{HEAD ~ Variability} in {TAIL ~ chemical sensitivity} from sensor to sensor is provided by qualitatively or quantitatively varying the composition of the conductive and nonconductive regions 
in
{ HEAD ~ Variability } in { TAIL ~ chemical sensitivity } from sensor to sensor is provided by qualitatively or quantitatively varying the composition of the conductive and nonconductive regions
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH