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.