Liquid-absorbing system-assisted intersecting jets printing of soft structures from reactive biomaterials

Abstract

Traditional three-dimensional (3D) bioprinting techniques of reactive materials usually include a mixing step of reactive agents prior to deposition, leading to potential changes in the rheological and biocompatibility properties of the resulting ink. During intersecting jets printing, reactive materials are dispensed separately, colliding and mixing with each other in air before landing on a previously deposited layer. While this enables reactive material printing using a printing-then-mixing approach, the resulting excess fluid may compromise the printing quality and accuracy. This study aims to improve the performance of intersecting jets–based reactive material printing by introducing a stainless-steel wire mesh and fibrous tissue paper–based liquid-absorbing system, which functions as a method to remove the excess resultant liquid from the printing zone. The proposed stainless-steel wire mesh and tissue paper-based liquid absorbing system effectively absorbs the excess liquid resulted during the printing process which enables higher-resolution and denser depositions of soft structures. By selecting a proper wire mesh, the proposed liquid-absorbing system can absorb up to 65–90 % of the excess liquid (water herein) resulting from printing aqueous reactive sodium alginate and calcium chloride inks, which are selected as model materials in this study. By controlling the tilt angles of intersecting jets, the incident angle of post-collision droplets is desirable to be less than 14° to avoid droplet bouncing on the top of a previously deposited layer during 3D bioprinting. Using the liquid-absorbing system, different 3D structures have been successfully printed using intersecting jets printing. For tubular alginate constructs printed in air from sodium alginate and calcium chloride inks, a 2.5 height-diameter ratio can be achieved. The proposed printing technology does not influence the post-printing cell viability while printing 3T3 cells, demonstrating its promising potential for bioprinting applications.