Facile Fabrication of Flexible Polymeric Membranes with Micro and Nano Apertures over Large Areas

Freestanding, flexible and open through-hole polymeric micro- and nanostructured membranes were successfully fabricated over large areas (>16 cm(2)) via solvent removal of sacrificial scaffolds filled with polymer resin by spontaneous capillary flow. Most of the polymeric membranes were obtained through a rapid UV curing processes via cationic or free radical UV polymerisation. Free standing microstructured membranes were fabricated across a range of curable polymer materials, including: EBECRYL3708 (radical UV polymerisation), CUVR1534 (cationic UV polymerisation) UV lacquer, fluorinated perfluoropolyether urethane methacrylate UV resin (MD700), optical adhesive UV resin with high refractive index (NOA84) and medical adhesive UV resin (1161-M). The present method was also extended to make a thermal set polydimethylsiloxane (PDMS) membranes. The pore sizes for the as-fabricated membranes ranged from 100 mu m down to 200 nm and membrane thickness could be varied from 100 mu m down to 10 mu m. Aspect ratios as high as 16.7 were achieved for the 100 mu m thick membranes for pore diameters of approximately 6 mu m. Wide-area and uniform, open through-hole 30 mu m thick membranes with 15 mu m pore size were fabricated over 44 x 44 mm(2) areas. As an application example, arrays of Au nanodots and Pd nanodots, as small as 130 nm, were deposited on Si substrates using a nanoaperture polymer through-hole membrane as a stencil.