Research Bits: May 23

DNA-based molecular computing; molecular teamwork in organic semiconductors; mass production of metalenses.


DNA-based molecular computing

Researchers at the University of Minnesota proposed a new method of biocomputing. Trumpet, or Transcriptional RNA Universal Multi-Purpose GatE PlaTform, uses biological enzymes as catalysts for DNA-based molecular computing.

Researchers performed logic gate operations in test tubes using DNA molecules. A positive gate connection resulted in a phosphorescent glow. The DNA creates a circuit, and a fluorescent RNA compound lights up when the circuit is completed.

The platform is reliable for encoding all universal Boolean logic gates (NAND, NOT, NOR, AND, and OR), and logic gates can be stacked to build more complex circuits. It also provides signal amplification and programmability. The team also developed a web-based tool facilitating the design of sequences for the Trumpet platform.

“Trumpet is a non-living molecular platform, so we don’t have most of the problems of live cell engineering,” said Kate Adamala, assistant professor in the College of Biological Sciences at University of Minnesota. “We don’t have to overcome evolutionary limitations against forcing cells to do things they don’t want to do. This also gives Trumpet more stability and reliability, with our logic gates avoiding the leakage problems of live cell operations.”

The researchers are exploring use of the platform to develop biomedical applications  for early diagnosis of cancer. Another potential use could be the combination of medical diagnostics and therapeutics inside the body, such as a biological circuit small enough to circulate in the bloodstream that could detect low insulin levels in a diabetes patient and activate proteins to manufacture the needed insulin.

Trumpet is an operating system for simple and robust cell-free biocomputing:

Molecular teamwork in organic semiconductors

Researchers at the University of Illinois Urbana-Champaign discovered a way to trigger cooperative behavior in organic semiconductors. “Our research brings semiconductors to life by unlocking the same dynamic qualities that natural organisms like viruses use to adapt and survive,” said Ying Diao, a researcher at the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign.

The behavior, called molecular cooperativity, is frequently observed in viruses and bacteria, such as the unison contraction of proteins that manipulates the microbes’ tails.

In non-living crystalline structures, however, structural transitions happen one molecule at a time. “Imagine taking down an elaborate domino display brick by brick. It’s exhausting and laborious, and once you’ve finished, you would most likely not have the energy to try it again,” said Daniel Davies, a researcher at the Beckman Institute at the time of the study. By contrast, cooperative transitions occur when molecules shift their structure together, like a row of dominoes flowing seamlessly to the floor. The researchers said that the collaborative method is fast, energy-efficient, and easily reversible.

The team investigated whether these transitions could be made to happen in organic semiconductors. “Molecular cooperativity helps living systems operate quickly and efficiently,” Davies said. ​“We thought, ​‘If the molecules in electronic devices worked together, could those devices display those same benefits?’”

Dominoes inspired the researchers’ approach to trigger molecular teamwork in a semiconductor crystal. They discovered that rearranging the clusters of hydrogen and carbon atoms spooling out from a molecule’s core — otherwise known as alkyl chains — causes the molecular core itself to tilt, triggering a crystal-wide chain of collapse the researchers refer to as an ‘avalanche.’

“Just like dominoes, the molecules don’t move from where they are fixed. Only their tilt changes,” Davies said.

By gradually applying heat to the molecule’s alkyl chain, they found that increased temperature induced the domino-like effect. Using heat to rearrange the molecules’ alkyl chains also caused the crystal itself to shrink, a property that could act as a temperature-induced switch.

While the researchers note this is an early stage of research, they think it could eventually improve performance of smartwatches, solar cells, and other organic electronics.

Unraveling two distinct polymorph transition mechanisms in one n-type single crystal for dynamic electronics:

Mass production of metalenses

Researchers from POSTECH, Korea University, and the Research Institute of Industrial Science and Technology developed a method to mass produce metalenses for visible light.

The method combines photolithography and nanoimprint lithography. The researchers first created a single pattern using electron beam lithography, then replicated the pattern using deep-ultraviolet ArF photolithography to create 12-inch master stamp. Using the stamp and nanoimprint lithography, they were able to successfully produce metalenses with a 1 cm diameter at a high speed.

Conventional nanoscale structures based on nanoimprint technology had low refractive indices, resulting in very low efficiencies of around 10%. The research team was able to improve the efficiency of the lens up to 90% by coating the lens with an approximately 20 nanometer thin layer of titanium dioxide (TiO2).

As a proof of concept, the team demonstrated the practicality of metalenses by creating lightweight virtual reality devices capable of displaying images in red, green, and blue.

“This study demonstrates the possibility of taking meta-material research, which has been in the research stage for 20 years without commercialization, to the industrial stage and making it applicable in real life. The significance of this achievement lies in the fact that we have succeeded in mass-producing metalenses for visible light on a wafer scale, which is the most advanced technology in the world,” said Junsuk Rho, a professor in the Department of Mechanical Engineering and Department of Chemical Engineering at POSTECH.

Scalable manufacturing of high-index atomic layer–polymer hybrid metasurfaces for metaphotonics in the visible:

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