Tomographic strain indicator of chiral liquid crystalline elastomer

Measurement of deformation is vital for designing shape-morphing devices in soft electronics, wearables, and robotics. However, existing strain sensors often face limitations due to their inability to detect internal deformations within objects. To address this challenge, we propose a thin film of deformable photonic crystals made from highly stretchable and conformable chiral liquid crystalline elastomer (CLCE). This film enables real-time visualization of 3-dimensional strain distribution when embedded in host objects. The CLCE films exhibit a strain-dependent color shift caused by changes in their helical structure, allowing accurate strain measurement without interfering with the object's deformation. The fidelity of strain visualization is studied through a comparison of the numerical simulations and experimental results. Furthermore, we demonstrate the application of CLCE films in mechanochromic displays and camouflage devices, which display different color patterns depending on the types of deformation.