Magnetically guided programmable thermomechanical protection enabled by biomimetic asymmetric design

Precision instruments operating in harsh environments require protective materials that can dissipate impact energy while resisting heat. However, actively tunable thermomechanical protection under coupled multiphysics conditions remains challenging. Inspired by shellfish and echinoderms, here we show that an asymmetrically engineered shear-stiffening gel (SSG) yields a Janus magnetorheological elastomer whose two faces mimic the brick-and-mortar architecture of shellfish and the impact-hardening behavior of echinoderms, respectively. Unlike single-modification anti-creep strategies of SSG that degrade shear-stiffening or severely increase initial modulus, our design achieves a 40-fold mechanical tunability, with the storage modulus ranging from 11.29 to 450.28 kPa, arising from the synergistic enhancement of strain-rate-dependent stiffening and magnetic interactions. The integration of magnetic and optical functions enables semiactive noncontact 2D-to-3D protection, achieving an 85% reduction in impact force and a 40 °C temperature difference via bidirectional photothermal regulation, demonstrating competitive thermomechanical protection performance. Furthermore, this strategy establishes a magnetically guided programmable pathway for thermomechanical protection and provides a generalizable blueprint for multifunctional intelligent materials, advancing protective technologies for outdoor equipment operating in extreme environments involving coupled physical fields.