Extended disjoint principal-components regression analysis of SAW vapor sensor-array responses

The application of a disjoint principal-components regression method to the analysis of sensor-array response patterns is demonstrated using published data from ten polymer-coated surface-acoustic-wave (SAW) sensors exposed to each of nine vapors. Use of the method for the identification and quantitation of the components of vapor mixtures is shown by simulating the 36 possible binary mixtures and 84 possible ternary mixtures under the assumption of additive responses. Retaining information on vapor concentrations in the classification models allows vapors to be accurately identified, while facilitating prediction of the concentrations of individual vapors and the vapors comprising the mixtures. The effects on the rates of correct classification of placing constraints on the maximum and minimum vapor concentrations and superimposing error on the sensor responses are investigated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30857/1/0000520.pd

Investigation of nematic liquid crystals as surface acoustic wave sensor coatings for discrimination between isomeric aromatic organic vapors

The use of thermotropic nematic liquid crystals (LC) as surface acoustic wave (SAW) vapor sensor coatings were investigated. Responses to four pairs of isomeric aromatic organic vapors were measured using two LC coatings and four isotropic polymer coatings. In most cases, the LC coatings showed higher sensitivity toward the more rod-like isomer within a pair due to the anisotropic nature of the deposited LC films. However, the importance of vapor-coating functional-group interactions as mediating factors in the sensor responses was evident in several cases. Incorporation of an LC coating into a four-sensor array improved the discrimination between isomers relative to an array employing only isotropic coatings. A persistent decline in the sensor baseline signal and vapor sensitivity observed over time with both LC coatings could be attributed to evaporative loss and/or changes in the elastic stiffness of the coatings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31640/1/0000574.pd