Microstructuring of Surfaces for Bio-Medical Applications

Abstract

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.