One-Port Surface Acoustic Wave Device and Platform Development for Mass-Loading Sensing Applications

Fast, accurate, reliable, noninvasive, and ultrasensitive parameters are essential in designing biosensors for early detection of various diseases. This study investigates a one-port high-frequency operated surface acoustic wave sensor (SAW) as a mass-loading sensor for detecting variations in density of nanoparticle-based solutions along with changes in concentration. The nanoparticle solutions were prepared by homogeneously mixing various nanoparticles in deionized water. The electrical reflection and sensitivity of the fabricated devices were measured using a vector network analyzer by monitoring the shift in resonant frequency (Δ f ) as a sensing parameter for detecting the low concentration of particles. A mechanism of placing a mass directly on the interdigitated electrode (IDT) surface resulted in an improved sensitivity of 120% in comparison to the traditional method of placing the mass adjacent to IDT on the lithium niobate surface. Various solutions of boron nitride (1.024 g/mL), zinc oxide (1.043 g/mL), and silver (1.092 g/mL) nanoparticles were effectively detected with a mass of 0.5 mg using a 250 MHz device, exhibiting a sensitivity of 913 Hz/μg at higher mass loading. The sensor demonstrated stable reproducibility over multiple measurements of nanoparticle solutions. A customized cooling system was developed and demonstrated to control the temperature of the SAW device during high-power experimental characterization, thereby reducing temperature dependent noises. These findings emphasize the potential of a one-port label-free ultrasonic SAW device for sensing minute changes in density and concentration with real-time monitoring for biological, biochemical, gas and liquid sensing, with reduced damping effects.