The market for wearable devices such as smart watches and smart glasses continues to grow rapidly. Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR). Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health. This paper presents a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses. It is accomplished by disassembling the state by wearing smart glasses into some parts, creating the equivalent thermal resistance circuit for each part, approximating heat-generating components such as integrated circuits (ICs) to simple physical structures, setting power consumption to the heat sources, and providing heat transfer coefficients of natural convection in air. The average temperature difference between the thermal network model and a commercial thermal solver is 0.9 °C when the maximum temperature is 62 °C. Results of an experiment using the model show that the temperature of the part near the ear that directly touches the skin can be reduced by 51.4% by distributing heat sources into both sides, 11.1% by placing higher heat-generating components farther from the ear, and 65.3% in comparison with all high conductivity materials by using a combination of low thermal conductivity materials for temples and temple tips and high conductivity materials for rims.

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Wearable technology has been rapidly evolving. Many functions beyond current smartphone capabilities must be realized in wearables that are smaller than smartphones. Heat generation due to power consumption may cause both circuit malfunctions and lowtemperature burns. This letter presents thermal design methods to promote heat dissipation of wrist wearables. First, the thermal model to easily obtain each part temperature is described. Next, belt heat dissipation effects are clarified by simulations with the model. The results indicate that each technique using the belt width, thickness, length, covering rubber, or heatsink has a high effect on heat dissipation. In addition, by combining these techniques, temperature rises of the display, bottom of device body, and belt can be reduced by 30.5%, 52.4%, and 52.7%.