Waterless virtual footbath using airflow and thermal contrast: design and exploratory evaluation of relaxation-oriented VR experience

Conventional footbaths promote relaxation but require water management and hygiene control, limiting portability and reproducibility. We propose a waterless virtual footbath system that reproduces immersion-like sensations using airflow-based tactile stimulation and controlled thermal contrast in virtual reality (VR). A membrane-guided airflow structure promotes surface-conforming flow around the feet, while a vertical thermal gradient simulates the boundary sensation of warm-water immersion. An exploratory within-subject study (n = 8) compared four conditions combining airflow and thermal stimulation. Subjective ratings (presence, comfort, discomfort) and physiological measures (heart rate and HRV) were recorded. Stimulation conditions were associated with reductions in heart rate relative to visual-only presentation, with effects depending on the combination of sensory stimuli. While airflow and thermal stimulation each reduced heart rate when presented individually, their combination did not produce an additional reduction. The combined airflow and thermal condition yielded the high frquency presence and comfort ratings without significantly increasing discomfort. These findings demonstrate the feasibility of reproducing footbath-like experiences without water and highlight the potential of airflow-based multisensory VR for relaxation-oriented applications.