Panida Lorwongtragool

A Novel Wearable Electronic Nose for Healthcare Based on Flexible Printed Chemical Sensor Array

A novel wearable electronic nose for armpit odor analysis is proposed by using a low-cost chemical sensor array integrated in a ZigBee wireless communication system. We report the development of a carbon nanotubes (CNTs)/polymer sensor array based on inkjet printing technology. With this technique both composite-like layer and actual composite film of CNTs/polymer were prepared as sensing layers for the chemical sensor array. The sensor array can response to a variety of complex odors and is installed in a prototype of wearable e-nose for monitoring the axillary odor released from human body. The wearable e-nose allows the classification of different armpit odors and the amount of the volatiles released as a function of level of skin hygiene upon different activities.

Development of Fabric-Based Chemical Gas Sensors for Use as Wearable Electronic Noses

Novel gas sensors embroidered into fabric substrates based on polymers/ SWNT-COOH nanocomposites were proposed in this paper, aiming for their use as a wearable electronic nose (e-nose). The fabric-based chemical gas sensors were fabricated by two main processes: drop coating and embroidery. Four potential polymers (PVC, cumene-PSMA, PSE and PVP)/functionalized-SWCNT sensing materials were deposited onto interdigitated electrodes previously prepared by embroidering conductive thread on a fabric substrate to make an optimal set of sensors. After preliminary trials of the obtained sensors, it was found that the sensors yielded a electrical resistance in the region of a few kilo-Ohms. The sensors were tested with various volatile compounds such as ammonium hydroxide, ethanol, pyridine, triethylamine, methanol and acetone, which are commonly found in the wastes released from the human body. These sensors were used to detect and discriminate between the body odors of different regions and exist in various forms such as the urine, armpit and exhaled breath odor. Based on a simple pattern recognition technique, we have shown that the proposed fabric-based chemical gas sensors can discriminate the human body odor from two persons.

An electronic nose for amine detection based on polymer/SWNT-COOH nanocomposites

An electronic nose (e-nose) system based on polymer/carboxylic-functionalized single-walled carbon nanotubes (SWNTs-COOH) was developed for sensing various volatile amines such as dimethylamine, dipropylamine, pyridine, and ammonia solution. The SWNTs-COOH were dispersed in the matrix of different polymers; polyvinyl chloride (PVC), cumene terminated polystyrene-co-maleic anhydride (cumene-PSMA), poly(styrene-co-maleic acid) partial isobutyl/methyl mixed ester (PSE), and polyvinylpyrrolidon (PVP). These composites were dropped on interdigitated gold electrodes to make the gas sensors. The response of these sensors to volatile amines was studied by both static and dynamic flow measurement. By using a simple pattern recognition based on the principle component analysis (PCA), the volatile amines can be discriminated. This e-nose will be useful for monitoring the freshness of foods and farm air quality.

Portable e-nose based on polymer/CNT sensor array for protein-based detection

Portable electronic nose (e-nose) consisting of polymer/carbon nanotube (CNT) sensor array was developed to detect protein-based foods. Gas sensors were fabricated by spin-coating functionalized CNT/polymer nanocomposite materials onto interdigitated electrodes. The sensors were tested with various types of volatile compounds such as ammonia, amine compounds, acetic acid, water and organic solvents in the range of ppm level. It was found that most sensors yield strong signals to ammonia, amine compounds and acetic acid as well, while they present quite low response to organic solvents and water. To understand the relation of the interaction of amine species related to the sensor response, we have performed molecular modelling based on the density functional theory (DFT) on one polymer structure providing the best response to volatile ammonia. Based on the principal component analysis (PCA), this portable e-nose was successfully applied for the classification of the seafood releasing different amount of amine compounds.

A Zigbee-based wireless wearable electronic nose using flexible printed sensor array

A wearable electronic nose (e-nose) has been developed by integrating a low cost chemical sensor array with a wireless communication for applications in healthcare. Its sensing unit was fabricated by a fully inkjet-printing technique, comprising eight different sensor elements manufactured by varying printing patterns and sensing materials. These sensors have shown response to a wide variety of complex odors. A wearable e-nose prototype using Zigbee wireless technology was designed as a compact armband for monitoring the axillary odor released from human body. Preliminary results based on principal component analysis (PCA) could classify different odors released from the human body upon various activities.

