Investigation of 3D nano printed on chip hollow core waveguides This thesis explores optical waveguides for integrated applications involving signal detection and object observation through guided light. Conventional optical waveguides use exposed evanescent fields to analyze water based solutions but their limited interaction area necessitates longer devices. To address this the thesis employs the anti resonant reflecting optical waveguide (ARROW) concept and presents novel microfluidic waveguides light cages and micro gap waveguides featuring side access to the core. These are manufactured using 3D nano printing based on two photon polymerization (TPP) technology. The thesis comprises two parts: the light cage and the micro gap waveguide. The light cage resembles a hollow core fiber with modal attenuation of 0.5 to 1.0 dB mm confirmed through experiments and simulations. It facilitates light guidance in liquids and is used for refractive index absorption and emission spectroscopy. Side access is emphasized via diffusion measurements outperforming capillary fibers. Unique nanoparticle tracking analysis (NTA) within the light cage detects scattered light from nanoparticles allowing measurement of solvency induced nanoparticle collapse in different liquid environments. The micro gap waveguide characterized by a narrow gap specific core size wall thickness and segment length demonstrates strong light matter interactions. It is applied in refractive index monitoring absorption spectroscopy and exhibits significantly faster diffusion compared to capillary fibers. In conclusion 3D printed hollow core waveguides offer advantages like easy integration rapid diffusion large exposed areas for analyte interactions design flexibility and reduced bubble defects. This research advances optical waveguide technology enabling enhanced light matter interactions for applications in sensing spectroscopy and nanoparticle analysis.