University of Southern California have devised 3D-printed rubber materials that are capable of readjusting back to their original shape when damaged. The technology involved is called photopolymerization. This is process that involves the use of an ultra-violet lamp and a photoinitiator, which can absorb in the same region as the light emitted from the lamp. The photoinitiator can generate radicals which trigger polymerization (a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks).
With the new material, the use of light solidifies a liquid resin, via 3D printing, into a desired shape or geometry. For the self-healing component, additional work was required with the material chemistry. This was achieved by adding an oxidizer to the process, triggering the material to transform into a disulfide. The disulfide group is capable of reforming when broken, fashioning the self-healing ability.
This is shown in the following video:
According to lead researcher Professor Qiming Wang: “”When we gradually increase the oxidant, the self-healing behavior becomes stronger, but the photopolymerization behavior becomes weaker…There is competition between these two behaviors. And eventually we found the ratio that can enable both high self-healing and relatively rapid photopolymerization.”
If commercialized, the new material could be of use to producers of shoes, tires, soft robotics, and electronics. The process would decreasing manufacturing time and increase product durability and longevity.
In related additive manufacturing news, scientists from the Karlsruher Institut für Technologie have managed to 3D print microstructures that change shape under the influence of temperature or light. This is based on a chemical compound termed poly(N-isopropysycraymide) which changes its shape when the the temperature is raised slightly above room temperature.
