Study on linear bio-structure print process based on alginate bio-ink in 3D bio-fabrication

Ink-jet printing is a non-impact printing technology in which drops jetted from an orifice onto a designated position.This technology can digitally transport fluids containing cells precisely onto desired substrates to construct three-dimensional organs.In order to obtain the stable uniform droplets,a stream is the key point of this technology.However,there are so many factors that affect the uniform droplet stream construction process:print parameters,material parameters,control method,etc.A good understanding of the various coupled transport processes that occur during bio-ink impact and spreading on bio-structure can improve the success of print-ability.This paper aims to obtain a good linear bio-structure with ink-jet printing technology.First,a typical droplet deposition process model is constructed;including droplet dynamics impact models and droplet diffusion cap models.Second,a model of successive droplet overlap,to form linear bio-structures,is constructed.Third,the finite element method is used to simulate the droplet impact,collision,and fusion process.Finally,the main influencing factors of the continuous injection printing process,namely the time interval between consecutive droplets and the droplet contact angles,are discussed.Sodium alginate is selected as bio-ink to verify the theory,and it is found that a good linear bio-structure could be obtained if the printing parameters are controlled optimally,i.e.,if the initial contact angle is set as 60 degrees and the trigger frequency is set as 150 kHz.With a proper printing speed and gel coating,a good survival rate of printed cells could be obtained.

Additive Manufacturing of Hydroxyapatite Bioceramic Scaffolds with Projection Based 3D Printing

Hydroxyapatite(HA)bioceramics have garnered considerable attention owing to their applications in the field of bone repair and excellent biocompatibility.Compared to extrusion-based 3D printing,projection-based 3D print-ing(3DPP)can fabricate parts with complex geometry,high accuracy,and efficiency,which is very promising for bioceramic scaffolds.However,conventional 3DPP using a paste with low viscosity will cause severe shrinkage of the parts after sintering,which makes it unsuitable for bioceramic scaffolds,and a system investigation of the printing process remains insufficient.In this study,we proposed a 3DPP device suitable for bioceramic scaffolds and investigated the additive manufacturing of HA scaffolds.Ceramic paste properties and process parameters of curing,debinding,and sintering were initially examined.The mechanical properties,shrinkage,and biocompati-bility in vitro of the sintered samples were further investigated.The obtained results indicate that HA bioceramics with uniform morphology,complex structure,and high accuracy can be manufactured using the 3DPP equip-ment.HA scaffolds have the mechanical strength of human cancellous bone,while HA scaffolds cultured with osteoblast precursor cells possess strong biocompatibility and can promote osteoblast adhesion,proliferation,and differentiation.These results suggest a promising application of the 3DPP technique in the preparation of bioceramic scaffolds,and the HA scaffolds fabricated using the 3DPP technique exhibit promising potential in fulfilling a constructive role in the biomedical field of human bone regeneration repair.