Zinc Oxide/SU-8/ultra-thin silicon/SU-8: A new multi-layered substrate to facilitate facile microfabrication of flexible one-port Lamb wave resonator sensors

Although flexible Lamb wave sensors have been extensively researched in the past decade towards wearable sensing applications, the excessive damping of acoustic waves caused by the polymer thick film used as substrate for these devices demands their expensive microfabrication for operation at extremely low device wavelengths. In this work, a novel multilayered flexible substrate utilizing polymer-encapsulated ultra-thin silicon with minimal damping is designed, fabricated, and tested for flexible Lamb wave humidity sensing applications. The resultant devices show a higher performance as compared to previous reports and the ability to operate at much higher device wavelengths, thereby facilitating their low-cost fabrication.