Antennas for in-body Biotelemetry Capsules Denys Nikolayev, PhD student at the University of Rennes, France and BioEM2015 Student Award winner reports about his research and experience at BioEM2015

Authored by: Denys Nikolayev

Published on: Sep 23, 2015

Denys Nikolayev (denys.nikolayev@univ-rennes1.fr), Maxim Zhadobov, Ronan Sauleau

In-body electronics first came into sight in the late 1950s when Rune Elmqvist developed the first implantable pacemaker. The first patient to receive the implant was 43-year-old Arne Larsson; he lived to the age of 86 years, outliving both the inventor and surgeon. In the meantime (1957), the first publications reported the successful development of wireless ingestible capsules. At that time, the potential of in-body devices was revealed: it can greatly improve diagnosis, treatment and prevention of disease, illness or injury. Apart from telemetering various diagnostic data—endoscopy, temperature, pressure, pH, oxygen and glucose levels—modern in-body biomedical applications also include brain–machine interfaces and visual prosthesis, pacemakers and defibrillators, drug delivery and hyperthermia.

Emerging biomedical wireless telemetry permits continuous monitoring of physiological parameters while maintaining mobility and increasing the quality of life of a patient or animal. It relies on an efficient and reliable communication with an external monitor via a radio frequency link. Although alternatives to RF transmission exist (e.g. inductive links), they are limited both in operational range and throughput. Antenna detuning and efficiency issues related to the lossy and dispersive nature of biological tissue. Energy and miniaturization problems have always been among the main challenges to face while developing in-body devices. Improving the transmission performance still remains one of the main research objectives, as modern deep in-body devices (e.g. ingestible capsules) are able to broadcast only within a few meters.

At the BioEM 2015 we presented the numerical and experimental results on reducing the near-field coupling of an antenna with the surrounding tissue of an ingestible capsule. We used dielectric loading by the ceramic superstrate of a miniature cylindrical-microstrip antenna. This approach enhances through-body transmission performance and reduces exposure level of the surrounding tissue. Namely, we increased threefold the operating range compared to a reference design, reduced the 1 g SAR by 30% (normalized by the radiated power) and achieved robust operation of the antenna both in human tissue as well as in air (S11 < –10 dB at 434 MHz for all environments). More details are to come in the future issues of the Bioelectromagnetics journal.

The conference was a remarkable experience for me. Apart from an appealing scientific program, I enjoyed a lot the Asilomar grounds with its architecture, flora and wildlife as well as the dinner at the Monterey Bay Aquarium accompanied with great jazz. I really look forward to attend the BioEM 2016.

Acknowledgements

We would like to express our gratitude and appreciation to the Bioelectromagnetics Society for providing a travel support and to the BodyCap Company without which this research would have been impossible. Support for our research was provided by the Eiffel Scholarship (the French Ministry of Foreign Affairs and International Development), the doctoral school MATISSE and the Grant project GACR P102/11/0498 by the Grant Agency of the Czech Republic.

About the author

Denys Nikolayev has been working towards his PhD degree since 2014 at the Institute of Electronics and Telecommunications of Rennes (IETR – Rennes, France), jointly with the University of West Bohemia (Pilsen, Czech Republic). His research interests include wireless biotelemetry, bioelectromagnetics, antennas and microwave engineering, and numerical methods for electromagnetics and coupled physical problems.