Stretchable translucent nanocomposite membranes with 3D heterogeneous interfaces derived from sugar templates for mechano-responsive optical applications

Stretchable nanocomposites with embedded three-dimensional (3D) heterogeneous interfaces that can dynamically adjust optical transparency over a wide range through mechanical deformation are promising as key materials for smart windows and flexible sensors. However, it is still difficult to inexpensively and easily fabricate these nanocomposites because previously reported fabrication methods rely mainly on complex lithography. Here, we propose an efficient method for fabricating stretchable nanocomposites that dynamically increase opacity when stretched. First, a microporous PDMS sponge is prepared by using a plate-shaped sugar cube prepared through a wet agglomeration process as a template. A 3D continuous ultrathin (∼60 nm) alumina layer is then conformally deposited onto the PDMS sponge via atomic layer deposition. Complete filling of the porous network inside the prepared specimen with PDMS yields a translucent nanocomposite embedded with a 3D continuous alumina layer. When the resulting nanocomposite is stretched, the significant difference in modulus between PDMS and alumina results in the generation of numerous scattering voids at the 3D continuous interface of PDMS and alumina. Depending on the thickness of the specimen, the initial transmittance and the degree of decrease in transmittance during deformation can be controlled. These results will provide an opportunity to economically fabricate advanced nanocomposites for mechanically driven smart window systems or optical strain gauges, as demonstrated in this study.