Method for forming and 3D printing double network hydrogels using temperature-controlled projection stereolithography

A method of forming a three-dimensional structure, comprising the steps of:

• providing a sample holder including a metal plate having a fabrication window formed therethrough and a transparent dish positioned on top of the metal plate, a source of heat coupled to the metal plate, and a source of modulated irradiation positioned below said metal plate and configured to deliver a spatially modulated pattern of light through said fabrication window;
• supplying a formulation including a set of components onto the sample holder to form a first layer of a double network hydrogel, wherein the first component of said set of components is a photo-crosslinked prepolymer and a second component of said set of components is a physical crosslinked prepolymer having a transition temperature;
• maintaining a temperature of the formulation in said sample holder above the transition temperature of the seconds component with the source of heat while simultaneously polymerizing the first component of said formulation with said spatially modulated pattern of light until the first component is selectively polymerized into a predetermined object;
• and
• cooling the formulation so that the second component polymerizes to form the double network hydrogel.