3D printing of nanoscale glass structures without sintering

June 15, 2023

(Nanowerk News) A new process developed at the Karlsruhe Institute of Technology (KIT) makes it possible to print nanometer-scale quartz glass structures directly onto semiconductor chips. Hybrid organic-inorganic polymer resin is used as a raw material for silicon dioxide 3D printing. Since the process works without sintering, the temperature required is much lower. Simultaneously, increased resolution enables visible light nanophotonics.

The researchers report in Science (“Sinterless low temperature route to nanoscale 3D printed optical grade glass”). The new low-temperature process makes it possible to fabricate a wide variety of nanoscale quartz glass structures. (Image: Dr. Jens Bauer, KIT)

Printing micro- and nanometer-scale structures of quartz glass from pure silicon dioxide opens up many new applications in optical, photonics and semiconductor technologies. So far, the process has been based on conventional sintering. The temperature required for sintering silicon dioxide nanoparticles is above 1100°C, which is too hot for direct deposition onto semiconductor chips. A team led by Dr. Jens Bauer of the Institute of Nanotechnology (INT) KIT has now developed a new process for producing transparent quartz glass with high resolution and excellent mechanical properties at much lower temperatures.

Hybrid Organic-inorganic Polymer Resin as Raw Material

Bauer, who heads the Emmy Noether Junior Research Group “Nanoarchitected Metamaterials” at KIT, and colleagues from the University of California, Irvine and Edwards Lifesciences company in Irvine presented the process in Science. They use a hybrid organic-inorganic polymer resin as raw material. This liquid resin is composed of so-called polyhedral oligomeric silsesquioxane (POSS) molecules, which are small cage-like silicon dioxide molecules equipped with organic functional groups.

After linking the materials through 3D printing to form 3D nanostructures, they are heated to 650°C in air to remove the organic components. At the same time, the inorganic POSS cage fuses and forms a quartz glass microstructure or nanostructure. The temperature required for this purpose is only half of the temperature required for processes based on sintering of nanoparticles.

Structure Remains Stable Even Under Challenging Chemical and Thermal Conditions

“The lower temperatures allow free-form printing of optically robust glass structures with the resolution required for visible-light nanophotonics, directly on semiconductor chips,” explains Bauer. In addition to excellent optical qualities, the resulting quartz glass has excellent mechanical properties and can be processed easily.

Researchers from Karlsruhe and Irvine used POSS resin to print a variety of nanostructures, including freestanding photonic crystals, 97 nm-wide beams, parabolic microlenses, and multilens microobjectives with nanostructured elements. “Our process results in a structure that remains stable even under harsh chemical or thermal conditions,” says Bauer.

“The INT Group led by Jens Bauer is associated with the 3DMM2O Excellence Cluster,” said Professor Oliver Kraft, KIT Vice President of Research. “Research results now published in Science are just one example of how early-stage researchers are being successfully supported in clusters.” 3D Matter Made to Order, or 3DMM2O for short, is a Cluster of Excellence jointly by KIT and Heidelberg University. It pursues a highly interdisciplinary approach by combining natural sciences and engineering. It aims to elevate 3D additive manufacturing to the next level – from the molecular level to the macroscopic dimensions.

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