The attachment of blood platelets to the surface of bare and protein-coated thickness-shear mode acoustic wave devices operating in a flow-through configuration has been studied. Platelets in washed from bind to the gold electrodes of such sensors, but the resulting frequency shifts are far less than predicted by the conventional mass-based model of device operation. Adherence to albumin and various types of collagen can be produced by on-line introduction of protein or by a pre-coating strategy. Differences in attachment of platelets to collagen types I and IV and the Horm variety can be detected. Platelets attached to collagen yield an interesting delayed, but reversible signal on exposure to a flowing medium of low pH. Scanning electron microscopy of sensor surfaces at various time points in this experiment reveals that originally intact platelets are eventually destroyed by the high acidity of the medium. The reversible frequency is attributed to the presence of removable platelet granular components at the sensor-liquid interface.

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