Research Of Automatic Analysis Method For Piezoelectric Biosensor

In this thesis, automated piezoelectric bioassays have been developed with the theoretical consideration, instrumentation and application of piezoelectric bioassays.First, the finite element method based on the Mindlin equations is employed to analyze piezoelectric sensors consisted of the AT-cut quartz crystal resonator with complex structures. As well-known, not only the wanted thickness-shearing (TS) mode but also many unwanted spurious modes can exist on an AT-cut quartz crystal plate. Coupling between the TS and spurious modes will degrade the quality of the resonators, e.g. decreasing the Q-factor and inducing mode jumping. This degrading quality of the resonator will reduce the performance of piezoelectric sensors. The theoretical results obtained by the finite element method show that when the mesa structure depth of the single-step-mesa structure reaches a certain value, further energy-trapping improvement cannot be achieved by increasing the mesa depth. A bi-mesa design can further improve the decoupling characteristics of the resonator beyond the single-step-mesa structure resonator, so as to improve the precision of piezoelectric sensors.Second, a seal-structured piezoelectric biosensor is developed with an AT-cut quartz crystal of a bi-mesa design. This special construction enables a flow sampling mode be applied. Thereafter, an analytical instrument has been developed with the support of computer, which can be auto-running under the control of CPU and exclude inherent errors of the manual operation. In order to be highly efficient, eight channels were integrated into the instrument providing that eight samples could be simultaneously analyzed. It was shown that the relationship of the chloramphenicol concentration with the piezoelectric frequency response was in agreement with the classical Sauerbrey's theory in some range, indicating the fabricated device could be used as a mass sensor.Moreover, the above piezoelectric biosensor and auto-analytical instrument have been exploited to set up a highly reproducible and sensitive platform for detection of nucleic acids. In the platform, the nanoparticle-bioconjugate formed by homogeneous hybridization of target sequences with thiol-modified and nanoparticle-labelled probes was adsorbed on the gold surface of piezoelectric sensors. This novel strategy is significant for several reasons. First, the target is captured by excess probes in solution, which is completed within 5 min under the conditions of a PCR-like''renaturing''.