Zhang Zhengyi, Xiong Ruitong, Corr David T, Huang Yong
Department of Mechanical and Aerospace Engineering, University of Florida , Gainesville, Florida 32611, United States.
Department of Biomedical Engineering, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
Langmuir. 2016 Mar 29;32(12):3004-14. doi: 10.1021/acs.langmuir.6b00220. Epub 2016 Mar 14.
Laser-induced forward transfer-based laser printing has been being implemented as a promising orifice-free direct-write strategy for different printing applications. The printing quality during laser printing is largely affected by the jet and droplet formation process and subsequential impingement. The objective of this study is to investigate the impingement-based printing type and resulting printing quality during the laser printing of viscoelastic alginate solutions, which are representative inks for soft structure printing such as bioprinting. Three printing types are identified: droplet-impingement printing, jet-impingement printing with multiple breakups, and jet-impingement printing with a single breakup. Printing quality, in terms of printed droplet morphology and size, has been investigated as a function of alginate concentration, laser fluence, and direct-writing height based on a time-resolved imaging approach and microarrays of printed droplets. Of these, the best printing quality is achieved with single-breakup jet-impingement printing, followed by multiple-breakup jet-impingement printing, with droplet-impingement printing producing the lowest quality printing. The printing quality can be improved by using high-concentration alginate solutions. The increase of laser fluence may lead to a well-defined primary droplet for low-concentration alginate solutions; however, this can cause the droplet diameter to increase, which may not be desirable. The direct-writing height (i.e., ribbon coating-receiving substrate distance) also influences the print quality. For example, an increase in direct-writing height can cause the printing type to change from the ideal jet-impingement with a single breakup, to the jet-impingement with multiple breakups, and even the least desired droplet-impingement printing, with only slight variations in droplet diameter.
基于激光诱导正向转移的激光打印已被用作一种有前景的无孔直写策略，用于不同的打印应用。激光打印过程中的打印质量在很大程度上受喷射和液滴形成过程以及后续撞击的影响。本研究的目的是研究在激光打印粘弹性海藻酸盐溶液时基于撞击的打印类型及其产生的打印质量，粘弹性海藻酸盐溶液是生物打印等软结构打印的代表性墨水。确定了三种打印类型：液滴撞击打印、多次破碎的射流撞击打印和单次破碎的射流撞击打印。基于时间分辨成像方法和打印液滴微阵列，研究了打印质量（以打印液滴的形态和尺寸表示）与海藻酸盐浓度、激光能量密度和直写高度的函数关系。其中，单次破碎的射流撞击打印获得的打印质量最佳，其次是多次破碎的射流撞击打印，液滴撞击打印产生的打印质量最低。使用高浓度海藻酸盐溶液可以提高打印质量。对于低浓度海藻酸盐溶液，激光能量密度的增加可能会导致形成明确的初级液滴；然而，这可能会导致液滴直径增大，这可能并不理想。直写高度（即色带涂层与接收基板的距离）也会影响打印质量。例如，直写高度的增加会导致打印类型从理想的单次破碎射流撞击变为多次破碎射流撞击，甚至变为最不理想的液滴撞击打印，而液滴直径仅有轻微变化。
