a) Chemical structure of PS-PI-PLA block polymer.
b) Self-assembly of PS-PI-PLA on Si3N4, which in turn is on top of a microporous silicon support membrane. “Test tube structures” of PLA cylindrical dots form a hexagonal array. Here only a cross-sectional slice of the array is shown. Layers are not drawn to scale since micro- and nanofeatures are of vastly different size.
c) Same as b but with PLA removed.
d) Removal of Si3N3 and wetting PS layer yields continuous nano-microporous membrane. Apparently “floating” nanostructures form a tubular hexagonal lattice in 3D.