Zhang Zhengyi, Xu Changxue, Xiong Ruitong, Chrisey Douglas B, Huang Yong
Department of Industrial, Manufacturing, and Systems Engineering, Texas Tech University, Lubbock, Texas 79409, USA.
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA.
Biomicrofluidics. 2017 Jun 15;11(3):034120. doi: 10.1063/1.4985652. eCollection 2017 May.
Laser-induced forward transfer has been a promising orifice-free bioprinting technique for the direct writing of three-dimensional cellular constructs from cell-laden bioinks. In order to optimize the printing performance, the effects of living cells on the bioink printability must be carefully investigated in terms of the ability to generate well-defined jets during the jet/droplet formation process as well as well-defined printed droplets on a receiving substrate during the jet/droplet deposition process. In this study, a time-resolved imaging approach has been implemented to study the jet/droplet formation and deposition processes when printing cell-free and cell-laden bioinks under different laser fluences. It is found that the jetting behavior changes from no material transferring to well-defined jetting with or without an initial bulgy shape to jetting with a bulgy shape/pluming/splashing as the laser fluence increases. Under desirable well-defined jetting, two impingement-based deposition and printing types are identified: droplet-impingement printing and jet-impingement printing with multiple breakups. Compared with cell-free bioink printing, the transfer threshold of the cell-laden bioink is higher while the jet velocity, jet breakup length, and printed droplet size are lower, shorter, and smaller, respectively. The addition of living cells transforms the printing type from jet-impingement printing with multiple breakups to droplet-impingement printing. During the printing of cell-laden bioinks, two non-ideal jetting behaviors, a non-straight jet with a non-straight trajectory and a straight jet with a non-straight trajectory, are identified mainly due to the local nonuniformity and nonhomogeneity of cell-laden bioinks.
激光诱导正向转移一直是一种很有前景的无孔生物打印技术，可用于从含细胞生物墨水直接书写三维细胞构建体。为了优化打印性能，必须仔细研究活细胞对生物墨水可打印性的影响，这涉及在喷射/液滴形成过程中产生清晰定义的射流的能力，以及在喷射/液滴沉积过程中在接收基板上形成清晰定义的打印液滴的能力。在本研究中，采用了一种时间分辨成像方法来研究在不同激光能量密度下打印无细胞和含细胞生物墨水时的喷射/液滴形成及沉积过程。研究发现，随着激光能量密度的增加，喷射行为从无材料转移变为具有或不具有初始凸起形状的清晰定义的喷射，再到具有凸起形状/羽流/飞溅的喷射。在理想的清晰定义的喷射条件下，确定了两种基于撞击的沉积和打印类型：液滴撞击打印和具有多次破碎的射流撞击打印。与无细胞生物墨水打印相比，含细胞生物墨水的转移阈值更高，而射流速度、射流破碎长度和打印液滴尺寸分别更低、更短和更小。活细胞的加入将打印类型从具有多次破碎的射流撞击打印转变为液滴撞击打印。在打印含细胞生物墨水的过程中，主要由于含细胞生物墨水的局部不均匀性和非均质性，确定了两种非理想的喷射行为，即轨迹非直线的非直线射流和轨迹非直线的直线射流。
