Showing papers by "Adisorn Tuantranont published in 2010"

Portable electronic nose based on carbon nanotube-SnO2 gas sensors and its application for detection of methanol contamination in whiskeys

Abstract: In this paper, a portable electronic nose (E-nose) based on hybrid carbon nanotube-SnO2 gas sensors is described. The hybrid gas sensors were fabricated using electron beam (E-beam) evaporation by means of powder mixing. The instrument employs feature extraction techniques including integral and primary derivative, which lead to higher classification performance as compared to the classical features (ΔR and ΔR/R0). It was shown that doping of carbon nanotube (CNT) improves the sensitivity of hybrid gas sensors, while quantity of CNT has a direct effect on the selectivity to volatile organic compounds, i.e., methanol (MeOH) and ethanol (EtOH). The real-world applications of this E-nose were also demonstrated. Based on the proposed methods, this instrument can monitor and classify 1 vol% of MeOH contamination in whiskeys.

Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.

Abstract: In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.

Design, Fabrication and Analysis of Silicon Hollow Microneedles for Transdermal Drug Delivery System for Treatment of Hemodynamic Dysfunctions

Abstract: In this paper, we present design, fabrication and coupled multifield analysis of hollow out-of-plane silicon microneedles with piezoelectrically actuated microfluidic device for transdermal drug delivery (TDD) system for treatment of cardiovascular or hemodynamic disorders such as hypertension. The mask layout design and fabrication process of silicon microneedles and reservoir involving deep reactive ion etching (DRIE) is first presented. This is followed by actual fabrication of silicon hollow microneedles by a series of combined isotropic and anisotropic etching processes using inductively coupled plasma (ICP) etching technology. Then coupled multifield analysis of a MEMS based piezoelectrically actuated device with integrated silicon microneedles is presented. The coupledfield analysis of hollow silicon microneedle array integrated with piezoelectric micropump has involved structural and fluid field couplings in a sequential structural-fluid analysis on a three-dimensional model of the microfluidic device. The effect of voltage and frequency on silicon membrane deflection and flow rate through the microneedle is investigated in the coupled field analysis using multiple code coupling method. The results of the present study provide valuable benchmark and prediction data to fabricate optimized designs of the silicon hollow microneedle based microfluidic devices for transdermal drug delivery applications.

Wireless wearable pulse oximeter for health monitoring using ZigBee wireless sensor network

Abstract: In this work, a portable real-time wireless health monitoring system is developed. The system is used for remote monitoring of patients' heart rate and oxygen saturation in blood. The system was designed and implemented using ZigBee wireless technologies. All pulse oximetry data are transferred within a group of wireless personal area network (WPAN) to database computer server. The sensor modules were designed for low power operation with a program that can adjust power management depending on scenarios of power source and current power operation. The sensor unit consists of (1) two types of LEDs and photodiode packed in Velcro strip that is facing to a patient's fingertip; (2) Microcontroller unit for interfacing with ZigBee module, processing pulse oximetry data and storing some data before sending to base PC; (3) ZigBee module for communicating the data of pulse oximetry, ZigBee module gets all commands from microcontroller unit and it has a complete ZigBee stack inside and (4) Base node for receiving and storing the data before sending to PC.

A low-cost data-glove for Human computer interaction based on ink-jet printed sensors and ZigBee networks

Abstract: In this paper, a data-glove based on new kind of sensors is presented as an alternative to expensive devices. These sensors were realized using a conductive polymer (PEDOT:PSS) thin film printed on glossy photo paper. To demonstrate the printed sensors, we constructed a data glove using such sensors and developed software for real-time hand tracking. Wireless networks based on low-cost ZigBee technology were used to transfer data from the glove to a computer. This data-glove is very useful in many contexts such as telerobotics, rehabilitation and HCI applications.

