23 Jan 2024
New technique employs superluminescent LEDs rather than femtosecond laser sources.
Methods based on 3D printing have to contend with the complexities of the melting and solidification processes taking place, the study of which required NIST researchers to utilize two different particle accelerator facilities to understand the chain of events.
Metal deposition techniques have also tended to be relatively slow, while faster methods based on photoreduction of metal ions into nanoparticles need expensive high-intensity femtosecond laser sources to achieve the high resolutions needed.
A project at Georgia Institute of Technology has now developed an alternative processing method that could offer a route to faster and cheaper creation and printing of metallic nanoparticles, and published the work in Advanced Materials.
"As a scientific community, we don’t have the ability to make enough of these nanomaterials quickly and affordably, and that is why promising technologies often stay limited to the lab and don't get translated into real-world applications," said Georgia Tech's Sourabh Saha.
"The question we wanted to answer is, do we really need a high-intensity femtosecond laser to print on the nanoscale? Our hypothesis was that we don't need that light source to get the type of printing we want."
Georgia Tech investigated whether superluminescent LEDs (SLEDs) might be the answer, and whether they could overcome the cost versus resolution tradeoff inherent in the use of more expensive and complex laser sources.
SLEDs have been employed in certain specific applications including OCT and optical sensing devices for some years, designed to combine the broadband optical spectra characteristics of LEDs with the diffraction-limited and spatially coherent emission of an edge-emitting laser diodes.
Leverage nanotechnology for societal benefit
The project built its SLED source into a novel metal printing platform, designed to convert digital images into optical images and display them on a glass surface, to test whether the properties of superluminescent light could generate sharply focused images with minimal defects.
This system uses a clear ink solution containing a silver salt and additional light-absorbing ingredients. When light from the SLED hits this ink it initiates a chemical reaction converting the salt solution into metal nanoparticles, which then stick to the surface of the glass and are agglomerated into desired nanostructures.
Trials of the superluminescent light projection (SLP) technique showed that it was able to rapidly print sub-diffraction nanostructures down to 210 nanometers and at periods as small as 300 nanometers, with light that is "a billion times less intense than femtosecond lasers," according to the project's paper.
Georgia Tech created arbitrarily complex 2D nanostructured silver patterns over areas of 30 × 80 microns in 500-millisecond time scales, said the team, which estimates that its method is up to 480 times faster and 35 times less expensive than printing with femtosecond lasers. This could make it attractive as a manufacturing route for a variety of complex metallic nanostructures useful in electronics, optics, and plasmonics.
"I think the metrics of cost and speed have been greatly undervalued in the scientific community that works on fabrication and manufacturing of tiny structures," commented Sourabh Saha.
"In the real world, these metrics are important when it comes to translating discoveries from the lab to industry. Only when we have manufacturing techniques that take these metrics into account will we be able to fully leverage nanotechnology for societal benefit."