-sectional area by the maximum load, at the matrix fracture was proportional to the polymer tensile strength.

An investigation into resonant frequency of trapezoidal V-shaped cantilever piezoelectric energy harvester

Abstract: Power supply is a bottle-neck problem of wireless micro-sensors, especially where the replacement of batteries is impossible or inconvenient. Now piezoelectric material is being used as an additional layer in cantilever beams to harvest vibration energy for self-powered sensors. However, the geometry of a piezoelectric cantilever beam will greatly affects its vibration energy harvesting ability. This paper deduces a remarkably precise analytical formula for calculating the fundamental resonant frequency of trapezoidal V-shaped cantilevers using Rayleigh---Ritz method. This analytical formula, which is very convenient for mechanical energy harvester design based on Piezoelectric effect, is then analyzed using MATLAB as well as finite element methods and validated by ABAQUS simulation. This formula raises a new perspective that, among all the trapezoidal V-shaped cantilevers with uniform thickness, the simplest triangular tapered cantilever, can lead to maximum resonant frequency and highest sensitivity and by increasing the ratio of the trapezoidal bases, the sensitivity decreases.

Analysis of novel transparent gate recessed channel (TGRC) MOSFET for improved analog behaviour

Abstract: In this paper, a novel device structure called transparent gate recessed channel MOSFET (TGRC-MOSFET) is proposed to alleviate the hot carrier effects for the advanced nanometer process. TGRC-MOSFET involving a recessed channel and incorporates indium tin oxide as a transparent gate. TCAD analysis shows that the performance of TGRC-MOSFET surpasses conventional recessed channel (CRC)-MOSFET in terms of high ION/IOFF ratio and better carrier transport efficiency in comparison to CRC-MOSFET. This simulation divulges the reduction in hot-carrier-effects metrics like electron velocity, electron temperature, potential, and electron mobility. Furthermore, the effect of gate length is observed on the analog behavior of TGRC-MOSFET. All the simulations have been done using DEVEDIT-3D and ATLAS device simulator. The work proposes the novel design for reduced hot carrier and low power switching applications.

Preliminary mechanical analysis of an improved amphibious spherical father robot

Abstract: Amphibious micro-robots are being developed for complicated missions in limited spaces found in complex underwater environments. Therefore, compact structures able to perform multiple functions are required. The robots must have high velocities, long cruising times, and large load capacities. It is difficult to meet all these requirements using a conventional underwater micro-robot, so we previously proposed an amphibious spherical father---son robot system that includes several micro-robots as son robots and an amphibious spherical robot as a father robot. Our father robot was designed to carry and power the son robots. This paper discusses improvements to the structure and mechanism of the father robot, which was designed to have a spherical body with four legs. Based on recent experiments in different environments, we have improved the father robot by adding four passive wheels, and we have redesigned its structure by means of three-dimensional printing technology, resulting in greatly improved velocity and stability. Moreover, due to the complexity and uncertainty of many underwater environments, it is essential for the father robot to have adequate structural strength. We analyzed the movement mechanisms and structural strength using finite element analysis to obtain the deformation and equivalent stress distributions of the improved robot. The results provide support for further analysis of the structural strength and optimal design of our amphibious spherical father robot.

Magnetron sputtering of piezoelectric AlN and AlScN thin films and their use in energy harvesting applications

