A Rayleigh surface acoustic wave (R-SAW) resonator biosensor based on positive and negative reflectors with sub-nanomolar limit of detection

A label-free sub-nanomolar Rayleigh surface acoustic wave (R-SAW)-based resonator biosensor is demonstrated for biomolecular detection in liquid after drying. The biosensor comprises two interdigital transducers for R-SAW generation and two positive and negative reflectors to confine the acoustic energy in the sensitive area. We benchmark this biosensor against biotin-streptavidin binding, which is a standard, well-known model for a variety of biosensing processes. The experiments demonstrate a limit of detection of 104 pM and a normalized sensitivity of −296 m2 kg−1. As a comparison with similar acoustic-wave based systems, both sensitivity and limit of detection are better than that of standard commercial gravimetric sensors (i.e., quartz-crystal-microbalances) and generally better than that of more common Love-SAW biosensors. Our biosensor has a dynamic range potentially compatible with several health- and safety-related assays, among all cancer biomarker detection.