Sub-wavelength lithography of complex 2D and 3D nanostructures without two-photon dyes

One-photon or two photon absorption by dye molecules in photopolymers enable direct 2D & 3D lithography of micro/nano structures with high spatial resolution and can be used effectively in fabricating artificially structured nanomaterials. However, the major bottleneck in unleashing the potential of this useful technique is the indispensable usage of dyes that are expensive, highly toxic and usually insoluble in commercially available photopolymers. Here we report a simple, inexpensive and one-step technique for direct-writing of micro/nanostructures, with sub-wavelength resolution at high speeds without using any one photon or two photon absorbing dye. We incorporated large amount (20 wt%) of inexpensive photoinitiator, which has not been done to best of our knowledge, into the photopolymer and utilized its two-photon absorbing property for sub-wavelength patterning. Complex 2D patterns and 3D meshes were fabricated with sub-micron resolution, in commercially available liquid photopolymer to show the impact/versatility of this technique.