Werkstoff- und Nanomechanik  
Nanomechanics
Materials Mechanics
Coatings and Miniature Mechanics
Low Dimensional Materials
Thin Film Deposition
Electrodeposition of metallic micro-nanostructures
Electroprocessing metal oxides and semiconductors
Micro-chemical analyses
Microstructural analyses
Scientific Instrumentation
Services
Cover gallery
Spin-Offs and Start-Ups
FEBIP Codes

Micro- and Nanopatterning of Medical Implant surfaces
Due to low cost process technology micro-/ nanopatterning and subsequent electroporosification or electrodeposition have a high potential for industrial application related to medical implants. Cheap masking technologies, however, are not available. For medical implants we concentrate all efforts on Ti02 surfaces. We synthesis the films either by anodic oxidation, electrodeposition or electrophoretic deposition of nanoparticles.
Running Projects
Local electron beam induced reduction and crystallization of amorphous titania films on conductive substrates
TEM micrograph of electrodeposited amorphous TiO2 on steel .

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.

e-beam induced crystallisation

 

 

Contact: Johann Michler

Electrochemical structuring/modification of titanium-like surfaces for biomedical applications
(top) Spark anodized Ti6Al4V surface with particular oxide morphology. (bottom) Engineered topography on Ti surface

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

Bioactive coatings for implants by electrophoretic deposition:
Zirconia-Bioglass composite coating deposited by electrophoretic deposition on a Ti6Al4V-substrate.

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

 

Services

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

 

 

Electrodeposition of energy related materials: from conformal deposition to nanostructures
Extremely thin absorber solar cell based on ZnO/CdSe/CuSCN

We study the electrodeposition of n-type ZnO (Band gap ~ 3.3 eV) nanostructures (nano/wires/tubes, urchin-like) with controlled dimensions and morphologies on transparent conductive substrates. The nanostructures were then used as building blocks for nanostructured solar cells. After the deposition of ZnO, we cover these nanostructures by an ultra-thin layer of a light absorber (CdSe) with narrow band-gap (Band gap ~1.7 eV) also by using the electrochemical deposition. To complete the fabrication of the nanostructured solar cell, we fill the space between the core/shell of ZnO/CdSe by a transparent p-type semiconductor (CuSCN) with a wide band-gap (Band gap ~ 3.4 eV) by using electrodeposition or by liquid infiltration followed by precipitation

ZnO urchin like nanostructures obtained by electrochemical deposition
Contact: Laetitia Philippe, Madoka Hasegawa
Running projects
Swiss Federal Office for Energy, CTI projects, European projects
Surface patterning through Self-assembly Methods
Highly organized polystyrene spheres assembled by dip-coating on TCO substrate.
 We produce patterns using self-assembly methods (spin-coating or dip-coating) with polystyrene or SiO2 nanospheres for producing mono- or multi-layers onto different kind of surfaces (e.g. Si, TCO, ITO, etc), com-bined with a subsequent electrochemical etching or deposition. We explore then, the possibility of producing highly organized monocrystalline nanodots, nanowires and nanorings onto flat or non-flat surface for diverse applications.
Si nanowire arrays obtained by chemical etching of Si wafer using self-assembled polystyrene as a template

Contact: Madoka Hasegawa, Maxime Mieszala
Running projects:
COST projects

Electrodeposition of TiO2
Optical images of TiO2 deposits grown on stainless steel for different times. The colour of the deposits is due to interference effects, and can be tuned by varying the thickness of the films.

TiO2 is a highly versatile and industrially attractive wide bandgap semiconductor. The oxide can be deposited in near-room temperature baths via electrochemically induced precipitation. However, it is challenging to deposit crystalline TiO2; typically it is amorphous and there are only a few examples of crystalline as-deposited films using additives. We are investigating different additive-containing and additive-free baths to induce crystallinity in our deposits. Toxicity is an important issue for biomedical applications, and the minimi-sation of contaminants from additives is desirable. Interference effects determine the colour of the thin films, and thus the colour of the deposits can also be tuned by varying their thickness.

Contact: Peter Dunne, Maxime Mieszala
Running project:
CTI Project


 

Electrodeposition of silicon thin films

The electrodeposition of amorphous silicon thin films in organic solvents on transparent conductive substrates is currently investigated. While playing on the bath chemical composition (solvent, precursor concentration, supporting electrolyte) and on the deposition conditions (potential, time), different film morphologies have been obtained. Our main goals are to meet the challenge of stabilizing these Si films against oxidation when exposed to air and to decrease the impurity content. Promising results have been obtained after annealing the films in inert atmosphere as shown by Raman spectroscopy in the illustrating figure.

Contact: Laetitia Philippe
Running Project:
Internal Project

Fabrication of nanoporous Anodic Aluminum Oxide

We produce nanoporous alumina membranes via a two-step anodization of Aluminum. The obtained porous layers are highly organized and their characteristic dimensions can be controlled by adjusting the anodization parameters. Fabricated membranes are used to electrodeposit nanowire arrays (e.g. Ni, Au, Ag, Bi2Te3, etc) via the so-called template assisted electrosynthesis. In addition, we study the influence of non-steady state anodization on the pore, offering the opportunity of controlling the nanowire geometry and surface characteristics.

Contact: Cédric Frantz

Physico-Chemical interactions between selected cultural metallic artefacts and indoor environment
Optical images in reflected light of non-aged and aged patinas on copper

Metallic objects are decoratively colored by patination in all great metalworking traditions over many hundreds of years. A patina is a corrosion layer of various chemical compounds formed on the surface of metals during chemical reactions or exposure to weathering. One example of a patina is a green surface texture cre-ated by slow chemical alteration of copper. Environmental factors in museums can affect metallic (art) objects. For example, zinc and lead objects will be corroded by reactions with formic acid which is emitted by wooden objects and paints. Black spots from copper sulfide are formed on copper objects by reactions with ammonia which is emitted from rubber objects and is also present in ambient air.
We investigate the reactions between pollutants and artificial patinas on copper (Picture). We investigate changes in chemistry and mechanical stability by in-situ spectroscopic and microscopic analysis to find out the mechanisms of interaction.

Contact: Laetitia Philippe

Services

We offer scientific advises on the electroplating bath development for UV-LIGA process and others. We offer advises with galvanic processes and related mechanical and structural properties to be investigated. We also have competence for anodisation processes.

 We offer:

-  Developed electroplating bath for UV-LIGA process
- Galvanic processes and related mechanical and structural properties.
- Anodisation processes (e.g. Al…).
- Optical properties (Transmission and reflectance) of different kind of semiconducting and metallic materials by using Spectrophotometer connected to integrated spheres.
- Photoconversion efficiency measurements (I-V curves) of solar cells using halogen light source.
- UV-lithography facility

Contact: Laetitia Philippe

Affiliation

Laboratory for Mechanics of Materials and Nanostructures
Empa - Materials Science & Technology
Feuerwerkstr. 39
CH-3602 Thun

Tel.:  +41 (0)58 765 1133
Fax: +41 (0)58 765 6990

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