Development and Characterization of FPW Based Allergy Biosensor

This paper presents a novel flexural plate wave (FPW) allergy microsensor with integrated cystamine-based self-assembly monolayers (SAMs) for the detection of immunoglobulin-E (IgE) concentration in human serum. The propagation membrane of the FPW biosensor is constructed with Si/SiO₂/Si₃N₄/ZnO multi thin-films and released from the 512 mum-thick 4-inch silicon substrate as a floating thin-plate by using bulk micromachining technology. To improve the yield and performance, a 3 mum-thick silicon diaphragm of the FPW device is designed in this research. 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, a 3 nm-height cystamine-glutaldehyde SAMs is developed for the immobilization of IgE antibody. The implemented FPW-based allergy biosensor with relatively high mass sensitivity (17200 cm²/g) and perfect sensing linearity (99.99%) of human IgE antigen is demonstrated in this paper.