Flat screen TVs that incorporate quantum dots are now commercially available, but it has been more difficult to create arrays of their elongated cousins, quantum rods, for commercial devices. Quantum rods can control both the polarization and color of light, to generate 3D images for virtual reality devices.
Using scaffolds made of folded DNA, MIT engineers have come up with a new way to precisely assemble arrays of quantum rods. By depositing quantum rods onto a DNA scaffold in a highly controlled way, the researchers can regulate their orientation, which is a key factor in determining the polarization of light emitted by the array. This makes it easier to add depth and dimensionality to a virtual scene.
"One of the challenges with quantum rods is: How do you align them all at the nanoscale so they're all pointing in the same direction?" says Mark Bathe, an MIT professor of biological engineering and the senior author of the new study. "When they're all pointing in the same direction on a 2D surface, then they all have the same properties of how they interact with light and control its polarization."
MIT postdocs Chi Chen and Xin Luo are the lead authors of the paper, which appears in Science Advances. Robert Macfarlane, an associate professor of materials science and engineering; Alexander Kaplan PhD '23; and Moungi Bawendi, the Lester Wolfe Professor of Chemistry, are also authors of the study.
Nanoscale structures
Over the past 15 years, Bathe and others have led in the design and fabrication of nanoscale structures made of DNA, also known as DNA origami. DNA, a highly stable and programmable molecule, is an ideal building material for tiny structures that could be used for a variety of applications, including delivering drugs, acting as biosensors, or forming scaffolds for light-harvesting materials.
Bathe's lab has developed computational methods that allow researchers to simply enter a target nanoscale shape they want to create, and the program will calculate the sequences of DNA that will self-assemble into the right shape. They also developed scalable fabrication methods that incorporate quantum dots into these DNA-based materials.
In a 2022 paper, Bathe and Chen showed that they could use DNA to scaffold quantum dots in precise positions using scalable biological fabrication. Building on that work, they teamed up with Macfarlane's lab to tackle the challenge of arranging quantum rods into 2D arrays, which is more difficult because the rods need to be aligned in the same direction.
Existing approaches that create aligned arrays of quantum rods using mechanical rubbing with a fabric or an electric field to sweep the rods into one direction have had only limited success. This is because high-efficiency light-emission requires the rods to be kept at least 10 nanometers from each other, so that they won't "quench," or suppress, their neighbors' light-emitting activity.
To achieve that, the researchers devised a way to attach quantum rods to diamond-shaped DNA origami structures, which can be built at the right size to maintain that distance. These DNA structures are then attached to a surface, where they fit together like puzzle pieces.
"The quantum rods sit on the origami in the same direction, so now you have patterned all these quantum rods through self-assembly on 2D surfaces, and you can do that over the micron scale needed for different applications like microLEDs," Bathe says. "You can orient them in specific directions that are controllable and keep them well-separated because the origam
is are packed and naturally fit together, as puzzle pieces would."
Assembling the puzzle
As the first step in getting this approach to work, the researchers had to come up with a way to attach DNA strands to the quantum rods. To do that, Chen developed a process that involves emulsifying DNA into a mixture with the quantum rods, then rapidly dehydrating the mixture, which allows the DNA molecules to form a dense layer on the surface of the rods.
This process takes only a few minutes, much faster than any existing method for attaching DNA to nanoscale particles, which may be key to enabling commercial applications.
"The unique aspect of this method lies in its near-universal applicability to any water-loving ligand with affinity to the nanoparticle surface, allowing them to be instantly pushed onto the surface of the nanoscale particles. By harnessing this method, we achieved a significant reduction in manufacturing time from several days to just a few minutes," Chen says.
These DNA strands then act like Velcro, helping the quantum rods stick to a DNA origami template, which forms a thin film that coats a silicate surface. This thin film of DNA is first formed via self-assembly by joining neighboring DNA templates together via overhanging strands of DNA along their edges.
The researchers now hope to create wafer-scale surfaces with etched patterns, which could allow them to scale their design to device-scale arrangements of quantum rods for numerous applications, beyond only microLEDs or augmented reality/virtual reality.
"The method that we describe in this paper is great because it provides good spatial and orientational control of how the quantum rods are positioned. The next steps are going to be making arrays that are more hierarchical, with programmed structure at many different length scales. The ability to control the sizes, shapes, and placement of these quantum rod arrays is a gateway to all sorts of different electronics applications," Macfarlane says.
"DNA is particularly attractive as a manufacturing material because it can be biologically produced, which is both scalable and sustainable, in line with the emerging U.S. bioeconomy. Translating this work toward commercial devices by solving several remaining bottlenecks, including switching to environmentally safe quantum rods, is what we're focused on next," Bathe adds.
The research was funded by the Office of Naval Research, the National Science Foundation, the Army Research Office, the Department of Energy, and the National Institute of Environmental Health Sciences.
Research Report:"Ultrafast dense DNA functionalization of quantum dots and rods for scalable 2D array fabrication with nanoscale precision"
Artificial Intelligence Analysis
Defense Industry Analyst:
A defense industry analyst may find this article relevant because it discusses a new technology that could be utilized in virtual reality devices. This could have broad implications for the defense sector as it could lead to the development of new products and services that are used in military operations. The primary audience for this type of analyst is military personnel, defense contractors, and other government entities.
Stock Market Analyst:
A stock market analyst may find this article relevant as it discusses a new technology that could potentially lead to the development of new products and services that could be sold to consumers and businesses. This could lead to an increase in stock value for companies that are involved in the development and distribution of these products. The primary audience for this type of analyst is investors, shareholders, and other stakeholders.
General Industry Analyst:
A general industry analyst may find this article relevant as it discusses a new technology that could lead to the development of products and services that could benefit the industry as a whole. This could open up new avenues of innovation and growth for the sector. The primary audience for this type of analyst is policymakers, business leaders, and industry experts.
Analyst Summary
: MIT engineers have developed a new method of assembling arrays of quantum rods that could potentially be used in TVs and virtual reality devices. This new technology could open up new avenues of innovation and growth for the defense, stock market, and general industry sectors. The process involves depositing quantum rods onto a DNA scaffold in a highly controlled way in order to regulate their orientation, which is a key factor in determining the polarization of light emitted by the array. This makes it easier to add depth and dimensionality to a virtual scene. Over the past 25 years, the space and defense industry has seen a number of significant developments, such as the emergence of new technologies and the development of products and services that are used in military operations. The new technology discussed in this article could potentially have a major impact on the defense industry, as well as the stock market and general industry sectors. Investigative
Question:
- 1. What potential applications could this new technology have for the defense industry?
- 2. How could this new technology be used to create more efficient and cost-effective products and services?
- 3.
What are the potential implications of this new technology for the stock market? 4. How could this new technology be used to improve virtual reality devices?
5. What potential risks are associated with this new technology?
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