Diphylleia grayi-Inspired Stretchable Hydrochromics with Large Optical Modulation in the Visible-Near-Infrared Region

Some animals and plants in nature are endowed with elegant color changing ability, which inspired the development of biomimetic systems with multifunctionality, such as controllable colors, transmittance, and mechanical pliability that are significant for the development of energy-efficient and deformable chromic devices, such as wearable displays, smart windows, decorative architectures, camouflage devices, etc. Inspired by the color-changing ability of Diphylleia grayi (commonly known as the skeleton flower), we developed a porous poly(dimethylsiloxane) (PDMS) film that dynamically and dramatically changes its color by the adsorption/desorption of a minute amount of water (5 g m(-2)) or other solvents. This hydrochromic phenomenon was analyzed in detail, and it matched well with the Mie scattering theory. The porous PDMS film of about 0.4 mm thickness exhibits a large optical modulation (about 75-80%) in the broad visible and near infrared region and a coloration speed of less than 9 min. Additionally, the PDMS film can sustain uniaxial strain up to 100% in both transparent and colored states. We believe this new strategy to develop highly scalable porous PDMS films offers a practical route to realize bionic and botanic inspired deformable energy-efficient facades, chromogenic wearables, smart windows, smart displays, camouflage devices, etc.