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Title: The dynamics of microplates and application in biosensing
Author: Wu, Zhangming
ISNI:       0000 0004 2689 2721
Awarding Body: Aston University
Current Institution: Aston University
Date of Award: 2009
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The thesis presents the work of dynamics study of fluid-loaded microplate and its application in a novel biosensing system, which is designed to be able to detect the properties of biological cells in a liquid (fluid) environment. Knowledge and understanding the dynamic characteristics of microplates in fluid is critical to its application in biosensing. The thesis presents the theoretical models and first analytical solution of the vibration of microplates involving two loading conditions, distributed mass and fluid loading. Various microplates with different dimensions and boundary conditions are manufactured using microfabrication techniques and their dynamics are experimentally tested. A novel biosensing system is developed utilising the dynamical characteristics of microplates. A new system identification methodology based on artificial neural network and distributive sensing approach for biosensing is also developed and tested using bio-experimental data. This work of the thesis paves the way of a real time continuous cell monitoring biosensing system. The thesis first proposes two mathematical models developed for the dynamics analysis of fluid-loaded microplate. The first model based on Rayleigh-Ritz energy method is to estimate the resonant frequencies and mode shapes, while damping mechanisms of this coupling system is analyzed by using the second model built upon Guz's formulations of hydroelasticity for compressible viscous fluid. Either the first model or the second model can be widely applied to dynamics analysis of fluid-loaded of rectangular plates with various boundary conditions. The equations derived for the damping mechanism analysis in second model is the first analytical solution to this problem. Moreover, these theoretical models and corresponding analytical solutions also give fundamental contributions to the general engineering problem of fluid-structure interactions. The dynamic properties of fluid-loaded micro-scale plates are examined and discussed through the numerical simulations based on these models. A testing system is then designed and employed to experimentally determine the dynamics of fluid-loaded microplates. In this experimental system, the base excitation technique combined with pseudorandom test signals and cross-correlation analysis is applied to test microplates. The dynamic experiments cover a series of testing of various microplates with different boundary conditions and dimensions, both in air and immersed in water. It firstly demonstrates the ability and performances of base excitation in the application of dynamic testing of microstructures that involves a natural fluid environment. Additionally, this experimental system and analytical methodologies presented in this part contribute a convenient and fast way in the field of dynamics testing of microstructures. The obtained experimental data provide important information to further understand the dynamic characteristics of fluid-loaded microplates, and also verified the proposed theoretical models. Next an integrated biosensing system, which is using the microplate as sensing platform and is capable to be self-sensing and self-excitation, is proposed and manufactured. In this microsystem, a scheme of distributed piezoresistive sensors is used to measure the deflection of the sensing surface that is actuated by the PZT thin films. This is the first design to apply a distributive sensing strategy into a microsystem. In addition, this novel configuration of actuators and sensors allows the microsystem is able to work both under static mode and dynamic mode. Finally biological cells are planted onto the sensing surface of microplates to test their performance in the application of biosensing. A series of bio-experiments are implemented on several different types of microplates. The bio-experiments involve planting different certain amount of cells onto the sensing surface of microplates, and measuring the corresponding dynamics information in the forms of a series of frequency response functions (FRFs). All of those experiments are carried in a truly cells culture medium to simulate a practical working environment and a large number of such bio-experiments are implemented, which are seldom achieved in other researches of biosensors. The shifts of resonant frequencies of microplates are firstly used to give a preliminary analysis on the coated cells. Afterwards, the distributed sensing scheme with artificial neural network algorithm is then used to process the measured data and perform a more accurate identification on the features of cells. The latter methodology has been widely used in many researches, but it is of a brand new concept in the area of biosensing. The analytical results in this work demonstrate great potential advantages of applying this methodology into the area of biosensing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Engineering