Modelling the deformation of nickel foil during manufacturing of nanostructures on injection moulding tool inserts

In the present work, a manufacturing process for transferring nanostructures from a glass wafer, to a double-curvedinsert for injection moulding is demonstrated. A nanostructure consisting of sinusoidal cross-gratings with a period of 426 nm issuccessfully transferred to hemispheres on an aluminium substrate with three different radii; 500 μm, 1000 μm and 2000 μm,respectively. The nanoimprint is performed using a 50 μm thick nickel foil, manufactured using electroforming. During theimprinting process, the nickel foil is stretched due to the curved surface of the aluminium substrate. Experimentally, it is possibleto address this stretch by counting the periods of the cross-gratings via SEM characterization. A model for the deformation of thenickel foil during nanoimprint is developed, utilizing non-linear material and geometrical behaviour. Good agreement betweenmeasured and numerically calculated stretch ratios on the surface of the deformed nickel foil is found, and it is shown, that fromthe model it is also possible to predict the geometrical extend of the nanostructured area on the curved surfaces.