Miniaturized Fully Passive Brain Implant for Wireless Neuropotential Acquisition

Kiourti

2021

Sensors

Self Cite

The idea of passive biosensing through inductive coupling between antennas has been of recent interest. Passive sensing systems have the advantages of flexibility, wearability, and unobtrusiveness. However, it is difficult to build such systems having good transmission performance. Moreover, their near-field coupling makes them sensitive to misalignment and movements. In this work, to enhance transmission between two antennas, we investigate the effect of superstrates and metamaterials and propose the idea of dielectric fill in between the antenna and the superstrate. Preliminary studies show that the proposed method can increase transmission between a pair of antennas significantly. Specifically, transmission increase of ≈5 dB in free space and ≈8 dB in lossy media have been observed. Next, an analysis on a representative passive neurosensing system with realistic biological tissues shows very low transmission loss, as well as considerably better performance than the state-of-the-art systems. Apart from transmission enhancement, the proposed technique can significantly mitigate performance degradation due to misalignment of the external antenna, which is confirmed through suitable sensitivity analysis. Overall, the proposed idea can have fascinating prospects in the field of biopotential sensing for different biomedical applications.

Section: Implementation: a Passive Neurosensing Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Novel Method of Transmission Enhancement and Misalignment Mitigation between Implant and External Antennas for Efficient Biopotential Sensing

Kiourti

2021

Sensors

Self Cite

IEEE Trans. Antennas Propagat.

“…WIMD based solutions are also relevant to new forms of brain interfacing and neuro-stimulators including urinary bladder control, the early detection and interruption of seizures or when monitoring brain functionality in patients diagnosed with Alzheimer's disease or related illnesses. Similarly, WIMDs have a role to play in directly improving patient quality of life through smart prosthesis or artificial organs [5]- [7].…”

Section: Introductionmentioning

confidence: 99%

“…Irrespective of the application it is clear that wireless communication with implanted medical devices is advantageous as it reduces the risk of infection [8] and offers much more flexibility in terms of selection of the implant site [5], [9]. Early medical implants utilized inductive coupling communication techniques but alignment concerns and the need for higher information rate operation led to studies at UHF Scanlon is with Tyndall National Institute, University College Cork (Ireland) and the remaining authors are with the Centre for Wireless Innovation, ECIT, Queen's University of Belfast (UK).…”

Section: Introductionmentioning

confidence: 99%

“…frequencies [10], [11] and now there are many commercial solutions available [12]. This interest in RF-based implant communication led to the establishment of the medical implant communication services (MICS) band at 402-405 MHz [5], [13]. More recently, researchers have also been considering the use of the industrial, scientific and medical (ISM) band at 2360-2483.5 MHz due to the ease of antenna design, particularly since WIMD applications are demanding much smaller device dimensions [14].…”

Section: Introductionmentioning

confidence: 99%

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Assessing the Intrinsic Radiation Efficiency of Tissue-Implanted UHF Antennas

El-Saboni

Zelenchuk

Conway

et al. 2020

Dielectric loss occurring in tissues in close proximity to UHF implanted antennas is an important factor in the performance of medical implant communication systems. Common practice in numerical analysis and testing is to utilize radiation efficiency measures external to the tissue phantom employed. This approach means that radiation efficiency is also dependent on the phantom used and antenna positioning, making it difficult to understand antenna performance and minimize near-field tissue losses. Therefore, an alternative methodology for determining the intrinsic radiation performance of implanted antennas that focuses on assessing structural and near field tissue losses is presented. The new method is independent of the tissue phantom employed and can be used for quantitative comparison of designs across different studies. The intrinsic radiation efficiency of an implant antenna is determined by assessing the power flow within the tissue phantom at a distance of at least λg/2 from the radiating structure. Simulated results are presented for canonical antennas at 403 MHz and 2400 MHz in homogeneous muscle and fat phantoms. These illustrate the dominance of propagating path losses in high-water content tissues such as muscle, whereas nearfield dielectric losses may be more important in low-water tissues such as fat due to the extended reactive near-field.

Wireless Wearables and Implants: A Dosimetry Review

Guido

Kiourti

2019

Bioelectromagnetics

Self Cite

Wireless wearable and implantable devices are continuing to grow in popularity, and as this growth occurs, so too does the need to consider the safety of such devices. Wearable and implantable devices require the transmitting and receiving of electromagnetic waves near and through the body, which at high enough exposure levels may damage proximate tissues. The specific absorption rate (SAR) is the quantity commonly used to enumerate exposure levels, and various national and international organizations have defined regulations limiting exposure to ensure safe operation. In this paper, we comprehensively review dosimetric studies reported in the literature up to the year 2019 for wearables and implants. We discuss antenna designs for wearables and implants as they relate to SAR values and field and thermal distributions in tissue, present designs that have made steps to reduce SAR, and then review SAR considerations as they relate to applied devices. As compared with previous review papers, this paper is the first review to focus on dosimetry aspects relative to wearable and implantable devices. Bioelectromagnetics. 2020;41:3–20 © 2019 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc.