3D Printing the Rainbow

Selective laser sintering (SLS) is currently one of the most efficient forms of 3D printing. The applications of this printing method are wide, ranging from the biomedical industry to food.

Image credit: American Chemical Society

SLS printers, however, have been lacking a fundamental feature: color. These printers could in fact only print objects in gray or black color.

Not anymore.

A new discovery by the Institute of Photonic Sciences (IFCO) in Spain is destined to change the way 3D printed objects will look.

Selective laser sintering (SLS) printers use a laser to heat specific regions of a powdered material, typically nylon or polyamide, so that the powder melts or sinters to form a solid mass. The printer adds then selectively sinters new powdered material layer by layer until the desired 3D structure is obtained. To reduce the energy requirements of the process, researchers have added compounds called photosensitizers to the polymer powders.

These materials, such as carbon nanotubes, carbon black and graphene, absorb light much more strongly than the polymers and transfer heat to them, enabling the use of cheaper, lower-power lasers. However, the carbon-based photosensitizers can only produce printed objects that are gray or black. Gerasimos Konstantatos, Romain Quidant and their coworkers at The Institute of Photonic Sciences (IFCO) wanted to find a photosensitizer that would enable color printing by the SLS method.

The researchers designed gold nanorods to strongly absorb in the near-infrared region of the spectrum while being almost transparent to visible light. They coated them with silica and then mixed them with polyamide powders to print 3D objects. They found that the gold nanorods were much better at converting light from the laser to heat than carbon black, the industry standard.

Manufacturers embracing SLS 3D printing consider this method a giant step forward as many think the lack of color was the main obstacle to the adoption of additive manufacturing as a whole.

Hopefully, the discovery marks the beginning of a colorful 3D printed future.

Categories: Innovation