The direct writing of complex three-dimensional (3D) metallic structures is of use in the development of advanced electronics. However, conventional direct ink writing primarily uses composite inks that have low electrical conductivity and require support materials to create 3D architectures. Here we show that Field’s metal—a eutectic alloy with a relatively low melting point—can be 3D printed using a process in which tension between the molten metal in a nozzle and the leading edge of the printed part allows 3D structures to be directly written. The use of tension avoids using external pressure for extrusion (which can cause beading of the printed structure), allowing uniform and smooth microwire structures to be printed on various substrates with speeds of up to 100 mm s⁻¹. We use the approach to print various free-standing 3D structures—including vertical letters, a cubic framework and scalable helixes—without post-treatment, and the resulting Field’s metal structures can offer electrical conductivity of 2 × 10⁴S cm⁻¹, self-healing capability and recyclability. We also use the technique to print a 3D circuit for wearable battery-free temperature sensing, hemispherical helical antennas for wireless vital sign monitoring and 3D metamaterials for electromagnetic-wave manipulation.

复杂三维 (3D) 金属结构的直接写入可用于先进电子产品的开发。然而，传统的直接墨水书写主要使用导电率低的复合墨水，并且需要支撑材料来创建 3D 架构。在这里，我们展示了 Field 金属（一种熔点相对较低的共晶合金）可以通过喷嘴中的熔融金属与打印部件前缘之间的张力进行 3D 打印，从而可以直接写入 3D 结构。张力的使用避免了使用外部压力进行挤压（这会导致打印结构成珠），从而允许以高达100 mm s ^-1的速度在各种基材上打印均匀且光滑的微线结构。我们使用该方法打印各种独立的 3D 结构，包括垂直字母、立方框架和可伸缩螺旋，无需后处理，所得 Field 的金属结构可提供 2 × 10 ⁴ S cm ^-1的电导率，自-修复能力和可回收性。我们还使用该技术打印用于可穿戴式无电池温度传感的 3D 电路、用于无线生命体征监测的半球形螺旋天线以及用于电磁波操纵的 3D 超材料。