As light passes through a patterned plate, it folds inside a transparent liquid into a three-dimensional pattern. Where the light is brighter, the resin hardens. After 7.5 seconds, a finished part is lifted out of the liquid — complete with cavities, channels, and tiny protrusions.
The secret lies in two parts. The first is a glass mask with a microscopic relief: it refracts light so that the desired pattern of bright and dark regions emerges inside the resin. The second is the resin itself: its composition is tuned so that light penetrates deeply, yet enough energy accumulates at each point to solidify it.
Currently, the speed is limited not by the mask itself, but by how quickly the resin hardens and how the light falls. By improving these aspects, printing could become tens of times faster, and then tiny lenses, scaffolds for tissue growth, and other precision parts would become commonplace.
In a single flash of light, more than a million tiny features solidify in the resin — about as many grains of sand as fit in a thimble.