Laser Polymer Tattooing: A Versatile Method for Permanent Marking on Polymer Surfaces

Abstract

A versatile and efficient method for the permanent marking of polymer surfaces that combines inkjet deposition and near-infrared (NIR) laser curing is investigated. The NIR laser treatment forces the ink particles to migrate into the upper layers of the polymer. This results in the fixation of a permanent grayscale image that can be applied to various polymers, such as polypropylene, which is widely used in industry but still difficult to mark. The physiochemical processes induced by laser curing are investigated by electronic and optical microscopy. The dependence of the thickness of the deposited ink and the laser power on the contrast of marking are also studied. A mechanism implying fast laser-induced melting of the polymer surface followed by displacement of carbon nanoparticles by convection is proposed. Finally, a comparison of the aging properties of samples prepared by this process and standard UV ink is proposed to illustrate the interesting nature of this new polymer marking process. Integrating the ink under the surface of the polymer, as in a skin tattooing procedure, by laser curing is an efficient way to generate permanent images on polymer surfaces.