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Nanomoulding with amorphous metals

Abstract

Nanoimprinting promises low-cost fabrication of micro- and nano-devices by embossing features from a hard mould onto thermoplastic materials, typically polymers with low glass transition temperature1. The success and proliferation of such methods critically rely on the manufacturing of robust and durable master moulds2. Silicon-based moulds are brittle3 and have limited longevity4. Metal moulds are stronger than semiconductors, but patterning of metals on the nanometre scale is limited by their finite grain size. Amorphous metals (metallic glasses) exhibit superior mechanical properties and are intrinsically free from grain size limitations. Here we demonstrate direct nanopatterning of metallic glasses by hot embossing, generating feature sizes as small as 13 nm. After subsequently crystallizing the as-formed metallic glass mould, we show that another amorphous sample of the same alloy can be formed on the crystallized mould. In addition, metallic glass replicas can also be used as moulds for polymers or other metallic glasses with lower softening temperatures. Using this ‘spawning’ process, we can massively replicate patterned surfaces through direct moulding without using conventional lithography. We anticipate that our findings will catalyse the development of micro- and nanoscale metallic glass applications that capitalize on the outstanding mechanical properties, microstructural homogeneity and isotropy, and ease of thermoplastic forming exhibited by these materials5,6,7.

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Figure 1: Temperature-dependent strength of materials used for moulds and imprints for micro/nanoimprinting.
Figure 2: Optical and scanning electron microscope images of three-dimensional microparts, including tweezers (top left), scalpels (bottom left), a gear (top right) and a membrane (bottom right).
Figure 3: Controlling the metallic glass moulding on scales smaller than 100 nm.
Figure 4: Schematic and experimental illustration of a processing technique based on the unique softening behaviour of BMG.

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Acknowledgements

We thank T. A. Waniuk and C. S. O’Hern for reading of the manuscript and E. R. Dufresne for discussion. This work was supported by the US National Science Foundation under the Material Processing and Manufacturing programme.

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Correspondence to Jan Schroers.

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Kumar, G., Tang, H. & Schroers, J. Nanomoulding with amorphous metals. Nature 457, 868–872 (2009). https://doi.org/10.1038/nature07718

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