Serpentine-Shaped Metamaterial Energy Harvester for Wearable and Implantable Medical Systems

Integration with the curvilinear, soft, and time-dynamic surfaces of the human body is critical for most implantable and wearable biomedical systems. Devices that can imitate the mechanics of the body provide opportunities to create human-machine interfaces. Additionally, wireless functionality is essential to monitor health/wellness, study disease conditions, and execute other functions. The use of metamaterials in wireless applications is becoming widespread due to its extraordinary properties such as evanescent wave amplification and negative refractive index. This paper studies a soft, flexible and stretchable Complementary Split Ring Resonator (CSRR) metamaterial energy harvester using a volume of 5.6 x 5.6 x 1 mm³ on a Polydimethylsiloxane (PDMS) substrate. The CSRR is backed by a ground plane to absorb the incident power, and a via (load) is used to maximize the power harvesting efficiency. For stretchability, a typically rigid patch of the CSRR is replaced by the serpentine mesh. From the ANSYS HFSS simulation, it is found that the serpentine structure helps to reduce the size of the CSRR due to an increase in electrical length. The structure can also achieve high-quality factor (Q-factor), thereby enabling almost unity efficiency. The CSRR metamaterials can be used in future for wireless applications to integrate with the skin, the heart, and the brain.