Compact Self-Powered Wearable IoT Device for Vital Sign Monitoring using
Hybrid Energy Harvesting Sources and Miniaturized EBG <Abstract> This paper presents a compact, self-powered wearable IoT device for monitoring vital signs, including heart rate, oxygen saturation (SpO2), and body temperature. The device integrates a low specific absorption rate (SAR), a high signal-to-noise ratio (SNR), and energy autonomy using a hybrid energy-harvesting solution. The paper's key contributions are: (1) a novel, compact wearable Image 1-shaped antenna is designed to operate within the Bluetooth frequency range; (2) A miniaturized electromagnetic bandgap (EBG) structure is implemented to minimize device-body interactions, ensuring low specific absorption rate (SAR); (3) A hybrid solar and thermoelectric energy harvesting system is employed to enable continuous self-powering; and (4) The PCB layout was optimized to integrate all essential components?including the antenna and energy management circuitry?onto a single low-cost substrate, thereby reducing both power consumption and device size. We have developed the device and have extensively evaluated it. The results show that the device achieves a 17.6% bandwidth at 2.45 GHz, efficiency above 77.2%, SAR value of 0.35 W/kg, and full self-powering capability. These results demonstrate the proposed device is a promising candidate for next-generation wearable health monitoring systems. |