Nanostructures have a great potential to generate special surface functionalities, without changing other material properties of the workpiece.
Generation of superhydrophobic surfaces with ultrashort laser pulses.
In case of certain materials (e.g. Polypropylene), micro- and nano- surface structures can change the wettability properties of the surface from neutral into superhydrophobic (so called “Lotus-effect”). Traditional methods of fabricating such surfaces are based either on chemical etching or special coating processes. However, low cost replication processes are mostly not supported. In cooperation with several partners, a new method was developed at LLG to fabricate micro-structured molds, capable to transfer the special properties into plastic surfaces. Maintaining a high durability necessitates the use of tough materials like tool-steel. Such materials with usually high thermal conductivity can only be sufficiently machined in the micro- and submicrometer range by applying ultrashort laser pulses. Highly efficient diffractive phase masks ensure the optimal use of the available laser energy. Such diffractive optics can efficiently be machined using special LLG-based technologies (Journal of Laser Micro/Nanoengineering 4, Appl. Phys A101, 225 (2010)). Such phase masks are optimal for fast and highly efficient laser processing of metallic stamps. In a subsequent process step, replicas of the processed stamp are produced by injection moulding, enabling the mass production of the surface patterns on plastics parts. The resulting topography facilitates a super-hydrophobic behavior of the fabricated components.
Surface Functionalization of Medicinal Stainless Steel
In modern medicine a numerous range of medicinal implants is used, including those not staying in the body permanently. Often, the ingrowth of an implant is unwanted, especially in the treatment of bone fractures by means of trauma implants or for intramedullary rods. Therefore, options are searched for to modify the implant surface such that the bone cell adhesion is impeded and thus the ingrowth is reduced. A reduced cell adhesion on the implant’s surface promises fewer complications during surgery when removing the implant and in particular a reduced risk for nerve injury. Medicinal stainless steel is commonly used as a material for trauma implants or intramedullary rods. With the objective “Light as a Tool” in collaboration with the Institute for Manufacturing Technology and Advanced Materials (IFAM) of the Fraunhofer Society, different methods for surface functionalizing of medicinal stainless steel were applied and tested under the aspect of cell adhesion.
For this purpose, at the LLG ultrashort pulses were utilized for the contactless, topographic direct structuring of stainless steel surfaces. That way, periodic structures were produced on the sample surface with periods ranging from 0.5 µm-1.5 µm and a structural amplitude of approx. 200-1000 nm.
The samples were characterized by an atomic force microscope (AFM) and a scanning electron microscope (SEM). Afterwards they were treated with MG63 osteoblasts-like cells for biological testing through cell culture at IFAM. The influence of the patterns was evaluated optically with a fluorescence microscope. This revealed that all of the periodically structured areas of the samples showed a distinctly decreased surface coverage for the cells and a strongly reduced cell cross-linkage. Hence, it was shown that it is possible to induce a considerably reduced cell adhesion for implant surfaces through periodic structuring.
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Laser-Laboratorium Göttingen e.V. (LLG)
Head of the Department
Dr. Peter Simon
"Short Pulses / Nanostructures"
Contact person for
Nano Structure Technology:
Dr. Jürgen Ihlemann