Florian Böhmermann

Co-spray-formed graded steel for micro rotary swaging tools

Micro rotary swaging tools are required to have different material properties in different functional areas. These requirements can be fulfilled by applying different materials in the specific regions of the tools. The different materials can be combined with a gradient zone in between to reduce critical stresses at the interface during heat treatment and in swaging process. Such graded tool materials are supposed to be manufactured by means of a newly developed co-spray forming process. In this study, a flat deposit of graded tool steel (HS6-5-3C/HS6-5-2C) was produced via co-spray forming, followed by hot rolling and heat treatment. Micro infeed rotary swaging tools with fine geometrical structures were precisely machined from the graded steel. The tool performance during swaging of stainless steel wires was evaluated.

Microstructuring of Surfaces for Bio-Medical Applications

In recent years microfluidic devices became of great interest, as they offer a wide range of bio-analytical and fluid processing applications through the utilization of size effects. Especially a mass manufacturing of disposable polymeric microfluidic devices by hot embossing or injection molding is expected to have high economic potential. It is known, that channels and areas showing a localized change in wettability can considerably improve fluid processing tasks like mixing or droplet generation. Chemical approaches, like the polymerization of lauryl acrylate, were successfully shown to achieve hydrophobic coatings for micro channels but are not suitable for a mass manufacturing. Since microstructures are known to provide water repellent properties of surfaces, this paper focuses on the applicability of diamond grooving and Diamond Micro Chiseling (DMC) processes for the manufacture of microstructured areas in brass molds inserts, in order to achieve hydrophobic properties of their replica. Major design features of structures, like a height range of 6 to 16μm or aspect ratios in between 0.5 and 3.2 are derived from the natural example of the lotus leaf. Molding is carried out by using a two component silicone filler. The performance of the replicated hydrophobic surfaces is evaluated by droplet contact angle measurements. After presenting methodology and results, the paper will conclude on how to transfer the investigated microstructuring methods to the manufacture of mold inserts for the replication of polymeric microfluidic chips with localized hydrophobic areas and channels.