Quantum dots promise better material properties in SLA 3D printing

Stereolithography (SLA) is a common 3D printing process in which photopolymerization plays a key role. However, conventional photoinitiators that trigger this process are toxic, expensive and difficult to adapt to different light wavelengths. In addition, organic UV-cured initiators degrade under sunlight, which affects the quality of 3D-printed parts.

Researchers from Carleton University and the University of Northern British Columbia have now presented a promising approach to overcome these problems. In their study, published in the journal Industrial Chemistry & Materials, they show that non-toxic and inexpensive titanium dioxide quantum dots can trigger photopolymerization in epoxy resin using UVC light. This short-wave UV radiation is not contained in sunlight. In addition, the quantum dots remain stable under UVA light, which is present in sunlight, so that finished printed parts retain their properties in the long term.

“Our approach enables precise control over the light wavelengths under which photopolymerization occurs or does not occur,” explain the scientists. This significantly improves the results of SLA 3D printing.

The titanium dioxide quantum dots were produced using flame spray pyrolysis, in which a liquid is heated by a flame and nanoparticles are formed. By adding silica, the researchers were able to produce very small, “quantum-physical” crystal sizes. The light wavelength to which the particles respond can be adjusted via the size – in this case UVC.

Compared to commercially available organic initiators, the 3D-printed epoxy films with the new quantum dots showed significantly better mechanical properties and much higher light resistance. After 500 hours of UVA irradiation, the samples remained stable, while comparative samples with organic initiators were already completely degraded after 300 hours.

The researchers see enormous potential for quantum dots in SLA printing, as titanium dioxide is non-toxic, inexpensive and available in large quantities. Further details can be found in the paper entitled: “Photo-polymerization using quantum dots for stable epoxy coatings”