Laser-induced forward transfer (LIFT) has emerged as a versatile technique for printing high-resolution metal microstructures. However, a common drawback of this method is the inadequate coalescence of the deposited metal microdroplets, which results in inferior electrical and mechanical properties. This paper proposes a novel approach for fabricating high-performance metal micropillars using a single-pulsed laser to alternately deposit and remelt metal microdroplets. Specifically, an ultraviolet nanosecond laser was used to induce the deposition of copper microdroplets, forming a patterned powder bed with high resolution. Subsequently, a laser pulse train was applied to fuse the patterned powder bed. The results showed that voids and microdroplet delamination were eliminated in the printed copper micropillars, whose yield strength and elastic modulus increased threefold, approaching 63% of those of the bulk metal. The remelting behavior of the deposited microdroplets was elucidated by modelling and analysing the thermal accumulation effects of a laser pulse train. A remelting map was proposed, including the non-melting, remelting, and vaporizing regimes. According to the depth of melt pool, the evolutions of morphology and microstructure in the depositing and remelting process were elucidated. Hence, this study advances the LIFT process for fabricating high-performance metal microstructures.

中文翻译：

---

通过单激光交替沉积和重熔微滴，用于打印低缺陷和高性能金属微柱

激光诱导正向转移 (LIFT) 已成为打印高分辨率金属微结构的通用技术。然而，这种方法的一个常见缺点是沉积的金属微滴聚结不充分，导致电气和机械性能较差。本文提出了一种利用单脉冲激光交替沉积和重熔金属微滴来制造高性能金属微柱的新方法。具体来说，使用紫外纳秒激光诱导铜微滴沉积，形成高分辨率的图案化粉末床。随后，应用激光脉冲序列来熔合图案化粉末床。结果表明，印刷铜微柱中的空隙和微滴分层被消除，其屈服强度和弹性模量提高了三倍，接近块体金属的63%。通过建模和分析激光脉冲串的热累积效应，阐明了沉积微滴的重熔行为。提出了重熔图，包括非熔化、重熔和汽化状态。根据熔池深度，阐明了沉积和重熔过程中形貌和微观结构的演变。因此，本研究推进了用于制造高性能金属微结构的 LIFT 工艺。