Provided herein according to some embodiments is a method of forming a three-dimensional object comprised of polyurethane, polyurea, or copolymer thereof. In some embodiments, the three-dimensional object is flexible, has a Young's Modulus of 25 to 250 megapascals, has a tensile strength of 3 to 30 megapascals, and/or has a percent elongation at break of from 100 to 175.