Han Jiawei, Wang Peng, Guo Yu, Pähtz Thomas, Yu Zhaosheng, Wu Chuan-Yu, Curtis Jennifer S
Department of Engineering Mechanics, State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China.
Huanjiang Laboratory, Zhuji, Zhejiang Province, 311800, China.
Nat Commun. 2025 Mar 7;16(1):2303. doi: 10.1038/s41467-025-57475-5.
Granular materials transition between unjammed (deformable) and jammed (rigid) states when adjusting their packing density. Here, we report on experiments demonstrating that the same kind of phase transition can be alternatively achieved through temperature-controlled particle shape change. Using a confined system of randomly-packed rod-like particles made of shape memory alloy (SMA), we exploit that shape recovery of these bent rods with rising temperature at a constant packing density leads to a jammed state. The responsible physical processes are elucidated with numerical simulations based on the Discrete Element Method. As an exemplary application of the uncovered mechanism, we engineer a smart clamp that can actively grip or release an object through the thermo-induced jamming or unjamming of the granular material, and robustly so under cyclic temperature changes. In the jammed state, its load-bearing capability surpasses the total SMA weight by a tunable margin, up to over 800-fold. The clamping design paves the way towards a new kind of functional devices based on the thermo-responsive jamming of shape memory granular materials.
当调整颗粒材料的堆积密度时，它们会在未压实（可变形）状态和压实（刚性）状态之间转变。在此，我们报告的实验表明，通过温度控制颗粒形状变化也可以实现同样的相变。利用由形状记忆合金（SMA）制成的随机堆积的棒状颗粒的受限系统，我们发现，在恒定堆积密度下，随着温度升高，这些弯曲棒的形状恢复会导致一种压实状态。基于离散元法的数值模拟阐明了其中的物理过程。作为所揭示机制的一个示例性应用，我们设计了一种智能夹具，它可以通过颗粒材料的热致压实或解压实现主动抓取或释放物体，并且在循环温度变化下能稳定地做到这一点。在压实状态下，其承载能力比SMA的总重量高出一个可调幅度，最高可达800倍以上。这种夹紧设计为基于形状记忆颗粒材料的热响应压实的新型功能装置铺平了道路。
