Rosminazuin Ab Rahim

Design and analysis of MEMS piezoresistive SiO 2 cantilever-based sensor with stress concentration region for biosensing applications

This paper uses finite element method to obtain the optimal performance of piezoresistive microcantilever sensor by optimizing the geometrical dimension of both cantilever and piezoresistor. A 250 mum times 100 mum times 1 mum SiO2 cantilever integrated with 0.2 mum thick Si piezoresistor was used in this study. The sensor performance was measured on the basis of displacement sensitivity and surface stress sensitivity. The resulting maximum displacement value is about 0.7 nm for an applied load of 250 pN. A comparison between polySi and SiO2 cantilever has been carried out which shows the latter gives higher displacement for the same applied load. The sensor sensitivity was investigated by varying cantilever thickness as well as piezoresistor thickness. Simulation results show that the cantilever sensitivity is maximum when both the cantilever and the piezoresistor thicknesses are at minimum. Simulations were also conducted on the effects of incorporating various stress concentration region (SCR) designs at the bottom of the cantilevers. Cantilevers with incorporated stress concentration regions shows improved sensitivity over the cantilever without SCR. The cantilever with a rectangular shaped SCR extended up to the edge of the cantilever width yields a maximum Mises stress of 0.73 kPa compares to the other designs. For the same design, the cantilever with minimum SCR thickness of 0.2 mum yields maximum stress which results in maximum sensitivity.

Performance analysis of zinc oxide piezoelectric MEMS energy harvester

This paper presents the design and analysis of MEMS piezoelectric energy harvester. Zinc oxide (ZnO) MEMS piezoelectric energy harvester has been utilized as piezoelectrically active cantilever for mechanical to electrical transduction. A COMSOL Multiphysics model was used which provide accurate information on the frequency, stress and voltage output of a ZnO piezoelectric energy harvester. Few design parameters have been studied which are rectangular cantilever, triangular cantilever, rectangular cantilever with proof mass and using different types of piezoelectric materials. The effects of varying geometrical dimensions of the device were also investigated. From simulation results, it was found out that ZnO piezoelectric energy harvester with the length of 150 μm, width 50 μm and thickness of 4 μm generates 9.9184 V electric potential under the resonance frequency of 0.71 MHz and 1 μN/m2 mechanical force applied.

Optimization of printing techniques for electrochemical biosensors

Electrochemical biosensors show great promise for point-of-care applications due to their low cost, portability and compatibility with microfluidics. The miniature size of these sensors provides advantages in terms of sensitivity, specificity and allows them to be mass produced in arrays. The most reliable fabrication technique for these sensors is lithography followed by metal deposition using sputtering or chemical vapor deposition techniques. This technique which is usually done in the cleanroom requires expensive masking followed by deposition. Recently, cheaper printing techniques such as screen-printing and ink-jet printing have become popular due to its low cost, ease of fabrication and mask-less method. In this paper, two different printing techniques namely inkjet and screen printing are demonstrated for an electrochemical biosensor. For ink-jet printing technique, optimization of key printing parameters, such as pulse voltages, drop spacing and waveform setting, in-house temperature and cure ann...

Design optimization of MEMS dual-leg shaped piezoresistive microcantilever

In this paper, an optimization on the mechanical behaviour of silicon piezoresistive microcantilever (PRM) has been carried out. Using CoventorWare 2008, the mechanical behavior of the PRM structure was investigated by studying few contributing factors that affect the performance of the device. The performance was represented with mechanical displacement of the suspended PRM sensor with regards to various factors such as the microcantilever shape and geometrical dimensions, the materials and the effect of incorporating stress concentration region (SCR) on the device structure. In this research work, a single-layer piezoresistive microcantilever in which both piezoresistor and microcantilever structures are made of the same material of single-crystalline silicon is utilized. Two dual-leg shaped piezoresistive microcantilever designs have been proposed: piezoresistive microcantilever with and without a square hole. From the simulation results, it can be seen that the maximum displacement is observed at maximum microcantilevers length and minimum thickness. The incorporation of a square hole as an SCR not only shows a significant increase in Mises stress value but also in the displacement of the microcantilever structure. Single-crystalline Si was chosen as the device material for the fabrication of single-layer piezoresistive microcantilever due to its high piezoresistive coefficients and thermal conductivity.

Fabrication of monolithic Wheatstone bridge circuit for piezoresistive microcantilever sensor

In this paper, the fabrication of monolithic Wheatstone bridge circuit on piezoresistive microcantilever sensor is presented. The development of the device is realized through silicon micromachining technology on silicon substrate through three major fabrication steps including silicon piezoresistive microcantilever formation, aluminum deposition of Wheatstone bridge interconnections and microcantilever release. The electrical discontinuity of interconnections which is one of the major issues encountered in the fabrication process is discussed and analyzed. Deposition of proper thickness of metal interconnection layers through metal evaporation process accompanied with annealing process at low temperature ensures complete electrical connections in the monolithic Wheatstone bridge configuration. Measurement of the fabricated Wheatstone bridge circuit shows a good agreement between theoretical and experimental values indicating successful fabrication of the device. Fabrication of piezoresistive microcantilever structure integrated with monolithic Wheatstone bridge circuit with resistance values in the range of 1 to 9 kΩ has been successfully realized using silicon micromachining technology.

