[论文解读] Topological Memory and Hysteresis in Ice-like Mechanical Metamaterials

Carl Merrigan, Yair Shokef+1 more|arXiv (Cornell University)|Oct 11, 2020

Pickering emulsions and particle stabilization参考文献 25被引用 3

一句话总结

本文提出一种受人工自旋冰启发的机械超材料，采用双稳态方形单元作为机械迟滞器，实现可调曲率与传播速度的拓扑畴壁。在纹理化循环边界驱动下，系统表现出动态迟滞与多个不同的稳定态，展示了基于初始构型拓扑的新形式拓扑记忆。

ABSTRACT

Intentionally incorporating frustration into mechanical metamaterials may enable complex functionalities. Within similar engineered magnetic systems, known as artificial spin ice, frustration engenders real-space topological structures whose dynamics determine the collective kinetics and response. We present a mechanical analogue of artificial spin ice built up from bistable square cells that act as simple mechanical hysterons. These unit cells deform spontaneously, so that the overall metamaterial contains competing local ground-state orientations, which are separated by locally-stressed domain walls that begin and end on the edges of the metamaterial. Tuning the stiffness of elements in the unit cell, we can control the characteristic curvature and propagation speed of these domain walls. Under textured, cyclic driving from the boundaries, the system exhibits dynamic hysteresis. Moreover, when driving the system from its boundary we can also observe multiple distinct steady states. These complex, multiple hysteresis cycles are a novel feature of our mechanical spin-ice analogue, which relies on the continuous nature of the elastic network as well on the ability to drive the system from its boundary in a textured way. This mechanical metamaterial exhibits a novel memory of the topology of its initial condition, and can thus have potential application in the development of a mechanical memory storage in materials.

研究动机与目标

• 开发一种人工自旋冰的机械类比，通过受控的几何 frustration 实现拓扑记忆。
• 探究在连续弹性网络中，竞争的局部基态与畴壁如何导致复杂的迟滞行为。
• 研究边界驱动的纹理加载在诱导多个稳定态与动态迟滞循环中的作用。
• 证明系统的记忆编码于初始构型的拓扑结构中，而不仅取决于其状态。

提出的方法

• 超材料由双稳态方形单元构成，其自发变形产生具有竞争倾向的局部基态取向。
• 不同局部取向区域之间形成畴壁，由于局部应力作用，畴壁在材料边缘终止。
• 通过调节内部元件的刚度，控制畴壁的曲率与传播速度。
• 采用纹理化加载协议从边界对系统进行周期性驱动，以诱导动态响应。
• 通过观察迟滞回线并识别不同的稳定态构型，分析系统的响应。
• 通过追踪系统对初始条件与边界协议的响应，评估其拓扑记忆特性。

实验结果

研究问题

• RQ1 初始构型的拓扑结构如何影响系统在循环边界驱动下的记忆与响应？
• RQ2 可调的畴壁特性在实现动态迟滞与多个稳定态中起什么作用？
• RQ3 具有局部双稳性的连续弹性网络能否支持类似于自旋冰系统中的拓扑记忆？
• RQ4 纹理化边界驱动如何在机械系统中引发复杂且多重的迟滞循环？

主要发现

• 在周期性边界加载下，该机械超材料表现出动态迟滞，其迟滞回线特征由系统的拓扑结构决定。
• 当以纹理化方式从边界驱动系统时，观察到多个稳定态，表明存在复杂的记忆行为。
• 通过调节单元胞元件的刚度，可实现对畴壁曲率与传播速度的控制，从而实现可编程的机械响应。
• 系统并非将记忆存储于局部状态，而是存储于初始构型的全局拓扑结构中，特别是畴壁的排列方式。
• 多重迟滞循环的出现是连续弹性网络与边界驱动纹理共同作用下产生的新特性。