Abstract: Fibrin is a promising tissue engineering scaffold material with excellent biocompatibility, while solid freeform fabrication is becoming an important technology for the fabrication of scaffolds with complex structure. Research on the solid freeform fabrication of fibrin can combine the advantages of both sides. A two-step gelatinization technology is presented for this end. Firstly rapid prototype a gelatin-fibrinogen hybrid scaffold in a low temperature environment, then put it in thrombin solution to catalyze fibrinogen into fibrin, lastly let the gelatin in the scaffold be dissolved in 37 ℃ water solution environment. Research on the gelation process shows that the thrombin concentration has influence on both gelation speed and final microstructure of fibrin, while microlite zones formed during the gelation process of gelatin makes its absorbance value keep declining slowly. Four filament status of gelatin are obtained corresponding to its gelatinization degrees, which includes droplet, continuous filament, unstable filament etc. An optimal temperature zone is identified for the solid freeform fabrication of gelatin. Scaffolds of various structures can be fabricated with two-step gelatinization technology, which includes grid-cubic, two-branch valve, etc. SEM observation of fibrin scaffolds shows both fiber network which is characteristic of fibrin and fiber network with membrane formed by the infiltration of gelatin into the fibrin network.

Key words: Fibrin, Solid freeform fabrication, Two-step gelatinization, field measurement, finite element analysis, rail corrugation, structure fracture, railway metro