Dip-pen nanolithography (DPN) is a low-cost, versatile, bench-top technology for direct patterning of materials over surfaces. Our study reports on the production of two-dimensional optical grating nanostructures based on polymers, using DPN. The influence of both the ink composition and the dwell time were investigated. Prototypes of phase masks were manufactured, and their main characteristics were analyzed. The results in our work may contribute to improving the fabrication process of optical structures, including the production of microlenses with controlled focal length.