Papers by Getachew Tizazu
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EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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Nanoscale, 2013
We report convenient methods for synthesis of nanopatterned, thermally responsive brushes of poly... more We report convenient methods for synthesis of nanopatterned, thermally responsive brushes of poly(N-isopropyl acrylamide) over large areas (e.g., 1 cm(2)) to form model, dynamic, biofunctional surfaces. The new nanopatterned brush structure can be used to control (i) the rate of both nonspecific and biospecific adsorption processes at the polymer-graft-free regions of the substrate, and (ii) the rate of cell detachment. These capabilities have potential implications in a number of areas of biotechnology including biosensing, separations and cell culture.
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Advances in Polymer Technology
This paper focuses on the effect of degree of polymerization (N), density ( σ ), and pattern size... more This paper focuses on the effect of degree of polymerization (N), density ( σ ), and pattern size ( x ) on the interaction force between a periodically patterned Poly(N-isopropylacrylamide) (PNIPAM) brush and protein. The hydrophobic interaction, the Van der Waals attractive force, and the steric repulsive force were expressed in terms of N , σ , and x . The osmotic constant (k1) and the entropic constant (k2) were determined from the fit of the steric repulsive force to an experimentally obtained force distance curve. The osmotic constant was 0.105, and the entropic constant was 0.255. Using these constants, the steric repulsive force was plotted as a function of the separation distance(s) between the substrate and the protein. The forces were determined at a separation distance equal to 0.3 nm, where L0 is the equilibrium thickness of the PNIPAM brush. At this separation distance, the value of the steric repulsive force was much higher than the value of the sum of the hydrophobic ...
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Biointerphases, 2012
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Journal of Nanotechnology
This paper describes a simple method to pattern nanoparticles on planar surfaces using the antifo... more This paper describes a simple method to pattern nanoparticles on planar surfaces using the antifouling property of poly(ethylene glycol) monolayers deposited from a solution on the native oxide of titanium. Atomic force microcopy was used to pattern the poly(ethylene glycol) monolayers producing protein active sites on the protein-resistant surface. Patterns with different sizes have been generated by shaving the monolayers with different repetitions. Friction force microscopy was used to image the patterns. The smallest patterns are 50 nm and the largest patterns are 500 nm at full width half maximum. The smallest pattern was produced with one shave, whereas the largest pattern was produced by shaving the monolayers 112 times. Protein-coated nanoparticles were immobilised on the shaved (protein active) part of the monolayers by dipping the patterned samples into a solution that contains 2% by volume protein-functionalized nanoparticles with a nominal diameter of 40 nm. Atomic force...
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Langmuir, 2009
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Langmuir, 2010
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We demonstrate that interferometric lithography offers a fast, simple route to nanostructured sel... more We demonstrate that interferometric lithography offers a fast, simple route to nanostructured self-assembled monolayers of alkylphosphonates on the native oxide of titanium. Exposure at 244 nm using a Lloyd's mirror interferometer caused the spatially periodic photocatalytic degradation of the adsorbates, yielding nanopatterns that extended over square centimetre areas. Exposed regions were re-functionalised by a second, contrasting alkylphosphonate, and the resulting patterns were used as templates for the assembly of molecular nanostructures; we demonstrate the fabrication of lines of polymer nanoparticles 46 nm wide. Nanopatterned monolayers were also employed as resists for etching of the metal film. Wires were formed with widths that could be varied between 46 and 126 nm simply by changing the exposure time. Square arrays of Ti dots as small as 35 nm (λ/7) were fabricated using two orthogonal exposures followed by wet etching.
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Papers by Getachew Tizazu