Hydroptical Thermal Feedback: Spatial Thermal Feedback Using Visible Lights and Water

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We control the temperature of materials in everyday interactions, recognizing temperature's important influence on our bodies, minds, and experiences. However, thermal feedback is an under-explored modality in human-computer interaction partly due to its limited temporal (slow) and spatial (small-area and non-moving) capabilities. We introduce hydroptical thermal feedback, a spatial thermal feedback method that works by applying visible lights on body parts in water. Through physical measurements and psychophysical experiments, our results show: (1) Humans perceive thermal sensations when visible lights are cast on the skin under water, and perceived warmth is greater for lights with shorter wavelengths, (2) temporal capabilities, (3) apparent motion (spatial) of warmth and coolness sensations, and (4) hydroptical thermal feedback can support the perceptual illusion that the water itself is warmer. We propose applications, including virtual reality (VR), shared water experiences, and therapies. Overall, this paper contributes hydroptical thermal feedback as a novel method, empirical results demonstrating its unique capabilities, proposed applications, and design recommendations for using hydroptical thermal feedback. Our method introduces controlled, spatial thermal perceptions to water experiences.