<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces"^^ . "Surface patterning is important in a wide spectrum of applications ranging from\r\nmicroelectronics, sensors design and material science to high throughput screening, tissue\r\nengineering and cell biology. A number of methods for specific patterning applications,\r\nsuch as photolithography, soft lithography, or electron beam and dip-pen nanolithography,\r\nhave been developed. However, there is still a clear need for the development of novel\r\nmethods permitting patterning of different cell types, nano- and microparticles as well as\r\nhydrogels incorporating cells. These novel patterning methods are vital for the\r\nadvancement of such research fields as tissue engineering, biomaterials and for\r\nfundamental investigation of cell-cell communication, tissue and organ development.\r\nThe aims of this PhD thesis were: a) develop a technique for creating droplets of\r\nliquid with defined geometries that can be used for patterning water soluble components;\r\nb) optimize the conditions for the fabrication of porous polymer surfaces for the liquid\r\npatterning; c) characterize the produced patterned polymer surfaces; d) further develop the\r\ntechnique for maskless generation of liquid patterns with arbitrary geometry; e) optimize\r\nthe method for the patterning of different materials (chemicals, hydrogels, microparticles);\r\nf) show an application of the method for patterning of living cells and characterize their\r\nbehavior on the composite surface during cultivation; g) show an application of the\r\ntechnology to mimic natural cell-cell communication in vitro via signaling protein\r\npropagation between patterned cell populations in co-culture.\r\nThe first part of the work was devoted to the development of porous polymer layers\r\nwith precise micropatterns of hydrophilic and hydrophobic areas. In order to fabricate\r\nthese patterns, UV-initiated photografting of 2,2,3,3,3-pentafluoropropyl methacrylate\r\n(PFPMA) on porous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate)\r\n(HEMA-EDMA) was optimized. Before and after photografting, both polymer substrates\r\nwere thoroughly characterized using water contact angle measurement, UV-Vis\r\nspectroscopy, scanning electron microscopy (SEM) and time of flight secondary ion mass\r\nspectrometry (ToF-SIMS). Porous properties were characterized by UV-Vis spectroscopy,\r\nSEM and dynamic light scattering techniques (DLS). Due to the high difference in\r\nwettability of the hydrophilic HEMA-EDMA polymer film and hydrophobic regions\r\ncoated with PFPMA polymer brushes, aqueous solutions can be trapped in the hydrophilic\r\nareas, taking the shape of these areas. The transparency of the HEMA-EDMA monolith\r\noriginated from porous properties of the polymer makes it suitable for microscopic\r\nmonitoring of liquid patterns during experiments.\r\nThe method was for the first time applied for the simultaneous micropatterning of\r\nmultiple cell types. More than ten different cell populations separated by hydrophobic\r\nborders could be cultured in microreservoirs. After adhesion, the cells could be placed in\r\nthe mutual culture medium, allowing cell-cell communication among populations. During\r\n3 days co-culture in the mutual medium, cross-contamination was shown to be less than\r\n1,5%, although the cells were pre-patterned in the hydrophilic areas separated by\r\nhydrophobic borders of only two to three cell diameters. The capability of cell patterning\r\nand long term cultivation opens the way for many interesting bio-applications, such as in vitro mimicking important biological processes that involve and depend on the\r\norganization of multiple cell types into complex micropatterns in vivo. As a case study, I\r\ntogether with Dr. Steffen Scholpp and Dipl. Eliana Stanganello (ITG, KIT) used the\r\ndeveloped technique to visualize spreading of signaling molecules (Wnt protein) from one\r\nmicropatterned population of fibroblast cells to another fibroblast population by activation\r\nof the reporter system. Thus, we were able to simulate paracrine signaling system in vitro.\r\nIn addition, I further developed our technique into a new type of mask-less liquid\r\npatterning or digital liquid patterning (DLP) method. The idea of this method is similar to\r\nthe working principle of a digital score board. A digital score board consists of many small\r\nbulbs, which generate light symbols on it. In the case of DLP, instead of the bulbs, small\r\nliquid droplets (digits) form a more complex liquid pattern on a substrate. The substrate for\r\nDLP is a composite surface, consisting of a grid of hydrophilic HEMA-EDMA spots\r\ndivided by hydrophobic PFPMA barriers. The method allows on-demand fabrication of\r\nliquid patterns without the need to change the substrate and use an additional photomask.\r\nPatterns with customized geometries can be prepared manually by simply pipetting liquid\r\ninside the spots and successively coalescing the generated droplets to form a liquid\r\nmicropattern. The DLP does not require clean room or high-precision microfabrication and\r\nallows the manual positioning of microdroplets in the range of micrometer scale. It was\r\nalso shown that using superhydrophilic/superhydrophobic patterned surfaces leads to\r\nspontaneous dewetting of the coalesced microdroplets on the interface of the\r\nsuperhydrophobic border and the superhydrophilic spot. Hence, the usage of\r\nhydrophilic/hydrophobic patterned surface ensures the stability of liquid patterns during\r\nmanipulations. Furthermore, the developed technique enables patterning of not only\r\nsolutions, e.g. different chemicals, but also suspensions of living cells and microparticles,\r\nhydrogels, or formation of liquid multi-component gradients with complex geometries.\r\nThus, this method will be especially useful for biological studies, which require the\r\ngeneration of complex patterns of different or the same cell types, or bioactive materials\r\nand cellular gradients without the need for sophisticated microfluidic and printing\r\nequipment, or for designing additional masks"^^ . "2014" . . . . . . . "Alexander"^^ . "Efremov"^^ . "Alexander Efremov"^^ . . . . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (PDF)"^^ . . . "Dissertation_A Efremov.pdf"^^ . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Fabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #17070 \n\nFabrication and application of hydrophilic-hydrophobic micropatterned polymer surfaces\n\n" . "text/html" . . . "540 Chemie"@de . "540 Chemistry and allied sciences"@en . .