The present invention provides a novel method to fabricate silica nanostructures on thin polymer films based on silica deposition and self-wrinkling induced by thermal shrinkage. These micro- and nano-scale structures have vastly enlarged the specific area of silica, thus the silica nanomembranes can be used for solid phase extraction of nucleic acids. The inventive silica nanomembranes are suitable for nucleic acid purification and isolation and demonstrated better performance than commercial particles in terms of DNA recovery yield and integrity. In addition, the silica nanomembranes have extremely high nucleic acid capacity due to its significantly enlarged specific surface area of silica. Methods of use and devices comprising the silica nanomembranes are also provided.