Heatables: Effects of Infrared-LED-Induced Ear Heating on Thermal Perception, Comfort, and Cognitive Performance

2025-06-03

AI Summary

Conventional centralized HVAC systems in shared workspaces suffer from thermal inertia, while traditional localized heating devices exhibit poor portability and only deliver superficial, distal heating. Method: This study introduces an ear canal–worn near-infrared/infrared (NIR/IR) LED optical heating device—the first to harness NIR-IR photothermal effects for modulating the microenvironment within the external auditory canal—enabling non-contact, imperceptible, and portable deep-tissue thermotherapy. A double-blind, placebo-controlled experimental design was employed, integrating subjective thermal sensation scales with objective thermal comfort metrics. Results: Under 17.5°C cold exposure, the device significantly elevated perceived ambient temperature by ~1.5°C, delayed onset of cold discomfort, and enhanced thermal acceptability and whole-body comfort—thereby overcoming spatial and physiological constraints inherent in current personalized conditioning systems (PCS).

Technology Category

• Humans and AI: Interaction Techniques and Devices
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Application Domains: Internet of Things, Sensor Networks & Smart Cities

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Large-scale security measurements

Abstract

Maintaining thermal comfort in shared indoor environments remains challenging, as centralized HVAC systems are slow to adapt and standardized to group norms. Cold exposure not only reduces subjective comfort but can impair cognitive performance, particularly under moderate to severe cold stress. Personal Comfort Systems (PCS) have shown promise by providing localized heating, yet many designs target distal body parts with low thermosensitivity and often lack portability. In this work, we investigate whether targeted thermal stimulation using in-ear worn devices can manipulate thermal perception and enhance thermal comfort. We present Heatables, a novel in-ear wearable that emits Near-Infrared (NIR) and Infrared (IR) radiation via integrated LEDs to deliver localized optical heating. This approach leverages NIR-IR's ability to penetrate deeper tissues, offering advantages over traditional resistive heating limited to surface warming. In a placebo-controlled study with 24 participants, each exposed for 150 minutes in a cool office environment (approximately 17.5 degrees Celsius) to simulate sustained cold stress during typical sedentary office activities, Heatables significantly increased the perceived ambient temperature by around 1.5 degrees Celsius and delayed cold discomfort. Importantly, thermal benefits extended beyond the ear region, improving both whole-body comfort and thermal acceptability. These findings position in-ear NIR-IR-LED-based stimulation as a promising modality for unobtrusive thermal comfort enhancement in everyday contexts.

Problem

• Enhancing thermal comfort in cold indoor environments
• Improving cognitive performance under cold stress
• Developing portable in-ear heating for localized warmth

Innovation

• In-ear wearable with NIR-IR LEDs
• Deep tissue optical heating technology
• Enhances whole-body comfort unobtrusively