Simple RC low pass filter circuit fabricated by unmodified desktop inkjet printer

Abstract: In this work, we present resistor-capacitor circuit (RC circuit) or simple RC low pass filter circuit was fabricated by using simple inkjet printing technique. A conductive polymer, Poly (3, 4-ethylenedioxythiophene)/poly-styrene-sulfonic acid (PEDOT/PSS) was used as a resistive component and electrode material for the capacitor. Commercially available Ethyl-2-cyanoacrylate was applied as the dielectric of the capacitor. The device was inkjet printed by using a normal desktop printer CANON IP 4500. It was shown that the cut-off frequency of the device could be tuned to 10 kHz. The finding indicate the practical use of PEDOT/PSS RC low pass filter in flex sensor.

Cardiac troponin T detection using polymers coated quartz crystal microbalance as a cost-effective immunosensor.

Abstract: Cardiac troponin T (cTnT) detection has been the focus of increased interest due to its role in myocardial infarction diagnosis. In this study, we report a relatively low coat technique to detect cTnT using a quartz crystal microbalance (QCM) sensor. A sensitive detection is achieved by introducing a QCM surface with a carboxylic polyvinyl chloride immobilization layer. The surface morphologies of this polymer film under varied deposition thickness have been investigated by field emission scanning electron microscopy and atomic force microscopy. A cTnT detection result from a modified QCM surface can be obtained within a short response time by a direct detection of the immunoreaction and a direct conversion of mass accumulation into a frequency shift, representing a measurable electrical signal. The relationship between the cTnT concentration and the response current from a QCM sensor shows detectability at the concentration of cTnT as low as 5 ng/ml.

Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field.

Abstract: An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius–Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques.

Real-time monitoring of GPS-tracking tractor based on ZigBee multi-hop mesh network

Abstract: This research is a part of smart farm system in the framework of precision agriculture. The system was installed and tested over a year. The tractor tracking system employs the Global Positioning System (GPS) and ZigBee wireless network based on mesh topology to make the system communicate covering a large area. Router nodes are used for re-transmission of data in the network. A software was developed for acquiring data from tractor, storing data and displaying in real time on a web site.

Novel anodic aluminum oxide (AAO) nanoporous membrane for wearable hemodialysis device

Abstract: In this paper a novel structure of AAO membrane is reported. The AAO membrane was fabricated from commercial grade impure aluminum sheet. The fabricated membrane has hexagonal structure and the nanopores appeared at the bottom of that honeycomb structure. The thickness of fabricated membrane is 42.5µm. The average diameter of upper layer pore is 350nm and average diameter of lower layer pore is 50nm. The nanopores inside the fabricated membrane are highly straight and perpendicular to the surface. This two layer AAO membrane will speed up the hemodialysis process.

Design, analysis and fabrication of MEMS-based silicon microneedles for bio-medical applications

Abstract: In this paper we present the design, analysis and fabrication of silicon hollow out-of-plane microneedles for transdermal drug delivery (TDD) applications. The fabrication process of silicon microneedles involves combination of isotropic and anisotropic etching process using inductively coupled plasma (ICP) etching technology. Finite Element Analysis (FEA) using ANSYS rather than analytical system has been used to perform the structural analysis. The effect of axial and transverse load on the microneedles during skin insertion is investigated in the stress analysis. The analysis predicts that the resultant stresses due to applied bending and axial loads are in the safe range below the yield strength of the material.

Low-cost and high-resolution x-ray lithography utilizing a lift-off sputtered lead film mask on a Mylar substrate

Abstract: In this work, a low-cost and high-resolution x-ray micromask is developed by sputtered lead film on a Mylar sheet substrate with the lift-off process and the x-ray mask is experimented for patterning SU-8 negative photoresist on a glass substrate. Sputtering is selected for Pb thick film deposition due to its high sputtering yield. The Pb mask is used for x-ray lithography of SU-8 photoresist with 5 ?m closely spaced square array patterns, designed for electrowetting electrodes on a microfluidic chip. For 140 ?m thick SU-8 photoresist, a Pb film thickness of around 10 ?m was used to block x-rays with 95% x-ray image contrast at a critical dose of 4200 mJ cm?3. A high aspect ratio of 26.5 of SU8 microstructure with 5 ?m lateral resolution has been demonstrated by the developed low-cost Pb-based x-ray mask. In addition, a steep sidewall angle of nearly 90? for SU-8 structure is confirmed. The results demonstrate that the Pb-based x-ray mask offers high-resolution x-ray lithography at a very low cost. Therefore, it is highly promising for commercial applications.

