Mass sensing with film bulk acoustic resonator

This thesis addresses the applications of radio frequency (RF) microelectromechanical systems (MEMS) in the area of film bulk acoustic resonator (FBAR) and its uses as a mass sensor in biological and chemical applications. An abridged review of FBAR, its underlying physics, and its sensing mechanism are first introduced.;In regards to FBAR itself, we introduced the MBVD model, with or without mass loading, and the Mason model for analyzing an FBAR, as well as the considerations that needs to be taken in designing such a device. The fabrication process of the diaphragm supported FBAR that can be used for mass sensing applications is then presented. The measurement setup, with a network analyzer and a LabVIEW program, used to characterize these FBARs is described, and the discussion on spurious mode suppression is also presented.;The first application of FBAR for mass sensing is explosive trace detection with antibody coating. Antibodies were immobilized on the backside of FBAR mass sensors using an antibody immobilization protocol. When the specific explosive is exposed to the sensor, it binds to the antibody on the sensor, causing a shift in the resonant frequency of the FBAR sensor. We demonstrate here selective detection of vapor traces of TNT (Trinitrotoluene, a common explosive) and RDX (Cyclotrimethylenetrinitramine which has one of the lowest vapor pressures among various explosives) without any pre-concentrator. Experimental results on the long-term reliability issue of the FBAR sensors are also presented.;Another application presented here is real-time detection of DNA polymerase reaction with FBAR coated with self-assembled DNA sequences. This label-free, real-time detection of DNA synthesis can potentially lead to detection of single nucleotide addition for DNA sequencing application, which can be developed into a low-cost, third-generation DNA sequencing system. Though in our preliminary study, we observed only the difference before and after the completion of all the DNA bases, it is conceivable to observe addition of a single DNA base with improved FBAR sensors. To achieve this ultimate goal, issues relevant to mass detection in liquid environment, including optimization of FBAR and noise reduction in experimental data acquisition, are addressed here.;The last application presented here is real-time, label-free detection of PSA through mass sensing with FBAR coated with an oriented antibody layer. The first prototype sensor is capable of detecting PSA concentration in hundreds of ng/ml range, and can be regenerated. Also, preliminary testing shows the absence of cross-reaction with bovine serum albumin (BSA). An improved version of the sensor utilizing DTSSP (3,3´-Dithiobis[sulfosuccinimidylpropionate]) crosslinker shows a better response, and increases the sensitivity to a level where PSA detection down to ng/ml range is possible. Other relevant works in connection with the PSA sensing project is also presented to wrap up the thesis.