Impulsively actuated jets from thin liquid films for high-resolution printing applications

Abstract

Blister-actuated laser-induced forward transfer (BA-LIFT) is a versatile printing technique in which fine jets of ink are ejected from a thin donor film onto an acceptor substrate, enabling high-resolution patterns to be formed. Fluid ejections are initiated by the rapid expansion of micrometre-sized blisters that form on a polymer film underneath the ink layer. Recent work has demonstrated that these ejections exhibit novel flow phenomena due to the unique dimensions and geometry of the BA-LIFT configuration. In this work, we study the dynamics of BA-LIFT printing using a computational model in which fluid is forced by a boundary that deforms according to experimental time-resolved measurements of an expanding blister profile. This allows the model's predictions to be unambiguously correlated with experimental blister-actuated ejections without any fitting parameters. First, we validate the model's predictive capabilities against experimental results, including the ability to accurately reproduce the size, shape and temporal evolution of the jet as well as the total volume of ink released. The validated model is then used to interrogate the flow dynamics in order to better understand the mechanisms for fluid ejection. Finally, parametric studies are conducted to investigate the influence of ink density, surface tension, viscosity and film thickness as well as the size of the blister used. These results provide key insights into avenues for optimization and better control of the BA-LIFT process for improved resolution and repeatability of the printed features.

Laser-induced forward transfer of pure metals

“…This literature includes velocity data below and above the ejection threshold. First, for numerical work on LIFT of Newtonian liquid films deposited on a dynamic release layer [24], a threshold ejection Weber number We ej = 1.1 is obtained, which is in agreement with the We ej = 1 criterion proposed here. Further, Young et al [21] found no detachment of the film even for experiments performed at We ≈ 80.…”

“…This is the case, even at fluence levels just above the ejection threshold, as shown in figure 5.6. Previous reports by Brown et al [24] have shown that for sub-ejection threshold fluence levels the film is accelerated, but retracted by surface tension before it can escape the liquid donor layer. This suggests that ejection only takes place if the kinetic energy of the ejected material exceeds its surface energy.…”

“…Time-resolved imaging is a suitable method to visualize the ejection process and to gain further insight into the ejection process during LIFT. However, due to the challenging visualization conditions, time-resolved visualization has only been achieved for relatively thick liquid-film [21][22][23][24][25] and solid phase [26][27][28] or paste-transfer [29,30] processes. Attempts to visualize LIFT-processing of Au [31], Ni [32], Al [33], and Cr [34] do not provide sufficient spatial resolution to track the process in detail.…”

“…Recent investigations on blister-actuated LIFT (BA-LIFT) were performed by Brown et al [82]. Based on the finite volume (FVM) and the volume-of-fluid method (VOF), the driving mechanisms starting with the expansion of the laserinduced bubble, and the related fluid dynamics, which ultimately lead to an ejection of liquid ink, were analyzed.…”

Laser-assisted bioprinting at different wavelengths and pulse durations with a metal dynamic release layer: A parametric study

“…They are combined with different DRL materials, including metals (gold, silver, or titanium), polymers (triazene, polyethylene naphthalate, polyimide, or cyanoacrylate), or hydrogels (gelatin). Most groups using LaBP for printing biomaterials apply ultraviolet (UV) lasers with 3 to 30 nanoseconds pulse durations and 193-nm [1,2] , 248-nm [3,4] , 266-nm [5] , 337-nm [6] , or 355-nm [7,8] wavelengths.…”