https://phys.org/news/2018-11-inkjet-printers-cheap-micro-waveguides-optical.html

Most researchers now suggest complex and expensive technologies for creating waveguides, for example, laser ablation or photolithography. These are time-consuming procedures requiring complex equipment, rare materials and additional sample processing. Scientists from ITMO University now offer an alternative method for creating optical micro-waveguides, based on a common inkjet technology.

Waveguide printing begins with the preparation of special ink. Its main ingredient is a suspended solution, or sol, of titanium dioxide nanoparticles. Such a material was chosen due to the high refractive index, which is necessary for the waveguide to conduct the signal. In order to achieve suitable ink parameters, the scientists selected the solvents, the concentration of the main component and the surfactants. The inkjet printer applies the material according to a given geometry on a clean glass substrate.