Large nanomembranes, which are characterized by aspect ratios (size/thickness) of greater than one million, are described. The combination of nanometer thickness and macroscopic size facilitates important applications in materials separation, selective transport and electrochemical devices. In the past, only small pieces of nanomembranes have been fabricated, in spite of intensive research. We describe here the first examples of a general fabrication procedure. Spin coating of the precursor solutions on appropriate underlayer was effectively used to prepare 10-30 nm thick nanomembranes of metal oxides, interpenetrating network of cross-linked acrylate with metal oxide, and highly cross-linked organic polymers (epoxy resin, etc.). The underlayer is composed of an affinity (e.g., poly(vinyl alcohol)) layer and/ or sacrificial layer, and the role of these layers is discussed. Some of the mechanical properties of nanomembranes were measured by using a bulge test and a compression method. The nanomembranes of the organic and inorganic hybrids and the purely organic resins were surprisingly robust and defect-free.
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