Sandcastles inspire a way to 3D-print with silicone

The researchers used a similar approach to that of children building sandcastles from wet sand in order to achieve 3D printing of the flexible, porous rubber structures.

Professor Orlin Velev – INVISTA professor of chemical and biomolecular engineering at North Carolina State University – and his team at the department reported on the successful technique in the latest issue of Advanced Materials.

“There is great interest in 3D printing of silicone rubber, or PDMS, which has a number of useful properties,” said Professor Velev.

“The challenge is that you generally need to rapidly heat the material or use special chemistry to cure it, which can be technically complex.”

The engineers found that by combining water with liquid silicone rubber, they could induce the formation of tiny bridges between silicone rubber beads. This allowed them to link the beads together to form structures, much as adding a small amount of water can allow dry, formless sand to be sculpted into sandcastles.

The resulting paste could be printed to form 3D structures, which, according to the Advanced Materials paper, are “remarkably elastic, flexible and extensible”. As the ink is made of porous, biocompatible silicone, it can be printed directly into wet and dry surroundings, and could even work within live tissue.

This could allow the printing of a bioscaffold onto live tissue, the creation of a flexible mesh holding a droplet of therapeutic, or a soft bandage that could be directly printed onto the human body.

“Our method uses an extremely simple extrudable material that can be placed in a 3D printer to directly prototype porous, flexible structures, even under water,” Professor Velev said.

“And it is all accomplished with a multiphasic system of just two materials, no special chemistry or expensive machinery is necessary. The “trick” is that both the beads and the liquid that binds them are silicone, and thus make a very cohesive, stretchable and bendable material after shaping and curing.”