Surface acoustic wave devices using coupled resonance with nano- and microstructures for biosensing applications

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Surface acoustic wave (SAW) is an elastic wave that propagates on the surface of a material with its energy mainly confined to a depth of about one wavelength at the surface. Usually, SAW devices are realized on polished piezoelectric substrates with metallic interdigital transducer (IDT) made on the surface for the transduction of electrical energy to acoustic energy and vice versa. In the last few years, the demand for low cost, compact and sensitive biosensors for the detection of disease-causing pathogens has increased. SAW biosensor is an analytical device that comprises IDT on a piezoelectric substrate as transducer and a chemically functionalized active area that electivity detects a specific biological analyte. SAW biosensors are helpful because they offer real-time, label-free detection with high sensitivity and selectivity. They are a promising low-cost alternative to the conventional fluoroimmunoassay, radioimmunoassay and surface plasmon based optical biosensing techniques. Of all the SAW-based biosensing systems, Love wave (LW) devices are the most promising choice for biosensor design. Guiding layer of the LW devices keeps the energy of the wave at the surface providing high mass sensitivity and also shields the IDT from liquids. Finite element (FE) simulation of LW device considering different guiding layer materials to calculate mass sensitivity, insertion loss and the coupling coefficient of the device are presented in the thesis.
Supervisor: Harshal B. Nemade