1 Advisor : Cheng-Hsin Chuang Advisee : Hsun-pei Wu Department of Mechanical Engineering & Institute of Nanotechnology, Southern Taiwan University, Tainan, TAIWAN Date ﹕ 2010/11/05 Paper Survey Gas sensors development using supercritical fluid technology to detect the ripeness of bananas C. Steffens, E. Franceschi, F.C. Corazza, P.S.P. Herrmann Jr., J. Vladimir Oliveira Journal of Food Engineering 101 (2010) 365–369

Outline Paper: Experimental Results and discussion Conclusions Furture work Polyaniline synthesis doped with DBSA (PANI–DBSA) Development of electrodes Film coating deposition Voltage measurement during the ripeness of bananas Effect of moisture on the response behavior of the tested sensors

Experimental Development of electrodes Fig. 1. Detail of the interdigitate electrode of graphite on tracing paper with 11 fingers. Graphite : Water mass ratio 1 : 4

Polyaniline synthesis doped with DBSA (PANI–DBSA) Two solutions were prepared (solution A and solution B). DBSA (0.15 mol) 500 mL of water solution A 0.3 mol of aniline Stirring solution A 100 mL of water APS (0.18 mol) Dissolved 0℃0℃ Rection 40 hours Wash Dried under vacuum for 12 hours

Film coating deposition In Situ (HCl) RESS(rapid expansion of supercritical solutions) :  CO2= 100 bar, flow rate of 30 mL/min  solution flow rate of 2 mL/min  100 lmcapillary tubing.  2700 psi in liquid pump in pressurized fluid. Precipitation:  CO2= 200 bar, flow rate of 20 mL/min  100 lmcapillary tubing.  2900 psi in liquid pump  Drying step: 500 mL of CO2

Results and discussion Dry nitrogen gas 10min Laboratory (air) 10min Fig. 2. Effect of moisture on the response behavior of the tested sensors exposed to cyclic flowing dry nitrogen and laboratory ambient air. Effect of moisture on the response behavior of the tested sensors

Voltage measurement during the ripeness of bananas 4.5 L chamber, 25 ℃, Humidity 60%, Voltage 400mV => LabVIEW 5 min during 5 days AIR Sensor into In the air 30 min fruits

Voltage measurement during the ripeness of bananas Fig. 6. Electronic-nose response of in situ, RESS and precipitation sensors to volatile organic compounds evolved during banana maturation. After 24 s

Conclusions The line patterning technique using graphite was applied to the design and development of extremely low-cost, disposable interdigitated electrodes. Precipitation and RESS proved was to be promising to detect the ripeness of banana in electronic-nose thus indicating a potential technology. In future cost-effective methods for monitoring the maturation of fruits, avoiding food losses and bringing satisfaction to consumers through availability of better quality products.

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