In the ideal case, the coating will not be sensitive to water or to other potential interferants. The objective is to develop a matrix of coatings and chemicals and to calibrate the response of each coating to the BTEX chemicals and to water vapor.
Researchers can use the matrix to determine which coatings to use for the actual sensor designs.
In screening candidate sensor coatings, the researchers have concentrated on polymer materials and have identified several as potentially suitable candidates. In the screening process, the researchers first coated the waveguide surface with a candidate material and then observed the sensor's response when exposed to contaminants at a known concentration. They were looking for fast responses that quickly returned to the zero point. Once a coating was selected, researchers calibrated the coated sensor by measuring the response at different concentration levels. The calibration data and field measurements will be used Waveguide Protection to characterize contaminant concentration levels.