The Buckling Spectra of Nanoparticle Surfactant Assemblies.

Abstract

Fine control over the mechanical properties of thin sheets underpins transcytosis, cell shape, and morphogenesis. Applying these principles to artificial, liquid-based systems has led to reconfigurable materials for soft robotics, actuation, and chemical synthesis. However, progress is limited by a lack of synthetic two-dimensional membranes that exhibit tunable mechanical properties over a comparable range to that seen in nature. Here, we show that the bending modulus, <i>B</i>, of thin assemblies of nanoparticle surfactants (NPSs) at the oil-water interface can be varied continuously from sub-<i>k</i>_B<i>T</i> to 10⁶<i>k</i>_B<i>T</i>, by varying the ligands and particles that comprise the NPS. We find extensive departure from continuum behavior, including enormous mechanical anisotropy and a power law relation between <i>B</i> and the buckling spectrum width. Our findings provide a platform for shape-changing liquid devices and motivate new theories for the description of thin-film wrinkling.