Study of Droplet Formation Process during Drop-on-Demand Inkjetting of Living Cell-Laden Bioink

Abstract

Biofabrication offers a great potential for the fabrication of three-dimensional living tissues and organs by precisely layer-by-layer placing various tissue spheroids as anatomically designed. Inkjet printing of living cell-laden bioink is one of the most promising technologies enabling biofabrication, and the bioink printability must be carefully examined for it to be a viable biofabrication technology. In this study, the cell-laden bioink droplet formation process has been studied in terms of the breakup time, droplet size and velocity, and satellite formation using a time-resolved imaging approach. The bioink has been prepared using fibroblasts and sodium alginate with four different cell concentrations: without cells, 1 × 10(6), 5 × 10(6), and 1 × 10(7) cells/mL to appreciate the effect of cell concentration on the droplet formation process. Furthermore, the bioink droplet formation process is compared with that during the inkjetting of a comparable polystyrene microbead-laden suspension under the identical operating conditions to understand the effect of particle physical properties on the droplet formation process. It is found that (1) as the cell concentration of bioink increases, the droplet size and velocity decrease, the formation of satellite droplets is suppressed, and the breakup time increases, and (2) compared to the hard bead-laden suspension, the bioink tends to have a less ejected fluid volume, lower droplet velocity, and longer breakup time.

Measurement of the oscillatory flow field inside tapered cylindrical inkjet nozzles using micro-particle image velocimetry

“…This distinct droplet formation mechanism is compatible with a wider range in the rheology of the printed inks (Yang et al 1997;Schoeppler 2006;Fakhfouri et al 2009;Magdassi 2009) when compared to other droplet generation systems such as thermal inkjet printheads. As a result, piezoelectric DOD inkjet printers have been used for printing colloidal suspensions in numerous life science applications including proteomics, DNA sequencing, therapeutics and tissue engineering (Chee et al 1996;Lemmo et al 1998;Cooley et al 2001;Boland et al 2006;Chahal et al 2012;Lorber et al 2014;Xu et al 2014). Understanding the hydrodynamics of suspension flow inside the inkjet nozzle is an essential step in the optimization of these printheads.…”

3D bioprinting for tissue engineering: Stem cells in hydrogels

“…A modification of this process uses ultrasound to create an acoustic radiation field and form droplets from an air-liquid interface. Control of droplet size and rate of deposition comes from ultrasound pulse, duration and amplitude [18] . The acoustic methods can be modified so that they are not reliant on nozzles [19] .…”

Drop-on-demand inkjet-based cell printing with 30-μm nozzle diameter for cell-level accuracy

“…From the cell diameter and cell number (or concentration), the value of u was calculated as 1.25%, similar to the value of 0.88% reported in a previous study. 29 This value indicates that the cell-laden bioink belongs to a diluted suspension (u 2%) 33 and that the selected concentration of the cell is weakly associated with the behavior of dynamic surface tension and shear viscosity.…”

“…In general, the cells affect the morphology of the jet with irregularity. 17,29 Especially in the case of long ligaments, the morphology of the jet ligament, including cells, is anomalistic owing to the larger diameter of cells compared with that of a thinned ligament. However, if the cells are located at the main head, the morphology is stable and regular and is indiscernible from a jet morphology without a cell.…”

“…28 Moreover, Xu et al studied the droplet formation processes of cell-laden bioink using a nozzle with a diameter of 120 lm. 29 As reviewed, relatively large nozzle sizes have been used for inkjet-based cell printing in consideration of the level of stress that cells can experience during the printing process.…”