Chiral Mechanical Metamaterials for Tunable Optical Transmittance

Flexible metamaterials have been increasingly harnessed to create functionality through their tunable and unconventional response. Herein, chiral unit cells based on Archimedean spirals are employed to transform a linear displacement into twisting. First, the effect of geometry on such extension-twisting coupling is investigated. This unravels a wide range of highly nonlinear behaviors that can be programmed. Additionally, it is demonstrated that by combining the spirals with polarizing films one can create mechanical pixels capable of modulating the transmission of light through deformation. Guided by experiments and numerical analyses, pixels are arranged in 2D arrays to realize black and white and color displays, which reveal distinct images at different states of deformation. As such, the study puts forward a methodology for the design of an emerging class of flexible devices that can convert nonlinear elastic deformation to tunable optical transmittance.