Complex 3D structures via double imprint of hybrid structures and sacrificial mould techniques

The preparation of transparent complex 3D structures over large areas at low cost paves the way for numerous optical applications. We prepared nanostructures on the surface of microstructures in a negative tone photoresist by a double imprint process combined with VUV-induced surface hardening. Successful preparation of the aforementioned structures asks for a compromise between the surface hardening of the nanostructures and the replication fidelity of the microstructures. Our results show that a VUV treatment time of at least 3s is required so that the cross-linked layer does not break-up. Adequate process parameters as well as their limiting values were identified by using high aspect ratio microstructures. The complex 3D structures were successfully replicated in UV-PDMS to provide long-term stable templates. To ensure effective separation despite of the undercuts a sacrificial mould technique is applied. [Display omitted] •Combination of micro- and nanostructures without laborious writing techniques•Limitation of a surface-hardened SU-8 layer with high aspect ratio structures•Successful replication of complex 3D structures in UV-PDMS