Figure 5.

Representative EM images of (A) an ultrafiltration polyethersulfone (PES) membrane showing irregular pores with different radii and (B) our track-etched membranes with uniform pore radius. Fractionation of cell culture media using track-etched membranes show significant filter cake formation and EV coalescence as schematically shown in (C) that results in a poor size fractionation and leads to particles about twice the average EV size in the flow through (D) (Reproduced from Supplementary Materials of [42] with permission). These large particles are larger than the pore size by 100 nm and hence are believed to be created by coalescence events in the pore.