3D Printing of Near-Ambient Responsive Liquid Crystal Elastomers with Enhanced Nematic Order and Pluralized Transformation

Liquid crystal elastomers with near-ambient temperature-responsiveness (NAT-LCEs) have been extensively studied for building biocompatible, low-power consumption devices and robotics. However, conventional manufacturing methods face limitations in programmability (<i>e</i>.<i>g</i>., molding) or low nematic order (<i>e</i>.<i>g</i>., DIW printing). Here, a hybrid cooling strategy is proposed for programmable three-dimensional (3D) printing of NAT-LCEs with enhanced nematic order, intricate shape forming, and morphing capability. By integrating a low-temperature nozzle and a cooling platform into a 3D printer, the resulting temperature field synergistically facilitates mesogen alignment during extrusion and disruption-free ultraviolet (UV) cross-linking. This method achieves a nematic order 3000% higher than NAT-LCEs fabricated using traditional room temperature 3D printing. Enabled by shifting of transition temperature during hybrid cooling printing, printed sheets spontaneously turn into 3D structures after release from the platform, exhibiting bidirectional deformation with heating and cooling. By adjusting the nozzle and plate temperatures, NAT-LCEs with graded properties can be fabricated for intricate shape morphing. A wristband system with enhanced heart rate monitoring is also developed based on 3D-printed NAT-LCE. Our method facilitates developments in soft robotics, biomedical devices, and wearable electronics.