ThermEarhook: Investigating Spatial Thermal Haptic Feedback on the Auricular Skin Area

Haptic feedbacks are widely adopted in mobile and wearable devices to convey various types of notifications to the users. This paper investigates the design and the evaluation of thermal haptic feedback on an earable form factor with multiple thermoelectric (i.e. Peltier) modules. We propose ThermEarhook, a wearable device that can provide hot and cold stimuli at multiple points on the auricular skin area. To investigate users' thermal perception on the auricular area, we develop a series of ThermEarhook prototypes with 3, 4, and 5 Peltier modules. While most existing research utilized the constant level of haptic signal for different users, our pilot study with ThermEarhook shows that the auricular thermohaptic threshold varies across the feedback locations and the users. With the user-customized thermohaptic signals around the ear, our first study with 12 participants reports on the selection of the auricular configuration with four TEC modules on each side, considering the users' identification accuracy (averagely 99.3%) and preference. We then conduct three follow-up studies and a total of 36 participants to further evaluate users' perception of spatial thermal patterns with ThermEarhook, and finalize a set of multi-points auricular thermal patterns that can be reliably perceived by the users with the average accuracy of 85.3%. Lastly, we discuss the user-proposed potential applications of the thermal haptic feedback with ThermEarhook.