Artificial Å-scale fluidics

Due to severe shortage of accessible clean water, the world is looking at alternate technologies/mechanisms by which efficient separation of ions and molecules at the smallest length scale can be realized. The importance of membranes with goodion/water separation capabilities is ever increasing. Reducing the size of capillaries to match the hydrated size of the ions is one of the approaches. Graphene oxide (GO) has been widely explored for this purpose, however swelling of capillaries while inside water makes it not very useful. To avoid swelling, we have mechanicallyconfined graphene oxidecapillariesto Å-scale dimensions, which is a great step forward. We studied ion transport through these capillaries and found that while ion permeation is exponentially decreased when the size of the capillaries are diminished; water permeation is weakly affected [1], making it very promising for water purification. Though GO is promising, it lacks the integration capabilities required for nano-fluidic circuits. Recently, we reported [2] a novel approach of utilizing the atomic flatness of van der Waals layered materials for the fabrication of Å-scale channels, beating the surface roughness limit traditionally encountered in lithographically fabricated systems. This technique utilizes a combination of van der Waals assembly of layered materials and lithography to create fluidic channels of 1 atom thick ‘at will’ and ‘choice’, pushing the boundaries of nanofluidics to the next level. We systematically studied the water and ion transport through these highly confined channels. The multifunctional capabilities of these artificial channels will be discussed in detail. On adifferent note, we tried to push the boundaries of nanofluidics further by accessing the interlayer space in van der Waals crystals and some of the important findings will also be discussed. 

[1]	J. Abraham, K. S. Vasu, C. D. Williams, K. Gopinadhan, Y. Su, C. T. Cherian, J. Dix, E. Prestat, S. J. Haigh, I. V. Grigorieva, P. Carbone, A. K. Geim, R. R. Nair, Tunable sieving of ions using graphene oxide membranes. Nat. Nanotechnol.12, 546-550 (2017).
[2]	B. Radha, A. Esfandiar, F. C. Wang, A. P. Rooney, K. Gopinadhan, A. Keerthi, A. Mishchenko, A. Janardanan, P. Blake, L. Fumagalli, M. Lozada-Hidalgo, S. Garaj, S. J. Haigh, I. V. Grigorieva, H. A. Wu, A. K. Geim, Molecular transport through capillaries made with atomic-scale precision. Nature538, 222-225 (2016).