Kush Agarwal
Doctoral Research Scholar
National University of Singapore
Department of Electrical and Computer Engineering and SINAPSE
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Research
Wireless power delivery and telemetry have enabled completely implantable neural devices. Current day implants are controlled, monitored and powered wirelessly, eliminating the need for batteries and prolonging the lifetime. My doctoral research primarily focuses on antennas and wireless power transfer systems and topologies focussing such biomedical applications. Bioelectronics, such as pacemakers, cochlear implants, and deep-brain stimulators, restore health through patterns of electrical impulses. To make such treatments practical, future bioelectronic devices must be miniaturized, and new ways must be found to target specific neural circuits, process real-time signals, and wirelessly transfer data or power. I am broadly interested in developing technologies for the integration of bioelectronics with living systems. Approaches include fundamental studies in wave-tissue interactions, engineering of microelectronic devices, and experiments in both computational and animal models like rodents and non-human primates.
Wireless Power Transfer
Neural implants have become common in recent times with few of them getting FDA approved after clinical trials. Some of these neural implants are powered using non-rechargeable batteries, whereas some of them are using rechargeable batteries or being sustainably powered by wireless power transfer schemes. Implants powered using batteries have limited lifetime and a surgical intervention is required to replace them each time. As batteries have finite recharge cycles, wirelessly charging the batteries only provides an incremental lifetime. Battery-free operation using sustainable wireless powering can extend the lifetime of implants as long as needed. A part of my doctoral research focuses on topology, design and system integration of such wireless power transfer schemes with respect to various implant requirements, and testing them in rodents and NHPs (monkeys).
R. Jegadeesan, S. Nag, K. Agarwal, N. V. Thakor and Y. X. Guo, “Enabling Wireless Powering and Telemetry for Peripheral Nerve Implants”, IEEE Journal of Biomedical and Health Informatics, 2015.
R. Jegadeesan*, K. Agarwal*, Y. X. Guo, S. C. Yen and N. V. Thakor, "Wireless Power Delivery to Flexible Subcutaneous Implants using Capacitive Coupling", IEEE Transactions on Microwave Theory and Techniques, 2016. (*co-first authors)
Wearable Antennas
The integration of wireless sensing and communication into clothing is a very attractive solution in many sectors; for example, in the medical monitoring of hospitalised or home-bound patients, or by emergency personnel in search and rescue missions, particularly in hazardous environments. Wearable antennas are light-weight, low-cost and unobtrusive compared to the usual rigid antenna structures. The electromagnetic interaction between the human body and the antenna is a serious issue as: firstly, the irradiation of the human body over longer periods of time may present a health risk; and secondly, the body may strongly affect the performance of the antenna. As a part of my doctoral research, I am working on novel periodic metasurfaces to improve the stability of the antenna performance on human body and reduce the body absorbed radiations (SAR values) for on/off body communications. I am also investigating materials like latex/PDMS etc. for fully flexible non-textile antennas.
K. Agarwal, Y. X. Guo and B. Salam, “Wearable AMC backed Near-Endfire Antenna for On-Body Communications on Latex Substrate”, IEEE Transactions on Components, Packaging and Manufacturing Technology, 2016.
Implantable Antennas
Out of the several components present in an implantable medical device, the implantable antenna is the only radiating structure and hence its performance is significantly affected by the surrounding human tissue environment. The design challenges of implantable antennas include wide bandwidth, compact antenna size, good radiation efficiency, and FCC’s patient safety requirements. As a part of my doctoral research, I am working on completely flexible, conformal and biocompatible antennas on materials like PDMS/Silk etc. for bidirectional wireless data telemetry in human implants.
K. Agarwal and Y. X. Guo, "Interaction of Electromagnetic Waves with Humans in Wearable and Biomedical Implant Antennas", APEMC' 2015.
Metasurface based antennas
In the recent years, electromagnetic metamaterials have been
intensely studied and used for enhancing the radiation properties of the antennas like frequency bandwidth and direction of antenna radiation for the circularly polarized microstrip antenna designs with size miniaturization. Reactive impedance surfaces (RISs), comprising of the square periodic patches on a grounded high dielectric substrate have been used for antenna size miniaturization and performance enhancement. Artificial magnetic conductors (AMC), such as electromagnetic band-gap (EBG) structures have also been used to achieve a zero degree reflection phase for wideband antenna designs and better impedance matching. Continuing graduate research work done on metasurface based antennas during my M.Sc., I also investigate novel compact/miniaturized antenna designs with metamaterials for enhancing the antenna properties for various system level applications.
K. Agarwal, Nasimuddin and A. Alphones, “Wideband Circularly Polarized AMC Reflector Backed Aperture Antenna”, IEEE Transactions on Antennas and Propagation, 2013.
K. Agarwal, Nasimuddin and A. Alphones, “RIS-based Compact Circularly Polarized Microstrip Antennas”, IEEE Transactions on Antennas and Propagation, 2013.