A Coaxial Extrusion Feeding System For3D Printing Composite Forming For Osteochondral Integrated Regenerated Scaffolds

Defect or injury of human joint tissue caused by work-related injuries, sportsinjuries, accidents, natural disasters and other reasons is very common in clinicalpractice, which has now become one of the main causes of disability. Humanosteochondral injury is usually accompanied by changes in mechanical stress on thejoints. If not treated timely, it will further lead to osteoarthritis which seriously affectspeople’s quality of life. Due to the special physiological structure of the human jointtissue, the ability to repair itself after the osteochondral tissue defects is poor.Traditional osteochondral repair method is difficult to obtain satisfactory repair effect;using tissue engineering technology to repair osteochondral defects has become thecurrent focus of research at home and abroad. However, due to the limitation ofprocess and equipment technology, the preparation of osteochondral scaffolds is oftenlack of the transition layer between the bone and cartilage. There are some limitationsin the integrated forming of osteochondral scaffolds. Therefore, the repaired tissue cannot meet the clinical needs in distributing stress, resisting shear force and restrictingthe free exchange of tissue fluid between the bone and cartilage function. The3Dprinting composite forming process combined with3D printing technology andelectrostatic spinning technology. By using some kinds of nozzles working together, itcan form an osteochondral integrated regenerated scaffolds with gradient distributionin material and the internal gradient pore structure in the three layers structure, whichconsists of cartilage layer, transition layer, and bone layer. It provides a new way ofthinking and method to effectively solve the osteochondral defects.In this paper, the key technology of3D print composite forming process and itsequipment of osteochondral integrated regenerated scaffolds was used as the startingpoint. Aiming at the forming of transition layer of osteochondral integratedregenerated scaffolds, a coaxial material feeding method was studied and itscorresponding feed device was developed. The paper focused on the optimizationmethods of the coaxial scaffolds forming process parameters and the modeling andcontrol methods of the forming process. The specific results obtained are as follows:(1) Focusing on the3D printing composite forming process and system architecture for osteochondral integrated regenerated scaffolds, a coaxial extrusionfeeding device was designed and manufactured, and the on-line monitoring of thefeeding device was realized. Finally, the feasibility of the device for coaxial structurescaffolds was verified by experiments;(2) Aiming at coaxial extrusion feeding method and device, the key criticalprocess parameters were researched and given which impacted the forming precisionof the pore size and the ratio of the height and width of the coaxial fiber. The keyprocess parameters are optimized by adopting the method of orthogonal experimentand combining with theory of grey relational analysis.(3) Under the conditions of assuring the forming quality of the3D throughstructure of the coaxial scaffolds and in order to achieve effective control for thecross-sectional width of the coaxial fiber, a mathematical relationship between thespeed of motion of the platform and the fiber cross-sectional width model wasestablished and the regulation and control strategy was studied. Finally, it was verifiedby experiments.The feeding method and device proposed in the paper is an important part of3Dprinting composite forming test system. With its working coordinately with othersubsystems, the osteochondral integrated regenerated scaffolds was prepared withgradient materials distribution and the internal gradient pore structure, whicheffectively verified the validity of the results of this study.