Free Battery-based Energy Harvesting Techniques for Medical Devices

Abstract

Many wearables or portable medical devices have limited battery energy. Such batteries cannot operate for a long time and require recharging or periodic replacement. A piezoelectric transducer (PZT), ultrasonic sensor (USS), and magnetic resonator coupling (MRC) are potential technologies for solving this problem, being promising technologies that can be used to generate free power for low-power medical applications. The USS and MRC optimize transfer power, efficiency, and distance between the transmitter and receiver. These three technologies can generate power to wearable and implantable medical devices (IMDs). To validate the proposed PZT, USS, and MRC, we supplied electromyography (EMG) sensor, a heart rate sensor, and oxygen saturation (SpO2) sensor with adequate power to measure the subject’s muscle activity, heart rate (beats per minute, bpm), and SpO2 rate, respectively. The proposed system consists of four parts: power system, measurement part, wireless transmitter, and monitoring part. We found that 5 V could be used for charging 0.25, 0.33, 0.5, and 1 Farad supercapacitors based on the PZT at duration. Furthermore, the 0.25 F supercapacitor was fully charged in 41 min; compared with previous closed-circuit studies, it achieved high power of 197 μW at resistive load 15 kΩ. In addition, USS-based transfer efficiencies and powers could be used with 1, 4, and 8 F supercapacitors. The system had transfer efficiency and power of 69.4% and 0.318 mW, respectively, at 4 cm when 4 F was adopted. Furthermore, the MRC system had transfer efficiency and power of 21.14% and 2.079 W, respectively, at 7 cm at resistive load 70 Ω. Our results show that the PZT, MRC, and USS in the present study outperformed previous works in terms of power generation, transfer power, and efficiency.