Joining forces: ultra-fast 3D micro-printing with two lasers

In light sheet 3D printing, red and blue laser light is used to print objects with precision and speed at the micrometer scale (Photo: Vincent Hahn, KIT)

Accurate, fast and inexpensive printing of plastic objects is the goal of many 3D printing processes. However, speed and high resolution remain a technological challenge. A research team from Karlsruhe Institute of Technology (KIT), University of Heidelberg and Queensland University of Technology (QUT) have come a long way towards achieving this goal. It has developed a laser printing process capable of printing micrometric-sized parts in the blink of an eye. The international team published the work in Nature Photonics. (DOI: 10.1038/s41566-022-01081-0)

Stereolithography 3D printing is currently one of the most popular additive manufacturing processes for plastics, both for private and industrial applications. In stereolithography, the layers of a 3D object are projected one by one into a container filled with resin. The resin is cured by UV light. However, prior stereolithography methods are slow and have too low a resolution. Lightsheet 3D printing, used by KIT researchers, is a fast, high-resolution alternative.

3D printing with two colors in two steps

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

Micrometric structures in the blink of an eye

To take advantage of this new resin, the researchers built a special 3D printer. In this printer, blue laser diodes are used to project images into the liquid resin using a high resolution screen with a high frame rate. The red laser is formed into a thin “sheet of light” beam and passes through the blue beam vertically into the resin. Thanks to this arrangement, the team was able to 3D print micrometer-sized parts in a few hundred milliseconds, that is, in the blink of an eye. However, we must not stop there: “With more sensitive resins, we could even use LEDs instead of lasers in our 3D printer”, explains Professor Martin Wegener of the APH. “Ultimately, we want to print centimeter-sized 3D structures, while maintaining micrometer resolution and high print speeds.”

The publication was produced as part of the joint center of excellence “3D Matter Made to Order” of KIT and the University of Heidelberg. Junior Professor Dr Eva Blasco, group leader at the Institute of Organic Chemistry and the Institute for Molecular Systems and Advanced Materials Engineering, was involved on behalf of the University of Heidelberg.

Original edition:

V. Hahn, P. Rietz, F. Hermann, P. Müller, C. Barner-Kowollik, T. Schlöder, W. Wenzel, E. Blasco, and M. Wegener: Three-dimensional light-sheet microprinting via two-color absorption in two times. Nature Photonics, 2022. DOI: 10.1038/s41566-022-01081-0

https://www.nature.com/articles/s41566-022-01081-0

Center of Excellence “3D Matter Made to Order”

In the “3D Matter Made to Order” Cluster of Excellence, scientists from the Karlsruhe Institute of Technology (KIT) and the University of Heidelberg conduct interdisciplinary research into innovative technologies and materials for digitally additive manufacturing scalable to improve the accuracy, speed and performance of 3D printing. The objective of the work is to fully digitize the 3D manufacturing and processing of materials from the molecule to the microstructure. In addition to being funded as a Cluster of Excellence within the Excellence Strategy Competition of the German Federal and State Governments, “3D Matter Made to Order” is funded by the Carl Zeiss Foundation.

Robert M. Larson