Researchers have figured out a method to generate full colour using the TPP 3D printing process.
The TPP (Two Photon Polymerization) process involves precisely focusing a laser to a point within a tank of photopolymer resin. The focal point is the only region in the laser beam that is strong enough to cause polymerization. Therefore, a physical voxel is formed at that focal point, which is moved throughout the 3D space of the resin tank to form 3D objects.
TPP is able to create very small objects because the laser focal point can be extremely small. It’s possible to create features as small as 100nm (0.0001mm), and it’s used for a variety of unusual applications.
However, it’s always done with a single resin and therefore single colour. That’s how resin 3D printing works.
Until now, that is. The researchers have developed a way to introduce colour into the printing process in a very unusual way using a new process they call “EF-TPP”.
The technique integrates an electric field into the TPP process, enabling dynamic control over the optical properties of resins as they solidify. These resins respond to electric fields by changing their internal helical pitch, resulting in visible structural colour changes.
In other words, each voxel can be made to have a specific colour by varying the electrical field during printing.
Depending on the specific resin mix used, it’s also possible for objects printed with EF-TPP to change colour after printing when responding to different temperatures.
One benefit is that this could remove the toxic chemicals used in traditional lithography processing for some applications.
As this is an entirely new capability, it’s not yet known what possible applications might be enabled by EF-TPP. The ability to create colour in microscopic 3D prints could be used in optical applications, wearable devices, and other concepts.
EF-TPP is an unusual approach, as there have been very few electrical processes used in 3D printing. One from five years ago was an Essentium project to counter the isotropic nature of FFF 3D prints. They used an electric field to heat up additives in the filament to increase layer adhesion. However, that didn’t catch on.
EF-TPP might have a different fate, as there are new application possibilities.
Via PNAS NEXUS
