3D printing: Laser-based technique produces complex objects in any order

Existing 3D printers work by building up an object one layer at a time, making it difficult to produce some intricate shapes, but a new technique involving lasers could change that

By Matthew Sparkes

A 3D printer that uses lasers to build up an object in any order, rather than layer by layer, could produce more advanced designs than is currently possible.

Existing 3D printers work by depositing layers of a plastic filament from a nozzle or by curing layers of resin with UV light. In both cases objects are built up one layer at a time, meaning that overhanging parts of a structure – the outstretched arms of a model human, say – must be propped up by temporary supports until printing is complete. These supports must then be carefully removed manually.

To get around this, Dan Congreve at Stanford University in California and his colleagues created a 3D-printing system that involves focusing a red laser at a particular point in a pool of resin. The resin is impregnated with particles 80 nanometres wide that convert red light into blue once the light hits a certain energy threshold, which only occurs at the point where the red laser is precisely focused.

When this happens, the surrounding resin reacts to the blue light, hardening. This means that individual points within the material can be fixed without curing the resin along the entire beam of light.

This flexibility removes the need to print layer by layer and paves the way for more advanced printing. Congreve says that one or more lasers could rotate around a pool of resin and print an object in any order as it stays suspended in the thick material. The finished product is simply removed from the remaining liquid resin and rinsed. Overhanging areas and delicate designs that would be difficult using existing 3D printers can be easily printed.

“Because our resin is self-supporting during the printing process, we don’t need to print any supports, making post-processing of the parts much simpler,” he says. “Because we aren’t confined to this layer-by-layer process, we can print structures such as overhangs which are traditionally challenging. This is a brand-new technology, and we are just starting to scratch the surface of what it’s capable of.”

Journal reference: Nature, DOI: 10.1038/s41586-022-04485-8