A piezoelectric SH-leaky SAW biosensor for antibody detection

The latest trend in medical diagnosis is the use of biochips to perform molecular-level detections on diseases. With the unique and exclusive recognition ability between biomolecules, this work develops an antibody biosensor that is able to perform qualitative and quantitative bacterial analysis. The proposed biosensor includes a piezoelectric sensing device, automatic gain control amplifier and reader. The piezoelectric sensing device is built with shear horizontal (SH) leaky surface acoustic wave (SAW) material to have characteristics that change in frequency parallels with the change in object mass on the surface of the sensing area. With designing two inter digital transducers on our piezoelectric device, insertion loss is the least, at around -23dBm, between 6.8MHz and 7.2MHz and with phase shift at around 70 degrees. Additionally, the automatic gain control amplifier effectively enlarges an oscillation signal from the piezoelectric sensing device, and provides this enlarged signal to a reader and back to the piezoelectric sensing device. In the initial stage, antibody molecules are substituted with viscose glycerol in testing to derive at an output frequency of 6.874MHz under no-glycerol state, and an output frequency of 6.836MHz with glycerol in the proposed biosensor. The detection is highly sensitive that the minimum detectable mass change of each square millimeter is up to 1.44 × 10 ^∼7 gram. These results illustrate that mass change generated from combination of antigen and antibody can be utilized in the proposed biosensor to reduce measurement time and cost associated with disease detection.