Folding and bending of self-assembled nanoparticle membranes

We demonstrate that self-assembled nanoparticle monolayers can be folded into 3 dimensional hollow structures -- nanoparticle scrolls, by utilizing their internal strain gradient. Using an Atomic Force Microscope (AFM), indentation measurements were made on these nanoparticle scrolls, and the bending modulus of the nanoparticle membrane is obtained for the first time. The resulting bending modulus is two orders of magnitude larger than that predicted by classical continuum elastic theory, we show this can be explained by a micropolar theory as the material thickness approaches single nanoparticle size.