Development of Wireless Electronic Nose for Environment Quality Classification

Abstract: The ambient air quality in the live stock farm has an effect heath of animal. Therefore, we have developed a device for monitoring air quality of environment. In this work, wireless electronic nose has developed by deploying commercial gas sensor arrays, microcontrollers and ZigBee wireless network. They system is applied for environment classification in various laboratories including biological, chemical and clean rooms. Air data measured by multi-sensor array are delivered via ZigBee network to a database station where PCA as linear explorative technique analysis is used to obtain odor dispersion and environment prediction. The air environment of various laboratories has been successfully classified by the developed system. Thus, the wireless electronic nose approach is potential for automatic environment monitoring with many industrial applications including livestock farm environmental control.

Notice of Retraction Fabrication of Anodic Aluminum Oxide (AAO) nano-porous membrane on both sides of aluminum sheet

Abstract: Fabrication of AAO Membrane is a time consuming and sensitive process. Several attempts have made to speed up this process. This paper reports the fabrication of AAO membrane at both sides of aluminum sheet. This method speeds up the fabrication process. This method of fabrication is easier because the aluminum sheet does not need to protect from the back side. This type of fabrication minimizes the total cost of nano-porous membrane. The fabrication of nano-porous membrane has been done by homemade system. The developed system can be used for mild anodization (MA), hard anodization (HA) and electro-polishing. This paper represents the fabrication of AAO membrane using 99.999% pure aluminum and commercial grade impure aluminum. The fabrication was done by MA and HA.

Structural and microfluidic analysis of MEMS based out-of-plane hollow silicon microneedle array for drug delivery

Abstract: Microneedles are gaining popularity because of the ability to deliver the drug through the skin at desire therapeutic range. In this paper, design, structural analysis and fabrication of tapered tip out-of-plane hollow silicon microneedle array for transdermal drug delivery (TDD) applications is first presented. Then computational fluid dynamic (CFD) static analysis is presented to investigate the pressure distribution and velocity distribution of fluid through 5 × 5 microneedle array. The static pressure 10 kPa to 130 kPa was applied for fluidic analysis. Inductively coupled plasma (ICP) etcher machine is used to facilitate the isotropic and anisotropic etching process during the fabrication. Finite element method (FEM) using ANSYS rather than analytical system has been used to perform the simulation. The effect of axial and transverse loads on the microneedles during skin insertion is investigated in the stress analysis. The analysis predicts that the resultant stresses due to applied bending and axial loads are in the safe range. The presented research work provides predicted data to fabricate optimized designs of silicon microneedle array for biomedical applications.

Temperature cycle and surface treatment study of thermoelectric based micro PCR

Abstract: In this work, a rapid thermo-cycling micro PCR system with low reagent loss is developed. Peltier thermoelectric devices were used to provide fast heating and cooling for polydimethylsiloxane (PDMS) based micro PCR chamber. The temperature control was accomplished by PID controller. A single PCR microchamber was fabricated by PDMS casting on SU-8 micromold and oxygen plasma assisted bonding of PDMS on a glass substrate. The PDMS chamber was treated by tween 20 polymer in order to suppress the loss of reagent in PCR chamber. The treatment condition was optimized to yield minimum reagent loss. The PCR process began with preheat treatment at 92 °C for 180 s. After preheating, thermocycling was then performed for 30 cycles. Each temperature cycle consists of denaturation at 92 °C for 30 s, annealing at 54 °C for 30 s, and extension at 72 °C for 30 s. After thermocycling process, the temperature was maintained at 72 °C for 180 s before cooling down to room temperature. The fast heating and cooling rate of ~2 °C/s and ~1 °C/s were achieved. The whole process was completed in about 2.5 h. Therefore, the developed themocycling micro PCR system is potential for PCR-on-a-chip applications.

