Self-Healing Polymer May Lead to Self-Healing Smartphones

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Self-Healing Polymer May Lead to Self-Healing Smartphones
A new material not only heals itself, but it also stretches up to 50 times its usual size; these properties could fix your phone's battery if it cracks or prevent it from breaking in the first place. Credit: Wang lab

Researchers at American chemical society have recently developed a self-healing polymer material to aid electronics and soft robotics. This newly developed stretchable and transparent material enables smartphones or robots to heal themselves i.e., self-healing smartphones or robots and conducts ions to produce current.

Due to chemical bonding, the material has the ability of self-repairing. Actually, the material consists of two types of bonds- the covalent bonds and the non-covalent bonds. The Covalent bonds are strong and don’t readily reform once broken. At the other side, the non-covalent bonds are weaker and more dynamic. For example, the hydrogen bonds that connect water molecules to one another are non-covalent, breaking and reforming constantly to give rise to the fluid properties of water.

Chao Wang, Ph.D. said, “When I was young, my idol was Wolverine from the X-Men. He could save the world, but only because he could heal himself. A self-healing material, when carved into two parts, can go back together like nothing has happened, just like our human skin. I’ve been researching making a self-healing lithium ion battery, so when you drop your cell phone, it could fix itself and last much longer.”

“Most self-healing polymer materials form hydrogen bonds or metal-ligand coordination, but these aren’t suitable for ionic conductors.”

Instead of using hydrogen bonds, scientists turned to a different type of non-covalent bond called an ion-dipole interaction. An ion-dipole interaction, a force between charged ions and polar molecules. This is for the first time scientists have used an ion-dipole interaction to design polymer.

Wang said, “Ion-dipole interactions have never been used for designing a self-healing polymer, but it turns out that they’re particularly suitable for ionic conductors.”

The material consists of a polar, stretchable polymer, poly (vinylidene fluoride-co-hexafluoropropylene), plus a mobile, ionic salt. The polymer chains are linked to each other by ion-dipole interactions between the polar groups in the polymer and the ionic salt. This causes the material to be stretched up to 50 times than its usual size. After being torn in two, the material automatically stitched itself back together completely within one day.

During the experiment, scientists placed a non-conductive membrane between two layers of the ionic conductor and created an artificial muscle. The new material responded to electrical signals, bringing the motion to these artificial muscles, so named because biological muscles similarly move in response to electrical signals.

By looking forward, scientists are now working on altering the polymer to improve the material’s properties. They are testing the material in harsh conditions, such as high humidity.