Surface Acoustic Wave Oxygen Sensor

A surface acoustic wave (SAW) device that responds to oxygen pressure was developed by coating a 158-MHz quartz SAW device with an oxygen-binding agent. Two types of coatings were used. One type was prepared by dissolving an oxygen-binding agent in a toluene solution of a copolymer containing the axial ligand. A second type was prepared with an oxygen-binding porphyrin in a toluene solution containing excess axial ligand without a polymer matrix. In the polymer-based coatings, the copolymer served to provide the axial ligand to the oxygen-binding agent and as a coating matrix on the surface of the SAW device. The oxygen,sensing SAW device has been shown to bind oxygen following a Langmuir isotherm and may be used to measure the equilibrium constant of the oxygen-binding compound in the coating matrix.