Design and simulation of flow cell chamber for quartz crystal microbalance sensor array

Abstract: In this paper, the cause of significant variation in sensing responses of identical QCM sensors array in a circular QCM chamber is analyzed by fluid dynamic simulation. Moreover, the simulation is used to determine an appropriate shape of flow chamber for QCM sensor array. Simulation results show that the flow in a circular-shaped QCM chamber design is primarily turbulent. In addition, the degree of turbulence is increased with flow rate. Thus, sensors at various locations see different sample dispersions causing their sensing behaviors to be significantly different. The QCM chamber has been redesigned to be rectangular line and simulation results indicate that it can be the solution to the problem because flow in the new design is primarily laminar with uniform sample velocity.

Effect of substrate position on the formation of ZnO nanostructures synthesized by thermal evaporation of ZnO-CNTs mixture

Abstract: In this work, the effect of substrate position on the formation of ZnO nanostructures synthesized by thermal evaporation of zinc oxide (ZnO) and carbon nanotubes (CNTs) on silicon substrate is investigated The multi-wall CNT powder made by chemical vapor deposition was mixed with ZnO powder with a molar ratio of 1∶1 The source material was put into the middle of chamber while Si substrates were placed at various locations from the center to the end of the tube furnace The evaporation took place at 950 °C and 2 Torr under argon gas flow rate of 500 sccm and the system was vented at this temperature at the end of process Structural characterization by scanning electron microscopy showed that ZnO tetrapod-like structures are formed in samples at different positions but they have different densities, sizes and morphologies The density and size of ZnO nanotetrapods are found to decrease as the distance from source powder increases and substrate temperature decreases In addition, considerable carbon content and high crystallinity of wurtzite ZnO nanostructure were observed by energy dispersive x-ray spectrometry and x-ray diffraction Moreover, ZnO nanostructures have a wide blue-green luminescent band between 380 and 600 nm

Notice of Retraction Two layered novel Anodic Aluminum Oxide nanoporous membrane

Abstract: A new structure in Anodic Aluminum Oxide (AAO) membrane is reported. This new membrane consists of two layers. The upper layer of membrane has hexagonal structure and the lower layer have smaller holes compared to upper layer. This membrane is fabricated using two step hard anodization. The voltage in second step of anodization was kept constant at 126V. Nanopores inside the fabricated membrane are highly straight and perpendicular to the surface. This two layer AAO membrane will support the hemofiltration and hemodialysis processes.

Effect of anodization voltage on electron field emission from carbon nanotubes in anodized alumina template

Abstract: In this work, electron field emission from AAO-CNT structure is studied as a function of anodizing voltage. It is found that the turn-on electric field of AAO-CNTs reduces from 5 V/µm to 4 V/µm as anodization voltage increase from 20 to 30 V. On the other hand, CNTs the turn-on electric field of AAO-CNTs increases from 4 V/µm to 6 V/µm as anodization voltage increase from 30 to 40 V. SEM and F-N analyses can to explain the effect of anodization voltage on field emission from AAO-CNTs based on field screening effect.

Electronic tongue based on modified carbon nanotube electrochemical sensor array

Abstract: In this work, carbon nanotube based electrochemical sensor array was developed as electronic tongue for beer discrimination without sample pretreatment using chronoamperometry. To form the sensor array, carbon nanotubes were modified by oxygen plasma and electrochemical oxidation using NaOH and KClO 3 to yield electrochemical sensors with distinct characteristics. The current sensitivities from differently functionalized CNTs were analyzed by principal component analysis. Four different brands of beer, including Chang Classic, Heineken, Leo and Cheers, have been successfully distinguished by the developed electronic tongue system with high sensitivity.

Coupled Multifield Analysis of Piezoelectrically Actuated Microfluidic Device for Transdermal Drug Delivery Applications

