In this project, SiC based MEMS capacitive microphone was developed for detecting leaked gas in extremely harsh environment such as coal mines and petroleum processing plants via ultrasonic detection. The MEMS capacitive microphone consists of two parallel plates; top plate (movable diaphragm) and bottom (fixed) plate, which separated by an air gap. While, the vent holes were fabricated on the back plate to release trapped air and reduce damping. In order to withstand high temperature and pressure, a 1.0 μm thick SiC diaphragm was utilized as the top membrane. The developed SiC could withstand a temperature up to 1400°C. Moreover, the 3 μm air gap is invented between the top membrane and the bottom plate via wafer bonding. COMSOL Multiphysics simulation software was used for design optimization. Various diaphragms with sizes of 600 μm2, 700 μm2, 800 μm2, 900 μm2 and 1000 μm2 are loaded with external pressure. From this analysis, it was observed that SiC microphone with diaphragm width of 1000 μm2 produced optimal surface vibrations, with first-mode resonant frequency of approximately 36 kHz. The maximum deflection value at resonant frequency is less than the air gap thickness of 8 mu;m, thus eliminating the possibility of shortage between plates during operation. As summary, the designed SiC capacitive microphone has high potential and it is suitable to be applied in ultrasonic gas leaking detection in harsh environment.
First pristine graphene was successfully produced by mechanical exfoliation and electrically characterized in 2004 by Andre Geim and Konstantin Novoselov at University of Manchester. Since its discovery in 2004, graphene also known as ‘super’ material that has enticed many researchers and engineers to explore its potential in ultrasensitive detection of analytes in biosensing applications. Among myriad reported sensors, biosensors based on field effect transistors (FETs) have attracted much attention. Thus, implementing graphene as conducting channel material hastens the opportunities for production of ultrasensitive biosensors for future device applications. Herein, we have reported electrical characteristics of graphene based field effect transistor (GFET) for ADH detection. GFET was modelled and simulated using Lumerical DEVICE charge transport solver (DEVICE CT). Electrical characteristics comprising of transfer and output characteristics curves are reported in this study. The device shows ambipolar curve and achieved a minimum conductivity of 0.23912 e5A at Dirac point. However, the curve shifts to the left and introduces significant changes in the minimum conductivity as drain voltage is increased. Output characteristics of GFET exhibits linear Id - Vd dependence characteristics for gate voltage ranging from 0 to 1.5 V. In addition, behavior of electrical transport through GFET was analyzed for various simulation temperatures. It clearly proves that the electrical transport in GFET is dependent on the simulation temperature as it may vary the maximum resistance in channel of the device. Therefore, this unique electrical characteristics of GFET makes it as a promising candidate for ultrasensitive detection of small biomolecules such as ADH in biosensing applications.
Dielectrophoresis (DEP) is a phenomenon in which force exerted on a dielectric particle when it is subjected to a nonuniform electric field. There are many applications of dielectrophoresis and one of them is the separation of particles. In this paper, castellated and straight electrodes are being introduced for negative dep filter of an artificial kidney. In order to avoid the filters from clogging, negative dep will take part to repel the particles. Thus, a simulation by using COMSOL Multiphysics had been done to compare the electrical performances of electrodes. The intensities of electric field were stimulated on the planar electrodes from top to bottom and left to right. Electrodes are made of aluminum and both have thickness of 50μm. Distance between the castellated electrodes are 100μm while the straight electrodes are 300μm. Three graph of electric field vs. length had been compared. The first comparison shows that both designs have similar flow of electric field. The second graphs show that castellated electrodes have higher electric field, 27.14kV/m and third comparison shows a cluster increase for castellated electrodes and uniform increase for straight electrodes. Final result shows that castellated electrodes are intended to use for artificial kidney.
In the field of science, there is a significant interest in graphene due to its extraordinary properties such as high electrical
conductivity, good electrochemical stability and excellent mechanical behavior. This paper presents the direct graphene
growth on interdigital electrodes by plasma enhanced chemical vapor deposition (PECVD) using Ni catalyst and
methane (CH4) as the carbon source. The 100 nm of Ni was deposited on the top of SiO2 substrate functional as catalyst
and electrode of MEMS supercapacitor. The growth of graphene was investigated at temperature 1000°C at 10 minutes
and at fix power of 40 Watt. The morphology and structure of as- grown graphene were characterized by Raman
spectroscopy, Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). From
Raman spectra, it is observed that the intensity ratio of the 2D band to G band produced a good quality bilayer graphene.
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