The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced—achieved by an 80% shrinkage of the polymer during pyrolysis—and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm−3 are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.
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The authors thank M. Madou for stimulating discussions introducing us to the concept of pyrolysis of resist structures. Financial support of this work by the Robert Bosch-Foundation is gratefully acknowledged.
The authors declare no competing financial interests.
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Bauer, J., Schroer, A., Schwaiger, R. et al. Approaching theoretical strength in glassy carbon nanolattices. Nature Mater 15, 438–443 (2016). https://doi.org/10.1038/nmat4561