Abstract: This paper reports on the deposition of AlN and AlXSc1źXN films by pulse magnetron sputtering. The first part will focus on the AlXSc1źXN deposition process in comparison to the already established AlN process. The effect of doping AlN with Sc regarding piezoelectric and mechanical properties is presented. The films show the expected increase of piezoelectric properties as well as the softening of the material with higher Sc concentrations. Above a threshold concentration of around 40 % Sc in the AlXSc1źXN films, there exists a separation into two phases, an Al-rich and a Sc-rich wurtzite phase, which is shown by XRD. At Sc concentrations higher than 50 %, the films are not piezoelectric, as the films are composed primarily of the cubic ScN phase. The second main part of this paper evaluates the films for application in energy harvesting. Especially the Sc doping allows a significant increase in the energy generated in our test setup. Directly measuring the AC voltage at resonance depending on load resistance with base excitation of ±2.5 µm, 350 µW power have been generated under optimum conditions compared to 70 µW for pure AlN. For a more application oriented measuring setup, a standard and a SSHI-based ("Synchronised Switch Harvesting on Inductor") AC/DC converter circuit have been tested. The SSHI interface showed a significant improvement to 180 % compared to the standard interface.

Five topologies of cantilever-based MEMS piezoelectric vibration energy harvesters: a numerical and experimental comparison

Abstract: In the realm of MEMS piezoelectric vibration energy harvesters, cantilever-based designs are by far the most popular. For cantilever-based vibration energy harvesters, the active piezoelectric area near the clamped end is able to accumulate maximum strain-generated-electrical-charge, while the free end is used to house a proof mass to improve the power output without compromising the effective area of the piezoelectric generator since it experiences minimal strain anyway. However, despite while other contending designs do exist, this paper explores five selected micro-cantilever (MC) topologies, namely: a plain MC, a tapered MC, a lined MC, a holed MC and a coupled MC, in order to assess their relative performance as an energy harvester. Although a classical straight and plain MC offers the largest active piezoelectric area, alternative MC designs can potentially offer larger deflection and thus mechanical strain distribution for a given mechanical loading. Numerical simulation and experimental comparison of these 5 MCs (0.5 µm AlN on 10 µm Si) with the same practical dimensions of 500 µm and 2000 µm, suggest a cantilever with a coupled subsidiary cantilever yield the best power performance, closely followed by the classical plain cantilever topology.

Theoretical analysis and experimental study for nonlinear hybrid piezoelectric and electromagnetic energy harvester

Abstract: A nonlinear hybrid piezoelectric (PE) and electromagnetic (EM) energy harvester is proposed, and its working model is established. Then the vibration response, output power, voltage and current of nonlinear hybrid energy harvester subjected to harmonic excitation are derived by the method of harmonic balance, and their normalized forms are obtained by the defined dimensionless parameters. Through numerical simulation and experimental test, the effects of nonlinear factor, load resistance, excitation frequency and the excitation acceleration on amplitude and electrical performances of hybrid energy harvester are studied, which shows that the numerical results are in agreement with that of experimental tests. Furthermore, it can be concluded that the bigger nonlinear factor, the lower resonant frequency; moreover, there is an optimal nonlinear factor that make the harvester output the maximum power. In addition, the output power of nonlinear hybrid energy harvester reaches the maximum at the optimal loads of PE and EM elements, which can be altered by the excitation acceleration. Meanwhile, the resonant frequency corresponding to the maximum power rises firstly and then falls with PE load enhancing, while it rises with EM load decreasing; furthermore, the frequency lowers with the acceleration increasing. Besides, the larger acceleration is, the bigger power output and the wider 3 dB bandwidth are. Compared with performances of linear hybrid energy harvester, the designed nonlinear energy harvester not only can reduce the resonant frequency and enlarger the bandwidth but also improve the output power.

Optical fiber resonance-based pH sensors using gold nanoparticles into polymeric layer-by-layer coatings

