Novel Radio-Frequency Devices and Systems for Wearable Electronics and Wireless Power Transfer

Wearable and implantable systems have transformed the way we monitor and interact with our bodies. These systems are designed to be seamlessly integrated into daily life and have the potential to provide valuable health information to patients and healthcare providers. With the aging population, there is a growing need for remote monitoring and diagnostics, making wearable and implantable systems increasingly important. However, current wearable and implantable systems have limitations, such as the need for batteries or wire connections, which can make the devices bulky and uncomfortable. The use of rigid circuit components can also restrict the application of these systems. Therefore, there is a need for alternative approaches to improve the performance, versatility, and wearing comfort of these systems. In this dissertation, our primary objective is to address the prevalent constraints in wearable and implantable systems. Specifically, our approach leverages harmonic re-radiation and parity-time symmetry to develop wireless and fully passive systems that are compatible with soft nanomaterials such as silver nanowires and liquid metal. We present a series of innovative biomedical systems, including a breathable, reusable and zero-power smart face mask for wireless cough and mask-wearing monitoring, as well as multimodal wireless wound sensors for monitoring wound healing process. Additionally, we explore multi-band parity-time-symmetric wireless power transfer systems for bio-implantable applications, and an ultra-sensitive sensing mechanism grounded in parity-time-reciprocal scaling symmetry. The proposed systems are characterized by their compactness, light weight, battery-free nature, multiplexing capacity, and sensitivity, possessing the capability to meet the demands of healthcare internet-of-things applications. We envision that these systems hold great potential as promising solutions for next-generation wireless wearable devices and smart health monitoring systems.