No abstract

Temperature is an important influencer of homeostatic comfort for humans, and its influence extends beyond life-preservation functions into cognitive and emotional effects. To augment metabolic processes in cold climates, many on-body heating solutions are currently available in the commercial market, ranging from chemical heat packs to electrically heated accessories and clothing. These products typically prioritize heating the body core in extreme conditions. By contrast, the experience of thermal comfort in the band around homeostatic comfort temperatures is much more strongly driven by experience of temperature in the body’s periphery: the hands, feet, and face [1]. Thermal sensitivity is highest in the distal extremities and has been established as the best correlate of overall perception of thermal comfort [2], [3]. In the medical context, this is especially significant in treating vasospastic disorders such as Raynaud’s Syndrome, where a spastic vascular response in peripheral vessels results in an over-reaction to cold temperatures proximal to the thermoneutral zone [4].

Supplemental heating systems for the distal extremities often require a tradeoff between wearability and thermal comfort. Textile-based thermal actuation helps manage this tradeoff by increasing comfort of on-body systems. However, textile-based thermal actuation also presents important limitations in the form of current requirements, control structures, and thermal flux afforded. Further, on-body active thermal control is affected by three intersecting thermal systems: the environment, the human body, and the active heating system. Here, we present lessons learned from iterative development of textile-based wearable systems (V1, V2) designed to heat the distal extremities. Experimental characterization of textile actuator power/temperature relationships and limits; actuator performance in cool ambient temperatures and in on-body conditions; and efficacy of closed-loop duty cycle control of actuated skin temperature are presented, and implications of these characteristics for garment system design are discussed.

No abstract

Thermal physiology and psychophysics are complex and nuanced, with significant variability between individuals. Wearable devices have the potential to offer customizable microclimate control. However, individual experiences with different supplemental heating strategies are likely to vary considerably in unconstrained environments. The physiological responses, psychophysical effects, and qualitative experiences of participants using five readily available heating strategies were collected in a quasi-field study environment ( n=17). Although all devices maintained or increased fingertip temperature, effects observed from controlled studies of thermal physiology are not clearly seen. Physiological, perceptual, and experiential data are presented, exploring heating technologies and thermal comfort in typical indoor environments.