Abstract: The development of new nanocoatings onto optical fiber core is a hot topic within the optical fiber devices. The possibility of fabricating hybrid nanocoatings based on inorganic (gold nanoparticles, AuNPs) and organic materials (polymeric structure) can be performed using the layer-by-layer embedding deposition technique. The deposition of a nanostructure coating onto an optical fiber core has been performed in order to obtain optical fiber resonance-based pH sensors. The incorporation of gold nanoparticles (AuNPs) into polymeric thin films has been confirmed by atomic force microscopy, scanning electron microscopy and UV---Vis spectroscopy. In addition, two electromagnetic resonances known as localized surface plasmon resonance (LSPR) or lossy mode resonance (LMR), can be generated as a function of the resultant thickness coating. In this work, the fabrication of a dual LSPR-LMR optical fiber pH sensor is presented where the LSPR is used as a reference signal and the LMR is used as a sensing band due to the great difference in their corresponding sensitivities to pH changes of the surrounding medium. It has been demonstrated that LMR improves the sensitivity of the LSPR band in more than one hundred times. The device shows a high sensitivity, fast response time and large dynamical range of 134.7 nm from pH 4.0 to pH 6.0.

Low power highly sensitive platform for gas sensing application

Abstract: This paper reports a low power miniaturized MEMS based integrated gas sensor with 36.84 % sensitivity (ΔR/R0) for as low as 4 ppm (NH3) gas concentration. Micro-heater based gas sensor device presented here consumes very low power (360 °C at 98 mW/mm2) with platinum (Pt) micro-heater. Low powered micro-heater is an essential component of the metal oxide based gas sensors which are portable and battery operated. These micro-heaters usually cover less than 5 % of the gas sensor chip area but they need to be thermally isolated from substrate, to reduce thermal losses. This paper elaborates on design aspects of micro fabricated low power gas sensor which includes `membrane design' below the microheater; the `cavity-to-active area ratio'; effect of silicon thickness below the silicon dioxide membrane; etc. using FEM simulations and experimentation. The key issues pertaining to process modules like fragile wafer handling after bulk micro-machining; lift-off of platinum and sensing films for the realization of heater, inter-digitated-electrodes (IDE) and sensing film are dealt with in detail. Low power platinum microheater achieving 700 °C at 267 mW/mm2 are fabricated. Temperature calculations are based on experimentally calculated thermal coefficient of resistance (TCR) and IR imaging. Temperature uniformity and localized heating is verified with infrared imaging. Reliability tests of the heater device show their ruggedness and repeatability. Stable heater temperature with standard deviation (ź) of 0.015 obtained during continuous powering for an hour. Cyclic ON---OFF test on the device indicate the ruggedness of the micro-heater. High sensitivity of the device for was observed for ammonia (NH3), resulting in 40 % response for ~4 ppm gas concentration at 230 °C operating temperature.

Reliability based design optimization of wire bonding in power microelectronic devices

Abstract: This paper presents a numerical investigation of the probabilistic approach in estimating the reliability of wire bonding, and develops a reliability-based design optimization Methodology (RBDO) for microelectronic device structures. The objective of the RBDO method is to design structures which should be both economical and reliable where the solution reduces the structural weight in uncritical regions. It does not only provide an improved design, but also a higher level of confidence in the design. The Finite element simulation model intends to analyze the sequence of the failure events in power microelectronic devices. This numerical model is used to estimate the probability of failure of power module regarding the wire bonding connection. However, due to time-consuming of the multiphysics finite element simulation, a response surface method is used to approximate the response output of the limit state, in this way the reliability analysis is performed directly to the response surface by using the First and the Second Order Reliability Methods FORM/SORM. Subsequently the reliability analysis is integrated in the optimization process to improve the performance and reliability of structural design of wire bonding. The sequential RBDO algorithm is used to solve this problem and to find the best structural designs which realize the best compromise between cost and safety.

Design enhancement of a chevron electrothermally actuated microgripper for improved gripping performance

Abstract: In this paper design modifications are proposed in microgripper design using two in-plane chevron electrothermal actuators. The design modifications are, converting free---free gripping arm into a clamped-free gripping arm and inclusion of the heat sinks in the shuttle. The modified design provides reduced temperature at the gripping jaws and higher gripping force. The proposed microgripper is modelled analytically and numerically using MEMS CAD tool CoventorWare. The performance of the microgripper such as displacement, force and temperature for the voltage range of 0---1.2 V is evaluated through numerical and analytical simulation. The results demonstrate the feasibility of fabrication. Further the gripper is made of polysilicon which allows operating the gripper at lower voltage.

