Investigations of TiO₂ as a protective coating on diaphragm-based in vivo sensors

The motivation for these experiments has been to investigate the influence of a biocompatible protective coating on diaphragm-based in vivo sensors. The investigated device is a resonator for fish identification. Such a diaphragm-based configuration is also commonly used for pressure sensors. Six passive ID tags with a set of acoustic resonators have been coated with a 12 nm thin TiO₂ film by the atomic layer deposition (ALD) technique. The frequency response in the 200 kHz to 400 kHz range has been measured in water before and after coating. The resonance peaks can still be detected after coating, but an increase in the resonance frequencies of about 2 % is measured. The increase is explained by a thicker diaphragm due to the TiO₂ film.