Elucidating Hydrodynamics at Confined Interfaces for Artificial Active Fluidics and Beyond

The surfaces of the living cells that make up our bodies consist of exquisitely engineered tiny pores of size less than a nanometer (i.e., one ten-thousandth of the diameter of a human hair). Nature has evolved these pores to efficiently harness inter-molecular forces and surface effects for achieving exceptional water/ion selectivity and ion transport even counter to concentration gradients. Therefore, they play a critical role in functioning of human kidneys to remove waste/extra-fluids from the blood and, allow brain-cells (i.e., neurons) to generate electrical pulses required for the brain to sense and compute. For example, concentration gradients driven ion transport across a neuron cell membrane generates electrical signals and transmit them with speeds of tens of meters per second as a means of communication. The proposed research aims at making similar pores inside a laboratory to make (i) artificial fluidic devices that allow direct communication to/from cells in their language (exchanging ions/water molecules), and (ii) membranes for producing energy by mixing fresh water with seawater and energy efficient removal of salt from seawater with minimal production of carbon dioxide.

Unlike water flow in a garden hose, the physics of fluidic motion through the pores of nanometer-size is barely understood. Also, machine-made pores still struggle to separate ions (like sodium and potassium) with similar size and properties. Therefore, there remains much to be understood on fundamental issues such as friction of liquids on solid surfaces, mechanisms for enhanced molecular separation, and ionic transport in confined geometries and its control. The proposed research aims at establishing a comprehensive understanding of how ions/water molecules interact with the walls of machine-made tiny pores under extreme confinements. This will be achieved through investigation of microscopic flows (in terms of flow rate/ionic flux) emerging out of such tiny pores while tuning electric conductivity and electric charge of the walls of the pore. These studies will provide a systematic realization of friction for liquids on solid surfaces with quantification, which acts as reference for choosing appropriate channel wall materials for precisely controlling the fluidic transport at confined geometries to achieve enhanced water/ion selectivity like biological pores. Throughout this Fellowship, I will also develop essential theoretical understanding and advanced modelling at fundamental/device level for advancing the experiments and optimization of device-prototyping.

Building on these findings, this fellowship will establish the fabrication of (i) artificial fluidic devices for ion-transport based bioelectronic interfaces and memory devices and (ii) membranes for water purification and energy harvesting from salt-concentration gradients. From the fourth year of this Fellowship, I will work with Graphene Engineering Innovation Centre at Manchester to scale up fluidic devices and membrane fabrication for energy and environmental applications with an aim of contributing to the UK's Energy Independence and achieving net zero greenhouse gases emission by 2050.

Further to this Fellowship, my team and I will develop schemes for the experimental determination of the molecular arrangement in confined geometries to rationalize its contribution on confined fluidic transport. Therefore, this Fellowship comprehensively addresses knowledge gaps in present-day nanofluidics research and paves path to establish a new direction of research at the interface of confined fluidic transport, surface science and solid-state physics. All this, besides producing high-impact publications and patents, enables me to grow as a leader in this field to progress towards my long-term aim of establishing Nature-Inspired Nanofluidics Research Center in the UK to address a number of Grand Challenges (clean growth; sustainability; water and energy for food) across the world.