Stimuli-triggered Permeation of Ionic Analytes Through Nanopores Functionalised with Responsive Molecules

Here, we will describe the design and functioning of two nanofluidic systems based on arrays of nanopores fabricated in heavy ion tracked polymer membranes, that respond to soft ultraviolet (UV₃₆₅) light, and environmental temperature (separately). For the case of photosensitive membranes, the inner pore walls are decorated with photolabile 4-oxo-4-(pyren-4-ylmethoxy) butanoic acid (PYBA) protecting groups. Subsequently, the hydrophobic pyrene moieties are removed by UV light irradiation, leading to the exposure of hydrophilic groups, which are responsible for the permselective transport of ionic molecules across the responsive membrane. For the case of temperature responsive nanofluidic system, the inner pore walls are chemically modified with amine-terminated poly(N-isopropylacrylamide) [PNIPAAM–NH₂] chains via “grafting to” approach through carbodiimide coupling chemistry. The effective nanopore diameter is tuned by manipulating the environmental temperature due to the swelling/shrinking behaviour of polymer brushes attached to the inner nanopore walls, leading to a decrease/ increase in the permeation of charged molecular species across the membrane. This process should permit thermal gating and controlled release of ionic drug molecules through the nanopores of the membrane.