Requirements, challenges, and novel ideas for wearables on power supply and energy harvesting

Smart wearables are receiving increasing attention. Different forms of wearables have a wide range of power requirements, and lithium-ion batteries are now the most popular energy storage option. This paper discusses the trends and challenges of smart wearables. Future wearable technology will be more compact and integrated. For the specificity of future wearables, new energy harvesting technologies that are more practical, durable, and ecologically beneficial are needed. This paper summarizes the research on the human body and environment based energy harvesting techniques, including solar, thermal, Radio frequency (RF) energy, kinetic energy, and biomass energy. We deeply analyze the application potential and limitations of each new energy harvesting technology and summarize the relationship between the energy required by wearables and the new energy harvesting systems. Solar and kinetic energy generation technologies have higher energy density and are suitable for application in outdoor sports wearables. RF energy, thermal energy, and biomass energy have less energy dense and can be used as auxiliary power sources for small wearables. The combination of the energy harvesting system and the micro energy storage unit enables the continuous power supply of wearables in different circumstances of daytime, nighttime, indoor and outdoor. The significance of this work stems from providing guidance for future energy supply methods of wearables.