Recyclable electronics are important in green manufacturing and sustainable development, but in infancy, printing strategies still need more exploration and improvement. Metal drop-on-demand (DOD) printing is an ideal candidate for fabricating recyclable circuits, owing to its advantage of inherent direct recyclable feedstocks. Liquid metals with melting points at room temperature have been utilized to print circuits. However, developing liquid metal-based composites or encapsulation is still needed to maintain shapes of printed patterns and improve the adhesion between liquid metals and substrates, restricting the directly recycling of printed circuits. Herein, tin solder is utilized to directly print recyclable circuits via metal drop-on-demand printing method. The molten tin solder droplets directly melt plastic substrates and partially embed the substrate to obtain good adhesion. Molten droplets solidify timely to maintain the shapes of printed 2D conductive patterns and 3D microstructures without encapsulation. Moreover, the electrical conductivity of printed lines is close to the homogeneous bulk metal due to the direct metallurgical bonding between droplets. The conductive traces can be directly recycled by mechanically peeling from the substrate and remelting in the crucible. To validate this concept, a 555 circuit is successfully printed and recycled to fabricate a new 3D cross circuit. This work opens a new direction to directly fabricate recyclable circuits by using metal drop-on-demand printing.

可回收电子产品在绿色制造和可持续发展中很重要，但处于起步阶段，印刷策略还需要更多的探索和改进。金属按需滴墨 (DOD) 印刷是制造可回收电路的理想选择，因为它具有固有的可直接回收原料的优势。在室温下具有熔点的液态金属已被用于印刷电路。然而，仍然需要开发液态金属基复合材料或封装来保持印刷图案的形状并提高液态金属与基板之间的附着力，限制了印刷电路的直接回收利用。在此，锡焊料用于通过金属按需印刷方法直接印刷可回收电路。熔化的锡焊料滴直接熔化塑料基板并部分嵌入基板以获得良好的附着力。熔滴及时固化以保持打印的 2D 导电图案和 3D 微结构的形状而无需封装。此外，由于液滴之间的直接冶金结合，印刷线的导电性接近于均质的块状金属。可以通过从基板上机械剥离并在坩埚中重新熔化来直接回收导电迹线。为了验证这一概念，成功打印并回收了 555 电路以制造新的 3D 交叉电路。这项工作为使用金属按需印刷直接制造可回收电路开辟了新方向。熔滴及时固化以保持打印的 2D 导电图案和 3D 微结构的形状而无需封装。此外，由于液滴之间的直接冶金结合，印刷线的导电性接近于均质的块状金属。可以通过从基板上机械剥离并在坩埚中重新熔化来直接回收导电迹线。为了验证这一概念，成功打印并回收了 555 电路以制造新的 3D 交叉电路。这项工作为使用金属按需印刷直接制造可回收电路开辟了新方向。熔滴及时固化以保持打印的 2D 导电图案和 3D 微结构的形状而无需封装。此外，由于液滴之间的直接冶金结合，印刷线的导电性接近于均质的块状金属。可以通过从基板上机械剥离并在坩埚中重新熔化来直接回收导电迹线。为了验证这一概念，成功打印并回收了 555 电路以制造新的 3D 交叉电路。这项工作为使用金属按需印刷直接制造可回收电路开辟了新方向。可以通过从基板上机械剥离并在坩埚中重新熔化来直接回收导电迹线。为了验证这一概念，成功打印并回收了 555 电路以制造新的 3D 交叉电路。这项工作为使用金属按需印刷直接制造可回收电路开辟了新方向。可以通过从基板上机械剥离并在坩埚中重新熔化来直接回收导电迹线。为了验证这一概念，成功打印并回收了 555 电路以制造新的 3D 交叉电路。这项工作为使用金属按需印刷直接制造可回收电路开辟了新方向。