Repairing and reusing plastics and delivering cancer drugs more effectively are two of the many potential applications a new 3D/4D printing technology might have. The technology merges 3D/4D printing and photo-controlled/living polymerization — a chemical process to create polymers. 4D printing is a subset of 3D printing where the printed object can transform its shape in response to certain conditions. The new method uses visible light to create an environmentally friendly “living” plastic or polymer. Polymers can be synthetic, such as plastic, as well as biological; for example, DNA.
The research builds upon the discovery of Photoinduced Electron/energy Transfer-Reversible Addition Fragmentation Chain Transfer polymerization (PET-RAFT polymerization), a new way to make controlled polymers using visible light. Such polymers can be reactivated for further growth, unlike traditional polymers that are “dead” after being made.
In contrast to conventional 3D printing, the new method of using visible light allows control of the architecture of the polymers and tunes the mechanical properties of the materials prepared by the process. For example, a 3D object starts as a flat plane and when exposed to certain conditions, it will start to fold — a 4D material. So, the fourth dimension is time.
The main application is recycling because instead of using a plastic object once, it can be repaired and reused. For ordinary recycling, materials are taken away and reconstructed; for the new “living” material, it will be able to repair itself. Another major benefit of the new process is its compatibility with biomedicine because extreme conditions were unnecessary. Current 3D printing approaches are typically limited by the harsh conditions required, such as strong UV light and toxic chemicals, which limits their use in making biomaterials. With the application of PET-RAFT polymerization to 3D printing, long polymer molecules can be produced using visible light rather than heat, which is the typical polymerization method.