Scaffold For Tissue Engineering The Supercritical Foam And Permeability Characteristics

Most of the existing fabrication techniques for tissue engineering scaffolds require the use of organic solvents that may never be fully removed, even after long processing hours. The residuals of these organic solvents may reduce the ability of cells to form new tissues in vivo. To overcome the problems associated with the existing methods, this thesis fabricated the PLA tissue engineering scaffold with the solid-state foaming process. The solid-state foaming process does not involve any organic solvents or chemical blowing agents. Instead, it uses inert gases CO2 as the physical blowing agent. The pore sizes that have been achieved range from sub-micrometers to a few hundred micrometers. The solid-state foaming process is simple, the process parameters are easy to control and the foaming result is stable.This thesis firstly introduced the basic principle of solid-state foaming process, and then a solid-state foaming system was designed to perform the microcellular foam fabrication for the biodegradable material PLA and several PLA foams with different pore sizes fabricated at various parameters. The experiment results show that the average pore size of PLA foams have a direct relation with the saturation press, saturation time and foaming temperature, it follows basic rule of homogeneous phase foaming. The thermogravimetry was applied to analyze the thermal stability and the onset temperature of the fabricated PLA foams, and the raw PLA material was also investigated for comparison. It is proved that the bigger pore size and the higher cell density are can be obtained with lower onset temperature and longer degradation time at body temperature of 37℃. So the stable property can be effectively controlled with appropriate fabrication condition to adapt the requirement for various applications of tissue engineering scaffold. Since the pores in the microstructures from solid foaming process are mostly closed and isolated, and not suitable for biomedical applications where interconnected porous structures are needed to allow particles and fluids to flow through. So ultrasound was applied to break the pore walls and enhance the interconnectivity of the porous structures from the solid-foaming process. Finally, this thesis applied ultrasound measuring permeability of PLA tissue engineering scaffold.