Sheet shape-controlling method for hundreds-of-nanometer-thick polymer film using soluble polymer layer

We proposed a sheet shape-controlling method for a hundreds-of-nanometers-thick polymeric ultrathin film (referred to as a "nanosheet") for folding the film into a cylindrical shape and unfolding the film into a flat shape. To control the shape of the nanosheet, we used a triple-layered structure, which included a nanosheet and additional two layers of a water-soluble polymer. The additional two layers are thicker than the nanosheet, and one of the two layers was loaded to prestretch that layer. Therefore, the triple-layered structure was folded into a cylindrical shape owing to strain mismatch between the two layers and unfolded into a flat shape after the dissolution of the two layers. In this study, we could successfully estimate the radius of curvature of the triple-layered structure by considering the strain mismatch between the two layers. In addition, we confirmed that the triple-layered structure unfolded into a flat shape by the dissolution of the two layers.