Local electron beam induced reduction and crystallization of amorphous titania films on conductive substrates: We recently succeeded in electrodeposition of uniform films of TiO2, Nb2O5 and ZrO2 valve metal oxides. Local electron beam irradiation can induce reduction and crystallization of electrolytic amorphous TiO2 films deposited on e.g. stainless steel. In-situ substrate temperature measurements and beam heating calculations demonstrate the formation of anatase (Raman) below 270°C, clearly beneath the crystallization temperature of non-irradiated films (440°C). Atomic force microscopy revealed well defined cavities with Gaussian shape. The enhanced e-beam sensitivity of amorphous TiO2 allows for high-resolution patterning of macroscopic films, inducing local changes in oxidation state, phase, topography or even electrical properties.

Contact: Johann Michler

Anodic oxidation of titanium in acid containing electrolytes is a well established technique to increase the thickness of its oxide layer. It is of great value in biomedical applications for improving biocompatibility and corrosion resistance as well as for color coding purpose. Additionally to the chemical composition of an implant surface, also its topography is known to greatly influence the biological response. Besides aiming at a better understanding of film growth, crystallization, incorporation of impurities etc. we study the properties of anodic oxide films in view of its application as natural mask material for subsequent micropatterning via electron and ion beams, as well as via YAG laser irradiation.
For particular interest in applications where chemical inertness, biocompatibility and enhanced osteointegration is desired, we have developed a spark anodization process for Ti and Ti-alloys, resulting in a novel oxide morphology very different from the well-known micro/nano porous oxides on Ti-like materials. These crystalline oxides feature increased open porosity and chemical purity with respect to harmful substrate elements (V, Al, etc).
Advanced chemical and topographical surface patterning of metals is achieved via a combination of maskless (3D) UV lithography and through-mask electrochemical micromachining. This novel approach allows for creation of precise and almost ideal topographies in the micro- to macro range for use in biological cell studies, microfluidics and stamping applications.

Contact: Johann Michler

In the field of orthopaedic implants, hydroxyapatite (HA) plasma-spray coatings have been traditionally used in order to enhance implants fixation. However, due to high temperatures, the plasma spray process does not allow for a rigorous control of the final chemical and structural coating properties. Also, it is not straight-forward to deposit a uniform film on complex or even hidden surfaces. Electrophoretic deposition (EPD) is an alternative coating technique with the following advantages: Control of the stoichiometry, uniformity on any shape, flexibility in the choice of materials, simplicity and low cost. We are about to develop graded coatings by EPD, consisting of a biocompatible matrix with well-defined interconnected porosity and bioactive elements with different rates of bioresorbability.

Contact:  Johann Michler

Chemical and microstructural analyses of surfaces, oxides and coatings (GD-OES, topography, roughness etc.)
Transfer of know-how related to surface functionalization of metal based implants (Ti, steel, etc.), biomedical engineering electrochemical technology.

Contact: Johann Michler