Development of nano-scale sensing device using dielectrophoresis

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(A) Functionalization of DEP-fabricated CNT gas sensor with Pd nanoparticles using liquid-phase reducing reactions and its application to a hydrogen gas sensor(1) The CNT-retaining microelectrode was immersed in a palladium acetate solution together with a graphite rod. DC voltage was applied between the microelectrode (cathode) and the graphite rod (anode) so that palladium acetate could be reduced and catalytic Pd could be electrodeposited on the CNT surface.(2) The CNT sensor could reversibly respond to hydrogen gas in the air in the range of 0.01% - 1% concentration at room temperature.(B) Bacterial detection using a carbon nanotube gas sensor coupled with a microheater for ammonia synthesis by aerobic oxidization(1) We proposed a new bacteria sensing device, which is based on a CNT gas sensor and micro heater. Bacteria were heated by the micro heater in air so that ammonia (NH3) gas can be generated by oxidation reaction of organic components of bacteria.(2) Thus generated NH3 gas was detected by using the CNT gas sensor, which was fabricated by dielectrophoresis and installed in a small chamber together with the micro heater. The proposed device could detect and quantify 107 bacteria (Escherichia coli).