MIMICKING THE OLFACTORY SYSTEM BY A THICKNESS-SHEAR-MODE ACOUSTIC SENSOR ARRAY

Mimicking the mammalian olfactory system by an array of twelve thickne ss-shear-mode (TSM) acoustic wave sensors with different adsorptive ma terials to form an artificial odour-sensing system has been investigat ed. The adsorptive materials chosen include polyethylene glycol-20M, h exadecyltriphenyl phosphonium iodide, N-(2hydroxylbenzyl) dodecylamine , tween 65, dinonyl phthalate, polyethylene glycol 400-monostearate, e poxy resin, tri-n-octylphosphinoxid, di-iso-octyl phthalate, polyethyl ene glycol-6000, thionalid and dimethylpropaneldiol succinate. The fre quency shift data obtained from the sensor array responding to the odo urs originated from different groups of organic compounds such as keto nes (acetone, butanone, acetophenone, cyclohexanone, and acetylacetone ), esters (methyl acetate, ethyl acetate, n-propyl acetate, and n-buty l acetate), and aldehydes (formaldehyde, benzaldehyde, glyoxal and fur fural) are transformed to relative values to compensate the effect of the variation of the actual coating frequency shift, Delta f. The rela tive frequency shift data matrices are subjected to modified principal component analysis (MPCA) treatment with or without data preprocesssi ng. The odours of different organic molecule samples are easily recogn ized from the two-dimensional displays of the first two principal comp onents. The discrimination of aromas originated from different essenti al oils from France (Adoucissant TM663, Atlantic TM3387, and Spat Tacu s TM5970) and different fruits such as apples, bananas, oranges, and p ears is also possible.