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Subject: search.filters.subject.Chemical sensor

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    Quartz crystal microbalance coated with 18-crown-6 ether film for 2, 4, 6-trinitrotolurene (TNT) vapor detection
    (2017-01-01)
    Phuvanatai, Pavaris
    ;
    Phetchakul, Toempong
    The 2, 4, 6- trinitrotoluene (TNT) vapor detection by quartz crystal microbalance (QCM) coated with 18-crown-6 ether film is introduced. The film acts as selective or sensitive layer for detecting TNT molecule. The frequency shift response is depend on the amount of mass of molecule adhere on the coated film surface. In this study, the concentrations of TNT vapor which is related to responses are studied. It shows that the TNT vapor concentration is related to the time for steady state condition and the frequency shift response. The high concentration vapor will increase the frequency shift response but increase the steady state time.
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    Prototype microfluidic system for fluorescence-based chemical sensing
    (2014-01-01)
    Kittidachachan, Pattareeya
    ;
    Rujihan, Suparat
    ;
    Damrongsak, Badin
    A prototype microfluidic system for fluorescence detection is presented in this paper. The system consists of an excitation light source, a polymer-based microfluidic channel and an optical detector. Experiments are conducted to demonstrate use of the developed system for fluorescence detection in chemical applications. Three fluorescent dyes - Rhodamine 6G, Coumarin 153 and DCM - with different concentrations ranging from 100 nM to 5 mM are used as the analyte in the experiments. Relationship between the photo-response of the microfluidic system and concentration of fluorescent dyes is investigated. The results are compared to that obtained from a bulk system where the analyte under test is dispensed into a standard-size cuvette. In the bulk system, we found a decrease in the fluorescence signal when dye concentration is higher than 10-5 M for Rhodamine 6G and 10-4 M for Coumarin 153 and DCM. This is probably due to the re-absorption and self-quenching phenomena, which result in low quantum yield of fluorescent dyes at high concentration. However, this problem is not found in microfluidic systems with a low detection volume. In addition, the relationship between the photo-response of the system corresponding to different dye concentrations was modeled based on Beer Lambert's law. The measured results agreed will with the theoretical model.
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    Poly(dimethylsiloxane) microlens array integrated with microfluidic channel for fluorescence spectroscopy detection
    (2013-09-18)
    Rujihan, Suparat
    ;
    Damrongsak, Badin
    ;
    Kittidachachan, Pattareeya
    Fluorescence spectroscopy detection has been commonly used in chemical and biochemical applications as it provides a good reliability and high sensitivity. Commercially available fluorescence spectroscopy system is typically bulky and expensive, hence making it inconvenience for on-site measurement which requires portable systems. However, the drawback of small devices is that it has a low detection volume, resulting in low fluorescence signal. In this paper, we report a microfluidic channel implemented with a microlens array for enhancing the performance of fluorescence spectroscopy detection. The microlens array was used to focus an excitation light onto the microchannel, thus expecting the increase in fluorescence detection signal. Both microchannels and microlens arrays were individually fabricated from poly-dimethylsiloxane (PDMS) using low-cost printed-circuit-board master molds. The fabrication and characterization of PDMS-based microlens arrays are discussed. In short, the microlens in plano-convex shape was designed with diameters of 700, 800 and 900 microns. The fabricated microlens arrays were characterized for radius of curvatures, SAGs and focal lengths. The plano-convex microlens array was then integrated into a microfluidic system in order to investigate the overall performance of fluorescence spectroscopy detection. Experiments were conducted with two fluorescence dyes, i.e. Rhodamine 6G and Coumarin 153. The preliminary results revealed that the PDMS microlens array implemented on the designed system shows potential for improving excitation and emission light intensity and, as a consequence, signal to background ratio of the fluorescence spectroscopy detection. © 2013 SPIE.
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    Alcohol sensor based on multi-wall carbon nanotube
    (2009-12-01)
    Sutthinet, Chalin
    ;
    Sangnual, Assuchol
    ;
    Phetchakul, Toempong
    We have demonstrated multi-walled carbon nanotube (MWCNTs) based sensors, which are capable of detecting alcohol vapor. The properties of the sensor were as a function of baking times at ethanol flow rate 200 cc/min and nitrogen gas flow rate 200 cc/min. Moreover, the various of baking times were observed that the highest sensitivity was obtained at baking time of 25 minutes at 70 ° C can be explained for residual of ethanol on the surface .It was found that the optimum operating at room temperature (25 °C). It is expected that many applications of CNTs-based sensors will be explored in future as the interest of the nanotechnology research in this field increases.
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