WO3 Nanoparticles for High Color Purity 3D Printing

Mixing tungsten oxide (WO₃) nanoparticles with polyamide as a photosensitizer for color 3D printing can avoid the problem of discoloration caused by traditional carbon-based photosensitizers and contribute to the realization of high-fidelity 3D color printing, the discovery has been published by the Institute of Science and Technology of Barcelona (ICFO) in Spain in NanoLetters recently.

Selective powder sintering for 3D printing has recently become an increasingly affordable solution for manufacturing made-to-order elements of almost any shape or geometry. This technique involves heating a bed of powder to just below its melting point, using an IR light source to selectively melt a cross section of the powder, then adding more powder and repeating to form a 3D object.

To reduce costs and increase printing speed, a photothermal sensitizer is often added to the powders, which can accelerate the speed at which incident light is converted into heat. However, when printing white and color products, commonly used carbon-based sensitizers which will cause the work to change color. Previous ICFO related research has used gold-coated silica nanoparticles to overcome the above problems. Although the effect is obvious in color printing, there are still limitations in the printing of large-scale colorful high-fidelity and pure white.

In the study, ICFO uses nanoparticles made of WO₃ as a photothermal sensitizer, which greatly reduces the production difficulty and material cost. They are colorless at high concentrations and have strong absorption in the near-infrared region, proving their capability of turning light into heat at a fast rate, and thus enabling them as fast fusing agents. Besides, they can be efficiently turned on or off with electricity or ultraviolet radiation. Even more, they are stable at very high temperatures and demonstrate a heating-to-color change rate superior when compared to other available sensitizers.

Finally, when mixed with other color inks, these WO₃ nanoparticles can reproduce the same color as the original powder, maintaining the color purity of the original sample. This could also open up a new pathway for high-fidelity 3D printing.

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