Design and performance evaluation of a biomimetic microrobot for the father---son underwater intervention robotic system

Abstract: Underwater intervention is a favorite and difficult task for AUVs. To realize the underwater manipulation for the small size spherical underwater robot SUR-II, a father---son underwater intervention robotic system (FUIRS) is proposed in our group. The FUIRS employs a novel biomimetic microrobot to realize an underwater manipulation task. This paper describes the biomimetic microrobot which is inspired by an octopus. The son robot can realize basic underwater motion, i.e. grasping motion, object detection and swimming motion. To enhance the payload, a novel buoyancy force adjustment method was proposed which can provides 11.8 mN additional buoyancy force to overcome the weight of the object in water. Finally, three underwater manipulation experiments are carried out to verify the performance of the son robot. One is carried by swimming motion and buoyancy adjustment; the other two are only carried by buoyancy adjustment. And the experimental results show that the son robot can realize the underwater manipulation of different shape and size objects successfully. The swimming motion can reduce the time cost of underwater manipulation remarkably.

Effect of annealing temperatures on the morphology, optical and electrical properties of TiO2 thin films synthesized by the sol---gel method and deposited on Al/TiO2/SiO2/p-Si

Abstract: Fabrication and characterization of titanium dioxide (TiO2) thin film on Al/TiO2/SiO2/p-Si MIS structure for the study of morphology, optical and electrical properties were reported. A transparent and high crystallinity of TiO2 thin films were prepared at room temperature (~25 °C) by sol---gel route. TiO2 sol suspension were prepared at molar ratio of TTIP:EtOH:AA = 2:15:1 using titanium tetra-isopropoxide (TTIP) and a mixture of absolute ethanol (EtOH) and acetic acid (AA) which used as a precursor and catalyst for the peptization, respectively. The TiO2 thin films were deposited on a thermally grown SiO2 layer of p-type silicon (100) substrates and were thermally treated at different annealing temperatures of 300, 500, 700 and 900 °C. For study of optical properties, the TiO2 thin films were deposited on a glass slides substrate and were annealed from 200 to 700 °C. The XRD results show that the presence of an amorphous TiO2 phases were transformed into the polycrystalline (anatase or rutile) with good crystallinity after treated at higher annealing temperatures. Besides, the surface roughness of TiO2 thin films increased with increasing annealing temperatures. In addition, the resistivity of the thin films decreased from 2.5751E+8 to 6.714E+7 ? cm with the increasing temperatures. Moreover, the optical absorbance of TiO2 thin films exhibited high UV---visible light absorption with band gap energy shifted to the higher wavelength (low energy photons). The band gap energy (Eg) of the films decreased from 3.79 to 3.16 eV and from 3.95 to 3.75 eV significantly for direct band allowed and indirect band allowed, respectively, with the increasing annealing temperatures.

Experimental evaluation of sensitivity and non-linearity in polysilicon piezoresistive pressure sensors with different diaphragm sizes

Abstract: MEMS-based piezoresistive pressure sensors are widely popular due to advantages such as small size, low cost, simple fabrication, and DC output. In this work, the design simulation, fabrication process, and characterization of four pressure sensors with square diaphragms of edge-length 1,060, 1,280, 1,480, and 1,690 µm are reported. Several design principles such as appropriate boundary condition, piezoresistor placement, and fracture stress are considered in the design phase. The sensors have novel shaped polysilicon piezoresistors and equal diaphragm thickness of 50 µm. The sensors are fabricated simultaneously by putting the different designs on the same mask set so that the best design can be determined after characterization. The uncompensated and unamplified output response of the different sensors are reported at three temperatures (?5, 25 and 55 °C). Out of the four sensors with different diaphragm sizes, the sensor with a diaphragm edge length of 1,280 μm is found to have optimum characteristics. For the diaphragm with edge-length of 1,280 µm, in the pressure range of 0---30 Bar, sensitivity of 3.35---3.73 mV/Bar, non-linearity of <0.3 %, and hysteresis of <0.1 % are obtained. The different sensors can be used in the specified pressure range for suitable applications.

