Bending-dominated chiral metastructures with tunable thermal expansion: Planar-to-cylindrical design and dual-mechanism modeling

Precise control of the coefficient of thermal expansion (CTE) is essential for reducing harmful thermal deformation. However, customizing CTEs remains inefficient due to a lack of precise design methods. This work presents composite bending-dominated chiral metastructures with a planar-to-cylindrical design approach that achieves CTE tunability from −1000 to 1000 ppm/°C. The key innovation is a dual-mechanism analytical model that accurately predicts thermal deformation by separating the global response into rotation and deflection components, and is supported by an interference criterion that sets deformation limits. Validation demonstrates that the model predictions deviate by less than 10% from experimental results using shape memory deformation as a surrogate for thermally induced deformation and by less than 5% from finite element simulations, confirming the high fidelity of the proposed model. Parametric analysis highlights the main geometric sensitivities: beam half-width > beam length > radius of the central support structure. Importantly, a bi-row assembly strategy is developed to eliminate inter-row interference in gradient design, with only a 5% deviation from finite element results. Ultimately, this work introduces a universal design framework enabling programmable, complex 3D thermally induced deformations, laying the groundwork for passive thermal actuators in aerospace and biomedical fields.