4D-Printed metamaterials with thermally tunable negative stiffness

This study presents a 4D-printed metamaterial with thermally programmable negative stiffness, addressing the critical need for adaptive materials in dynamic environments. Conventional mechanical metamaterials suffer from fixed functionalities and limited adaptability, restricting their use in applications requiring responsive behavior. By leveraging the thermomechanical properties of shape memory polylactic acid, we developed a distributed thermal control system capable of tuning the nonlinear force – displacement response. Through systematic material modeling and structural optimization, the metamaterial achieves controlled buckling and sequential collapse under compressive loads, significantly enhancing adaptability. In the vibration tests of the metamaterial base, different programming states markedly modify the vibration-isolation response and enable a tunable isolation region, while under impact loading the structure exhibits effective energy dissipation and impact-mitigation capability. Experimental validation demonstrates its potential in aerospace applications, where it attenuates shocks, suppresses vibrations, and dissipates energy across the spacecraft’s lifecycle. This work pioneers a systematic framework for programmable metamaterial development, offering a versatile solution for advanced engineering challenges.