While additive manufacturing (AM), commonly known as 3D printing, is enabling engineers and scientists to build parts in configurations and designs never before possible, the impact of the technology has been limited by layer-based printing methods, which can take up to hours or days to build three-dimensional parts, depending on their complexity.
A new process, called volumetric 3D printing, uses laser-generated, hologramlike 3D images flashed into photosensitive resin to build 3D parts in one step. The process works by overlapping three laser beams that define an object's geometry from three different directions, creating a 3D image suspended in the vat of resin. The laser light, which is at a higher intensity where the beams intersect, is kept on for about 10 seconds — enough time to cure the part. The excess resin is drained out of the vat, leaving a fully formed 3D part. The approach results in parts built many times faster than other polymer-based methods and most, if not all, commercial AM methods used today. The process offers low cost, flexibility, speed, and geometric versatility.
Most 3D printing and additive manufacturing technologies consist of either a one-dimensional or two-dimensional unit operation. While conventional 3D printing has difficulty with spanning structures that might sag without support, volumetric printing has no such constraints; many curved surfaces can be produced without layering artifacts. Because all features within the parts are formed at the same time, there are no surface issues.
Volumetric printing could be made even faster with a higher-power light source. Extra-soft materials such as hydrogels could be wholly fabricated; these would otherwise be damaged or destroyed by fluid motion. The process also is the only additive manufacturing technique that works better in zero gravity, expanding the possibility of space-based production.
The technique does have limitations; for example, because each beam propagates through space without changing, there are restrictions on part resolution and on the kinds of geometries that can be formed. Extremely complex structures would require multiple intersecting laser beams, and would limit the process. Additional polymer chemistry and engineering also would be needed to improve the resin properties and fine-tune them to make better structures.