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Body-Coupled Powering for Pervasive Wearables
Professor Jerald Yoo
National University of Singapore

Pervasive wearables is an attractive method for continuous health monitoring, smart electronics, and personal Body-Area Network (BAN). However, powering wearable electronics such as earbuds, smart band-aids, and electrocardiography (ECG) sensors are challenging. The limited battery lifetime incurs charging overhead, causes service disruptions, and inconveniences to the users; this is one of the biggest obstacles in increasing the number of wearables. To address the issue and allow for sustainable operations, power transmission, and energy harvesting approaches have been proposed. Near-field power transmission approaches using the inductive link impose stringent requirements on the alignment and are typically designed for short distances. RF-based power transmission covers a longer distance but is severely limited by the "Body-Shadowing Effect" - human body absorbs large amount of RF waves at GHz band; when in proximity to body, the antenna pattern is distorted, and an 20-40 dB pathloss occurs under non-line-of-sight (non-LoS) transmission. On the other hand, conventional energy harvesting approaches are effective only for particular locations on the body. This tutorial introduces the Body-Coupled Powering (BCP) mechanism for power transmission and ambient energy harvesting to the wearables in the entire body area. We will then look into what circuit designers should consider in such non-conventional environments. Lastly, we will discuss the opportunities lying ahead with BCP.

Jerald Yoo received the B.S., M.S., and Ph.D. degrees in the Department of Electrical Engineering from the Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea, in 2002, 2007, and 2010, respectively. From 2010 to 2016, he was with the Department of Electrical Engineering and Computer Science, Masdar Institute of Science and Technology (now Khalifa University), Abu Dhabi, United Arab Emirates, where he was an Associate Professor. From 2010 to 2011, he was also with the Microsystems Technology Laboratories (MTL), Massachusetts Institute of Technology (MIT), as a visiting scholar. Since 2017, he has been with the Department of Electrical and Computer Engineering, National University of Singapore, Singapore, where he is currently an Associate Professor.

He has pioneered research on Body-Area Network (BAN) transceivers for communication/powering and wearable body sensor network using the planar-fashionable circuit board for a continuous health monitoring system. He authored book chapters in Biomedical CMOS ICs (Springer, 2010), Enabling the Internet of Things--From Circuits to Networks (Springer, 2017), The IoT Physical Layer (Chapter 8, Springer, 2019) and Handbook of Biochips (Biphasic Current Stimulator for Retinal Prosthesis, Springer, 2021). His current research interests include low-energy circuit technology for wearable bio-signal sensors, flexible circuit board platform, BAN for communication and powering, ASIC for piezoelectric Micromachined Ultrasonic Transducers (pMUT), and System-on-Chip (SoC) design to system realization for wearable healthcare applications.

Dr. Yoo is an IEEE Circuits and Systems Society (CASS) Distinguished Lecturer (2019-2021). He also served as the IEEE Solid-State Circuits Society (SSCS) Distinguished Lecturer (2017-2018). He is the recipient or a co-recipient of several awards: IEEE International Solid-State Circuits Conference (ISSCC) 2020 and 2022 Demonstration Session Award (Certificate of Recognition), IEEE International Symposium on Circuits and Systems (ISCAS) 2015 Best Paper Award (BioCAS Track), ISCAS 2015 Runner-Up Best Student Paper Award, the Masdar Institute Best Research Award in 2015 and the IEEE Asian Solid-State Circuits Conference (A-SSCC) Outstanding Design Award (2005). He was the founding vice-chair of the IEEE SSCS United Arab Emirates (UAE) Chapter and is the chair of the IEEE SSCS Singapore Chapter. Currently, he serves as an Executive Committee as well as a Technical Program Committee Member of the IEEE International Solid-State Circuits Conference (ISSCC), ISSCC Student Research Preview (chair), and IEEE Asian Solid-State Circuits Conference (A-SSCC, Emerging Technologies, and Applications Subcommittee Chair), and Steering Committee Member of IEEE Transactions on Biomedical Circuits and Systems (TBioCAS). He is also an Analog Signal Processing Technical Committee Member of IEEE Circuits and Systems Society and an Associate Editor of IEEE Transactions on Biomedical Circuits and Systems (TBioCAS) and IEEE Open Journal of Solid-State Circuits Society (OJ-SSCS).