a method of making a porous biodegradable polymer is disclosed , which comprises placing a biodegradable polymer and a solvent in a chamber ; adding a supercritical fluid to the chamber and maintaining the chamber at a predetermined temperature for a sufficient period of time to allow the supercritical fluid to dissolve into the biodegradable polymer with the help of the solvent ; and venting the supercritical fluid and the solvent by reducing the pressure in the chamber , thereby obtaining a porous biodegradable polymer .