Rashidah Arsat

Pt/graphene nano-sheet based hydrogen gas sensor

In this paper, we present gas sensing properties of Pt/graphene-like nano-sheets towards hydrogen gas. The graphene-like nano-sheets were produced via the reduction of spray-coated graphite oxide deposited on SiC substrates by hydrazine vapor. Structural and morphological characterizations of the graphene sheets were analyzed by scanning electron and atomic force microscopy. Current-voltage and dynamic responses of the sensors were investigated towards different concentrations of hydrogen gas in a synthetic air mixture at 100°C. A voltage shift of 100 mV was recorded at 1 mA reverse bias current.

Graphene-like nano-Sheets/36° LiTaO 3 surface acoustic wave hydrogen gas sensor

Presented is the material and gas sensing properties of graphene-like nano-sheets deposited on 36deg YX lithium tantalate (LiTaO3) surface acoustic wave (SAW) transducers. The graphene-like nano-sheets were characterized via scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The graphenelike nano-sheet/SAW sensors were exposed to different concentrations of hydrogen (H2) gas in a synthetic air at room temperature. The developed sensors exhibit good sensitivity towards low concentrations of H2 in ambient conditions, as well as excellent dynamic performance towards H2 at room temperature.

Micropump Pattern Replication Using Printed Circuit Board (PCB) Technology

This article shows a low-cost rapid hot embossing poly (methylmeth acrylate) (PMMA)–based micropump replication with printed circuit board (PCB) mold. PCB material offers advantages of low cost, rigid, and rapid thermal response characteristic. Unlike conventional hot embossing setup, the presented process involved the usage of simple machinery tools: laboratory oven (heat transfer), G-clamp (force deliver), and two aluminium plates (isothermal heat plates). Diffuser and pump chamber were successfully imprinted with the depth of 450 µm and verified pump performance with other reported literatures. To avoid complex bonding process between actuator and membrane, electromagnetic pinch actuation is introduced. The micropump poses flow rate characteristic of 6.66 ml/min and a back pressure of 1.6 kPa under optimum pinch frequency.

Low cost diffuser based micropump using pinch actuation

Planar pinch micropump with the integration of two diffuser valve elements has been reported. The fabrication of the micropump is carried out by utilizing simple hot embossing technique for microdiffuser imprinting and spin coating for membrane construction. Parameter of diffuser design is optimized via finite element analysis (FEA). The experiment result shows that the pump works well at low frequency of 29 Hz.

Polyvinylpyrrolidone/Multiwall Carbon Nanotube Composite Based 36° YX LiTaO3 Surface Acoustic Wave For Hydrogen Gas Sensing Applications

Poly‐vinyl‐pyrrolidone (PVP) /Multiwall Carbon Nanotubes (MWNTs) based Surface Acoustic Wave (SAW) sensors are fabricated and characterized, and their performances towards hydrogen gas are investigated. The PVP/MWNTs fibers composite are prepared by electrospinning of the composite aqueous solution deposited directly onto the active area of SAW transducers. Via scanning electron microscopy (SEM), the morphology of the deposited nanostructure material is observed. From the dynamic response, frequency shifts of 530 Hz (1% H2) and 11.322 kHz (0.25% H2) are recorded for the sensors contain of 1.525 g and 1.025 g PVP concentrations, respectively.

Polyvinylpyrrolidone/multiwall carbon nanotube composite based 36° YX LiTaO 3 surface acoustic wave H 2 gas sensor

Poly-vinyl-pyrrolidone (PVP) is one of the actylene chemistry products founded by Prof Walter Reppe [1]. In most cases, PVP usually presents as an essential auxiliary, not an active substance itself [2]. Until recently, He et al. [3] has reported the application of PVP fibers as H2 gas sensor. Extending from the reported investigation, this work shows the gas sensing properties of PVP/MWNTs composite/36° YX LiTaO3 SAW device.

Reverse biased Schottky contact hydrogen sensors based on Pt/nanostructured ZnO/SiC

Pt/nanostructured ZnO/SiC Schottky contact devices were fabricated and characterized for hydrogen gas sensing. These devices were investigated in reverse bias due to greater sensitivity, which attributes to the application of nanostructured ZnO. The current‐voltage (I‐V) characteristics of these devices were measured in different hydrogen concentrations. Effective change in the barrier height for 1% hydrogen was calculated as 27.06 meV at 620° C. The dynamic response of the sensors was also investigated and a voltage shift of 325 mV was recorded at 620° C during exposure to 1% hydrogen in synthetic air.

Pt/anodized TiO2/SiC-based MOS device for hydrocarbon sensing

Pt/anodized TiO2/SiC based metal-oxide-semiconductor (MOS) devices were fabricated and characterized for their sensitivity towards propene (C3H6). Titanium (Ti) thin films were deposited onto the SiC substrates using a filtered cathodic vacuum arc (FCVA) method. Fluoride ions containing neutral electrolyte (0.5 wt% NH4F in ethylene glycol) were used to anodize the Ti films. The anodized films were subsequently annealed at 600 °C for 4 hrs in an oxygen rich environment to obtain TiO2. The current-voltage (I-V) characteristics of the Pt/TiO2/SiC devices were measured in different concentrations of propene. Exposure to the analyte gas caused a change in the Schottky barrier height and hence a lateral shift in the I-V characteristics. The effective change in the barrier height for 1% propene was calculated as 32.8 meV at 620°C. The dynamic response of the sensors was also investigated and a voltage shift of 157 mV was measured at 620°C during exposure to 1% propene.

A hydrogen gas sensor fabricated from polythiophene nanofibers deposited on a 36°YX LiTaO3 layered surface acoustic wave transducer

A gas sensor was developed by depositing polythiophene nanofibers on the surface of ZnO/36° YX LiTaO3 layered surface acoustic wave (SAW) transducer and tested towards different concentrations of hydrogen gas in synthetic air. Polythiophene nanofibers were synthesized by using a template-free method through the introduction of an initiator into the reaction mixture of a rapidly mixed reaction between the monomer (thiophene) and the oxidant. The yield of the reaction was characterized using scanning electron microscopy (SEM) as well as Ultraviolet-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopies. The frequency shift due to the sensor response was ~17 kHz towards 1% of H2. All tests were conducted at room temperature. The sensor performance was assessed over a two day period and a high degree of repeatability was obtained.

Pt/TiO 2 nanotubes/SiC schottky diodes for hydrogen gas sensing applications

Titanium oxide nanotubes Schottky diodes were fabricated for hydrogen gas sensing applications. The TiO2 nanotubes were synthesized via anodization of RF sputtered titanium films on SiC substrates. Two anodization potentials of 5 V and 20 V were used. Scanning electron microscopy of the synthesized films revealed nanotubes with avarage diameters of 20 nm and 75 nm. X-ray diffraction analysis revealed that the composition of the oxide varied with the anodization potential. TiO2 (anatase) being formed preferentially at 5 V and TiO (no anatase) at 20 V. Current-voltage characteristics of the diodes were studied towards hydrogen at temperatures from 25°C to 250°C. At constant current bias of −500 μA and 250°C, the lateral voltage shifts of 800 mV and 520 mV were recorded towards 1% hydrogen for the 5 V and 20 V anodized nanotubes, respectively.