Unraveling the relationship between molecular properties and rapid diffusion in smooth nanopores

Synthetic materials designed to enable rapid and finely tuned diffusion through semi-permeable nano and microscale pores have generally fallen short when compared to their biological counterparts. As a result, applications such as hemodialysis, drug delivery, and biomolecule purifications often require extensive run times and produce imperfect permeate solutions. Towards bridging this gap, we have recently demonstrated that, under a concentration gradient, a wide range of ions diffuse through atomically smooth carbon nanotube pores at rates more than an order of magnitude above those seen in bulk. This observation comes in a pore/molecule size regime where hindered diffusion was previously thought to apply. Here, we extend these results to include more complex and biologically relevant molecules and study how transport rates driven by diffusion depend on molecular properties such as size and flexibility. Further, we work to understand how the unique nanofluidic phenomena occurring in our pores may enable improved performance in dialysis applications by impacting selectivity, permeability, and molecular cutoff profiles. These results help to shed light on mechanisms governing diffusive transport in certain nanoscale pores that remain only partially understood and bring us closer to harnessing them in future separation technologies.