Interaction of structured surfaces and biological sytems
Titanium biotemplatesIt is well known that surface topography influences cell behavior like adhesion, migration, and growth. In order to understand the influence of micro- and nano-structured material surfaces on adjacent biosystems, a broad investigation of cellular reactions and material surfaces is needed. Since titanium is the most common implant material due to its high bio-compatibility and good corrosion resistance, it is appropriate to study well-defined titanium surfaces. For this purpose in an initial simple approach, photoresist patterns on a Si or glass substrate were coated by a thin Ti layer. Much sturdier samples which are suitable for adhesion experiments can be obtained by Ti coated Si or SiO2 structures. Additionally, an approach is followed to achieve regularly structured bulk titanium surfaces by reactive ion etching (RIE).
Regularly patterned microstructures for the investigation of interactions between surfaces and cells
Structures and methods for the investigation of cellular adhesionThe behavior of biological cells strongly depends on their interaction with the environment. Besides signaling pathways that are mainly triggered chemically, physical contact between a cell and its surroundings, i.e. cellular adhesion, plays an important role for the control of cellular behavior. For example, changes in surface structure or of the substrate material characteristics can influence cellular processes like cell migration or even trigger certain pathways during cell differentiation.It is the aim of our research to find novel methods for the investigation of cellular adhesion by creating micro- and nanostructured surfaces or substrates specifically tailored for this task. One approach we follow is the use of elastic substrate materials like poly(dimethyl)siloxane (PDMS), that are specially structured to act as adhesion force sensors in the nanoNewton range.
a) Typical layout of an elastic substrate used for the determination of cellular adhesion forces
Nanopatterning with Diblock CopolymersDue to their low throughput, conventional methods for the fabrication of structures with dimensions of few tens of nanometres, like e.g. electron beam lithography, are only limitedly suited as an alternative to the industrially used optical lithography. Hence, novel concepts for creating nanostructures have to be found. One of these concepts is the use of diblock copolymers.Diblock copolymers generally consist of two distinct polymer species, covalently bound to form the diblock. In our case, we use the combination of a hydrophilic and a hydrophobic polymer. If solved in a solvent which solves only one of the polymer species, the diblock copolymer forms micelles. These micelles can be cast on a surface as a thin layer. Due to self-assembly, the micelles arrange in a regular order. By adding certain metal salts to the diblock copolymer, this self assembly process can be used to produce ordered structures of metal clusters. This way large-area patterning with typical structure sizes in the nanometre range can be realised with comparatively low effort. Furthermore, as diblock copolymers generally have chemical properties similar to those of resists used in conventional lithography, they can be easily combined with established methods of nanopatterning. The aim of our work is to explore the parameter space with which regular structures with long range order can be reliably produced. 
Polystyrene-block-polyvinylpyridine on silicon with a native oxide layer with short range order, size of the micelles approx. 50-60 nm |