Nebula: An Affordable Open-Source and Autonomous Olfactory Display for VR Headsets.

The impact of olfactory cues on user experience in virtual reality is increasingly studied. However, results are still heterogeneous and existing studies difficult to replicate, mainly due to a lack of standardized olfactory displays. In that context, we present Nebula, a low-cost, open-source, olfactory display capable of diffusing scents at different diffusion rates using a nebulization process. Nebula can be used with PC VR or autonomous head-mounted displays, making it easily transportable without the need for an external computer. The device was calibrated to diffuse at three diffusion rates: no diffusion, low and high. For each level, the quantity of delivered odor was precisely characterized using a repeated weighting method. The corresponding perceived olfactory intensities were evaluated by a psychophysical experiment on sixteen participants. Results demonstrated the device capability to successfully create three significantly different perceived odor intensities (Friedman test p < 10(-6), Wilcoxon tests p(adj) < 10(-3)), without noticeable smell persistence and with limited noise and discomfort. For reproducibility and to stimulate further research in the area, 3D printing files, electronic hardware schemes, and firmware/software sourcecode are made publicly available.