A compact ACS-fed dual-band monopole antenna for LTE, WLAN/WiMAX and public safety applications

Abstract: In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for dual frequency operation is presented. The proposed antenna is composed of an ACS-fed monopole structure and two semi circle shaped radiating branches, which occupies a very small size of 13.4 ? 22.7 mm2 including the ground plane. By properly selecting the length and position of these branches, two desired operating bands can be achieved and tuned independently. The simulated and measured return loss results shows that the proposed antenna can be used for long term evolution 2500 (2500---2690 MHz), WLAN 5.2 GHz (5.15---5.35 GHz)/5.8 GHz (5.725---5.825 GHz), WiMAX 5.5 GHz (5.28---5.85 GHz) and 4.9 GHz (4.94---4.99 GHz) public safety applications. The omnidirectional and bidirectional radiation pattern characteristics in H-plane and E-plane of the proposed antenna along with acceptable peak gain make the best suitable candidate for the above intended applications.

Performance analysis of RF MEMS capacitive switch with non uniform meandering technique

Abstract: This Paper reports on investigation of High Con Coff ratio Capacitive Shunt RF MEMS Switch and detailed comparison between uniform three meander beam with non-uniform single meander beam RF MEMS switch. RF MEMS Switches are designed for operation in the range 5---40 GHz. Pull in analysis is performed with gold as a beam material. Simulation reveals that use of high K dielectric material can drastically improve the capacitance ratio of switch. For the same geometry, pull in voltage is 2.45 V for HfO2, 2.7 V for Si3N4 and Capacitive Ratio of the switch with Si3N4 is 83.75 and Capacitive Ratio with HfO2 is 223 at 2g0 (air gap) and 0.8 μm thickness of beam. The Radio Frequency performance of RF MEMS switch is obtained by scattering parameters (insertion loss, Return loss and isolation) which are mainly dominated by down to up capacitance ratio and MEMS bridge geometries. RF analysis shows that insertion loss as low as ź0.4 dB at 20 GHz and isolation as high as 80 dB at 20 GHz can be achieved. Investigation of three uniform meander Design and non-uniform single meander design reveals that use of non-uniform design reduces the design complexity and saves substrate area still maintaining almost same device performance. S-parameter analysis is carried out to compare device performance for both structures. DC analysis of the proposed switch is carried out using Coventorware and RF analysis is performed in MATLAB.

A complete analytical model for clamped edge circular diaphragm non-touch and touch mode capacitive pressure sensor

Abstract: Capacitive pressure sensor have become good substitute for piezoresistive pressure sensor because of low power consumption. In order to evaluate the characteristic profile for touch mode micro pressure sensor an accurate and simple model needs to be designed. Hence preferable analytical model is necessary to design and characterize the device. Lot of study has been done on touch mode capacitive sensing but no elaborate work has been presented to clearly understand the underlying expressions and the role of key performance parameters. With this step by step theoretical evaluation model the key performance parameter such as deflection, capacitance and sensitivity can be easily studied for both non-touch and touch mode capacitive pressure sensor. The next aspect has been to simulate the findings in order to validate the results and hence MATLAB has been introduced. It also eliminates the need for design using FEM and hence the study becomes lot easier.

