Micro 3D printing

Scientists develop new 2PP 3D printing capabilities

Including the production of embedded microfluidic chips as well as tungsten and platinum microstructures with sub-micron resolution thanks to UpNano's NanoOne printer

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In a series of high-profile publications, scientists from the NeptunLab at the University of Freiburg, in Germany, have pushed the potential of 2-Photon Polymerisation (2PP) 3D printing beyond existing limits. Having demonstrated their ability to print complex platinum 3D microstructures with an astonishing sub-micron resolution in 2021, this year, the team succeeded in producing similar structures made of tungsten as well as embedded microfluidic chips with single μm resolution at unprecedented speed. In all three papers, the leading scientist Manuel Luitz used a NanoOne 2PP 3D printer from UpNano GmbH. In the meantime, having successfully recruited Luitz for UpNano, the company will continue to develop the technology.

Two major limitations for a wider application of high-resolution 2PP 3D printing are the printing speed and the available materials for the necessary photopolymerization. Now, Manuel Luitz, during his time at the Laboratory of Process Technology (NeptunLab) at the University of Freiburg, has significantly reduced these limitations in a work spanning several years. The results of this work have been published in three successive papers, the latest of which now appears in Advanced Materials Technology.

Scientists develop new 2PP 3D printing capabilities including the production of novel microstructures thanks to UpNano's NanoOne printer.
Single-micron embedded microfluidic chips using the NanoOne 2PP 3D printer.

Chip channel cleaning

In this latest development, Luitz and colleagues have defined a development scheme for single-micron embedded microfluidic chips using the NanoOne printer. Using the printer’s power, the team was able to print a chip that could be connected via a chip-to-world interface to a pressure-driven pump. “This is a breakthrough in microfluidic chip manufacturing because one of the major obstacles to high-resolution 3D printing of microfluidic chips is washing the embedded channels free of uncured material. This made it possible to produce meander chips with channel lengths of up to 20cm, droplet generator chips, and a cell sorting chip based on deterministic lateral displacement with column diameters of 30 μm and column spacing of 4 μm,” said Manuel Luitz. “Microfluidic chips with centimeter dimensions and μm resolution are thus printable in a reasonable time frame of less than 12 hours using the NanoOne.”

Scientists develop new 2PP 3D printing capabilities including the production of novel microstructures thanks to UpNano's NanoOne printer.
Microstructures made of tungsten (carbide) for the first time with a NanoOne 2PP 3D-printer. The printed polymer (left) was debounded by Manuel Luitz et al. (center) and reduced to tungsten carbide (right).

Tungsten

Just before that, Luitz used the NanoOne printer for a very different purpose – one that would significantly expand the range of materials that can be 3D printed with 2PP. He ‘tamed’ tungsten and tungsten carbide for this high-resolution additive manufacturing process. This was not an easy task as both materials are known for their extreme hardness (Mohs scale 9.0) and heat resistance (melting point > 3,400 degrees Celsius), making them difficult to work with. However, high-resolution objects made from tungsten and its carbides are in high demand for applications such as emitter tips, probes, microtools, as well as metamaterials or catalysis.

“Using a NanoOne printer, we were able to design a manufacturing process based on an organic-inorganic photoresin containing tungsten ions. The polymer parts are then thermally debound and reduced, leaving tungsten parts with a final resolution of 2 μm and tungsten carbide parts with a resolution of 7 μm,” said Manuel Luitz.

Scientists develop new 2PP 3D printing capabilities including the production of novel microstructures thanks to UpNano's NanoOne printer.
Novel platinum microstructures produced with a NanoOne 2PP 3D-printer.
Platinum woodpile structure (left) and shown magnified (middle) as well as freestanding platinum nanopillars (right) were printed bei Manuel Luitz et al.

Platinum

Luitz’s success at the NeptunLab at “Institut für Mikrosystemtechnik – IMTEK” in ‘taming’ tungsten for 2PP 3D printing did not come out of the blue. The team had previously achieved a similar result with platinum, where they were able to produce free-standing nanopillars as well as complex 3D platinum microstructures with a resolution of 300 nm. Such small structures will find use in various engineering applications, including metamaterials and catalysis, where the large surface area and physicochemical properties of platinum are highly desirable.

“We are very excited to have Manuel join our growing UpNano team,” said Denise Hirner, COO and Co-founder of UpNano, “As a senior member of our Applications and Materials Development team, he will continue to push the boundaries of 2PP 3D printing.”

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Composites AM 2024

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Edward Wakefield

Edward is a freelance writer and additive manufacturing enthusiast looking to make AM more accessible and understandable.

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