Modeling carbon black/polymer composite sensors (original) (raw)
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Sensors Journal, …, 2002
The performance of polymer carbon-black composite chemical vapor sensors as a function of underlying electrode size and geometry has been studied. The sensor performance parameters investigated were sensor response magnitude to a toluene analyte (100, 500, and 1000 ppm), fundamental sensor noise in the presence of air, and two concentrations of toluene (100 and 500 ppm), and signal-to-noise ratio (100 and 500 ppm). An array of sensors with 42 different circular electrode configurations were designed, fabricated, and tested where electrode gap was varied from 10 to 500 m and the diameter of the sensors was varied from 30 to 2000 m. Each array of electrodes was coated with an approximately 1-m-thick layer of conducting polymer carbon-black composite with an insulating poly(alkylacrylate) polymer. The response magnitude, fundamental noise, and signal-to-noise ratio of each sensor was measured and compared to electrode geometry, such as electrode gap, aspect ratio, and overall size. No significant dependence of sensor response magnitude and noise to electrode configuration has been observed to be larger than the variation from sensor to sensor. However, the signal-to-noise ratio tended to decrease for sensors with the smallest scales.
Properties of Multifunctional Polymers–Carbon Black Composite Vapor detectors
In this work the electrical properties of vapor detectors, formed from composites of conductive carbonblack and insulating organic multifunctional polymers having metal ions complexing ability, were investigated. The new composites are tailored to produce increased sensitivity toward specific classes of analyte vapors. Resonant frequency shift of a Quartz Crystal Microbalance (QCM) and dc resistance measurements have been also performed simultaneously on polymer-carbon black composite materials. For comparison purpose, poly(vinyl chloride) (PVC) with di(2-ethylhexyl)phthalate (DOP), a traditional low molecular weight plasticizer, is used as a representative of the behaviour of a traditional composite vapor detector. These new detectors showed an enhanced sensitivity upon exposure to acetic acid and amines vapors; the performances of our systems are 10 3 times higher than those of a traditional composite vapor detector. Moreover the extent of such responses is beyond that expected by mass uptake upon exposure to the same vapors and cannot be attributed solely to differences in polymer/gas partition coefficients. In this respect, several different chemical factors determine the dc electrical response of this system: in our opinion changes in polymer conformation during the adsorption process also play a significant role. The effects of the temperature on the electric resistance of the vapor detectors have also been studied. These materials showed a discontinuity in the temperature dependence of their resistance, and this discontinuity provided a simple method for determining the T g of the composites.
Novel phenomena-based dynamic model of carbon black/composite vapour sensors
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2007
A novel physically based mathematical model of carbon black/polymer vapour sensors is described, which incorporates parameters that have physical meaning. This model has an analytical solution and so requires negligible computational power to analyse a sensor's response to a particular form of input. Another advantage of this modelling approach is that the environmental dependencies of sensor responses may be compensated for and so help in the design of better pattern-recognition algorithms for electronic nose systems. This also means that the underlying chemistry of the sensors may be decoupled from their physical non-analyte specific properties. Experimentally, three different conducting nanocomposite polymers, poly(styrene-cobutadine), poly(ethyl-co-vinyl acetate) and poly(caprolactone), were tested. Each experiment consisted of separate exposures of the sensors to acetone and ethanol vapour in ambient air. A total of 336 such experiments were performed over a two-week period. The model was validated with respect to these data and was then fitted to the two vapour responses simultaneously, demonstrating its applicability to 'real world' systems. The temperature dependence of the model parameters was judged to be the most important factor and it needs to be compensated for when applying this type of sensor in practice.
PROPERTIES OF caRbOn-black cOmPOSITE vaPOuR dETEcTORS baSEd On mulTIFuncTIOnal POlymERS
Journal of the Balkan Tribological Association
in this work the electrical properties of vapour detectors, formed from composites of conductive carbon-black and insulating organic multifunctional polymers having metal ions complexing ability, were investigated. the new composites are tailored to produce increased sensitivity towards specific classes of analyte vapours. resonant frequency shift of a Quartz crystal Microbalance (QcM) and dc resistance measurements have been also performed simultaneously on polymercarbon black composite materials. For comparison purpose, poly(vinyl chloride) (PVc) with di(2-ethylhexyl)phthalate (doP), a traditional low-molecular weight plasticiser, is used as representative of the behaviour of a traditional composite vapour detector.
Chemistry of Materials, 2006
Chemically sensitive resistors have been fabricated from composites of carbon black and low volatility, nonpolymeric, organic molecules such as propyl gallate, lauric acid, and dioctyl phthalate. Sorption of organic vapors into the nonconductive phase of such composites produced rapid and reversible changes in the relative differential resistance response of the sensing films. Arrays of these sensors, in which each sensing film was comprised of carbon black and a chemically distinct nonpolymeric organic molecule or blend of organic molecules, produced characteristic response patterns upon exposure to a series of different organic test vapors. The use of nonpolymeric sorption phases allowed fabrication of sensors having a high density of randomly oriented functional groups and provided excellent discrimination between analytes. By comparison to carbon black-polymer composite vapor sensors and sensor arrays, such sensors provided comparable detection limits as well as enhanced clustering and enhanced resolution ability between test analytes.
