Recent developments in smart responsive composites have utilized various stimuli including heat, light, solvents, electricity, and magnetic fields to induce a change in material properties. Here, we report a thermodynamically driven mechanically responsive composite, exploiting irreversible phase-transformation (relaxation) of metastable undercooled liquid metal core shell particle fillers. Thermal and mechanical analysis reveals that as the composite is deformed, the particles transform from individual liquid droplets to a solid metal network, resulting in a 300% increase in Young's modulus. In contrast to previous phase change materials, this dramatic change in stiffness occurs autonomously under deformation, is insensitive to environmental conditions, and does not require external energy sources such as heat, light, or electricity. We demonstrate the utility of this approach by transforming a flat, flexible composite strip into a rigid, 3D structure that is capable of supporting 50× its own weight. The ability for shape change and reconfiguration are further highlighted, indicating potential for multiple pathways to trigger or tune composite stiffness.

中文翻译：

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通过热力学松弛（ST3R）机械触发的复合材料刚度调整†

智能响应复合材料的最新发展已经利用了各种刺激，包括热，光，溶剂，电场和磁场，以引起材料性能的变化。在这里，我们报告了一种热力学驱动的机械响应复合材料，它利用了亚稳态过冷液态金属核壳颗粒填料的不可逆相变（松弛）。热和机械分析表明，随着复合材料变形，颗粒从单个液滴转变为固体金属网络，导致杨氏模量增加300％。与以前的相变材料相比，刚度的这种剧烈变化在变形时自动发生，对环境条件不敏感，不需要外部能源，例如热，光或电。通过将平坦的柔性复合材料带材转换为能够支撑自身重量50倍的刚性3D结构，我们证明了该方法的实用性。形状更改和重新配置的能力得到了进一步强调，表明了多种途径触发或调整复合材料刚度的潜力。