Non-invasive study of the three-dimensional structure of nanoporous triblock terpolymer membranes

Nanoporous media are of great importance for drug delivery or filtration. Typically the pore structure of such media is characterized using high-resolution techniques such as electron microscopy or atomic force microscopy. However, these techniques are restricted to the surface of the material and/or are highly invasive. In a proof-of-concept experiment we have employed three-dimensional single-particle orbit tracking for testing the three-dimensional pore structure of a liquid filled nanoporous polystyrene-block-polyisoprene-block-poly(N-isopropylacrylamide) (PS-b-PI-b-PNiPAAm) triblock terpolymer membrane. Using fluorescent tracers with a diameter of about 10% of the relevant void structures, the tracking experiments yielded results that were comparable to those obtained from reference experiments using environmental scanning electron microscopy (eSEM). This testifies that single-particle orbit tracking can serve as a useful non-invasive alternative for characterising the structure of nanoporous materials.