Low-Cost Nanoscale Metal Printing Beyond the Diffraction Limit via Off-Focus Light Projection

Abstract

Abstract Nanoscale patterning of metallic structures is desired in various fields such as electronics, biosciences, and plasmonics. However, their practical applicability is often constrained by the high cost of the fabrication techniques. Here, we have developed the off-focus light projection (OF-LP) technique to print sub-micron metal features through localized reduction of metal ions into metal nanoparticles. The OF-LP technique implements printing of sub-micron features with low-intensity light and is therefore significantly more affordable than multi-photon printing techniques that require expensive femtosecond lasers. On-focus projection of light is limited by the optical diffraction limit and it is therefore not capable of generating fine nanoscale structures. Here, we present a modified light projection technique by leveraging the projection of images on planes away from the focal plane to achieve sub-diffraction printing. We demonstrate printing of silver nanowires finer than 380 nm, which is the diffraction limit of the optical system. Therefore, this new projection strategy transforms light projection into a low-cost and high-resolution technique for fabrication of metallic nanostructures.