Development of a Novel Flexural Plate Wave Biosensor for Immunoglobulin-E Detection by Using SAM and MEMS Technologies

This paper presents the design, fabrication and characterization of a novel flexural plate wave (FPW) microsensor for immunoglobulin-E (IgE) detecting applications. The propagation membrane is constructed with SiO₂/Si₃N₄/ZnO multilayers and be released from the silicon substrate as a floating thin-plate by using bulk micromachining technology. The ultrasonic flexural plate waves are launched and received by a pair of Cr/Au interdigital transducers (IDTs) on the surface of the ZnO piezoelectric thin film. In this study, we demonstrated a high C-axis orientation ZnO piezoelectric thin film deposition, an IgE self-assembly monolayer (SAM) immobilization and a FPW allergy microsensor with 21 MHz center frequency and 233 cm³/g mass sensitivity. This is the first report demonstrating human IgE detection by an FPW-based microsensor.