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Digital laser micro/nano printing (Conference Presentation)

Laser-induced forward transfer (LIFT) has demonstrated its ability for high resolution printing of a large set of materials in solid or liquid phase. The typical dimension of the LIFT-printed structures is of few micrometers. By downscaling the donor film thickness together with the pulse duration and the spot size of the laser, sub-micrometers metal droplets have also been printed. Recently, we have proposed the double pulse LIFT process (DP-LIFT) which relies on the use of two laser beams to transfer metal droplets in liquid phase from a solid donor thin film. First, a quasi-continuous wave laser irradiates the thin metal donor film to locally form a liquid film, then, a second short pulse laser irradiates this area to induce the formation of a liquid jet and the printing of a small droplet on the receiver substrate.

We used time-resolved shadowgraphy to investigate the dynamics of high-velocity nanojets generated from solid copper ﬁlms. These experiments show that this DP-LIFT approach induces the formation of very thin and stable liquid jets that expands over distances of few tens of micrometers for a large range of process conditions. We also demonstrated that the size of the melted metal pool plays an important role in the jet dynamics and allows controlling the size of the printed droplets. This process has been used to print 2D and 3D structures with micro and nano-meter sizes while avoiding the generation of any debris and these results demonstrates the high potential of DP-LIFT as a digital nano-printing process.