The optical performance of a 3D printed, titanium dioxide painted, Ganzfeld bowl

The emergence of three dimensional (3D) printing has inspired creative ways to enable clinicians to make their own medical devices at low cost, a process called distributed manufacture. Devices for light stimulation, such as for visual electrophysiology or pupillometry, require both physical and optical properties. Here we tested whether a 3D printed (fused deposition modelling, FDM) poly-lactic acid (PLA) surface can exhibit Lambertian reflectance, and tested the behaviour of a 3D printed Ganzfeld bowl as an integrating sphere. White PLA transmits light, so a painted inside surface was necessary. We tested whether the spectral and Lambertian reflecting properties of low cost titanium dioxide (TiO₂) based paint was equivalent to specialist barium sulphate (BaSO₄) coating. Our measurements indicated that our prototype Ganzfeld with TiO₂ coating reflected all wavelengths equally and had radiance uniformity of 90 % which compared well to other published designs. In many jurisdictions regulation prevents a do-it-yourself approach to medical devices, but these approaches might facilitate interested clinicians to create devices for ethically approved research and assist those with severe resource limitations.