“4D printing” refers to creating materials that can change shape or properties over time in response to an external stimulus such as heat, light, or moisture. This is achieved using materials programmed to transform from one shape to another when exposed to a particular stimulus.
The researchers have developed a new material for 4D printing using silicone-based ink and hollow gas-filled micro-balloons. The material can be compressed or “programmed” at an elevated temperature and retain that shape when cooled. When reheated, the gas-filled micro-balloons expand, causing the structure to return to its original shape. The material’s ability to recover its original shape is predictable and repeatable due to the utterly cross-linked silicone network, which holds the part together.
The researchers initially tested the material as an accelerated aging test, and they were surprised to find that it had a large compression set. Still, they were able to recover their shape when heated successfully.