An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.


  • Published
  • DAF T3

The Department of the Air Force’s Technology Transfer and Transition Office is proud to highlight the work of Dr. Richard A. Vaia, Chief Scientist for the Materials and Manufacturing Directorate of the Air Force Research Laboratory at Wright Patterson AFB, and team, including Drs. Kyoungweon Park and Clare Mahoney, for their achievements in the forefront of cutting-edge research in the field of nanomaterials. Proudly, we delve into this groundbreaking patent that has emerged from the team's research—“Selective reshaping of nanoparticles in three dimensional articles” that holds promise across various sectors.

The work of Dr. Vaia’s team spans diverse areas, from the chemistry and physics of nanomaterials to the development of multifunctional structures, coatings, inks, flexible electronics, optical devices, and autonomous concepts. More recent work has focused on solving some of the scale up problems so the advanced materials can be provided at quantity and cost for integration into a whole variety of applications.

The development of advanced materials, including those with noble metal nanoparticles, has been a key focus of scientific research and technological innovation. The intense light-matter interactions and large optical cross-section of metallic nanoparticles and their assemblies enable efficient focusing of optical fields at nanoscale. This unique capability is highly dependent on the shape and size of the nanoparticles enabling them to be a potential platform for a range of applications, including sensing, photo-detection, spectroscopy, and optical information processing. In order to realize the potential of these nanoparticles for practical use, it is crucial to develop scalable, reproducible, and cost-effective manufacturing processes that involve efficient synthesis with tunable structures, robust processing, and integration.

Reshaping Gold Nanorods for Spatially Multiplexed Plasmonic Effects:

Certain cutting-edge technologies, such as imaging taggants, colorimetric sensors, and bulk optical components, necessitate the multiplexing plasmonic effects. Various individual plasmonic units, composed of nanoparticles or discrete assemblies, are synthesized, surface-modified, and deposited on a substrate or dispersed in a film. Achieving spatial multiplexing of plasmonic effects in a film is challenging, requiring complex fabrication and assembly. The challenges have been addressed through a post-fabrication process that reshapes a stock plasmonic unit by combining features of photo-thermal processes with photo-chemistry at the gold nanorods (AuNR) surface which would afford substantial efficiency in constructing such pixelated and voxelated materials. The innovative process utilizes a low energy light sources to provide localized heating that drives redox processes of cetyltrimethylammonium bromide-stabilized AuNRs embedded in polyvinyl alcohol (PVA). This results in a controlled isovolumetric reduction of the surface-to-volume ratio of the NRs. The reshaping rate is over 100 times faster than the thermal annealing methods, occurring in seconds rather than days. The precise control of the reshaping is achieved by selectively varying key parameters such as bromide and oxygen content and results in tuning of the aspect ratio of AuNRs, enabling multi-color patterning and gradient plasmonic properties.

The Birth of the Patent:

The idea behind this patent emerged from the desire to create adaptable films with versatile plasmonic properties. AuNR-polymer composite film offer a unique blend of plasmonic properties, versatility, tunability, and ease of processing. The observation of the film's color alterations upon light exposure sparked systematic experiments, revealing that controlled chemical reactions during reshaping were responsible. The patent's post-fabrication process achieves remarkable reshaping speeds, preserves particle integrity, and enables the creation of intricate patterns and gradients.

Collaboration and Experimentation:

The development of this technology was a collaborative effort involving regular communication through weekly group meetings. While Dr. Park initially observed the phenomena, the group collectively investigated potential mechanisms, designing experiments based on their discussions. Results were shared and deliberated upon in subsequent meetings, gradually refining the idea. The collaborative effort, with contributions from various researchers, was crucial to the success of this innovative breakthrough.

Applications Across Diverse Sectors:

The technology's optically driven process offers promising routes to cost-effective, rapid manufacturing of materials with pixelated, voxelated, or gradient plasmonic properties. Potential applications span diverse sectors, including the military, civilian, and academia. The USAF might find applications in optical collection systems, pilot eyeglass displays, sensors, and even space materials. “You can't really decide in which application it's going to make a difference until you solve the problems of availability, processability, ability to manipulate manufacturing,” Dr. Vaia said. He continued, “You're in a chicken and egg predicament: if you don't push the technology forward far enough to a large enough scale, you can't adequately assess to know exactly where it's going to be used.”

The Importance of Experimentation and Curiosity:

As a diverse group of individuals involved, with constant communication, each brought different skills and perspectives, ultimately leading to a groundbreaking breakthrough in plasmonic material science. Experimentation played a vital role in the development process. Testing ideas, gathering feedback, and iterating on designs by Dr. Mahoney led to refinements and valuable lessons. Failure provided insights that contribute to the next steps of scientific discovery. Curiosity, it seems, is necessary for developing new ideas and the team’s projects thrived on that inquisitiveness. “I think it's a kind of interesting because everything starts with pure scientific, you know, curiosity,” Dr. Park noted. She added, “If you spend a lot of time in the lab, then you will find very interesting things daily... there is no specific motivation to, you know, invent this stuff; I think for myself it's mostly from my scientific curiosity... I think that's my motivation; keep doing the research.”