Ultra-fast gas leaks through smaller holes in thin-walled membranes – confirm the century-old equation of fluid dynamics

The researchers identify ultra-fast gas flows through atomic-scale openings in the 2D membrane and prove a centuries-old equation of fluid dynamics. Credit: N Hassani & M N-Amal, Shahid Rajee University

Researchers from the Graphene National Institute at the University of Manchester and the University of Pennsylvania identify ultrafast gas flows through atomic scale openings in the 2D membrane and prove a centuries-old equation of fluid dynamics.

Researchers from the Graphene National Institute at the University of Manchester and the University of Pennsylvania have identified ultra-fast gas flows through the smallest holes in aatom-thin membranes, in a study published in Advances in Science.

The work – along with another study by Penn on the creation of such nano-porous membranes – promises multiple application areas, from water and gas purification to air quality monitoring and energy harvesting.

In the early 20th century, renowned Danish physicist Martin Knudsen formulated theories to describe gas flows. New systems in the display of narrower pores challenged Knudsen descriptions of gas flows, but they remained valid and it was unknown at what point of the reducing scale they might fail.

The Manchester team – led by Professor Radha Boya, in collaboration with the University of Pennsylvania team led by Professor Marija Drndić – has shown for the first time that Knudsen’s description seems to stand true at the last atomic limit.

The science of two-dimensional (2D) materials is advancing rapidly and it is now routine for researchers to make thin membranes with one atom. Professor Drndić’s group in Pennsylvania developed a method of drilling holes, with a wide atom, in a tungsten disulfide layer. An important question remained, however: to check if the atomic scale holes were through and transmitted, without seeing them manually, one by one. The only way beforehand to confirm if the holes were present and of the intended size was to check them on a high-resolution electron microscope.

Professor Boya’s team developed a technique to measure gas flows through atomic holes, and in turn use flow as a tool to determine the amount of hole density. She said: “Although it is unquestionably reliable to see, science has been very limited in being able to see only atomic pores in a fancy microscope. Here we have devices through which we can not only measure gas flows, but also use the flows as a guide to estimate how many atomic holes there were in the membrane to start. “

J Thiruraman, co-author of the study, said: “To be able to reach that atomic scale experimentally, and to image that structure accurately, in order to be more confident that it is a pore of that size and form, it was a challenge. “

Professor Drndić added: “There is a lot of equipment physics between finding something in a laboratory and creating a usable membrane. This came with the advancement of technology as well as our methodology, and what is new here is to integrate this into a device that you can actually remove, transport across the ocean if you wish [to Manchester], and measure. “

Dr. Ashok Keerthi, another lead author from the Manchester team, said: “Manually inspecting the formation of atomic holes over large areas in a membrane is meticulous and perhaps impractical. Here we use a simple principle, the amount of gas the membrane allows is a measure of how much the hole is. “

The gas flows achieved are several orders of magnitude larger than the fluxes previously observed in angstrom scale pores in the literature. A one-to-one correlation of atomic aperture density from transmission electron microscopy image (measured locally) and from gas flows (measured on a large scale) was combined from this study and published by the team. S Dar, a co-author from Manchester added: “Surprisingly there is no minimum energy barrier to flow through such small holes.”

Professor Boya added: “We now have a strong method to confirm the formation of atomic apertures in large areas using gas streams, which is an essential step in pursuing their potential applications in various fields including molecular separation. , sensing and monitoring gases at ultra-low concentrations. ”

Reference: “Gas flow through atomic scale openings” by Jothi Priyanka Thiruraman, Sidra Abbas Dar, Paul Masih Das, Nasim Hassani, Mehdi Neek-Amal, Ashok Keerthi, Marija Drndic and Boya Radha, 18 December 2020, Advances in Science.
DOI: 10.1126 / sciadv.abc7927

This work was carried out through an international collaboration and, includes experimental teams from Manchester and Philadelphia, as well as theoretical groups from Shahid Rajee University, Iran and the University of Antwerp, Belgium.

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