Valeria Tohver Milam leads the Macromolecular Materials at Biotic and Abiotic Interfaces research initiative for the Institute for Materials (IMat) and the Parker H. Petit Institute for Bioengineering and Biosciences at Georgia Tech. In this role, she is working to build an inclusive and active community across and beyond Georgia Tech to identify emerging research directions in macromolecular materials for biological and nonbiological applications. Milam is an associate professor in Materials Science and Engineering and a program faculty member of the Bioengineering graduate program at Georgia Tech.

In this brief Q&A, Milam discusses her research focus, how it relates to materials research, and the impact of this initiative.

What is your field of expertise and at what point in your life did you first become interested in this area?

My field of expertise lies in bio-inspired materials science and engineering. Natural macromolecular components of biological systems such as cell receptors or antibodies rely on recognition-based binding events to, for example, allow a cell to take up particular nutrients or to neutralize a specific pathogen threat. Inspired by nature’s capabilities, my group’s research strives to identify and study synthetic macromolecular materials with bio-inspired compositions and self-folded structures. I first became interested in using DNA for its recognition capabilities during my postdoc at the University of Pennsylvania. For the first several years as an assistant professor at Georgia Tech, my group used DNA duplexes as a temporary glue between particle surfaces. Our more recent efforts focus on finding oligonucleotides to function as ligands or capture agents for a specific biological or nonbiological target.

What questions or challenges sparked your current materials research?

Polymers or macromolecules hold a lot of promise as a class of materials for various applications. Synthetic macromolecules, however, pose a lot of synthesis and post-use challenges that can hinder the discovery and practical use of novel macromolecular chemistries. Natural polymers such as oligonucleotides and proteins, on the other hand, have their own elegant synthesis and degradation pathways. To promote discovery of novel macromolecular materials, my group uses nature’s reagents and building blocks to synthesize numerous artificial biopolymer candidates. Since we do not start with any sequence design rules, we rely on maximizing the composition diversity of these artificial biopolymers. We then test all candidates collectively to efficiently choose ones with the desired functionality.

Why is your initiative important to the development of Georgia Tech’s Materials research strategy?

One of the challenges to discovering macromolecular systems that are both novel and practical is the lack of design rules. For example, how does one choose the right number and composition of repeat units for a macromolecule that binds to a particular material surface or to a particular biological target. If you can take advantage of nature’s building blocks and enzymes, then you can explore a wide chemical combinatorial space without having to follow any prerequisite design rules. Better yet, you can then use your initial findings to come up with design rules to explore additional, possibly better macromolecular candidates. This approach to macromolecule discovery is inherently interdisciplinary since one must combine or adapt techniques and approaches developed by biologists, polymer scientists, and materials engineers. Thus, Georgia Tech is a great place to foster this interdisciplinary strategy to research.

What are the broader global and social benefits of the research you and your team conduct?

In addition to training members of our future workforce with interdisciplinary skill sets, we want to carve out a pathway to designing, synthesizing and using environmentally friendly, multiuse macromolecules with commercial promise.

What are your plans for engaging a wider GT faculty pool with IMat research?

Currently, we are primarily in the brainstorming stage. To this end, I am engaging with science and engineering faculty at GT as well as Emory. As cross-disciplinary ideas start to brew, we will work towards multi-PI funding opportunities that engage the broader GT faculty and community.

Researchers at the Georgia Institute of Technology have developed a light-based means of printing nano-sized metal structures that is significantly faster and cheaper than any technology currently available. It is a scalable solution that could transform a scientific field long reliant on technologies that are prohibitively expensive and slow. The breakthrough has the potential to bring new technologies out of labs and into the world.

Technological advances in many fields rely on the ability to print metallic structures that are nano-sized — a scale hundreds of times smaller than the width of a human hair. Sourabh Saha, assistant professor in the George W. Woodruff School of Mechanical Engineering, and Jungho Choi, a Ph.D. student in Saha’s lab, developed a technique for printing metal nanostructures that is 480 times faster and 35 times cheaper than the current conventional method.

Their research was published in the journal Advanced Materials.

Printing metal on the nanoscale — a technique known as nanopatterning — allows for the creation of unique structures with interesting functions. It is crucial for the development of many technologies, including electronic devices, solar energy conversion, sensors, and other systems.

It is generally believed that high-intensity light sources are required for nanoscale printing. But this type of tool, known as a femtosecond laser, can cost up to half a million dollars and is too expensive for most research labs and small businesses.

“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,” Saha said.

“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.”

They searched for a low-cost, low-intensity light that could be focused in a way similar to femtosecond lasers, and chose superluminescent light emitting diodes (SLEDs) for their commercial availability. SLEDs emit light that is a billion times less intense than that of femtosecond lasers.

Saha and Choi set out to create an original projection-style printing technology, designing a system that converts digital images into optical images and displays them on a glass surface. The system operates like digital projectors but produces images that are more sharply focused. They leveraged the unique properties of the superluminescent light to generate sharply focused images with minimal defects.

They then developed a clear ink solution made up of metal salt and added other chemicals to make sure the liquid could absorb light. When light from their projection system hit the solution, it caused a chemical reaction that converted the salt solution into metal. The metal nanoparticles stuck to the surface of the glass, and the agglomeration of the metal particles creates the nanostructures. Because it is a projection type of printing, it can print an entire structure in one go, rather than point by point — making it much faster.

After testing the technique, they found that projection-style nanoscale printing is possible even with low-intensity light, but only if the images are sharply focused. Saha and Choi believe that researchers can readily replicate their work using commercially available hardware. Unlike a pricey femtosecond laser, the type of SLED that Saha and Choi used in their printer costs about $3,000.

“At present, only top universities have access to these expensive technologies, and even then, they are located in shared facilities and are not always available,” Choi said. “We want to democratize the capability of nanoscale 3D printing, and we hope our research opens the door for greater access to this type of process at a low cost.”

The researchers say their technique will be particularly useful for people working in the fields of electronics, optics, and plasmonics, which all require a variety of complex metallic nanostructures.

“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,” Saha said.

“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.”

Citation: J. Choi, S. K. Saha, Scalable Printing of Metal Nanostructures through Superluminescent Light Projection. Adv. Mater. 2024, 36, 2308112.

DOI: https://doi.org/10.1002/adma.202308112

Funding: Funding includes grants from the G.W.W. School of Mechanical Engineering and the EVPR’s office at the Georgia Institute of Technology. Imaging was performed at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (ECCS-2025462).