Ultra-low-energy operation of electromagnetic bi-stable actuator under restricted energy supply

Abstract

During the periodic drug administration for chronic diseases, unexpected battery depletion can be significantly problematic for the patients. While body heat harvesting utilizing the wearable thermoelectric generator (WTEG) shows the significant potential in continuous drug delivery systems (DDSs) by providing ceaseless power source, the power and the voltage output might not be sufficient to drive micropump actuators in such drug delivery systems. The continuous actuating current also imposes an additional challenge in developing efficient and compact voltage boosting circuits. In this paper, we propose an ultra-low-energy operating method of the WTEG-powered electromagnetic micropump system. In combination with our electromagnetic bi-stable actuator (EBA) where the energy demand is discretized, we present (1) the dedicated high-efficient charge pumps (CPs) (2) and the actuating pulse control method to prevent redundant energy waste. The proposed 10-stage charge pump is designed to reduce the conversion loss by utilizing multiple flying-capacitor switching structure, and the 2-stage series–parallel charge pump (SPCP) is fabricated with flexible thin-film super-capacitors (TFSCs) to realize the high boosting performance within compact and wearable features. Applying the proposed control method with the 10-stage CP in our WTEG-powered micropump system, we significantly reduce the charging time per actuation by 88.8% compared to the commercial boosting circuit. Also, the 2-stage SPCP achieves 84.0% reduction in the charging time while utilizing flexible and wearable features, showing a significant potential for self-powered wearable healthcare applications.