Portable electronic nose for beverage quality assessment

A portable electronic nose (e-nose) was appropriately designed for investigating quality of beverages such as juice or wine, etc. The e-nose system comprises of sample and reference containers, air flow unit, sensing unit and data acquisition unit. All of the hardware units were controlled by in-house software under LABVIEW program via USB port of a DAQ card. The sensing unit includes eight different metal oxide gas sensors from Figaro Engineering Inc. Principal component analysis (PCA) was used as a statistical method in order to discriminate and assess the experimental data as defined by the percentage change in sensor resistances that correlates directly to difference in the aroma characteristics. Drift compensation model was applied to the raw data that sometimes suffer from the effects of sensor drift. Constructed portable e-nose has been tested on-field in a winery to evaluate wine aroma during process of wine bottling. The e-nose using PCA algorithm can distinguish the wine bottling under nitrogen from the bottling under partial vacuum. We also demonstrated that e-nose can be used to help wine maker to design the appropriate process of wine bottling achieving a high quality of wine product.

Inkjet printing of chemiresistive sensors based on polymer and carbon nanotube networks

We report about the manufacturing of sensor devices for detection of volatile organic compounds (VOCs) in the air. The sensor comprises three fully inkjet-printed layers of (i) silver interdigitated electrodes (SIDE), (ii) multi-walled carbon nanotubes (MWCNTs) and (iii) poly (styrene-co-maleic acid) partial isobutyl/methyl mixed ester (PSE). We have found that inkjet printing of MWCNT layers and a PSE layer on top yields an interfacial layer leading to the formation of a MWCNTs/PSE composite-like structure. The printed layers act as chemiresistive vapor sensors due to the change of electrical resistance in presence of selected VOCs. The sensor responses to various VOCs were studied by varying the concentration of the chemicals in the air between 50 and 500 ppm. The sensing mechanism can be understood as a fractional volume change of the inkjet-printed polymer that occurs during exposure to VOCs, resulting in a structural alteration of the MWCNT-polymer network. We have found that the sensor response can be defined as a function of the VOCs concentration. To investigate the morphologies of the inkjet-printed thin films, profilometry and scanning electron microscopy (SEM) were employed.

E-nose based on metallo-tetraphenylporphyrin/ SWNT-COOH for alcohol detection

A handheld electronic nose (e-nose) based on metallo-tetraphenylporphyrin/carboxylic-functionalized single- walled carbon nanotube (MTPP/SWNT-COOH) chemical gas sensors has been demonstrated as a promising instrument for monitoring in food production process. In this work, the gas sensor array was fabricated by dispersing SWNT-COOH in the matrix of different MTPP compounds, namely, MnTPP, FeTPP, ZnTPP, CoTPP and CuTPP. The sensing responses were studied in terms of the changing sensor resistance under the atmosphere of various volatile compounds. The results show that the central metals in tetraphenylporphyrin (TPP) ring play a major role in the selectivity of each gas sensor to each volatile gas. We have investigated the functionality of this handheld e-nose by monitoring the odor of fermented rice during the 5-day fermentation process. Based on the principal component analysis, it was found that the handheld e-nose can track the change of odors generated from the fermentation, in which largest odor change happens on the fifth day.

Effect of Annealing Temperature on Structure and Optical Properties of Ta2O5 Thin Films Prepared by DC Magnetron Sputtering

Tantalum oxide (Ta2O5) films at 400 nm thickness were prepared at room temperature by DC reactive magnetron sputtering. The effect of annealing temperature on film crystallinity, microstructure and optical properties were investigated. In order to indentify the crystalline structure and film morphology, X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) measurements were performance. The optical properties were determined by UV-Vis spectrophotometer and spectroscopic ellipsometry (SE). The result showed that, with the annealing treatment at high temperature (700-900°C), the as-deposited films were crystallized to orthorhombic phase of tantalum pentaoxide (β-Ta2O5). In addition, the transmittance spectrum percentage indicated 87%, which corresponded to the obtained optical characteristic. The refractive index varied at 550 nm from 2.17 to 2.21 with increased of the annealing temperature.

The Efficiency Development of Ammonia-Odor Sensor Based on PSE-Polymer/SWNT Nanocomposite

In this work, we have investigated and optimized the fabrication process of ammonia sensor based on poly (styrene-co-maleic acid) partial isobutyl/methyl mixed ester/single-wall carbon nanotubes (PSE/SWNT) nanocomposite leading to the standardized and highly efficiency of device. The proper ratio of sensing material loading was achieved by varying the SWNT concentration to reach to the best sensing properties. PSE/SWNT sensors were fabricated by spin-coating technique on the interdigitated gold electrodes by controlling the reference resistance in range of 1-10 kΩ. Two groups of the fabricated sensors (carboxylic functionalized SWNT (SWNT-COOH) and hydroxyl functionalized SWNT (SWNT-OH)) with five different percent loadings were tested with various concentrations of ammonia volatile. Electrical resistances of these sensors were measured and modeled on the percolation theory approach, in order to explain and determine the appropriate composition from their mechanisms.