Figure 2.

NPN membranes manufactured with different nanomorphologies. (A–D) TEM images (63 kx, 0°) of four different varieties of NPN. The sizes and shapes of the pores can range from largely open (A,D) to pitted and under-etched (B,C). White arrows indicate open nanopores in low-porosity films. Parameters derived from histograms of counted pores (Supplemental Section S1) show the wide variety of membrane porosities and pore diameters. x = Average Pore Diameter, Φ = Porosity, ρ_n = Pore Density, η = Circularity.