Here we report on a novel method to measure the concentration of different vapours in air using a single carbon black/polymer composite resistive sensor. A carbon black/polyvinylpyrrolidone (PVP) composite film was deposited onto a single crystal silicon micro-hotplate, and its temperature stepped between 25 o C and 35 o C. We have extracted a novel pre-processing feature that we describe as the "fractional transient response", which is produced from analyzing the temperature transients measured with and without vapours. We have found that the shape of the fractional difference of transient conductance curve depends only on vapour type and so can be used for vapour identification; whereas the amplitude of fractional difference of transient conductance curves is proportional to the concentration of the vapour and so can be used to predict vapour concentration. Therefore, we show experimentally that it is possible to detect different vapours using a single carbon black polymer/composite sensor. Results are given for detecting water, methanol and ethanol vapours in ambient air.
Conductive polymer-carbon black composites-based sensor arrays for use in an electronic nose
Sensor Review - SENS REV, 1999
Polymer-carbon black composites are a new class of chemical detecting sensors used in electronic noses. These composites are prepared by mixing carbon black and polymer in an appropriate solvent. The mixture is deposited on a substrate between two metal electrodes, whereby the solvent evaporates leaving a composite film. Arrays of these chemiresistors, made from a chemically diverse number of polymers and carbon black, swell reversibly, inducing a resistance change on exposure to chemical vapors. These arrays generate a pattern that is a unique fingerprint for the vapor being detected. With the aid of algorithms these patterns are processed and recognized. These arrays can detect and discriminate between a large number of chemical vapors.
Properties of multifunctional polymers – carbon black composite vapor
Publishing House of Lviv Polytechnic National University, 2011
In this work the electrical properties of vapor detectors, formed from composites of conductive carbonblack and insulating organic multifunctional polymers having metal ions complexing ability, were investigated. The new composites are tailored to produce increased sensitivity toward specific classes of analyte vapors. Resonant frequency shift of a Quartz Crystal Microbalance (QCM) and dc resistance measurements have been also performed simultaneously on polymer-carbon black composite materials. For comparison purpose, poly(vinyl chloride) (PVC) with di(2-ethylhexyl)phthalate (DOP), a traditional low molecular weight plasticizer, is used as a representative of the behaviour of a traditional composite vapor detector. These new detectors showed an enhanced sensitivity upon exposure to acetic acid and amines vapors; the performances of our systems are 10 3 times higher than those of a traditional composite vapor detector. Moreover the extent of such responses is beyond that expected by mass uptake upon exposure to the same vapors and cannot be attributed solely to differences in polymer/gas partition coefficients. In this respect, several different chemical factors determine the dc electrical response of this system: in our opinion changes in polymer conformation during the adsorption process also play a significant role. The effects of the temperature on the electric resistance of the vapor detectors have also been studied. These materials showed a discontinuity in the temperature dependence of their resistance, and this discontinuity provided a simple method for determining the T g of the composites.
Phenomena based dynamic model of carbon black-polymer composite sensors
A novel physically based mathematical model of carbon black-polymer sensor-analyte uptake and response is proposed. The advantage of this modelling approach is that the environmental dependencies of sensor responses may be investigated. It also permits the chemical kinetics of the sensors to be separated from the physical aspects of the sensors. Data were collected under varying ambient environmental conditions. Three different polymers were tested. A total of 336 such experiments were performed over a 2-week period. The model was validated with respect to these data, and was fitted to two vapour responses in parallel, showing its applicability to 'real world systems'. Evident temperature dependence of the parameters were judged to be most important outcome of this study.
Progress in Solid State Chemistry, 2005
This paper investigates the use of NiO particles to enhance the vapour sensing properties of polyethylene adipate (PEA)\carbon black (CB) composite materials. Four PEA\CB suspensions were prepared with 0, 10, 20 and 30 w/w% NiO, respectively. Hypermer PS3 surfactant was shear mixed into each of the suspensions for 300 s to achieve a homogenous dispersion and to prevent reagglommeration of both the CB and NiO particles. A 0.1 ml drop of each composite was deposited between Cu electrodes on a printed circuit board (PCB) substrate using a microlitre syringe. The samples were allowed to dry for 24 h in an oven at 333 K to remove any remaining solvent. After preparation, the sensors were exposed to propanol and butanol at concentrations ranging from 0 to 25 000 ppm in steps of 5000 ppm. The response of the PEA\CB sensors improved significantly as the concentration of NiO particles in the material increased and maximum relative differential responses as high as 37% and 92.8% were recorded after exposure to 25 000 ppm propanol and butanol, respectively. This high response can be explained using the FloryeHuggins interaction parameter along with structural changes in the polymer composite caused by the addition of NiO. This paper concludes that NiO particles can be used as a method to increase the sensitivity of existing conducting polymer composite gas sensing materials.