Body Temperature Actuated Liquid Crystal Elastomers from Hyper Tensile Preprogramming

Creating thermally actuated liquid crystal elastomers (LCE) traditionally requires mechanical pre-straining to cure in an aligned state, with higher pre-strains generally improving alignment and actuation. However, excessive pre-strains risk damaging the material, making it difficult to quantitatively relate synthesis strategies with mechanical behavior. Here, a method allowing pre-strains up to 2500% while preserving sample integrity is introduced. Using this method, scaling laws are established that relate actuator thickness and pre-strain to performance, showing that actuation speed scales with a power-law factor of 0.7. The actuators presented here exhibit an superior energy density of 1.5 MJ m⁻³ and demonstrate a highly sensitive bending actuation mode in ultrathin (20 µm) samples, responsive to human body temperature. A comprehensive thermomechanical analysis of these materials based on modern theories in nematic elastomers and structure–property relationships is provided. Finally, two soft robotic designs utilizing the material's rapid recovery are demonstrated, achieving cyclic behaviors unattainable in traditionally pre-strained liquid crystal elastomers.