Programmable Reconfiguration of Hybrid 4D Chiral Metamaterials via Mechanical and Thermal Stimuli

Mechanical metamaterials with programmable reconfiguration ability are essential for applications such as adaptive sensors, actuators, and smart wearable systems. However, existing strategies often suffer from limited tunability, requiring predefined material properties or boundary conditions to achieve functional deformations. Herein, a class of hybrid chiral mechanical metamaterials composed of rigid square units connected via specially designed soft components, including soft networks, soft hinges, and bilayer joints, is presented. These soft connectors are responsive to external mechanical and thermal stimuli, enabling controlled pattern transformations and tunable reconfiguration. Prototypes of selected designs are fabricated using multimaterial 3D printing, and experimental validations are conducted under equi-biaxial mechanical compression and thermal activation. The results demonstrate that significant volume changes can be achieved, with optimized deformation pathways identified through controlled biaxial displacement ratios. Furthermore, by tailoring hinge configurations and material interfaces, both positive and negative thermal expansion coefficients are realized. This design framework offers a versatile platform for programmable morphing structures, providing new opportunities for multifunctional devices in sensing, soft robotics, adaptive optics, and wearable technologies.