A COMPLETE FAMILY
r a t e . M a s s d e t e c t i o n is n o t t h e only, nor always the dominant, mechan i s m by w h i c h a c o u s t i c w a v e devices function as sensors, a n d piezoelect r i c i t y is s i m p l y a m a t e r i a l p r o p e r t y t h a t is useful, b u t n o t n e c e s s a r y , for g e n e r a t i n g acoustic waves in small devices. T h e r e c o g n i t i o n of a d d i t i o n a l m e c h a n i s m s by which a n acoustic w a v e device c a n a c t a s a s e n s o r c r e a t e s m a n y n e w o p p o r t u n i t i e s for t h e d e s i g n of p h y s i c a l a n d c h e m i c a l s e n sors a n d p r o v i d e s t h e m e a n s by which sensitivities can be m u c h g r e a t e r t h a n t h o s e t h a t m i g h t be achieved by m a s s detection alone. T h e a c o u s t i c w a v e s e n s o r field h a s expanded tremendously in recent y e a r s . A t t h e r e s e a r c h e n d of t h e R & D s p e c t r u m , t h e r e is a n e w e m p h a s i s o n t h e d e t a i l s of m o l e c u l a r a n d physical events at interfaces and in t h i n films, a n d development h a s proceeded to sensor a r r a y s a n d complete m i c r o a n a l y t i c a l s y s t e m s . Select i v i t y a n d l i m i t s of d e t e c t i o n c o n t i n u e to improve, and great strides h a v e b e e n m a d e in reducing t h e size a n d p o w e r c o n s u m p t i o n of s e n s o r sytems. Many exciting applications are being explored, including elect r o n i c n o s e s for o d o r s e n s i n g , b i o s e n s i n g , s y s t e m s for s e c u r i t y a p p l i c a t i o n s ( s u c h a s t h e d e t e c t i o n of explosives, drugs, and chemical a g e n t s ) , a n d s y s t e m s for m e a s u r i n g c o n c e n t r a t i o n s of specific g a s e s a n d particulates in the stratosphere. The authors gratefully acknowledge Richard Baer, Hewlett-Packard Laboratories, for valuable suggestions on the relationships of the various acoustic devices to one another and for advance information on the STW devices. We also acknowledge Michael Thompson and David Stone, University of Toronto, for helpful discussions on interdigital capacitance, flexural rod devices, and response mechanisms in liquidphase sensing. Input on certain FPW device characteristics by Ben Costello and Stuart Wenzel, Berkeley Microinstruments, is also appreciated. Pacific Northwest Laboratory is operated for the U. S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830. References (1) G r a t e , J. W.; M a r t i n , S. J.; W h i t e , R. M. Anal. Chem. 1993, 65, 940 A. (2) Wohltjen, H. Sens. Actuators 1984, 5, 307—25 (3) Tiersten, H. F.; Sinha, B. K. /. Appl. Phys. 1978, 49, 8 7 - 9 5 . (4) Wohltjen, H.; Dessy, R. E. Anal. Chem. 1979, 51, 1458-70. (5) F e r r y , J . D. Viscoelastic Properties of Polymers, 3rd éd.; John Wiley and Sons: New York, 1980. (6) Hartman, B. In Encyclopedia of Polymer Science and Engineering, 2nd éd.; Mark, H. F., Ed.; J o h n Wiley and Sons: New York, 1984; Vol. 1; pp. 131-60. (7) Massines, R.; Piche, L.; Lacabanne, C. Makromol. Chem., Macromol. Symp.
