“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. MIT 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.”