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The method, which produced structures with high resolution and ‘excellent’ mechanical properties, was developed by a team led by Dr Jens Bauer at the Karlsruhe Institute of Technology (KIT) in Germany, along with colleagues at the University of California, Irvine, and the Edwards Lifesciences company in Irvine.
Printing of micro- and nanometre-scale quartz glass structures from pure silicon dioxide “opens up many new applications in optics, photonics, and semiconductor technologies”, the researchers said, but processes have so far been based on conventional sintering. Temperatures required for sintering silicon dioxide nanoparticles are above 1,100°C, which is much too hot for direct deposition onto semiconducting chips.
In the new work, the team used a ‘hybrid’ organic-inorganic polymer resin as the feedstock material. The liquid resin consisted of polyhedral oligomeric silsesquioxane (POSS) molecules, which are small cage-like silicon dioxide molecules equipped with organic functional groups.
After cross-linking the material via 3D printing to form a 3D nanostructure, it was heated to 650°C in air to remove the organic components. At the same time, the inorganic POSS cages coalesced and formed continuous quartz glass microstructures or nanostructures. The required temperature is only half the temperature needed for processes based on sintering of nanoparticles, the researchers said.
“The lower temperature enables the free-form printing of robust, optical-grade glass structures with the resolution needed for visible-light nanophotonics, directly on semiconductor chips,” Dr Bauer said.
Both the optical quality and mechanical properties are “excellent”, a research announcement added, and the quartz glass can reportedly be processed easily.
The researchers used the POSS resin to print various nanostructures, including “photonic crystals of free-standing, 97nm wide beams, parabolic microlenses, and a multi-lens micro objective with nanostructured element”, according to the announcement.
“Our process produces structures that remain stable even under harsh chemical or thermal conditions,” Dr Bauer added.
The work was published in Science.
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