UV CROSS-LINKED POLYSILOXANES AS NEW COATING MATERIALS FOR SAW DEVICES WITH HIGH LONG-TERM STABILITY

We present investigations of ultraviolet (UV) crosslinked polysiloxane s as new coating materials for surface acoustic wave (SAW) devices. Lo w-loss filters based on horizontal polarized shear waves were used ins tead of 'standard' Rayleigh-type SAW devices since a larger freedom in the choice of coating thickness can be obtained. Polysiloxane coating s show excellent properties for sensor applications; in particular, th ey promise high sensor stability and reproducibility of measurement ov er a long time period. A considerable improvement of long-term stabili ty is achieved by UV crosslinking of the coatings in comparison to not crosslinked polymers. The ageing behaviour was investigated and deter mined over a testing period of 50 days. Sensitivity and selectivity ca n be controlled by the choice of appropriate functional side groups of the polysiloxanes. Thereby, a discrimination of different organic ana lyte vapours is possible by building up an array of SAW sensors coated exclusively with polymers from the group of UV crosslinked polydimeth ylsiloxane copolymers. (C) 1998 Elsevier Science S.A. All rights reser ved.