A flexible dry electrode based on APTES-anchored PDMS substrate for portable ECG acquisition system

Abstract: We developed a simple and low-cost flexible dry electrode with micro domes by depositing metal film directly on (3-aminopropyl)triethoxysilane (APTES)-anchored polydimethylsiloxane (PDMS) substrate for portable electrocardiogram (ECG) acquisition system. However, the adhesion between metal and PDMS was poor, and metal film on PDMS always exhibited wrinkles. To overcome these difficulties, before depositing Cu, PDMS substrate was treated by APTES aqueous solution. Then, we evaluated the metal film through the microscopic photographs, the surface roughness measurements and the adhesion tests. On the base of the deposition technique improvement, a PDMS-based dry electrode for ECG monitoring was fabricated. We studied the performance of the flexible dry electrode and the results showed the fabricated electrode produced good ECG signals with distinct P, QRS, and T waves. In addition, the fabricated flexible dry electrode with micro domes showed lower skin-contact impedance and could obtain ECG signals with higher SNR than the flat dry electrode.

A very small asymmetric coplanar strip fed multi-band antenna for wireless communication applications

Abstract: In this paper, a compact tri-band monopole antenna with asymmetric coplanar strip (ACS)-fed structure is proposed for long term evolution (LTE), Wireless Broadband (WiBro), Worldwide Interperability for Microwave Access (WiMAX), wireless local area network (WLAN) and 4.9 GHz public safety applications. The proposed antenna consists of an F-shaped radiating element along with a meanderd line structure, which occupy a compact size of 10 × 17.5 mm2 including the ground plane. The desired resonant frequencies at 3.5/5.5 GHz for WiMAX and 5.2/5.8 GHz WLAN can be achieved by properly selecting the length of the two horizontal branches in F-shaped patch and by introducing a meanderd line structure, another desired resonant frequency at 2.3 GHz for LTE/WiBro has been achieved. A prototype of the proposed antenna is designed, fabricated and validated experimentally. The measured results demonstrate that the proposed antenna has ź10 dB impedance bandwidth of 120 MHz (2.3---2.42 GHz), 450 MHz (3.3---3.75 GHz), and 1500 MHz (4.5---6.0 GHz) along with good onmi-directional radiation patterns and acceptable peak gains in all the three operating bands.

An overview of magnetic micro-robot systems for biomedical applications

Abstract: Untethered and wirelessly-controlled micro-robots have been catching substantial attention for a long time due to their great potentials in biomedical areas. Their small sizes and property of wireless magnetic actuation and control make them fit in tiny and closed environments both in vitro and in vivo such as lab-on-a-chip and human blood vessels for micromanipulations, minimum/non-invasive theoretical and diagnostic applications, respectively. In recent years, micro-robots driven by magnetic fields become a hotspot due to their good controllability and motion performance they have shown in both wet and dry environments. And they hardly bring harm under magnetic actuation and control, which qualify them especially for biomedical applications. This paper reviews the state of the art of hjbvmagnetic-micro-robot systems, including the related knowledge and theories, design works of magnetic micro-robots and magnetic navigation systems. For a straightforward understanding, several types of magnetic micro-robot systems are presented. And some applications of magnetic micro-robot systems are introduced at the end to show their great potentials. However, for further developments, many obstacles still need to be solved.

Thermomechanical behavior of bulk NiTi shape-memory-alloy microactuators based on bimorph actuation

Abstract: Shape-memory-alloy (SMA) has attracted considerable attention in recent years as a smart and efficient material, due to its unique properties. SMA microactuators became one of the potential solutions for unresolved issues in microelectromechanical systems (MEMS). This paper presents a thermomechanical behavior analysis of bimorph SMA structure and studies the effect of varying the SMA layer thickness, the type of stress layer and its thickness, and the processing temperature on the displacement of the microactuator. Furthermore, the analyzed results were verified by experimental work, where the fabrication of the SMA microactuators followed the standards of the MEMS fabrication process. SiO2, Si3N4 and Poly-Si were used as stress layers. The fabrication results showed that the bimorph SMA structure achieved maximum displacement when SiO2 was used. The SMA structure with dimensions of 10 mm (length) × 2 mm (width) × 80 µm (thickness), had maximum displacement of 804 µm when 4.1 µm of SiO2 layer was deposited at a temperature of 400 °C.

