Heatables

Maintaining thermal comfort in shared indoor environments remains an ongoing challenge. Conventional heating, ventilation, and air-conditioning (HVAC) systems are slow to respond and typically optimized for population averages rather than individual needs. These systems also contribute significantly to energy consumption and carbon emissions.

Heatables introduces a fundamentally different approach by providing localized, low-power optical heating through in-ear wearables. Leveraging the ear’s rich vascularization and its proximity to thermoregulatory centers, the project investigates how subtle, targeted thermal stimulation can elicit a broader perceptual effect of warmth throughout the body. This work positions the ear as a promising site for efficient, perception-driven thermal feedback.

The primary objective of Heatables is to understand how localized infrared stimulation in the ear canal can influence whole-body thermal perception, comfort, and cognitive performance. The project aims to establish empirical evidence for:

• The perceptual coupling between localized and systemic thermal experience,

• The feasibility of in-ear thermal interfaces as components of personal comfort systems, and

• The absence of adverse effects on cognition and user comfort during extended use.

Long-term, Heatables contributes to the development of adaptive thermal technologies that enhance well-being while reducing the energy footprint of environmental conditioning.

The Heatables prototype builds upon the OpenEarable 2.0 platform, integrating multi-chip LEDs emitting at 810 nm and 950 nm to provide controlled infrared stimulation. The system delivers gentle, perceptually meaningful heat by modulating optical power at low frequencies, ensuring safe deep-tissue coupling without visible light emission.
A placebo-controlled mixed factorial study with 24 participants was conducted in a thermally controlled office environment (17.5 °C). Participants engaged in sedentary tasks over 150 minutes while physiological and subjective measures were continuously recorded. Results demonstrate that localized in-ear stimulation significantly increased perceived warmth and comfort, extending beyond the stimulation site to other body areas, while maintaining cognitive stability and high usability ratings.

Our findings demonstrate that localized in-ear NIR/IR stimulation can induce a systemic increase in perceived warmth, extending beyond the stimulation site to distal body regions. Participants reported significantly higher thermal comfort and acceptability under Heatables conditions compared to both placebo and control groups, indicating a robust perceptual effect despite minimal physical heating. Cognitive performance remained stable across all conditions, confirming that the intervention did not impose any cognitive load or distraction. Furthermore, participants consistently rated the device as comfortable, unobtrusive, and safe, with only minimal reports of heat buildup during extended wear, underscoring its suitability for sustained real-world use.

These results collectively support the concept of the ear as a thermal gateway, where minimal localized stimulation can produce perceptual benefits disproportionate to energy input.

This work was recognized with the Best Paper Award at ISWC 2025 (UbiComp/ISWC, Espoo, Finland).

Project Lead: Valeria Zitz (M.Sc.), Karlsruhe Institute of Technology (KIT) – TECO Group
Supervision: Dr. Tobias Röddiger & Prof. Dr. Michael Beigl
Collaborators: Michael Küttner, Jonas Hummel, Dr. Michael Knierim