Steinberg, ChristianChristianSteinbergRumler, MaximilianMaximilianRumlerRunkel, ManuelManuelRunkelPapenheim, MarcMarcPapenheimWang, SiSiWangMayer, AndreAndreMayerBecker, MarcoMarcoBeckerRommel, MathiasMathiasRommelScheer, Hella-ChristinHella-ChristinScheer2022-03-052022-03-052017https://publica.fraunhofer.de/handle/publica/24700210.1016/j.mee.2017.01.009The 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 3 s 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 lo ng-term stable templates. To ensure effective separation despite of the undercuts a sacrificial mould technique is applied.enSU-8CAR44UV-PDMS3D structuresVUV treatmentthermal imprintsacrificial mould technique621journal article