Hydrogel three-dimensional printing with self-crosslinking particulate build material

A method of three-dimensional printing a hydrogel comprising:

• iteratively applying individual layers of a particulate build material to a powder bed, wherein the particulate build material comprises from about 90 wt % to 100 wt % of a mixture of a powdered polyhydroxylated swellable polymer dry blended with powdered water-soluble crosslinker that is reactive with hydroxyl groups of the polyhydroxylated swellable polymer to crosslink the polyhydroxylated swellable polymer;
• and
• based on a three-dimensional object model, iteratively and selectively applying an aqueous agent onto the individual layers, wherein the aqueous agent comprises water and an organic co-solvent, wherein the aqueous agent does not include the crosslinker, thereby forming a three-dimensional printed hydrogel.

A hydrogel three-dimensional printing system comprising:

• a particulate build material including from about 90 wt % to 100 wt % of a mixture of a powdered polyhydroxylated swellable polymer dry blended with powdered water-soluble crosslinker that is reactive with hydroxyl groups of the polyhydroxylated swellable polymer to crosslink the polyhydroxylated swellable polymer;
• and
• a fluid applicator fluidly coupled or coupleable to an aqueous agent, wherein the fluid applicator is directable to iteratively apply the aqueous agent to layers of the particulate build material, wherein the aqueous agent comprises water and an organic co-solvent, wherein the aqueous agent does not include the crosslinker.