Preparation, characterization and applications of micro-rough polymethacrylate surfaces

Superhydrophobic surfaces have numerous important practical applications in research and industry. These materials have been widely used for production of self-cleaning, anti-icing, anti-corrosive, non-adhesive, anti-biofouling coatings and surfaces. The phase separation method of producing porous polymer films is a simple and cheap approach that allows producing materials with desired physical and chemical properties, such as polymer globule size, porosity, hydrophobicity or hydrophilicity and surface functional groups. Additionally, the surface can be also later functionalized using available surface modification techniques. However, so far, due to the not optimal surface topography the produced surfaces have exhibited large contact angle hysteresis which limits their practical applications. The goals of this PhD thesis were to: (1) develop a method for the preparation of superhydrophobic polymer surfaces with high water contact angles and low contact angle hysteresis; (2) to characterize the produced surfaces; (3) to investigate the effect of the surface topography and hierarchy on the surface wettability; (4) and to explore their properties in microfluidic and biological applications. The task to design surfaces with outstanding surface characteristics requires understanding of the influence of the surface topography on the wettability. Due to the ease of production, porous poly(2-hydroxyethylmethacrylate-co-ethylene dimethacrylate) (polyHEMA) and poly(butyl methacrylate-co-ethylene dimethacrylate) (polyBMA) surfaces with different surfaces topographies prepared for these studies. The polymer surfaces with protruded and grooved surface topography were prepared simultaneously by photopolymerization in a mold consisting of two glass slides. However, due to the breakage of the polymer film during separation, surfaces with characteristic protruded and grooved topography were made. Photografting of the polyHEMA surfaces with 2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) resulted in the formation of a complex hierarchical structure. The surface functional groups of polyHEMA could be modified through consecutive esterification and thiol-yne reaction. Influence of the surface topography, hierarchy and chemistry on the surface wettability were investigated by Scanning Electron Microscopy (SEM), confocal optical profiler and water contact angle measurements. Recently, microfluidic devices attracted a lot of attention as they allow handling of small liquid volumes and miniaturization of the measurement systems. In this thesis, open microfluidic channels based on the Laplace micro-pump were prepared by photografting PFPMA on the grooved polyHEMA surface creating superhydrophilic micro-channel surrounded by superhydrophobic borders. The working principle of the passive Laplace micro-pump in the produced micro-channel was investigated. The formation of a laminar flow in the absence of an external force was studied. Additionally, the kinetics of the flow in the micro-channels with different dimension was examined. The ability to control stem cell differentiation shows great promise for numerous applications such as stem cell therapy, treatment of diabetes, Parkinson and Alzheimer diseases and many other. However, it is a complex process that depends on both the physical and chemical cues. In this thesis, polyHEMA surfaces with different roughness and surface chemistry were used to investigate the influence of the surface properties on the stem cell differentiation. Retardation of stem cell differentiation for over three weeks of culture on the micro-rough surfaces was shown