Tobias Senn

Replica molding for multilevel micro-/nanostructure replication

The development of micro- and nanofabrication processes with the capability to achieve three-dimensional structures is of great interest for a wide variety of applications. In this paper, a replica molding process for the replication of combined micro- and nanostructures in an epoxy-based photo resin is reported. First, multilevel masters were realized using standard micro- and nanofabrication processes. The structures from these masters were transferred to poly(dimethylsiloxane) (PDMS) stamps by soft lithography. Finally, the PDMS stamps were used for the replication of nano- and microstructures in the epoxy-based resin by UV casting. With this process, micro- and nanostructures of minimal dimensions of 50 nm were successfully replicated. Furthermore, the capabilities of the process were confirmed by the fabrication of a microfluidic device. In this system, the surface of micro channels was structured to modify its wetting properties and create hydrophobic and hydrophilic areas without any additional chemical treatment.

Integration of moth-eye structures into a poly(dimethylsiloxane) stamp for the replication of functionalized microlenses using UV-nanoimprint lithography

The increasing demand for low cost camera modules for mobile devices requires technological solutions for the manufacturing process. One of the most promising fabrication processes for microlenses for camera modules is UV-nanoimprint lithography. In a typical fabrication process, an elastomer stamp is used to replicate microlenses. In this work, a method is presented to integrate moth-eye structures as an antireflective layer into a poly(dimethylsiloxane) (PDMS) stamp containing a microlens array. The integration of these structures is done by a thermoforming process. Due to the integration of the moth-eye structures into the PDMS stamp, the optical performance of the replicated microlenses can be improved and no additional processing steps are necessary after the replication process.

Replication of HARMST and large area nanostructured parts using UV cationic polymerization

This paper reports on the development of a reaction casting process for the fabrication of high aspect ratio microstructures (HARMST) and large area nanostructured parts, using UV cationic polymerization. Besides the process itself, materials had to be characterized to achieve thick layers. An epoxide resin, a bis-cycloaliphatic epoxide (BCE) and a divinylether of triethylene glycol (DVE-TEG) were used as monomers and triaryl sulfonium salt (TAS) was used as the photoinitiator. The materials were characterized relative to their rheological properties, the degree of polymerization and their hardness. The test structure consists of columns with an aspect ratio of 10. The results reveal that the materials used show excellent behavior for the replication of high aspect ratio structures. The replication of a nanostructured area of 10 × 10 cm2 could also be realized with the presented process. The used structure is a 2D optical grating with a period of 2.5 µm and a diameter of the tip of 300 nm.