The primary objective of this research is to dramatically reduce the power needed to communicate information around the body in order to help enable the next generation of wearable medical and wellness devices. Current wearables tend to utilize Bluetooth for communication around the body, which despite operating fairly reliably, is extremely energy inefficient, resulting in poor device battery life. A conventional Bluetooth device found on a wearable medical patch, for example, will broadcast radio waves in all directions, with as little as 0.000001% of the transmitted energy received by the radio on your smartwatch or smartphone, in part due to large absorption of electromagnetic energy by the human body at 2.4GHz. To improve the efficiency of wireless communication, the proposed research endeavors to leverage the human body itself as a communication channel. Specifically, rather than broadcasting information in all directions, which has severe energy inefficiencies and privacy/security concerns, the proposed approach utilizes wired coils placed within the band of a smartwatch, in a wearable patch, or on a smartphone, to generate small magnetic fields that safely and efficiently pass through the body. The electromagnetic properties of the human body at the much lower targeted frequencies (10-50MHz) are more favorable than at 2.4GHz, enabling efficiencies as high as 10%, with rapid fall-off away from the body, for inherently more efficient, secure, and private communications. The generated magnetic fields are of lower strength than Earth's natural magnetic field, and orders of magnitude less than Bluetooth or mobile phones, and are thus considered to be safe. To demonstrate the effectiveness of this technique, several coil, circuit, and system prototypes will be developed and tested for a variety of healthcare-related applications such as in hearing aids and wearable glucose monitors. The program also includes an education plan that is synergistic with the research goals, including outreach to K-12 and underrepresented students in engineering.
The proposed communication system specifically leverages the high dielectric constant of biological tissue to attain high efficiency. Despite being largely magnetically-inert, magnetic energy delivered to the body at 10-50MHz has, due to the high dielectric constant of tissue, enhanced near- and mid-field components, while also generating far-field components that totally-internally reflect to create a human-body-based dielectric waveguide-like structure. The objectives of this CAREER proposal are to develop physical models that describe this behavior, optimize coils for low trans-body path loss, and design, fabricate, and test integrated circuits to communicate across the body at high efficiency. Successful development will enable body-area networking transceivers that operate at much higher efficiency than conventional techniques, enabling wearable devices that are smaller and have longer battery life than before, thereby opening up new avenues and applications in healthcare, wellness, and personal infotainment systems. To help broaden participation of members of underrepresented groups in STEM fields, related research results will be discussed at K-12 outreach events, including, for example, the creation of interactive body-area network communication experiences at summer technology camps.
