Mar 8 2019
Quite like computers that use electrons to carry out the calculations and logics, the entire circuitry in living beings is based on the transport of ions like chloride, sodium, calcium, and so on.
(Image credit: The University of Manchester)
Nature amazingly harnesses subtle transport of such elementary charges and an ordnance of ion channels to carry out sophisticated functions by exploiting the, typically exotic, behavior of ion transport at molecular levels. It remains a significant challenge to achieve such features in artificial channels.
As reported in Nature, scientists from the Micromegas group at the Physics Department at ENS, Paris worked with the Condensed Matter Physics laboratory and National Graphene Institute at The University of Manchester and have successfully characterized the mechano-sensitive properties of ion transport in artificial channels with a thickness of a few angstroms.
Only about two years ago, researchers from Manchester headed by Dr Radha Boya and Prof. Sir Andre Geim demonstrated that it is, in fact, feasible to assemble molecular and smooth channels at the atomic level in a controlled way by stacking two-dimensional (2D) atomic layers, similar to stacking Lego bricks. The atomic layers used for developing the channel are kept together by what are known as van der Waals forces. The new experiments use these channels to demonstrate that substantial amounts of ionic current can be produced by inducing a flow by applying a pressure difference. These angstrom-scale channels produced ionic current when two miniature baths of salt solutions were separated, making water molecules to be mechanically pushed through them.
According to Dr Timothée Mouterde, the first author of the study, “Even more surprising, by applying an electric field along with pressure, this flow current can be modulated extremely sensitively.”
Prof Lydéric Bocquet added that “This novel effect is akin to transistor but here for ion transport and can be understood as gating of mechanical ion flow by voltage. Furthermore interestingly, the electronic properties of the confining wall materials of the channel seem to influence this ‘voltage gating’. This effect can be understood by differential friction of water and ions on the walls at these molecular scales.”
Inside our artificial channels which are only couple of water atoms thick, water and ions are organized in a two-dimensional monolayer. The ability to make such precise angstrom scale channels has provided us with tools to explore anomalous properties of water and flows.
Dr Ashok Keerthi, Study Co-Author, The University of Manchester.
At the molecular scale, flows induced by pressure and voltage simply do not add up. This coupling between mechanical and electrical forces demonstrated at the ultimate scales shows strong similarities to those observed in mechanically sensitive biological ion channels such as PIEZO1. This new platform will allow exploring the physical mechanisms of these extreme confinement situations at work in living systems, and in the longer term, to mimic elementary calculus functions based on ion transport.
Dr Radha Boya, The University of Manchester.