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Simultaneous Surface Manipulation and Sensing in a Biosensor Using a Hexagonal Saw Device

Stefan Cular1, Venkat R. Bhethanabotla1, and Darren W. Branch2. (1) Department of Chemical Engineering, University of South Florida, 4202 East Fowler Ave., ENB 118, Tampa, FL 33620, (2) Biosensors and Nanomaterials Department, Sandia National Laboratories, Albuquerque, NM 87185

We present the development of a hexagonal surface acoustic wave (SAW) device to simultaneously sense and manipulate the biological sensing film in biosensor applications. The primary objective is to improve sensitivity and selectivity. A secondary objective is to regenerate the sensor for reuse. A hexagonal device fabricated in 36 lithium tantalate allows for propagation of both Rayleigh and shear horizontal (SH) wave modes simultaneously. The high electro-acoustic coupling in this piezoelectric material allows for efficient transfer of energy from electrical to mechanical form.

In this device, the Rayleigh acoustic waves stress the bonds between the sensing film and analyte forcing only the analyte with higher affinity for the sensing film to stay bound, while the SH SAWs are used for sensing. Additionally, the acoustic waves work to efficiently mix the liquid samples flowing through the micro-channels of the micro-sensor system, reducing the effects of diffusion-limited processes.

Results from using a sensing film of anti-mouse IgG covalently bound to the sensor-surface and mouse IgG as the analyte in buffer solution have shown improved sensor response, determined using fluorescent microscopy. Manipulation of liquid samples was achieved by strongly exciting the piezoelectric substrate with power levels of ~12 mW which is significantly greater than the 1 mW used for sensing. The larger electrical power creates an acoustic wave via piezoelectric coupling that can physically force loosely bound species from binding sites, reducing noise that can lead to inaccurate measurements.

Acknowledgments Support for this work has been provided by NSF grant number DGE-0221681, University of South Florida IDRG, and DoD Grant W81XWH-05-1-0585.