First Standardized Material Testing of 2PP 3D-Printed Parts

For the first time, mechanical properties of 2PP 3D-fabricated bulk specimens in the mm to cm range have been tested using established standardized methods. This breakthrough was made possible by combining the use of the fastest commercially available 2PP 3D-printer (NanoOne) with resins that can be processed at very high volumetric build rates, enabling upscaling. The test results, now published in "Advanced Materials", demonstrate the superior material quality of the UpPhoto and UpDraft resins compared to an acrylate resin (ETA/TTA). In addition, both materials are fully cured immediately after printing, eliminating the need for post-treatment. A multinational collaboration involving researchers from Technical University Vienna (TU Wien), California Institute of Technology (Caltech) and the RWTH Aachen University, along with materials experts from UpNano GmbH conducted the comprehensive study.

Two-photon polymerization (2PP) 3D-printing is a powerful, high-resolution technology for additive manufacturing. The latest generation of 2PP 3D-printers combines the achievable high-resolution with a high production speed (up to >450 mm3/h), enabling the manufacture of large structures up to several centimeters in size. This makes 2PP 3D-printing attractive for both industrial applications and large-scale production. As a result, standardized methods for the mechanical characterization of 2PP 3D-printed parts are becoming increasingly important. An international team has now succeeded for the first time in applying standard test methods to (macroscale) 2PP 3D-printed parts, e.g., 35 mm large ISO-standard test specimens, providing invaluable insight into their mechanical properties.

Commenting on this remarkable advance, Bernhard Küenburg, CEO of UpNano says: "Currently, there is no accepted standardized test method for micro- or nanoscale 2PP 3D-printed parts. But even if there were, the mechanical properties of a large-scale part could not simply be extrapolated from such small-scale samples. Therefore, the work of the TU Wien team and colleagues is a real breakthrough on the way to the industrial application of 2PP 3D-printing."

The team was able to test a wide range of mechanical properties of the 2PP 3D-printed material, including tensile, flexure and hardness, as well as creep and fracture behavior. The materials used were ETA/TTA – ethoxylated (20/3)-trimethylolpropane triacrylate (ETA) in combination with trimethylolpropane triacrylate (TTA) – and two commercially available materials from UpNano GmbH, UpPhoto and UpDraft. To achieve the production speed required for large samples, the team used 10x or 5x objectives mounted on a NanoOne printer from UpNano. This is currently the fastest commercially available 2PP 3D-printer on the market, capable of printing over 15 orders of magnitude with respect to print volume.

"One of the most remarkable results we obtained”, Markus Lunzer, Team Lead Materials and Application at UpNano and last author of the study explains, "was that of the three materials studied, only UpPhoto and UpDraft were suitable for upscaling. This was due to their wide processing window and overall well-balanced properties. ETA/TTA, on the other hand, was found to be unsuitable due to its small processing window, stress-induced microcracking and generally low toughness of the final product.”

In addition, UpPhoto's and UpDraft's 2PP 3D-printing had the advantage over other light-based 3D-printing processes of producing fully cured and therefore robust parts right after printing. No post-curing was required. This is a great advantage, especially for 3D-printing microfluidic devices, as it enables the production of complex internal microchannel structures.

In summary, the recent publication paves the way for the establishment of 2PP 3D-printing as a manufacturing method for volume production by establishing material testing methods that can meet ISO standards. The team shows what can be achieved when the fastest 2PP 3D-printer is used with advanced resins. The fact that both the printer and the resins are manufactured and sold by UpNano once again confirms the company's position as an innovation leader in the field.