of optical fibers. High aspect ratio nanostructuring High-aspect-ratio and hierarchically nanostructured surfaces can be cumbersome to fabricate and suffer from structural collapse. Using UV-NIL of off-stoichiometric thiol–ene-epoxy polymer it is possible to fabricate robust, large-area, and high-aspect-ratio nanostructures as well as complex hierarchically layered structures with limited collapse and defectivity. Alternative approaches Electrochemical nanoimprinting Electrochemical nanoimprinting can be achieved using a stamp made from a superionic conductor such as silver sulfide. When the stamp is contacted with metal, electrochemical etching can be carried out with an applied voltage. The electrochemical reaction generates metal ions which move from the original film into the stamp. Eventually all the metal is removed and the complementary stamp pattern is transferred to the remaining metal. Laser assisted direct imprint Laser assisted direct imprint (LADI) is a rapid technique for patterning nanostructures in solid substrates and it does not require etching. A single or multiple excimer laser pulses melt a thin surface layer of substrate material, and a mold is embossed into the resulting liquid layer. A variety of structures with resolution better than 10 nm have been imprinted into silicon using LADI, and the embossing time is less than 250 ns. The high resolution and speed of LADI, attributed to molten silicon’s low viscosity (one-third that of water), could open up a variety of applications and be extended to other materials and processing techniques. Ultrafast nanoimprint Ultrafast Nanoimprint Lithography or Pulsed-NIL is a technique based on the use of stamps with an heating layer integrated beneath the nanopatterned surface. Injecting a single, short (<100 μs), intense current pulse into the heating layer causes the surface temperature of the stamp to raise suddenly by several hundreds degrees °C. This results in the melting of the thermoplastic resist film pressed against it and the swift indentation of the nanostructures. In addition to the high throughput, this fast process has other advantages, namely, the fact that it can be straightforwardly scaled up to large surfaces, and reduces the energy spent in the thermal cycle with respect to the standard thermal NIL. This approach is currently pursued by ThunderNIL srl. Roller nanoimprint Roller processes are very well suited for large substrates (full wafer), and large scale production since they can be implemented into production lines. If used with a soft stamper, the process (imprint as well as demoulding) can be extremely soft and tolerant to surface roughness or defects.