Metamaterials are designed to realize exotic physical properties through the geometric arrangement of their underlying structural layout^1,2. Traditional mechanical metamaterials achieve functionalities such as a target Poisson’s ratio³ or shape transformation^4,5,6 through unit-cell optimization^7,8,9, often with spatial heterogeneity^10,11,12. These functionalities are programmed into the layout of the metamaterial in a way that cannot be altered. Although recent efforts have produced means of tuning such properties post-fabrication^{13,14,15,16,17,18,19}, they have not demonstrated mechanical reprogrammability analogous to that of digital devices, such as hard disk drives, in which each unit can be written to or read from in real time as required. Here we overcome this challenge by using a design framework for a tileable mechanical metamaterial with stable memory at the unit-cell level. Our design comprises an array of physical binary elements (m-bits), analogous to digital bits, with clearly delineated writing and reading phases. Each m-bit can be independently and reversibly switched between two stable states (acting as memory) using magnetic actuation to move between the equilibria of a bistable shell^{20,21,22,23,24,25}. Under deformation, each state is associated with a distinctly different mechanical response that is fully elastic and can be reversibly cycled until the system is reprogrammed. Encoding a set of binary instructions onto the tiled array yields markedly different mechanical properties; specifically, the stiffness and strength can be made to range over an order of magnitude. We expect that the stable memory and on-demand reprogrammability of mechanical properties in this design paradigm will facilitate the development of advanced forms of mechanical metamaterials.

超材料旨在通过其底层结构布局的几何排列来实现奇异的物理特性^1,2 。传统机械超材料通过晶胞优化^7,8,9实现目标泊松比³或形状变换^4,5,6等功能，通常具有空间异质性^10,11,12 。这些功能以无法更改的方式编程到超材料的布局中。尽管最近的努力已经产生了在制造后调整此类属性的方法^{13,14,15,16,17,18,19} ，但它们尚未证明类似于数字设备（例如硬盘驱动器）的机械可重编程性，其中每个单元可以根据需要实时写入或读取。在这里，我们通过使用可平铺机械超材料的设计框架来克服这一挑战，该超材料在单元单元级别具有稳定的内存。我们的设计包含一系列物理二进制元素（m 位），类似于数字位，具有清晰描绘的写入和读取阶段。每个m位可以使用磁驱动在双稳态壳^{20、21、22、23、24、25}的平衡之间移动，在两个稳定状态（充当存储器）之间独立且可逆地切换。在变形情况下，每种状态都与完全弹性的明显不同的机械响应相关联，并且可以可逆地循环，直到系统重新编程。将一组二进制指令编码到平铺数组上会产生明显不同的机械属性；具体来说，可以使刚度和强度的范围超过一个数量级。 我们期望这种设计范式中的稳定存储器和机械性能的按需可重编程性将促进先进形式的机械超材料的开发。