TNT detection with TF-BAR sensors coated with biochemical layers

摘要

This paper presents the development of a thin-film bulk acoustic resonator (TFBAR) sensor based system capable of multiple explosives detection. The effect on which the detection is based is represented by the immobilization of explosive vapors on a layer of antibodies, and it's subsequent detection via an electro-mechanical system (MEMS). The sensor consists of a thin piezoelectric layer (ZnO, AlN or PZT below 1μm), creating a resonator working in longitudinal vibration mode, in which the resonance frequency is determined by the reverse of the piezoelectric layer thickness and directly proportional to the material constant. The reduced dimensions allow it to operate at high frequencies (1-10GHz), and with a high quality factor. A silicon wafer coated with a SiN membrane will provide the necessary support structure, and the deposition of the antibodies is achieved with the help of two intermediate layers of gold and protein, thus creating a polarized link, leaving free the antigen binding. The binding of the explosive molecules to the antibodies changes the resonance frequency of the sensor, thus detecting it's presence. The system comprises of several sensors, each of which designed with it's own type of antibodies, for specific explosives. Each biochemical layer is chosen as to provide high affinity and discriminatory capabilities. A heater ensures the vaporization and the optimum condition for the explosive-antibody binding, and a flow controller routes the vapors through a cavity beneath the sensor. A network analyser, a PC and an interface are also required. The aim is to provide a cheap, portable and user friendly system.