GHz surface-wave phononic crystal biosensor using a Fano resonance at the bandgap edge

Abstract

We propose an ultrahigh-sensitivity biosensor based on a GHz surface-acoustic-wave nanopillar phononic crystal using a Fano resonance at the bandgap edge. By means of numerical simulations, we find that the asymmetric, sharp and controllable transmission dip at the bandgap edge of the phononic crystal arising from the Fano resonance, which is caused by mode coupling between a local nanopillar resonance and the surface acoustic waves, allows ultrasensitive detection of attached biomolecules. The effect of such mass loading is studied, showing an attogram detection limit, and a unique “on-off” triggering at the sub-femtogram level for each individual Au nanopillar. This study opens up frontiers for biosensing applications of phononic crystals and ultrahigh-frequency surface acoustic wave devices.