Selective powder sintering for 3-D 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 (such as polyamide, PA12) 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 3-D object. To reduce costs and increase printing speed, a photothermal sensitizer is often added to the powders. Typically carbon-based, with a strong broadband absorption, adding these sensitizers to the polymer powders increases the conversion of incident light to heat, which means greater print speeds. However, carbon-based sensitizers can only produce black or gray objects. To create white or colorful prints, visibly transparent equivalents are needed.