Abstract: In this paper, design, fabrication and coupled multifield analysis of hollow out-of-plane silicon microneedle array with piezoelectrically actuated microfluidic device for transdermal drug delivery (TDD) applications is presented. The fabrication process of silicon microneedle array is first done by series of combined isotropic and anisotropic etching processes using inductively coupled plasma (ICP) etching technology. Then coupled multifield analysis of MEMS based piezoelectrically actuated device with integrated 2×2 silicon microneedle array is presented. To predict the stress distribution and model fluid flow in coupled field analysis, finite element (FE) and computational fluid dynamic (CFD) analysis using ANSYS rather than analytical systems has been performed. Static analysis and transient CFD analysis were performed to predict the fluid flow through the microneedle array. The inlet pressure from 10 kPa to 150 kPa was considered for static CFD analysis. In the lumen region fluid flow rate 3.2946 μL/min is obtained at 150 V for 2×2 microneedle array. In the present study the authors have performed simulation of structural, piezoelectric and CFD analysis on three dimensional model of the piezoelectrically actuated mcirofluidic device integrated with 2×2 microneedle array. Keywords—Coupled multifield, finite element analysis, hollow silicon microneedle, transdermal drug delivery.

Disposable sensors based on chitosan film doped with multi-wall carbon nanotubes

Abstract: This paper reports on the analytical performance of a disposable electrochemical sensor for the detection of hydrogen peroxide, using screen-printed carbon based electrodes (SPCEs) modified with a dispersion of multi-wall carbon nanotubes in chitosan (CHIT/MWCNT). The modified sensors showed an excellent electrocatalytic activity towards hydrogen peroxide, respect to the high overvoltage characterizing unmodified screen-printed sensors. The modified electrode demonstrated to be highly reproducible, with 4.5% RSD for the sensitivity of hydrogen peroxide for 15 electrodes prepared using the same dispersion conditions. Preliminary experiments carried out using choline oxidase as biorecognition element has allowed us to obtain an excellent performance for choline biosensing.

Turbidity detection of shrimp Taura Syndrome Virus by loop-mediated isothermal amplification reaction

Abstract: Reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay is a novel method of gene amplification that amplifies nucleic acid, which can be applied for disease diagnosis in shrimp aquaculture. During the LAMP reaction, the white precipitate of magnesium pyrophosphate (Mg 2 P 2 O 7 ) is formed correlates with the amount of synthesized DNA. So, the turbidity can be measured. In this study, a portable turbidimeter has been developed for field to detection of Taura Syndrome Virus (TSV) that causes large economic losses to most major shrimp-producing countries including Thailand. The device could maintain an optimal temperature (63 °C) for 25 µl of LAMP sample solution contained in a 0.2 ml commercial PCR tube. We also applied the spectroscopic measurement technique to monitor a by-product of LAMP reaction, light emitting diode (LED) was used as a light source. Light dependent resistance (LDR) was used as detector. The results obtained from turbidity measurement revealed the same detection limit to those from agarose gel electrophoresis method.

Inkjet-printed optical gas sensor based on metallo-phthalocyanine layers

Abstract: Copper(II)-2,9,16,23-tetra-tertbutyl-29H,31H-phthalocyanine (CuTTBPc) containing inks based on different solvents and solvent mixtures are prepared. Surfactant and different polymers have been added to the ink systems in order to optimize the printing performance. Printability and printing performance have been evaluated. Furthermore the optical properties, namely absorbance in the UV/Vis range, of the printed films have been investigated in order to assess the applicability of ink jet printed phthalocyanine thin-films as transducers for optical sensors. Basic sensing experiments were performed under dynamic gas flow conditions, employing acetone and isopropanol as analytes.

DNA hybridization enhancement using piezoelectric microagitation through liquid medium coupling

Abstract: The DNA hybridization is a promising analysis technique in molecular biology. The target DNA were probed on the glass substrate layer then the complementary DNA sequence will diffuse passes the small bound probe. Conventional DNA microarray hybridization relies on diffusion of target to surface-bound probes, and thus is a rate-limited process. In this paper, an agitating technique based on piezoelectric actuators assisted with column of liquid that was developed to accelerate hybridization process is explained. The ultrasonic acoustic wave is transmitted through liquid medium laminated under the microarray. By measuring the movement of 4.5 µm diameter polystyrene bead, it shows that the velocity of the bead under the piezoelectric agitation were up to 5.8 µm/s. The hybridization results show that the hybridization intensity and homogeneity from this device are better than the signal from conventional method. Therefore, the advantages of this device are increasing the hybridization signal and improving homogeneity across the microarrays which lead to the application of analysis with small amount of samples.