In light-sheet 3D printing, blue light is projected into a container filled with a liquid resin. The blue light pre-activates the resin. In a second stage, a red laser beam provides the additional energy needed to cure the resin. However, 3D printing can only print quickly resins that quickly return from their pre-activated state to their original state. Only then can the next layer be printed. Consequently, the return time dictates the waiting time between two successive layers and thus the printing speed. "For the resin we used, the return time was less than 100 microseconds, which allows for high printing speeds," says first author Vincent Hahn from KIT's Institute of Applied Physics (APH).