We present successful demonstrations of a repeatable Surface Acoustic Wave (SAW) Sensor for bacterial biofilm growth monitoring in animal serum as an approximation to an in vivo environment.

One of the problems associated with medical implants is infection resulting from bacterial biofilms, which are often difficult to remove without invasive surgery. Hence, their detection at an early stage is critical for effective treatment.

SAW sensors have the advantage of exhibiting high sensitivity for biosensor applications also are compatible with a wireless communication which makes the sensor a unique tool for in vivo bacterial biofilm growth monitoring.

The detection of biofilm growth by the SAW sensor is achieved using a high quality zinc oxide (ZnO) piezoelectric thin film which is deposited by pulsed laser deposition. The device is passivated with 45 nm of Al2O3 deposited by atomic layer deposition to prevent ZnO damage due to the long term contact with bacteria growth media.

The SAW sensor can be reused after using O2 plasma biofilm cleaning for 30 seconds. Based on these O2 plasma cleaning and novel Al2O3 passivation, the SAW sensor is able to be used multiple times.

The SAW sensor was tested three times consecutively in 10% FBS, with O2 plasma cleaning in between uses, to inspect the performance of the sensor in a simulated in vivo environment. The resonant frequency shift results of the sensor are shown in figure 1. Results from these three experiments in 10% FBS consistently show an exponential increase of the resonant frequency of the sensor at the beginning and finally reach to plateau as nature of biofilm growth. These repeatable results in an animal serum support the novel application of a SAW sensor for biofilm growth monitoring and future development in in vivo applications.