Colorless polyimide (CPI) is a flexible, transparent alternative to glass, increasingly being utilized in bendable smartphone screens. It still can crack, however, which is why scientists have now developed a self-healing version of the material – and it incorporates linseed oil.
Led by Dr. Yong-Chae Jung, a team at the Korea Institute of Science and Technology started by creating linseed oil-loaded microcapsules, which were mixed with a clear type of silicone known as polydimethylsiloxane. This solution was then applied to a film of conventional CPI, and allowed to dry.
When the underlying CPI was subsequently stressed to the point of cracking, the surface layer of microcapsules also cracked, causing the capsules in that area to rupture and release their oil into the damaged CPI. Upon being exposed to the air, that oil proceeded to harden into a transparent solid, thus filling and repairing the crack.
Although the hardening process is fairly slow at room temperature (25 ºC/77 ºF), it can be sped up considerably by heating the bi-layer material to 70 ºC (158 ºF) and raising the ambient humidity to 70 percent. Alternatively, if the material is exposed to ultraviolet light, the released oil hardens within just 20 minutes, repairing cracks by over 95 percent in the process.
A paper on the research was recently published in the journal Composites Part B: Engineering.
Source: National Research Council of Science and Technology via EurekAlert
