• Polymer(Korea)
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• v.33 no.4
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• pp.326-332
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• 2009

New humidity-sensitive monomer, N-methacryloyl-N'-ethyl-N'-propyl piperazinium bromide (MANEPPB) was prepared by the quaternization reaction of N-methacryloyl-N'-ethyl piperazine (MANEP) with 1-bromopropane. Polyelectrolytes derived from the copolymers composed of MANEPPB/MMN/AA=60/35/5, 70/25/5, 80/15/5, 90/5/5 and 95/0/5 were prepared for the humidity-sensitive membranes, which were fabricated on the gold electrode by dipping method and were crosslinked by reacting copolymers with aziridine crosslinker, trimethylolpropane tris(2-methyl-1-aziridinopropionate) (TTAP). When the resistance dependences on the relative humidity of the sensors were measured, it was found that the resistance varied three orders of magnitude between 20 and 90%RH, which was satisfied with the requirement for the common humidity sensor operating at ambient humidity. Their hysteresis, temperature dependence, frequency dependence, response and recovery time and water durability were measured and evaluated as a humidity-sensing membrane.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.126-131
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• 2001

The mutually reactive copolymers poly[(vinylbenzyl chloride)-co-(n-butyl acrylate)-co-(2-hydroxyethyl methacrylate)] and poly[(4-vinylpyridine)-co-(n-butyl acrylate)-co-(2-hydroxyethyl methacrylate)] were synthesized for the humidity sensitive material by forming simultaneous quaternization. The humidity sensor showed an average resistance of 8.6 M$\Omega$, 310 k$\Omega$ and 12 k$\Omega$ at 30%RH, 60%RH and 90%RH, respectively. The hysteresis and temperature coefficient were $\pm$3%RH and -0.37~-0.40%RH/$^{\circ}C$. The introduction of n-BA and HEMA increased the resistance of the humidity sensor however it enhanced the adherence to the alumina substrate. The response time was 54 seconds changing from 33%RH to 85%RH and the difference of resistance was +0.2%RH after soaking in water for 2 hr.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.93-99
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• 1996

The formation properties and oxidation mechanism of electrochemically oxidized porous silicon(OPS) films have been studied. To examine the humidity-sensitive properties of OPS films, surface-type and bulk-type humidity sensors were fabricated. The oxidized thickness of porous silicon layer(PSL) increases with the charge supplied during electrochemical humidity sensor shows high sensitivity at high relative humidity in low temperature. The sensitivity and linearity can be improved by optimizing a porosity of PSL. (author). refs., figs.

• Polymer(Korea)
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• v.33 no.1
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• pp.19-25
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• 2009

New polyelectrolytes derived from ionene-containing photocurable reactive oligomer (PIDM) were prepared for water-resistant humidity-sensitive membranes. The mixture of PIDM, hexamethylene dimethacrylate (HDM), pentaerythritol triacrylate dimer (SP1013), and photoinitiator was simultaneously coated on the sensor electrode with photoinitiated radical polymerization. The pretreatment of the substrates with vinyl-type silane-coupling reagent was performed for improving the water durability and stability of the sensors at high temperature and humidity. When the resistance dependences on the relative humidity of the crosslinked PIDMs were measured, it was found that the resistance varied three orders of magnitude between 20 and 90%RH, which was required for the humidity sensor operating at ambient humidity. Their hysteresis, temperature dependence, response time, water durability, and high temperature/humidity stabilities were measured and evaluated as a humidity-sensing membrane.

• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.32-37
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• 1999

A capacitance-type humidity sensor with mesa structure in which porous silicon layer is used as humidity-sensing material is developed and its humidity sensing properties are measured. This sensor has a structure where two electrodes are set on the up-side of the wafer against the past typical structure having these electrodes on the up and down-side of the wafer. Therefore, the sensor can be fabricated monolithically to be more compatible with the IC process technology, and is possible to detect more correct output capacitance by removing the effect of the parasitic capacitance from the bottom layer and other junctions. To do this, the sensor was fabricated using process such as localized formation of porous silicon, oxidation of porous silicon layer, and etching of oxidized porous silicon layer. From the completed samples, the dependence of capacitance on the relative humidity of 55 to 90% more was measured at room temperature. As the result, the measured capacitance increased monotonously higher at the low frequency of 120 Hz, where the capacitance was observed to increase over 300%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.604-609
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• 2019

In this study, we fabricated a capacitive humidity sensor with interdigitated (IDT) electrodes using a thermosetting polyimide as a humidifying material. First, the number of electrodes, thickness, and spacing of the polyimide film were optimized, and a mask was designed and fabricated. The sensor was fabricated on a silicon substrate using semiconductor processing equipment. The area of the sensor was $1.56{\times}1.66mm^2$, and the width of the electrode and the gap between the electrodes were each $3{\mu}m$. The number of electrodes was 166, and the length of an electrode was 1.294 mm for the sensitivity of the sensor. The sensor was then packaged on a PCB for measurement. The sensor was inserted into a chamber environment with a temperature of $25^{\circ}C$ and connected to an LCR meter to measure the change in capacitance at relative humidity (RH) of 20% to 90%, 1 V, and 20 kHz. The results showed a sensitivity of 26fF/%RH, linearity of < ${\pm}2%RH$, and hysteresis of < ${\pm}2.5%RH$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.113-117
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• 1994

In this paper, an experiment about humidity sensing properties of oxide aluminum films by Anodic oxidation method was made. The humidity sensing properties of films were investigated in the relative humidity range of 10∼85(%RH) , changing the frequency from 1[kHz] to 100[kHz]. The impedance of humidity sensing films were decreased in accordance with the increase of relative humidity. The decreasing rate of impedance were larger at low measuring frequency. The decreasing difference changes from 17.7M$\Omega$ to 3.68M$\Omega$ at low measuring frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.448-451
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• 2004

Vanadium oxides have been widely used in a variety of technological applications such electrochromic devices as infrared detectors and are expected as a material suitable for gas sensing applications. Thin films of Vanadium oxide (VOx) have been deposited by r.f magnetron sputtering under different oxygen partial pressure ratios and substrate temperatures. Humidity-sensitive properties of resistive sensors having interdigitated electrode structure are characterized. Our sensors show good response to humidity over 20%RH to 80%RH. Vanadium oxide films deposited with 0% $O_2$ partial pressure at foot exhibit greater sensitivity to humidity change than others.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.21-27
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• 2003

The copolymers with various composition of methyl methacrylate (MMA), ethyl methacrylate (EMA), methacrylic acid (MA) and hydroxyethyl methacrylate (HEMA) were synthesized for capacitive humidity sensitive materials. The capacitive humidity sensor consisted of a polymethacrylate film coated on both sides with gold electrode. Capacitance versus relative humidity increased with HEMA content in the copolymer. In the case of self-crosslinkable MMA/MA/HEHA= 40/10/10, the average capacitance at 30%RH, 60%RH and 90%RH are 102, 134 and 166 pF, respectively. And also, the hysteresis, temperature cycle and long-term stability were evaluated as a capacitance humidity sensor.