Versatile Mechanochromic Sensor based on Highly Stretchable Chiral Liquid Crystalline Elastomer

A mechanochromic strain sensor that is capable of distinguishing the orientation, the location, and the degree of deformation based on the highly stretchable membrane of main‐chain chiral liquid crystalline elastomer (MCLCE) is proposed. The MCLCE film is designed to exhibit uniform and significant color shift upon the small strain by using step‐growth polymerization of liquid crystal (LC) oligomer and its phase‐stabilization in solvent mesogen. As conformally placed on the bottom elastomer sheet, the MCLCE film shows multimodal, instantaneous color change for sensing arbitrary in‐plane deformation, out‐of‐plane bending, and nonzero Gaussian deformation. Based on high freedom in the device design, it is also demonstrated that this sensor can display color patterns or encrypted images in response to the localized weight or strain. The simple and straightforward concept proposed here can be applicable in the fields of wearable devices, displays, and soft robotics. Main‐chain chiral liquid crystalline elastomer membrane can simultaneously differentiate the types, degrees, and directions of deformations in the supporting layers, including in‐ and out‐of‐plane bending and nonzero Gaussian strains. New types of mechanochromic applications such as strain‐optic scale, strain‐display, and strain detectable encryption are demonstrated.