Nanoscale Breakthrough – A Single-Molecule Valve

Schematic drawing of the working principle of the single-molecule valve. Credit: Yan Xu, Osaka Metropolitan University

A revolutionary paradigm shift that will transform chemical and biochemical synthesis is on the horizon.

The scientific community envisions utilizing minute molecules as foundational elements to construct objects, similar to how we assemble things with mechanical components. However, the challenge lies in the fact that molecules are incredibly small, approximately one hundred millionth the size of a softball, and they move randomly in liquids, making it difficult to control and manipulate them into a single form.

To overcome this obstacle, “nanofluidic devices” that can convey molecules through remarkably narrow channels, similar in dimension to one-millionth of a straw, have garnered interest as a means of directly controlling individual molecules in solutions.

A joint research team led by Associate Professor Yan Xu of the Osaka Metropolitan University Graduate School of Engineering has succeeded in regulating the flow of single molecules in solution by opening and closing a nanovalve in a nanofluidic device by applying external pressure.

Single-molecule flow of Cy3 in a nanochannel. Credit: Yan Xu, Osaka Metropolitan University

The research team fabricated a nanofluidic device with a thin, flexible glass sheet on the top, and a hard glass plate with small structures that forms nanochannels and nanovalve seats on the bottom. By applying external pressure to the flexible glass sheet to open and close the valve, they succeeded in directly manipulating and controlling the flow of individual molecules in solution.

They also found that when they trapped single fluorescent molecules in the nanospace inside the valve, the fluorescence of the single molecules became brighter. This happened because the small space made it harder for the single molecules to move around randomly.

Professor Xu said that “this effect of fluorescence signal amplification could help with detecting very small amounts of pathogens for early diagnosis of diseases such as cancers and Parkinson’s disease, without requiring expensive equipment.”

The findings of this study could be a significant step towards freely assembling materials using single molecules as building blocks in solution. This technology has the potential to be useful in various fields, such as developing personalized medicines for rare diseases and creating better displays and batteries. Its applications are limitless.

“We have been addressing various challenges by proposing and promoting the concept of ‘Single-Molecule Regulated Chemistry (SMRC),’ where molecules are treated as building blocks and all processes involved in chemical and biochemical reactions in solution are performed on a single-molecule basis. The single-molecule valve marks the first step towards the goal, which could one day revolutionize chemistry, biology, and materials science, as well as transform various industries,” said Professor Xu.

Reference: “Flexible Glass-Based Hybrid Nanofluidic Device to Enable the Active Regulation of Single-Molecule Flows” by Hiroto Kawagishi, Shun-ichi Funano, Yo Tanaka and Yan Xu, 6 March 2023, Nano Letters.
DOI: 10.1021/acs.nanolett.2c04807

The study was funded by the Japan Society for the Promotion of Science, the Ministry of Education, Culture, Sports, Science and Technology, the Japan Science and Technology Agency, and SiMS of Osaka Prefecture University.