Research on temperature control of smartwatch based on composite phase change material

Abstract

The smartwatch is one of the most widely used wearable electronics, which combines networking, health monitoring, communication, and other multifunctional features. As it gets smaller, more integrated, and denser, its power consumption increases. Owing to its strong sealing and waterproof capabilities, the equipment has trouble dissipating the heat produced during operation, which raises the equipment's temperature. Since smartwatches come into direct contact with human skin, they can burn skin when temperatures rise beyond 45 °C. Phase change material (PCM) is suitable for thermal management of intermittent electronic devices because they absorb a large amount of heat and can maintain a constant temperature during the phase transition, which means that they absorb heat when the device is in use and release heat when it is out of use. In this study, paraffin wax (PA) is used as the phase change material, styrene ethylene butylene styrene (SEBS) is used as the flexible support material, and expanded graphite (EG) is used as the thermal conductivity enhancer to prepare PCM sheets for thermal management of smartwatches. The effects of SEBS and EG on the shape stability, enthalpy, and thermal conductivity of the composite phase change material (CPCM) with different ratios were investigated, in which PA:SEBS of 7:3 has better shape stability, so CPCM with a PA:SEBS ratio of 7:3 and different EG contents was used to make PCM sheet, which were placed in the smartwatch, and it was verified experimentally that this PCM sheet could delay the temperature rise of the case and chip of the smartwatch and prolong its usage time. This CPCM is promising for smartwatch thermal management applications.