Theoretical study of a phononic structure for bio-sensing applications

In this work, we investigate the evolution of the properties of a pillar phononic crystal in order to simplify the fabrication process by reducing the thickness of the layer. The structure is constructed by stacking alternate layers of SiO2 and Tungsten. The reduction of the dimensions moves the band gap to the upper frequencies and it is possible to adjust its aperture with the ratio comparing the radius of the cylinder with the layers’ thickness. On a substrate, the pillars give resonant modes that can be excited by shear surface waves and gives a sharp peak in the transmission spectrum of the surface wave with a very high quality factor. We also study the theoretical mass sensitivity of the device and we propose a numerical method to determine the theoretical maximum sensitivity that could be obtain by the pillars system. This pillar based metasurface presents a very promising mass sensitivity and a possible way to increase the performance of SAW bio-sensors.