• Macromolecular Research
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• v.13 no.3
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• pp.265-272
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• 2005

Polyelectrolyte membranes for humidity-sensing were fabricated using a layer-by-layer adsorption process based on the spontaneous self-assembly of alternating layers of cationic and anionic polymers on a silanized ITO patterned glass substrate. The substrate is dipped successively into dilute solutions of a polyanion and a polycation. The homopolymers and copoymers of diallyldimethylammonium chloride (DDA), allylamine hydrochloride (AA), 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC) and vinylbenzyl tributyl phosphonium chloride(VTBPC) were used as the polycations. In this experiment, it was found that the resistance varied according to the chemical structure of the polycation. The resistance varied from $10^7$ to $10^5$ $\Omega$, as the humidity was increased from 60 (relative humidity) to $95\%$RH, which is the range of RH values required for a dew sensor operating at high humidity.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1233-1235
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• 1994

In this work, polyimide thin films fabricated by the electrophoretic deposition are investigated as a humidity sensing material. Capacitance and impedance are measured with increasing relative humidity to find the nature of the film. From the results, the polyimide humidity sensor is not classified impedance change type but capacitance change type and appear more sensitive in the region of higher humidity than that of lower humidity.

• Composites Research
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• v.18 no.4
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• pp.21-26
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• 2005

Nondestructive damage sensing and load transfer mechanisms of carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites have been investigated by using electro-micromechanical technique. The electrospun PVDF nanofibers were also prepared as a piezoelectric sensor. The electro-micromechanical techniques were applied to evaluate sensing response of carbon nanocomposites by measuring electrical resistance under an uniform cyclic loading. Composites with higher volume content of CNT showed significantly higher tensile properties than neat and low volume$\%$ CNT composites. CNT composites showed humidity sensing within limited temperature range. CNT composites with smaller aspect ratio showed higher apparent modulus due to high volume content in case of shorter aspect ratio. Thermal treated electrospun PVDF nanofiber showed higher mechanical properties than the untreated case due to crystallinity increase, whereas load sensing decreased in heat treated case. Electrospun PVDF nanofiber web also showed sensing effect on humidity and temperature as well as stress transferring. Nanocomposites and electrospun PVDF nanofiber web can be applicable for sensing application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.247-248
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• 2006

Carbon nitride films were evaluated that they had many advantages for miniature micro-humidity-sensors using the standard CMOS technology humidity sensing properties and CV characteristics of the carbon nitride films have been investigated for fabricating one chip HUSFET(Humidity Sensitive Field Effect Transistor) humidity sensors Carbon nitride films were deposited on silicon substrate with meshed electrodes by reactive RF magnetron sputtering system. The capacitor-type humidity sensor revealed good humidity-impedance characteristics with a wide range of relative humidity changes, decreasing $254k{\Omega}$ to $16k{\Omega}$ according to increase of relative humidity between 5% ~ 95% and the films were very stable on the Si wafer. These results reveal that $CN_x$ thin films can be used for Si based or HUSFET structure one chip micro-humidity sensors.

• 한국전기화학회:학술대회논문집
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• 1999.04a
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• pp.23-23
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• 1999

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.49-57
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• 2004

The modified polyionene polyelectrolyte inks were newly prepared and applied to the humidity-sensitive membrane of humidity sensor. The films were fabricated on the alumina substrate with comb-type gold electrode using a ink-jet printing technique. The copolymers of methyl methacrylate, acrylic acid, 2-hydroxyethyl methacrylate and [(2-methacryloyloxy)ethyl]trimethylammonium chloride were also prepared for the humidity-sensing material. which was fabricated by dip-coating method. Electrical measurements under various relative humidity were performed. The humidity-sensitive characteristics of sensors obtained by ink-jet printing technique were compared with that of dip-coating method. Humidity sensors showed a decrease in resistance as an increase of relative humidity and their resistance characteristics are in a close agreement each other.

• Journal of Sensor Science and Technology
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• v.15 no.3
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• pp.205-210
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• 2006

Hydrophobic polymer [ex. Poly(vinylidenfluoride)] layer was coated on polyaniline (PANi) sensor to reduce the contamination humidity. The differences in sensitivity to methanol gas detection in various humidity condition between pure-PANi sensor and sensor coated with poly(vinylidenfluoride) polymer (PVDF) (coated-PANi sensor) were investigated. Considering the relation between the density of pore, which was coated on the layer of the PANi sensor, and sensitivity was investigated. To fabricate the porous PVDF layer on PANi sensor, poly(vinylalcohol) (PVA), which is water-soluble polymer, was used. Coated-PANi sensor was less affected by humidity compared with pure-PANi sensor. And higher density of pore on PVDF layer led to higher sensitivity.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.182-186
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• 2013

We studied the possibility that an air capacitor can be used as a humidity sensor by measuring capacitance change. In order to investigate the possibility, the change of capacitance of an air capacitor due to moisture in air was first considered theoretically, and was then experimentally verified. The capacitance was measured by an LCR impedance meter with a 100-kHz and 1-V ac. The results revealed that the changes in the experimentally measured capacitances were greater than those in the theoretically calculated values. Based on this fact, we knew that an air capacitor could be used as part of a humidity sensing device. We expect the humidity sensor with an air capacitor has characteristics of fast response time, high reliability, and high durability compared with other conventional methods.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.703-708
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• 1996

Humidity sensing cheracterisrics of vacuum deposited plasma poly merized $YbPc_2$ films were evaluated. In both films, humidity caused an increase of pro-ton conduction. Polymerised film shows a threshold fo humidity increase and its sensitivity diminishes more than $38^{\circ}C$ of relative humidity. Furthermore, for the polymerized film, two min. of resssponse time and 1 min. of recovery time are also obtained. The sensitivity between 10% and 85% of relative hum-idities is found to be one hundred higher than that of the vacuum deposited film.

• Journal of Sensor Science and Technology
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• v.1 no.2
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• pp.125-130
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• 1992

A resistive-type humidity sensors have been fabricated using cross-linked PMMA thin film as sensing material and their humidity characteristics have been investigated. The sensor coated of the cross-linked PMMA with PVA exhibited largely variation of resistance by increase of relative humidity and less than 3% of hysteresis. Furthermore, the fabricated sensor exhibited superior long-term stability. The response time of the PMMA humidity sensor was about 7 min. for adsorption and about 5 min. for desorption respectively.