What can we learn from biology about designing membranes?

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Membranes are rapidly becoming the fastest growing platform for water purification, wastewater reuse, and desalination. They are also emerging in importance for carbon capture, hydrocarbon separations, and are being considered for applications involving catalysis and sensing. All synthetic membranes have selectivity-permeablility tradeoffs, i.e. if a membrane has high permeability, it will have a lower selectivity between two solutes or between a dissolved solute and a solvent. This is due to the mechanism of solution-diffusion through a wide distribution of free volume elements in non-porous membranes such as reverse osmosis membranes used for desalination and reuse, and a wide pore size distribution in porous membranes. A simple solution, in concept, to such a challenge is to do what nature does – design precise angstrom to micron scale pores with no polydispersivity. However, so far, such an ideal has not been realized in synthetic membranes and in particular for angstrom scale separations. We will discuss bioinspired ideas, and its realization in our lab, that could lead to an achievement of such an ideal membrane based on biological protein channels and artificial channels that mimic their structure.