Advances in Olfactory Displays for Multisensory Immersion: Principles, Applications, and Future Directions

• • Airflow-based olfactory displays dominate early stationary systems but suffer from lengthy scent transmission paths and slow residual odor clearing; the 1960 Smell-O-Vision prototype exemplifies this limitation, and no quantitative latency threshold has been standardized, leaving industrial adoption without a clear performance target. • • Atomization-based systems reduce form factor by generating fine droplets, yet face unresolved nozzle clogging and thermal management issues; the absence of reported mean-time-between-failure (MTBF) data in Section B prevents cost-of-ownership modeling for consumer VR deployment. • • Noninvasive electrical stimulation of the olfactory system—via transethmoid olfactory bulb stimulation (Holbrook et al., 2019), subdural electrodes on the olfactory tract (Kumar et al., 2012), and orbitofrontal cortex stimulation (Fox et al., 2018)—can elicit olfactory hallucinations, but these are invasive or clinically constrained, with no reported success rate or safety margin for chronic use. • • Flexible electronics and MEMS integration are driving wearable olfactory displays, yet Section B reveals a critical gap: no empirical data on scent delivery latency, cross-contamination rates, or power consumption under mechanical deformation, making it impossible to benchmark against visual-haptic interfaces where temporal delays of 118–134 ms are already documented (Vogels, 2004).