Biomedical subjects

Mika Linden

Publications and source records attributed to Mika Linden.

4 recordsLinked to original sources

PubMed2006

Topography and surface energy dependent calcium phosphate formation on Sol-Gel derived TiO2 coatings.

Heterogeneous nucleation and growth of calcium phosphate (CaP) on sol-gel derived TiO(2) coatings was investigated in terms of surface topography and surface energy. The topography of the coatings was derived from AFM measurements, while the surface energy was determined with contact angle measurements. The degree of precipitation was examined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The precipitation of CaP was found to be dependent on both topography and surface energy. A high roughness value when combining the RMS roughness parameter S(q) with the number of local maxima per unit area parameter S(ds) enhances CaP formation. The hydrophilicity of the coating was also found to be of importance for CaP formation. We suggest that the water contact angle, which is a direct measure of the hydrophilicity of the surface, may be used to evaluate the surface energy dependent precipitation kinetics rather than using the often applied Lewis base parameter.

Journal Article↗

PubMed2006

Detailed in situ XRD and calorimetric study of the formation of silicate/mixed surfactant mesophases under alkaline conditions. Influence of surfactant chain length and synthesis temperature.

The formation of mesoscopically ordered silica/surfactant composites under alkaline synthesis conditions has been studied by time-resolved in situ small-angle X-ray diffraction with synchrotron radiation. Alkyltrimethylammoniumbromide surfactants, C(n)()TAB, of different chain lengths (n = 14, 16, and 18) as well as mixtures thereof were used as structure directing agents and the measurements were carried out at two different temperatures. A linear relationship between the mean surfactant chain length and the d spacing of the hexagonal phase was observed, suggesting an ideal mixing of the surfactants in the supramolecular surfactant aggregates. It is shown that the formation of the hexagonal phase is kinetically controlled mainly by the rate of silicate condensation, while the effect of changes in the surfactant chain length on the kinetics is small under the studied conditions. Two concominant, albeit partly interlinked, processes, suggested being intra- and intermicellar condensation, followed by aggregate-aggregate condensation, govern the nucleation and growth of the hexagonal phase. The two-step mechanism is confirmed by a microcalorimetric study where the heat evolved during the hydrolysis-condensation reactions is followed as a function of time.

Journal Article↗

PubMed2006

Surface nanopatterning by organic/inorganic self-assembly and selective local functionalization.

Patterning silicon surfaces by well-ordered nanoperforated TiO(2) layers is achieved through a simple block copolymer-assisted liquid deposition technique followed by direct thermal treatment. The crater diameters are tuned between 10 and 50 nm, depending on the molecular weight of the surfactant patterning agent. The formation mechanism of such systems is discussed. The present nanopatterned heterogeneous surfaces (nanoholes with SiO(2) bottom surfaces and TiO(2) walls) are selectively functionalized with two different perfluorinated organic groups. The accessibility to the substrate surface through such nanoholes and the selective distribution of both functions on the surface is evidenced by water-contact-angle measurements, which satisfactorily verify the Cassie relationship. Such systems have wide application prospects in varied fields such as nanotechnology and engineering.

Adsorption↗

PubMed2004

Topographical parameters for specifying a three-dimensional surface.

The importance of different surface geometries and thereby the need for versatile surface identification by describing a number of different surface features is emphasized. A set of topographical parameters for the description of the amplitude and spatial and hybrid properties of surfaces was utilized for a versatile three-dimensional surface characterization of sol-gel samples with different topographies. The image data were measured by atomic force microscopy. The results demonstrate the power of the roughness parameters to identify surfaces according to their specific characteristics. An example is also given about how certain surface topographical properties may control the material reactivity.

Letter↗