Time-resolved Study of Droplet Formation Process during Inkjetting of Alginate Solution

Organ printing offers a great potential for the fabrication of three-dimensional (3D) living organs by precisely layer-by-layer placing various tissue spheroids. Such fabricated organs may replace some damaged or injured human organs, emerging as a promising solution to the problem of organ donor shortage. As one of the key enabling technologies for organ printing, inkjetting has been received much attention recently. It is of great importance to understand the jetting and droplet formation processes during the inkjetting of typical biomaterials such as alginate solution. The jetting behavior and breakup time during alginate inkjetting have been studied using a time-resolved approach, and different pinch-off behaviors are classified. The resulting knowledge will help better promote the inkjetting-based organ printing technology. Introduction The organ donor shortage is worsening with the growing national and international demand, especially as the organs of a longer-lived population deteriorate over time. As such, there is a critical need to create three-dimensional (3D) solid multi-material, heterogeneous living constructs to meet the demand for organ and tissue transplants. Fortunately, organ printing, a biomedical application of additive manufacturing, has emerged as a promising solution to this problem by fabricating three-dimensional (3D) living organs for transplantation based on layerby-layer deposition technique [Mironov2009] [Riggs2011]. Various technologies have been pioneered for organ printing including inkjet printing [Boland2007] [Calvert2007] [Xu2012], extrusion deposition [Khalil2005] and laser-induced forward transfer (LIFT) [Koch2010] [Schiele2010], to name a few. Of these enabling technologies, inkjet printing has gained much attention recently because of its great advantages in terms of moderate fabrication cost, inherent flexibility, and good spatial resolution and repeatability. There are two forms of inkjet printing, continuous inkjet (CIJ) printing and drop-ondemand (DOD) inkjet printing [Herran2012a]. DOD printing is favored due to its good controllability and less contamination. During DOD printing, droplets are generated only as required by propagating a pressure wave in a fluid filled chamber. The successful implementation of DOD printing directly affects the quality of fabricated structures as well as the fabrication efficiency, so numerous studies have devoted to understating DOD printing