Scientists have always been looking for ways to improve our daily lives. One of their focus areas undoubtedly is materials engineering, where they are trying, among other tasks, to improve or develop new devices which can be used for harvesting energy. Superconductors are one group of such devices, which have zero electrical resistance and thus allow electrons to flow unimpeded. It also means that they do not lose energy or create heat, unlike many current means of electrical transmission. One of the biggest drawbacks of modern superconductors is that they either need extremely high or extremely low temperatures to function well, which is why the focus of sciences has been placed om the development of a superconductor that could be used widely at room temperature. This may ultimately lead to hyper-fast computers, shrink the size of electronic devices, allow high-speed trains to float on magnets and slash energy use, among other benefits.
One variant of a superconductors was first proposed more than 50 years ago by Stanford physicist William A. Little. Scientists have spent many years to try and make it work. However, even though the feasibility of his idea has been validated, there was one challenge which seemed impossible to overcome. This might have changed now.
Now (2022), scientists at the University of Virginia School of Medicine and collaborators have used DNA to solve a seemingly unsolvable problem to engineer materials, particularly superconductors, capable of revolutionising electronics.
They modified lattices of carbon nanotubes, which are tiny hollow cylinders of carbon measured in billionths of a metre. There was, however, a massive problem which had to be overcome for the nanotubes to function precisely and according to their intention: finding the right approach to controlling chemical reactions along the nanotubes.
The scientists found an answer in basic elements all living things are made of: the DNA. They used DNA, the genetic material that tells living cells how to operate, to control a chemical reaction finally enabling the successful construction of Little's superconductor. In other words, chemistry aided them in performing incredibly precise structural engineering which helped them direct the within the tubes at the level of individual molecules. As a result, they received a lattice of carbon nanotubes assembled as needed for Little's room-temperature superconductor.
With the help of DNA screening they made out a sequence, C3GC7GC3, whose reaction with an (8,3) enantiomer resulted in minimum disorder-induced intensities of the molecule vibrations and photoluminescence Stokes shift, the shift in the wavelength or frequency of the absorption and emission spectra, suggesting ordered defect array formation. Single-particle cryo–electron microscopy proved that the C3GC7GC3 functionalized had an ordered helical structure with a 6.5 angstroms periodicity. Reaction mechanism analysis showed that the helical periodicity came from an array of G-modified carbon-carbon bonds separated by a fixed distance along an armchair helical line.
The lattice they built has so far not been tested for superconductivity, but it offers proof of principle and has great potential for the future. The technique the scientists used, cryo-EM, has become the main technique in biology for determining the atomic structures of protein assemblies, but in materials science it has had much less impact thus far.
DNA-assembled superconductivity has elicited a lot of scientific interest for quite some time. In 2015, scientists researched the assembly of clusters and lattices in which anisotropic polyhedral blocks coordinated isotropic spherical nanoparticles via shape-induced directional interactions facilitated by DNA recognition. They proved that these polyhedral blocks—cubes and octahedrons—when mixed with spheres, advanced the assembly of clusters with architecture determined by polyhedron symmetry. Also, three-dimensional binary superlattices were formed when DNA shells accommodated the shape disparity between nanoparticle interfaces. The crystallographic symmetry of assembled lattices, they found, was determined by the spatial symmetry of the block’s facets, while structural order depended on DNA-tuned interactions and particle size ratio. This lattice assembly strategy opened up new possibilities for by-design fabrication of binary lattices.
Image: Schematic of shape-induced directional bonds for DNA-linked nanoparticle assembly
Source: Fang Lu, Kevin G. Yager, Yugang Zhang, Huolin Xin & Oleg Gang/ Superlattices assembled through shape-induced directional binding/ Nature Communications volume 6, Article number: 6912 (2015), 23 April 2015/ doi.org/10.1038/ncomms7912/ Open Source This article is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0)
In 2020, scientists used a ‘bottom-up’ method to create 3D superconducting nanostructures with prescribed multiscale organisation with the help of DNA-based self-assembly methods. They built 3D DNA superlattices from octahedral DNA frames with incorporated nanoparticles, by means of connecting frames at their vertices, which resulted in cubic superlattices with a 48 nm unit cell. The superconductive superlattice was achieved by first converting a DNA superlattice into a highly-structured 3D silica scaffold, in order to receive a solid structure instead of a soft and liquid-environment dependent macromolecular construction, followed by its coating with superconducting niobium (Nb). Employing a low-temperature electrical characterisation the scientists showed that this process created 3D arrays of Josephson junctions, where the Josephson effect produces a current, known as a supercurrent, that flows continuously without any voltage applied. Their approach was intended for use in development of a variety of applications such as 3D Superconducting Quantum interference Devices (SQUIDs) for measurement of the magnetic field vector.
Image: Schematics of 3D superlattice assembly from octahedra DNA frames and gold nanoparticle, and its conversion into silica and superconductive structure: a DNA origami octahedral frames. b Integration of DNA frames with gold 10 nm nanoparticles and assembly of frames into superlattice with cubic unit cell. (AuNP used here for structural characterization and are not shown in other schematics). c Stepwise conversion process from DNA superlattices to SiO2 and to Nb-coated structures. d Schematic of the formed simple cubic arrangement of octahedra frames. A tetragonal arrangement AuNP’s is determined by SAXS: data (orange), model (blue), indexed diffraction peaks, (001), (100), (101), (111), (002), (200) etc., are shown with vertical black lines. SEM micrographs of e large scale and f close up images of fabricated silica superlattices. g Schematic of low-temperature electrical measurement setup for Nb superlattice using four-point probe
Source: Lior Shani, Aaron N. Michelson, Brian Minevich, Yafit Fleger, Michael Stern, Avner Shaulov, Yosef Yeshurun & Oleg Gang/ DNA-assembled superconducting 3D nanoscale architectures/ Nature Communications volume 11, Article number: 5697 (2020), 10 November 2020/ doi.org/10.1038/s41467-020-19439-9/ Open Source This article is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0)
There are several benefits which may be derived from constructing superconductors with DNA: the DNA-guided approach to lattice construction could have a great variety of useful research applications, especially in physics. It also gives proof that building Little's room-temperature superconductor is possible. Therefore, this work, together with other breakthroughs in superconductors in recent years, might finally transform the technology we are used to by enhancing it with a more efficient energy circuit.
"While we often think of biology using tools and techniques from physics, our work shows that the approaches being developed in biology can actually be applied to problems in physics and engineering," the chief scientist Egelman said. "This is what is so exciting about science: not being able to predict where our work will lead."