On-chip dynamic strain engineering requires efficient micro-actuators that can generate large in-plane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1 V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful “straintronic” devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe₂ causes large anisotropic in-plane strain: 5% in one in-plane direction and 0.1% in the other. This efficient stretching of the 2D WTe₂ layers contrasts to intercalation-induced strains in related materials which are predominantly in the out-of-plane direction. The unusual actuation of Li_xWTe₂ is linked to the formation of a newly discovered crystallographic phase, referred to as Td', with an exotic atomic arrangement. On-chip low-voltage (<0.2 V) control is demonstrated over the transition to the novel phase and its composition. Within the Td'-Li_0.5−δWTe₂ phase, a uniaxial in-plane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in-plane chemical expansion coefficient of Td'-Li_0.5−δWTe₂ far greater than of any other single-phase material, enabling fast and efficient planar electrochemical actuation.

中文翻译：

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通过离子插入对二维材料进行高效单轴面内拉伸

片上动态应变工程需要高效的微致动器，可以产生大的平面应变。无机电化学执行器的独特之处在于它们由低电压 ( ≈ 1 V) 驱动并产生相当大的应变 ( ≈ 1%)。然而，驱动速度和效率受到离子质量传输的限制。因此，最大限度地减少驱动所需的离子数量是启用有用的“应变电子”设备的关键。在这里，表明极少的锂离子电化学嵌入 WTe ₂会导致大的各向异性面内应变：一个面内方向为 5%，另一个为 0.1%。二维 WTe _{2 的}这种有效拉伸层与主要在面外方向的相关材料中的嵌入诱导应变形成对比。Li _x WTe ₂的异常驱动与新发现的晶体相的形成有关，称为 Td'，具有奇异的原子排列。片上低电压 ( < 0.2 V) 控制在向新相及其组成的过渡过程中得到证明。在 Td'-Li _{0.5- δ} WTe ₂相内，单轴面内应变为 1.4%，δ 的变化仅为 0.075。这使得 Td'-Li 的面内化学膨胀系数为_0.5-δ WTe ₂ 远远超过任何其他单相材料，实现快速有效的平面电化学驱动。