Method of 3D printing a cellular solid

A method of three-dimensional printing a cellular solid, the method comprising:

• introducing an ink formulation comprising a flowable polymer precursor and a gas into a nozzle comprising a core flow channel radially surrounded by an outer flow channel, the ink formulation being directed into the outer flow channel and the gas being directed into the core flow channel;
• ejecting the ink formulation and the gas out of the nozzle as a stream of bubbles, each bubble including a core comprising the gas and a liquid shell overlying the core comprising the ink formulation;
• after ejection, curing the flowable polymer precursor to form a solid polymeric shell from the liquid shell, the bubbles thereby being solidified;
• and
• depositing the bubbles on a substrate moving relative to the nozzle according to a predetermined geometry, thereby printing a polymeric cellular structure having the predetermined geometry,
• wherein curing occurs after deposition of the bubbles on the substrate and within one second of the deposition.