Verification of Quartz Crystal Microbalance Array using Vector Network Analyzer and OpenQCM

Received Jan 15, 2018 Revised Mar 14, 2018 Accepted Mar 30, 2018 Blood veins detection process can be cumbersome for nurses and medical practioners when it comes to special overweight type of patients. This simple routine procedure can lead the process into an extreme calamity for these patients. In this paper, we emphasized on a process for the detection of the vein in real time using the consecrations of Matlab to prevent or at least reduce the number of inescapable calamity for patients during the infusion of a needle by phlebotomy or doctor in everyday lives. Hemoglobin of the blood tissues engrossed the Near Infrared (NIR) illuminated light and Night vision camera is used to capture the scene and enhance the vein pattern clearly using Contrast Limited Adaptive Histogram Equalization (CLAHE) method. This simple approach can successfully also lead to localizing bleeding spots, clots from stroke ... etc among other things.

Queue Backlog as a Node Metric for RPL Protocol

The current de-facto routing protocol over WSN developed by IETF Working Group (6LOWPAN) named as Routing Protocol for Low Power and Lossy networks (RPL) [1], to enable IPv6 packets carrying over IEEE 802.4 and to empower the usage of IoT over WSN. Because of the potential large networks, number of nodes and the fact that multiple coexisting applications will be running in the same physical layer, RPL in the network layer faces throughput challenges. For the purpose of overcoming these problems many researchers focused on multipath solutions including a Back-Pressure routing protocol for data collection called BackIP [2], however it shows a superior throughput performance, BackIP have shortcomings of higher delay and limited applicability. In this paper, we introduce a node metric based on nodes Queue Backlogs for RPL protocol, which leads to better throughput performance while maintaining the delay and the ability to use with the different network applications. This metric depends on the Packet Queue length of the nodes with the consideration of other link and node metrics, like ETX or Energy usage, leading to better load balancing in the network. Moreover we discuss the needed design changes to enable our metric to perform in an efficient way.

Radiation Characteristics and SEU Rates in NEqO Environment Using SPENVIS

RazakSat1 was launched at Near Equatorial Orbit (NEqO) where Trapped Protons / Electrons (TP/TE) and Galactic Cosmic Rays (GCR) has intensive effect on satellites memory like SRAM based FPGA. Due to this devastating effect, it is important to investigate the radiation environment of the orbit to predict the SEU rate for 6T SRAM, which is the building block of SRAM based FPGA. This study investigates the radiation environment in NEqO specifically for the orbit of RazakSat satellite. Solar Event Particles (SEPs), Trapped Protons / Electrons (TP/TE) and Galactic Cosmic Rays (GCR) are the three main sources of radiation which are taken to consideration in this study. The fluxes spectra of these three types are simulated and SEU rates for 180nm 6T SRAM are predicted using SPENVIS models for NEqO orbit. The results show that GCR fluxes are the most dominant at NEqO which reached to 105 MeV whereas TE has 4MeV and TP has the second dominant fluxes with 400 MeV. However, if the magnetic shielding atmosphere is on, there are no solar particles fluxes and almost no SEU was detected. Results also illustrate that SEU rates at NEqO is 0.5 upset / bit day when there is no shielding to the device (6T SRAM) but this rates reduced by 1.6 x 106 times when the device shielded by 0.5 g/cm2 of Aluminium. Comparisons of NEqO with polar orbit in terms of shielding effect and SEU rates are also presented in this study.

Design and Simulation of MEMS Helmholtz Resonator for Acoustic Energy Harvester

An acoustic energy harvester using Helmholtz resonator with piezoelectric circular diaphragm has been studied using COMSOL Multiphysics 5.1. In this paper, multiple designs considerations for MEMS Helmholtz resonator and piezoelectric circular diaphragm including the length and radius of the tube, the radius of the cavity and the thickness of the circular piezoelectric cantilever have been studied and investigated by varying its size with 5 different values for each parts in order to find the best size for optimum output voltage. The input pressure have been set to 1 Pa as default. The simulation results demonstrated that under the same condition, a higher output pressure can be formed by having smaller tube radius and bigger cavity radius of the Helmholtz resonator. The resonance frequency of the Helmholtz resonator was found at 181 Hz. On the other hand, the interaction between air pressures vibration and piezoelectric diaphragm plays an important role in determining the amount of harvested acoustic power and the position of piezoelectric circular diaphragm in the Helmholtz resonator is at the optimum when it is placed at the end of the resonator compared to at the beginning of the resonators tube.

Modeling of a novel biosensor with integrated mass and electrochemical sensing capabilities

Rapid development in technology and society has generated diverse developments in many fields including biosensors in healthcare application. Here, the design of integrated biosensor comprises mass sensing (Quartz Crystal Microbalance) and electrochemistry sensing (Electrochemical Impedance Spectroscopy, EIS and Cyclic Voltammetry, CV) will be presented. The integrated sensor system is developed based on the innovative use of the top electrode of a quartz crystal microbalance (QCM) resonator as a working electrode for the electrochemistry technique. Integration of QCM with the electrochemistry technique is realized by fabricating a semicircular counter electrode near the upper electrode on the same side of the quartz crystal. CV and EIS measurement was conducted using finite element modeling, COMSOL™ 5.2 with the probe marker of 1 mmol L−1 of [Fe(CN)6]3-/4- CV test was done to study the effect between increasing scan rate and peak current (anodic and cathodic) in observing the reversible electrochemical process. This observation is crucial in ensuring the electrochemical processes follow the Randles-Sevcik equation in characterizing the platform changes behavior. Later, EIS test was performed in order to measure the radius of the semicircle which reflects the charge transfer resistance (RCT) of the redox marker. To show the effectiveness of this sensor, gold immobilization surface was electrochemically simulated and reported. Thus, an ultra-sensitive biosensor that capable to produce multi-analysis in the detection of biological targets in terms of electrochemical change of electrode interfaces, which is the crucial step towards the engineering of advanced bioelectronics.