Polymeric humidity sensors

Ingram JM, Grep M, Nicholson JA, Formtain AW (2003) Polymeric humidity sensor based on laser carbonized polyimide substrate Sensors and Actuators B 96 283-289... 

Huang, PH. (1988). Halogenated polymeric humidity sensors. Sensors <8 Actuators 13 329. 

Suitably modified fiber optic sensors can also be used for detecting gas vapors, humidity, ions, and organic compounds. Fiber inclusions that show length variation were used to develop humidity sensors, whereas ion-responsive lipid bilayers formed the basis for the detection of inorganic ions. Immobilized neutral and ionic crown ethers in polymeric membranes were designed as sensors for determination of barium and copper (Wolfbeis 2000). 

The processability of certain CEPs has been utilized in the construction of microsystems, particularly miniature sensor systems. For example, simply dip-coating connecting platinum wires with a polyaniline formulation produces a useful humidity sensor.133 CEPs can also be screen-printed or ink-jet-printed to produce the complex shapes needed for various devices. Electrodeposition of CEPs is also a popular processing method, and this technique is compatible with conventional MEMS fabrication, where lithography and etching can be used to prepattern metal electrodes. Subsequent deposition of CEP by electrochemical polymerization produces the CEP microdevice.129... 

Cho N, Lim T, Jeon Y, Gong M (2008) Inkjet printing of polymeric resistance humidity sensor using UV-curable electrolyte inks. Macromol Res 16 149-154... 

The absorption of water by polymers is especially suited to the development of a capacitive humidity sensor based on the high dielectric constant of water, since capacitance depends on the area, the thickness, and the dielectric constant of a dielectric. Uptake of water causes an increase in the dielectric constant followed by an increase in capacitance. Polyimide is a suitable sensitive material, but so are certain inorganic ceramics such as AI2O3 [142] and low-density Ta205, which change their capacitance with the formation of water dipoles. Low-density Ta20s layers can be formed by anodic oxidation of sputtered tantalum films, whereas polyimide films are deposited by spin coating and subsequent polymerization. 

Sakai Y (1993) Humidity sensors using chemically modified polymeric materials. Sens Actuators B 13(14) 82-85 Sakai Y, Sadaoka Y, Ikeuchi K (1986) Humidity sensors composed of grafted copolymers. Sens Actuators 9 125-131 Sakai Y, Sadaoka Y, Matsuguchi M (1996) Humidity sensors based on polymer thin films. Sens Actuators B 35-36 85-90... 

Besides the utilization of PANI/Sn02 as a humidity sensor device, many scientific works emphasized that nanocomposites developed from polyaniline (PANI) and metal oxides—especially Sn02—are good candidates as gas sensor deviees. Taking into account all these observations, the literature supports fabrication of PANI/Sn02 hybrid materials with different amounts of Sn02 content prepared by in situ chemical oxidative polymerization method, with the sensitivity of materials toward toluene... 

An important issue in the construction of humidity sensors is the selection of materials. Among the polymeric humidity-sensitive materials, polyimides represent a good choice because they exhibit excellent thermal stability, low dielectric constant, and low equilibrium moisture content. Conversely, polyimides are highly resistant to irradiation and are mechanically strong and chemically stable in the presence of most common contaminants. 

Sakai, Y, Sadaoka, Y, and Fukumoto, H. (1988). Humidity sensors and water-resistive polymeric materials. Sensors Actuators 13 243. 

Scientists investigated on optical inteferometric stmctures that can be applied in toxic gas sensors. The sensor head consists of PANi and nafion layers deposited on the face of the telecommunication optical fiber. Humidity sensors are useful for the detection of the relative humidity (RH) in various environments. Polymer composites and modified polymers with hydrophilic properties have been used in humidity sensor devices. Researchers prepared nanocomposite pallets of iron oxide and PPy for humidity and gas sensing by a simultaneous gelation and polymerization process. This resulted in the formation of a mixed iron oxide phase for... 

A new Pt(II) polyyne polymer, P15, prepared from the reaction of cfs-[Pt(PPh3)2Cl2] with l,4-diethynyl-2,5-dihexadecyloxybenzene using the extended one pot polymerization route, was tested for its sensing properties and showed fast and reproducible response to relative humidity variations and methanol vapor in surface acoustic-wave (SAW) sensors.46 A SAW sensor was fabricated from polymer P15 as a sensitive membrane, and the polymer was deposited as thin film on the surface of SAW delay lines implemented on three different piezoelectric substrates. High sensitivity and reproducibility were recorded for such devices. The acoustic characterization of the polymer film was also studied with the aid of theoretical results obtained by the perturbation theory. 

Y. Murayama and Y. Yoshida [119] fxepared polymeric diin films of dichlorobis (cyclopentadienyl) titanium by the rf ion plating method and investigated the structure and electrical diaracteristics. The films obtained exhibit a linear increase in electric conductivity with increasing humidity whidi, according to the authors, has potential plication for a humidily sensor. 

Traces of VOCs in human breath can be a symptom of diabetes, kidney failure, asthma or breast cancer. VOCs were mainly detected by mass spectroscopy with a ppb detection limit. The most advanced VOC sensor based on SWCNTs for medical application was introduced by Peng et al. (2008a, 2008b). This device is designed as an array of ten SWCNT chemiresistors coated with different non-polymeric organic layers. Since the responses of each chemiresistor are different, a principal component analysis of the measurement allows the direct discrimination between a healthy patient and a patient with cancer or renal diseases. The same authors have also highlighted the dramatic effect of humidity on the sensor response and have proposed coupling the device with a water extractor (Fig. 10.8). 

Electret is an important cross-scientific subject of dielectric physics, material science, sensor engineering, medical and bio-engineering (Sessler G., Sessler et al., Nalwa H., Goel M.)-Over the years, considerable interest has been shown in the surface potential decay of corona-charged polymeric materials. Besides the electrets material and conditions of producing electrets the surface potential decay depends on number of factors under which the electrets have been stored or used, for example temperature, humidity, pressure etc. (Zhongfu et al, Gang-Jin et al., Ribeiro et al.). 

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