FeetThrough: Electrotactile Foot Interface that Preserves Real-World Sensations

Haptic interfaces have been extended to the feet to enhance foot-based activities, such as guidance while walking or stepping on virtual textures. Most feet haptics use mechanical actuators, namely vibration motors. However, we argue that vibration motors are not the ideal actuators for all feet haptics. Instead, we demonstrate that electrotactile stimulation provides qualities that make it a powerful feet-haptic interface: (1) Users wearing electrotactile can not only feel the stimulation but can also better feel the terrain under their feet—this is critical as our feet are also responsible for the balance on uneven terrains and stairs—electrotactile achieves this improved "feel-through" effect because it is thinner than vibrotactile actuators, at 0.1 mm in our prototype; (2) While a single vibrotactile actuator will also vibrate surrounding skin areas, we found improved two-point discrimination thresholds for electrotactile; (3) Electrotactile can be applied directly to soles, insoles or socks, enabling new applications such as barefoot interactive experiences or without requiring users to have custom-shoes with built-in vibration motors. Finally, we demonstrate applications in which electrotactile feet interfaces allow users to feel not only virtual information but also the real terrain under their shoes, such as a VR experience where users walk on ground props and a tactile navigation system that augments the ground with virtual tactile paving to assist pedestrians in low-vision situations.