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Issue 45, 2018
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Conforming nanoparticle sheets to surfaces with Gaussian curvature

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Nanoparticle monolayer sheets are ultrathin inorganic–organic hybrid materials that combine highly controllable optical and electrical properties with mechanical flexibility and remarkable strength. Like other thin sheets, their low bending rigidity allows them to easily roll into or conform to cylindrical geometries. Nanoparticle monolayers not only can bend, but also cope with strain through local particle rearrangement and plastic deformation. This means that, unlike thin sheets such as paper or graphene, nanoparticle sheets can much more easily conform to surfaces with complex topography characterized by non-zero Gaussian curvature, like spherical caps or saddles. Here, we investigate the limits of nanoparticle monolayers’ ability to conform to substrates with Gaussian curvature by stamping nanoparticle sheets onto lattices of larger polystyrene spheres. Tuning the local Gaussian curvature by increasing the size of the substrate spheres, we find that the stamped sheet morphology evolves through three characteristic stages: from full substrate coverage, where the sheet extends over the interstices in the lattice, to coverage in the form of caps that conform tightly to the top portion of each sphere and fracture at larger polar angles, to caps that exhibit radial folds. Through analysis of the nanoparticle positions, obtained from scanning electron micrographs, we extract the local strain tensor and track the onset of strain-induced dislocations in the particle arrangement. By considering the interplay of energies for elastic and plastic deformations and adhesion, we construct arguments that capture the observed changes in sheet morphology as Gaussian curvature is tuned over two orders of magnitude.

Graphical abstract: Conforming nanoparticle sheets to surfaces with Gaussian curvature

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Article information

10 Aug 2018
10 Oct 2018
First published
11 Oct 2018

Soft Matter, 2018,14, 9107-9117
Article type
Author version available

Conforming nanoparticle sheets to surfaces with Gaussian curvature

N. P. Mitchell, R. L. Carey, J. Hannah, Y. Wang, M. Cortes Ruiz, S. P. McBride, X. Lin and H. M. Jaeger, Soft Matter, 2018, 14, 9107
DOI: 10.1039/C8SM01640B

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