Seung-Chul Ha

The application of carbon nanotube-polymer composite as gas sensing materials

This is the first report on the evaluation on the performance of the gas sensing properties of carbon nanotube-polymer composite materials for volatile organic compounds (VOCs). Single wall carbon nanotube-polymer (ethyl cellulose) (SWNT-EC) composite suspensions were prepared in chloroform with the help of poly(p-phenylenevinylene-co-2,5-dioctoxy-m-phenylenevinylene) (PmPV). The composite films were formed onto electrode substrates by spraying the suspensions. The gas sensing performance of the composite films well supports that these materials are suitable for VOC sensors. The dispersion quality of SWNT in the sol suspension is understood to be closely related to the sensing properties of the films. Enhancement in SWNT dispersion in the polymer matrix is expected to improve the sensing properties of the composite sensors.

A portable electronic nose (e-nose) system based on PDA

The electronic nose (e-nose) has been used in food investigation and quality controls in industry. Recently it finds its applications in medical diagnosis and environmental monitoring. Moreover, the use of portable e-nose enables the on-site measurements and analysis of vapors without extra gas-sampling units. In this study, a PDA-based portable e-nose was developed using micro-machined gas sensor array and miniaturized electronic interfaces. The computing power and flexible interface of the PDA are expected to provide the rapid and application specific development of the diagnostic devices, and easy connection to other information appliances. For performance verification of the developed portable e-nose system, Six different vapors were measured using the system. The results showed the reproducibility of the measured data and the distinguishable patterns between the vapor species. The application of two different artificial neural networks verified the possibility of the automatic vapor recognition based on the portable measurements.

Monolithic electronic nose system fabricated by post CMOS micromachining

A monolithic electronic nose system, which has 12 independent channels, was fabricated by post CMOS micromachining process. Read-out integrated circuits were fabricated with the standard CMOS processes with design rule of 0.8 mum. And, the MEMS parts of the electronic nose were fabricated by hybrid etching, composed of bulk micromachining with TMAH (tetramethy lammonium hydroxide) and deep dry etching, on the backside of the wafer after the CMOS processes. Resistance matching circuit, instrumentation amplifier, multiplexer, and transducer circuits with bridge structure were included in the read-out circuitry. And, heat control circuits were also implanted in the monolithic circuit to maintain the temperature of the MEMS sensing parts as constant. Carbon black-polymer composites and Au nano-particles were used as sensor materials. The MEMS parts of the electronic nose were designed to have well-shaped structures. These structures are considered to be suitable for drop coating procedure

A portable electronic nose (E-Nose) system using PDA device

The electronic nose (e-nose) has been used in food industry and quality controls in plastic packaging. Recently it finds its applications in medical diagnosis, specifically on detection of diabetes, pulmonary or gastrointestinal problem, or infections by examining odors in the breath or tissues with its odor characterizing ability. Moreover, the use of portable e-nose enables the on-site measurements and analysis of vapors without extra gas-sampling units. This is expected to widen the application of the e-nose in various fields including point-of-care-test or e-health. In this study, a PDA-based portable e-nose was developed using micro-machined gas sensor array and miniaturized electronic interfaces. The rich capacities of the PDA in its computing power and various interfaces are expected to provide the rapid and application specific development of the diagnostic devices, and easy connection to other facilities through information technology (IT) infra. For performance verification of the developed portable e-nose system, Six different vapors were measured using the system. Seven different carbon-black polymer composites were used for the sensor array. The results showed the reproducibility of the measured data and the distinguishable patterns between the vapor species. Additionally, the application of two typical pattern recognition algorithms verified the possibility of the automatic vapor recognition from the portable measurements. These validated the portable e-nose based on PDA developed in this study.