1989, 23, 121-37. (8) G r a t e , J . W.; K l u s t y , M.; McGill, R. Α.; Abraham, M. H.; Whiting, G.; Andonian-Haftvan, J. Anal. Chem, 1992, 64, 610-24. (9) Ballantine, D. S.; Rose, S. L.; Grate, J. W.; Wohltjen, H. Anal. Chem. 1986, 58, 3058-66. (10) Grate, J. W.; Snow, Α.; Ballantine, D. S.; Wohltjen, H.; A b r a h a m , M. H.; McGill, R. Α.; Sasson, P. Anal. Chem. 1988, 60, 869-75. (11) Grate, J. W.; Wenzel, S. W.; White, R. M. Anal. Chem. 1992, 64, 413-23. (12) Martin, S. J.; Frye, G. C. Proc. IEEE Ultrason. Symp. 1991, 393-98. (13) Martin, S. J.; Frye, G. C. Proceedings of the 1992 Solid State Sensor and Actuator Workshop; I E E E : New York, 1992; pp. 27-31. (14) Martin, S. J.; Ricco, A. J. Sens. Actua tors 1990, A21-A23, 712-18. (15) Martin, S. J.; Frye, G. C. Appl. Phys. Lett. 1990, 57, 1867-69. (16) Hughes, R. C ; Martin, S. J.; Frye, G. C ; Ricco, A. J. Sens. Actuators 1990, A21-A23, 693-99. (17) M u r a m a t s u , H.; K i m u r a , K. Anal. Chem. 1992, 64, 2502-07. (18) Okahata, Y.; Ebato, H. Anal. Chem. 1989, 61, 2185-88. (19) King, W. H. Anal. Chem. 1964, 36, 1735-39. (20) White, R. M.; Wicher, P. J.; Wenzel, S. W.; Zellers, E. T. IEEE Trans. Ultrason ics, Ferroelectrics, Frequency Control 1987, UFFC-34, 162-71. (21) Grate, J. W.; Abraham, M. H. Sens. Actuators Β 1991, 3, 8 5 - 1 1 1 . (22) Grate, J. W.; Klusty, M. Anal. Chem. 1991, 63, 1719-27. (23) G r a t e , J . W.; McGill, R. Α.; A b r a h a m , M. H. Proc. IEEE Ultrason. Symp. 1992 275—79 (24) Guilbault,' G. G ; Jordan, J. M. CRC Crit. Rev. Anal. Chem. 1988,19, 1-28. (25) Mierzwinski, Α.; Witkiewicz, Z. Envi ron. Pollut. 1989, 57, 181-98. (26) McCallum, J . J . Analyst (London) 1989, 114, 1173-89. (27) Nieuwenhuizen, M. S.; Venema, A. Sens. Mater. 1989, 5, 261-300. (28) Fox, C. G.; Alder, J. F. Analyst (Lon don) 1989, 114, 997-1004. (29) D'Amico, Α.; Verona, E. Sens. Actua tors 1989, 17, 55-66. (30) Carey, W. P.; Kowalski, B. R. Anal. Chem. 1986, 58, 3077-84. (31) Carey, W. P.; Beebe, K. R.; Kowal ski, B. R. Anal. Chem. 1987, 59, 1 5 2 9 34. (32) Ema, K ; Yokoyama, M.; Nakamoto, T.; Moriizumi, T. Sens. Actuators 1989, 18, 291-96. (33) Grate, J. W.; Rose-Pehrsson, S. L.; Venezky, D. L.; Klusty, M.; Wohltjen, H. Anal. Chem. 1993, 65, 1868-81. (34) Rose-Pehrsson, S. L.; Grate, J. W.; Ballantine, D. S.; J u r s , P. C. Anal. Chem. 1988, 60, 2 8 0 1 - 1 1 . (35) Kindlund, Α.; Sundgren, H.; Lundstrom, I. Sens. Actuators 1984, 6, 1-17. (36) Sensors and Sensory Systems for an Elec tronic Nose; G a r d n e r , J. W.; B a r t l e t t , P. N., Eds.; Kluwer Academic Publish ers: Dordrecht, The Netherlands, 1992. (37) Newman, A. R. Anal. Chem. 1991, 63, 585 A - 5 8 8 A. (38) Frye, G. C ; Martin, S. J. Appl. Spectrosc. Rev. 1991, 26, 73-149. (39) Ricco, A. J.; Martin, S. J. Thin Solid Films 1991, 206, 9 4 - 1 0 1 . (40) Ricco, A. J.; Martin, S. J.; Zipperian, T. E. Sens. Actuators 1985, 8, 319-333. (41) Vetelino, J. F.; Lade, R. K.; Falconer, R. S. IEEE Transactions Ultrasonics, Ferro-
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