Title:
|
The dynamics of microplates and application in biosensing
|
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.
|