Micro-Nano Hierarchical Structures in Biocompatible Thermoplastics and its Application for Fabrication of Polymeric Membranes with Regular and Straight Open Through Holes

We fabricate Micro-Nano Hierarchical (MNH) structures comprising arrays of nanopillars superimposed on micropillars over large areas. Both circular and oval shape nanopillars were successfully fabricated on biocompatible thermoplastic materials including polymethyl methacrylate (PMMA), polylactic acid (PLA) and cyclo olefin polymers (ZF14-188) by using hot-embossing techniques with intermediate fluorinated polymer molds replicated from Si master molds. The as-fabricated polymeric substrates with MNH structures shows a static contact angle >= 140 degrees. Superhydrophobic surfaces with a static contact angle as high as 162 degrees were achieved on ZF14-188 substrates patterned with MNH structures even without post-fluorocarbon coating. The as-fabricated thermoplastic substrates with MNH structures were also used as very effective templates to create open through hole polymeric membranes with micro-nano hierarchical structures including an 840 nm thick membrane featuring an array of 250 nm diameter nanoholes suspended within 13.5 mu m or 18.2 mu m diameter microholes.