Modelling the deformations during the manufacturing of nanostructures on non-planar surfaces for injection moulding tool inserts

This paper presents a new manufacturing process for transferring nanostructures from a glass wafer to a curved aluminium insert for polymer injection moulding. A nanostructure consisting of sinusoidal cross-gratings with a period of 426 nm is successfully transferred to hemispheres with different radii via an embossing process. The embossing is done into a glass-like resist called HSQ, using a 50 on thick nickel foil, manufactured with electroforming. During the imprinting process the nickel foil is stretched due to the curved surface of the aluminium substrate and it is experimentally possible to characterize this stretch by counting the periods of the cross -gratings via SEM characterization. A numerical model for simulating the deformation of the nickel foil during nanoimprint is also developed, utilizing non-linear material and geometrical behaviour. Good agreement between measured and numerically calculated stretch ratios on the surface of the deformed nickel foil is shown, and from the model it is also possible to predict the limiting boundary of the nanostructures on the curved surfaces, with decreasing radii.