Economic And Effective Micro-fabrication Methods And Their Application In Biomolecules Patterning And Microfluidic

Micro-machining technology gains tremendous attention and achieved great progress since 1990 s.The center of micro-machining is to produce miniaturized devices with fine channels and chambers.The flow velocity,mixing and separation are controlled at the micro-meter level to meet the characteristics of fluid behavior in the biomedical or chemical experiments.However,microfabrication technology directly developed from the semiconductor industry heavily relies on expensive professional equipment,clean-room facilities and should be operated by professional personnel.All those requirements greatly limit acceesibility of micro fabrication,miniaturized device to people work with limited resource.My work focuses on the establishment of low-cost micro-fabrication methods and explores the application of these methods in biomolecules patterning and microfluidic chips.The main contents of the thesis are as follows:1.Economical flash foam as a new microfabrication tool to build microfluidic device and surface patterningFlash foam—also called photosensitive foam—is an ultra-micro bubble material typically made by polyethylene.Due to the microporous structures inside,the foam can store solutions and dispense the solution by imposing pressure.Under strong light radiation,the flash foam absorbs light energy that can be transformed into heat energy to melt the polymer and cause fusion of the microporous structure of the foam.The diminished pore at the surface layer of the foam forms a barrier that blocks ink penetration.Its low cost,ease of fabrication and ink storage advantages drive us to explore the flash foam as an new stamp to print versatile chemical and biological“ink” on substrates for bioassays.(1)The flash foam-based stamp(FFS)was fabricated to print viscoelastichydrophobic polymer PDMS on filter paper to form a hydroponic barrier.By optimizing the conditions for preparing the FFS,the viscosity of PDMS precursor and printing pressure,hydrophobic PDMS barrier can be build on filter paper to fabricate paper based microfluidic device.(2)To investigate the applicability of printing versatile inks by foam stamp for protein patterning,glutaradehyde(GA)-medicated protein covalent immobilization was applied as a model system.The results show that APTES,GA,agarose gel and protein can be easily patterned on glass.Moreover,the protein pattern fabricated by flash foam stamp can guide the adhesion and growth of cells to form cell patterns.(3)Because the incident light can seal the microporous structures of the flash foam,we argued that by adjusting the grey intensity(darkness)of the mask we could fabricate FFS features with different pore sizes.The variety of the pore sizes within the feature can deliver a pattern with different ink densities.The fluorescent micrographs obtained from the microarray scanner.The fluorescent image and grey intensity plots show protein patterning with a concentration gradient was successfully established for a one-post ?PC process2.Fabrication of an in vitro model of the retinal microvascular to investigate the impact of TNF-alpha on peripheral blood mononuclear cells anchoring on vascular endotheliaRetinopathy is a complication of diabetes that affects the eyes;it stems from damage to the microvasculature of the retina and eventually compromises vision.The diagnosis of retinopathy is difficult to make because there are no early symptoms or warning signs.Dysfunction of the retina's microvascular networks is believed to be associated with inflammatory cytokines and tumor necrosis factor alpha(TNF-?).To investigate the effect of these cytokines,such as TNF-?,a polydimethylsiloxane(PDMS)/glass hydride microfluidic device reflecting the physiological structure of the retina's microvasculature was developed.In this model,the bifurcations and tortuosity of branch vessels were based on photographs of the fundus and an endothelial cell layer(EA.hy926 cells)were reconstructed within the microfluidic network.The adhesion,spreading,and growth of cells was ensured by optimizing the conditions for cell seeding and perfusion.Fluorescent staining was used to visualize the cytoskeleton and measurement of the nitric oxide(NO)level proved that the endothelial EA.hy926 cells had spread in the direction of flow typical of a perfusion system,forming artificial vascular networks.The endothelial layer was further challenged by TNF-?perfusion.Cytokine treatment increased the anchoring of peripheral blood mononuclear cells(PBMCs)on the endothelial layer.The microfluidic device developed in this study provides a low-cost platform reflecting the physiological structures of the retina's microvasculature.It is anticipated that this device will be useful in evaluating the diseased retina as well as in drug screening.