Making 3D nanosuperconductors with DNA

UPTON, NY – Three-dimensional (3-D) nanostructured materials – those with complex shapes on a dimensional scale of billionths of a meter – that can conduct electricity without resistance could be used in a range of quantum devices. For example, such 3-D superconducting nanostructures could find application in signal amplifiers to improve the speed and accuracy of quantum computers and ultra-sensitive magnetic field sensors for medical imaging and subsurface geological mapping. However, traditional fabrication tools such as lithography have been limited to 1-D and 2-D nanostructures such as superconducting wires and thin films.

Now, scientists from the Brookhaven National Laboratory of the US Department of Energy (DOE), Columbia University, and Bar-Ilan University in Israel have developed a platform to build 3-D superconducting nanostructures with a prescribed organization. As reported in the November 10 issue of Nature Communications, this platform is based on the self-assembly of DNA into desired 3-D forms at the nanoscale. In DNA self-assembly, a single long strand of DNA is folded from shorter complementary “staple” strands into specific positions – similar to origami, the Japanese art of folding paper.

“Because of its structural programmability, DNA can provide an assembly platform for building engineered nanostructures,” said co-correspondent author Oleg Gang, leader of the Soft and Bio Nanomaterials Group at Brookhaven Lab’s Center for Functional Nanomaterials. (CFN) and professor of engineering chemistry and applied physics and materials science at Columbia Engineering. “However, the fragility of DNA makes it seem unsuitable for fabrication of functional devices and nanofabrication that requires inorganic materials. In this study, we showed how DNA can serve as a scaffold for building 3-D nanoscale architectures that they can be completely “converted” into inorganic materials such as superconductors. “

To make the scaffold, scientists from Brookhaven and Columbia Engineering first designed octahedral-shaped DNA origami “frames”. Aaron Michelson, Gang’s graduate student, applied a programmable DNA strategy so that these frames assemble into desired lattices. Then, he used a chemical technique to coat the DNA lattices with silicon dioxide (silica), solidifying the originally soft constructions, which required a liquid environment to preserve their structure. The team adapted the fabrication process so that the structures were faithful to their design, as confirmed by imaging at the CFN Electron Microscopy Facility and small-angle X-ray scattering at the scattering beam line of complex materials from the Brookhaven National II synchrotron light source (NSLS-II). These experiments showed that structural integrity was preserved after coating the DNA lattices.

“In its original form, DNA is completely unusable for processing with conventional nanotechnology methods,” said Gang. “But once we coat the DNA with silica, we have a mechanically robust 3-D architecture on which we can deposit inorganic materials using these methods. This is analogous to traditional nanofabrication, in which precious materials are deposited on flat substrates, typically silicon. to add functionality. “

The team shipped the silica-coated DNA lattices from the CFN to the Bar-Ilan Institute of Superconductivity, led by Yosi Yeshurun. Gang and Yeshurun ​​met a couple of years ago when Gang gave a seminar on his research on DNA assembly. Yeshurun ​​- who for the past decade has been studying the properties of superconductivity at the nanoscale – thought that Gang’s DNA-based approach could provide a solution to a problem he was trying to solve: how can we fabricate superconducting structures at the nanoscale in three dimensions?

“Previously, making 3-D nanosuperconductors involved a very elaborate and difficult process using conventional fabrication techniques,” said Yeshurun, corresponding co-author. “Here, we have found a relatively simple way using Oleg’s DNA structures.”

At the Institute of Superconductivity, Yeshurun ​​graduate student Lior Shani evaporated a low-temperature superconductor (niobium) onto a silicon chip containing a small sample of the lattices. The evaporation rate and temperature of the silicon substrate had to be carefully controlled so that the niobium coated the sample but did not penetrate completely. If this happens, a short circuit may occur between the electrodes used for electronic transport measurements.

“We cut a special channel in the substrate to ensure that the current only passed through the sample itself,” explained Yeshurun.

The measurements revealed a 3-D matrix of Josephson junctions, or thin non-superconducting barriers through which superconducting current tunnels. Josephson junction arrays are critical for exploiting quantum phenomena in practical technologies, such as superconducting quantum interference devices for magnetic field detection. In 3-D, multiple junctions can be grouped into a small volume, increasing the power of the device.

“DNA origami has produced beautiful and richly decorated three-dimensional nanoscale structures for nearly 15 years, but DNA itself is not necessarily a useful functional material,” said Evan Runnerstrom, program manager for materials design at the US. Army Combat Capabilities Development Command Army Research Laboratory of the US Army Research Office, which partly funded the work. “What Prof. Gang showed here is that it is possible to exploit DNA origami as a model to create useful three-dimensional nanostructures of functional materials, such as superconducting niobium. This ability to arbitrarily design and fabricate complex three-dimensional structured functional materials from the bottom to top will accelerate the military’s modernization efforts in areas such as sensing, optics and quantum computing. “

“We have demonstrated a path for how complex DNA organizations can be used to create highly nanostructured 3-D superconducting materials,” said Gang. “This material conversion path gives us the ability to create a variety of systems with interesting properties – not only superconductivity but also other electronic, mechanical, optical and catalytic properties. We can imagine it as a” molecular lithography “, where the power of DNA programmability is transferred to the inorganic 3-D nanofabrication. “

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This research was supported by the US Department of Defense, Army Research Office; DOE Office of Science; Israeli Ministry of Science and Technology; and Israel Science Foundation. Both CFN and NSLS-II are facilities for users of the DOE Office of Science. Some imaging studies were performed at the City University of New York Advanced Science Research Center’s Imaging Facility.

Brookhaven National Laboratory is supported by the US Department of Energy’s Office of Science. The Office of Science is the largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https: //power.gov /science.

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Columbia Engineering, based in New York City, is one of the best engineering schools in the United States and one of the oldest in the nation. Also known as The Fu Foundation School of Engineering and Applied Science, the School expands knowledge and advances technology through the pioneering research of its more than 220 faculty members, while educating undergraduate and graduate students in a collaborative environment to become informed leaders from a solid foundation in engineering. The School’s faculty are at the heart of the University’s interdisciplinary research, contributing to the Data Science Institute, the Earth Institute, the Zuckerman Mind Brain Behavior Institute, the Precision Medicine Initiative, and the Columbia Nano Initiative. Guided by its strategic vision, “Columbia Engineering for Humanity”, the School aims to translate ideas into innovations that promote sustainable, healthy, safe, connected and creative humanity.