3D-printed doped optical waveguides for sensing applications: graphite- and zinc-doped structures

This study reports the design, fabrication, and optical characterization of stereolithography-printed waveguides doped with graphite and zinc oxide (ZnO). Effective refractive indices were predicted using the Bruggeman effective medium approximation and experimentally validated. The doped structures exhibited total internal reflection and were evaluated as optofluidic sensors for detecting variations in alcoholic beverages and telomeric DNA concentrations. Raman spectroscopy further confirmed molecular discrimination between male and female samples. The results demonstrate a reproducible approach for producing low-cost, application-specific optical waveguides suitable for chemical and biological sensing platforms, with tunable performance enabled through dopant selection.