Effect of piezoresistor configuration on output characteristics of piezoresistive pressure sensor: an experimental study

Abstract: Piezoresistive sensing is one of the most frequently used transduction mechanism in pressure sensors. The piezoresistor placement on the diaphragm and the piezoresistor configuration play a pivotal role in determining the output characteristics of a pressure sensor. In this work, two different pressure sensors with different transverse piezoresistor configurations are studied to determine the effect of piezoresistor configuration on the sensitivity and non-linearity of the pressure sensors. A sensor structure with a square diaphragm size of 1,480 µm edge length and diaphragm thickness of 50 µm is chosen for the study. The design considerations for piezoresistor placement and the piezoresistor shapes are discussed in detail. The sensors are fabricated with bulk micromachined diaphragm and polysilicon piezoresistors. The sensor characteristics are determined for three temperatures, namely, ?5, 25 and 55 °C and for a pressure range of 0---30 Bar. The characterization results indicate that the design with two piezoresistor arms in transverse piezoresistor configuration (2 × 2 Design) has higher sensitivity than the single arm configuration (2 × 1 Design) by about 25 % at 25 °C but it also has a higher non-linearity. The study shows the importance of selecting the proper piezoresistor configuration in the design of pressure sensors.

Miniaturized devices for isothermal DNA amplification addressing DNA diagnostics

Abstract: Microfluidics is an emerging technology enabling the development of lab-on-a-chip systems for clinical diagnostics, drug discovery and screening, food safety and environmental analysis. Currently, available nucleic acid diagnostic tests take advantage of polymerase chain reaction that allows exponential amplification of portions of nucleic acid sequences that can be used as indicators for the identification of various diseases. At the same time, isothermal methods for DNA amplification are being developed and are preferred for their simplified protocols and the elimination of thermocycling. Here, we present a low-cost and fast DNA amplification device for isothermal helicase dependent amplification implemented in the detection of mutations related to breast cancer as well as the detection of Salmonella pathogens. The device is fabricated by mass production amenable technologies on printed circuit board substrates, where copper facilitates the incorporation of on-chip microheaters, defining the thermal zone necessary for isothermal amplification methods.

Tunable MEMS piezoelectric energy harvesting device

Abstract: This work is focused on low frequency (<300 Hz) vibrations due to the fact that many industrial and commercial devices operate at those frequencies. The aim of the present work is to model by numerical simulation a Si cantilever beam with an AlN piezoelectric layer concept that tunes its resonant frequency post-processing, while reducing the separation of the first two modes of resonance in order to broaden its quality factor and, therefore, to harvest more environmental energy. This paper investigates by numerical simulation the influence of perforating sections of the Si beam has on the resonant frequencies of the cantilever. The authors have found that the distance between these modes is decreased by 30 % when 0.002 mm3 is extracted in a specific location of the initial structure. This difference between modes can be reduced above 80 % if a volume of 0.004 mm3 in a specific part of the initial design is subtracted. In these conditions, the first mode is decreased about 20 % the initial value and the second mode about 60 %.

Performance enhancement of FINFET and CNTFET at different node technologies

Abstract: Developing technologies need smaller and faster IC's, hence transistor size has to be scaled down. In order to satisfy this, transistor size in a chip has been decreased drastically from micro range to nano-range. MOSFET was the mass element in any IC at micro size, but when scaled down to nano regime performance degrades because of short channel effects. It is shown here that the FinFET, which gives the better performance and scalability, will replace it. However in 14 nm node and beyond, FinFET also has certain disadvantages; hence some performance enhancement techniques have been introduced to yield good results in 14 nm node. Such techniques include changing the channel materials, use of high-K gate dielectric, etc. We used parameters defined in ITRS update 2013 to simulate FinFET in 14 nm node and we adapted various techniques. Finally the performance enhancement of both finFET and CNTFET for 14 nm node is shown.