Taheny_2010_effect.pdf (3.8 MB)
On the effect of digitising flows in networked microfluidic systems for nucleic acid analysis
thesis
posted on 2022-11-16, 11:46 authored by Oliver TahenyThe integration of molecular diagnostics and microfluidics has the potential to
revolutionise human health care. The continuous discovery of genetic markers
that correspond to particular cancer types and subtypes offers a large potential
for non-invasive patient screening. Early and accurate diagnosis has the potential
to lead to tailored treatments and a better patient prognosis. The research
undertaken here at the Stokes Institute aims to develop a diagnostic tool through
current advancements in genomics and microfluidics, for the accurate and early
diagnosis of paediatric leukaemia. Applying microfluidics to the current molecular
diagnostic protocols offers a decrease in costs through a reduction in consumable
reagents and an increase in speed and consistency through integration of all the
functional steps of qPCR.
The research presented in this thesis focuses on the hydrodynamics of biphasic
flow. Encapsulating the genetic material and PCR reagents into a micro-reactor
(microfluidic plug) allows for individual and contamination-free processing.
The pressure drop of individual plugs under a range of operational conditions
is measured and presented. An analysis of the effect of the concentration of
surfactant that is employed has on the biphasic hydrodynamics is examined. The
data is subsequently analysed and compared to a theoretical approximation that
is present in the literature. The ratio of biphasic fluidic resistance to single phase
fluidic resistance is presented as a means to measure empirically the effect a
second immiscible phase has on the hydrodynamics. A train of immiscible plugs
is shown to have a lower pressure drop than a single plug of similar total length
when the inter-plug spacing is sufficiently large.
Three microfluidic manifolds were tested as microfluidic circuit elements.
Fluidic manifolds provide a controllable means of distributing a single flow across
numerous microfluidic capillaries and circuit elements. Two prototype manifolds
were designed and compared to a commercially available product. The sensitivity
of a manifold to changes in fluidic resistance and air contamination is also
presented. Liquid bridges were employed as circuit elements and pressure taps.
This is, to the best knowledge of the author, the first use of liquid bridges as
pressure taps. The liquid bridges isolated the aqueous plugs from the pressure
port taps preventing sense line contamination. A pressure transient analysis was
carried out to determine the effect of the liquid bridges on biphasic flow. The
incorporation of the three microfluidic elements into a single circuit was analysed
under biphasic flow conditions. Two analytical models of microfluidic circuits are
presented for the queuing and mixing of aqueous plugs prior to processing. The
pressure drop data was used to validate the employment of a modified single phase
analytical model for the design of biphasic microfluidic circuits for low Capillary
and Reynolds number flows.
History
Degree
- Doctoral
First supervisor
Davies, MarkNote
peer-reviewedLanguage
EnglishDepartment or School
- School of Engineering
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