Three-dimensional printing technology makes it possible to rapidly manufacture objects by depositing layer upon layer of polymers in a precisely determined pattern. Once these objects are completed, the polymers that form the material are “dead” — that is, they cannot be extended to form new polymer chains.
Chemists have now developed a technique that allows them to print objects and then go back and add new polymers that alter the materials’ chemical composition and mechanical properties. The researchers can also fuse two or more printed objects together to form more complex structures. This technique could greatly expand the complexity of objects that can be created with 3D printing
The researchers designed new polymers that are also reactivated by light, but in a slightly different way. Each of the polymers contains chemical groups that act like a folded accordion. These chemical groups, known as TTCs, can be activated by organic catalysts that are turned on by light. When blue light from an LED shines on the catalyst, it attaches new monomers to the TTCs, making them stretch out. As these monomers are incorporated uniformly throughout the structure, they give the material new properties.