Creating a library of complex metallic nanostructures via harnessing pattern transformation of a single PDMS membrane

By harnessing the elastic instability in a single PDMS membrane consisting of a square lattice array of circular pores, we fabricated a library of complex nanostructures in Au with variable feature size, connectivity, and geometry, including arrays of diamond-plate patterns (or elliptic herringbones), compound structures of circular dots and elliptical lines, heartbeat waves, aligned ovals, and a rhombus lattice of holes and lines. This was achieved first by swelling the PDMS membrane, followed by convective assembly of nanoparticles on the membrane. By taking advantage of the unique 3-D topography of the nanoparticle film and its photoresist replica, we could gradually etch the photoresist film to vary the feature size and connectivity of the underlying Au patterns. Further, through a combination of mechanical stretching (at different strain levels and stretching angles) and solvent swelling of the same PDMS membrane, we created a richer library of complex patterns in Au without application of new masters.