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Membrane integration in biomedical microdevices
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The present work has been performed under the Erasmus Mundus Doctorate in Membrane
Engineering (EUDIME) program. The home institute was the Chemical and Environmental
Engineering Department at the University of Zaragoza, within the Nanostructured Films and
Particles (NFP) group. The NFP is a member of the Nanoscience Institute of Aragon (INA).
Two host universities were: Faculdade de Ciências e Tecnologia at the University Nova de
Lisboa (Portugal) and Mesoscale Chemical Systems group at the University of Twente (The
Netherlands). This research has been carried out for approximately 4 years (2013-2017) and it
was part of the EUDIME (FPA 2011-0014, SGA 2012-1719), which was funded by the
European Union.
The target of the research presented in this thesis is a design, development and fabrication
of a microfluidic device with integrated membrane in the form of a membrane contactor for
various biological applications. The microfluidic devices are fabricated and tested for
oxygenation of blood and separation of anaesthetic gas.
In the first part of the work, the microfluidic system for blood oxygenation, so called lungon-
a-chip, is introduced. In such system, one chamber is devoted to pure oxygen, and the other
chamber is designed for blood and they are separated by a dense permeable membrane.
Computer modelling is performed in order to design the liquid chamber with homogenous
liquid flow, low pressure drop of the system and low shear stress without compensation of high
oxygenation. Two different microdevice geometries are proposed: alveolar and meander type
design with vertical membrane arrangement. Fabricated devices as well as integrated
membranes are made of PDMS by soft-lithography and their surface is modified in order to
make them more hydrophilic. The experiments of blood oxygenation are performed and the
oxygen concentration is measured by an oximeter electrode and compared to the
mathematically modelled values. The sensitivity analysis of the key parameters and the possible
improvements of the proposed architectures based on the mathematical simulations are
presented as well.
The second part of the thesis, introduces the concept of an alveolar microfluidic device as
gas-ionic liquid micro-contactor for removal of CO2 from anaesthesia gas, containing Xe. The
working principle involves the transport of CO2 through a flat PDMS membrane followed by
the capture and enzymatic bioconversion in the ionic liquid solvent. As proof of concept
demonstration, simple gas permeability experiments are performed followed by the
experiments with ionic liquid and ionic liquid with the enzyme. Finally, an alternative concept of a silicon/glass microfluidic device with an integrated
membrane in the form of a fractal geometry with nanonozzles as pores at the vertices of the
third-level octahedra for the controlled addition of gaseous species is introduced. Fractal
geometry, that is a three-dimensional repetitive unit, is fabricated by a combination of
anisotropic etching of silicon and corner lithography. As a proof of concept, simple gas
permeation experiments are performed, and the achieved results reveal the potentialities of the
chip for high temperature gas-liquid contactors.