Denys Nikolayev

French National Centre for Scientific Research | CNRS · IETR (UMR 6164) Rennes

Progress in implantable and ingestible wireless biotelemetry requires versatile and efficient antennas to communicate reliably from a body. We propose an ultra-miniature 434 MHz antenna immune to impedance detuning caused by varying electromagnetic properties of the surrounding biological environment. It is designed for a standard input impedance o...

Autonomous wireless body-implanted devices for biotelemetry, telemedicine, and neural interfacing constitute an emerging technology providing powerful capabilities for medicine and clinical research. We study the through-tissue electromagnetic propagation mechanisms, derive the optimal frequency range, and obtain the maximum achievable efficiency f...

Background and Objective: In-body biotelemetry devices enable wireless monitoring of a wide range of physiological parameters. These devices rely on antennas to interface with external receivers, yet existing systems suffer from impedance detuning caused by the substantial differences in electromagnetic properties among various tissues. In this pap...

Autonomous implantable bioelectronics requires efficient radiating structures for data transfer and wireless powering. The radiation of body-implanted capsules is investigated to obtain the explicit radiation optima for E- and B-coupled sources of arbitrary dimensions and properties. The analysis uses the conservation-of-energy formulation within d...

Wireless in-body bioelectronics offer powerful biosensing and therapeutic capabilities. Efficient and robust in-body antenna designs are required to ensure a reliable through-body link, increase data rates, and reduce power budgets. This study proposes and demonstrates a pattern- and frequency-reconfigurable capsule-conformal antenna array that res...

Implanted bioelectronic devices can form distributed networks capable of sensing health conditions and delivering therapy throughout the body. Current clinically-used approaches for wireless communication, however, do not support direct networking between implants because of signal losses from absorption and reflection by the body. As a result, exi...

Electronic boluses with biotelemetry capabilities enable wireless monitoring of animals’ physiological data (e.g., temperature, pH). The aim of this study was to design and experimentally validate a novel multiband (434, 868, 1400) MHz conformal patch antenna for in-body biotelemetry applications for cows. The optimal frequency band was studied pri...

This paper proposes a dual-band frequency scanning meandering microstrip leaky-wave antenna with linear polarization in the Ku-band and circular polarization in the K-band. This is achieved by making use of two spatial harmonics for radiation. The unit cell of the periodic microstrip antenna contains three meanders with mitred corners. To ensure ci...

Conformal phased arrays can be found in many applications due to their ability to fit tridimensional surfaces and, thanks to their scanning performance, can excel planar arrays. However, most of the previously proposed analysis methods can be applied only to canonical cases and do not consider the effects of polarization. Therefore, this paper pres...

A Leaky Wave Antenna (LWA) design with high scanning rate (the ratio of beam scanning range and band-width) is proposed in this work. The antenna is based on a periodic meandering microstrip line operating in K-Band with continuous beam scanning from backward-to-forward direction in the elevation plane. The height of the transverse lines is varied...

Objective: Numerical modeling of electric fields induced by transcranial alternating current stimulation (tACS) is currently a part of the standard procedure to predict and understand neural response. Quasi-static approximation for electric field calculations is generally applied to reduce the computational cost. Here, we aimed to analyze and quan...

During their travel through the gastrointestinal tract, ingestible antennas encounter detuning in their impedance response due to varying electromagnetic properties of the surrounding tissues. This paper investigates the possibility of using this impedance detuning to detect in which segment of the gastrointestinal tract – stomach, small intestine,...

This paper proposes a dual-band frequency scanning meandering microstrip leaky-wave antenna with linear polarization in the Ku-band and circular polarization in the K-band. This is achieved by making use of two spatial harmonics for radiation. The unit cell of the periodic microstrip antenna contains three meanders with mitred corners. To ensure ci...

The wireless power transfer (WPT) efficiency to implanted bioelectronic devices is constrained by several frequency-dependent physical mechanisms. Recent works have developed several mathematical formulations to understand these mechanisms and predict the optimal operating conditions. However, the existing approaches rely on simplified body models,...

The paper discusses an on-body V-band leaky­ wave antenna for navigation and safety applications. The antenna is based on meandering microstrip line operating in V-Band with continuous beam scanning from backward-to­ forward direction in the elevation plane. The width of the transverse line are alternatively varied to remove the open stop band (OSB...

This paper describes the exploration of the combined antenna–channel model for a horse hoof. An antenna of 25 mm × 40 mm is designed in the ISM 868 MHz band. During the characterization and design of the antenna, the dynamic and harsh environment of the horse hoof is taken into account throughout every step of the procedure because it is impossible...

During their travel through the gastrointestinal tract, ingestible antennas encounter detuning in their impedance response due to varying electromagnetic properties of the surrounding tissues. This paper investigates the possibility of using this impedance detuning to detect in which segment of the gastrointestinal tract - stomach, small intestine,...

The lossy and heterogeneous nature of the body tissues and the significant wave-impedance contrast as the electromagnetic wave propagates inside the body limits the fundamentally achievable efficiency of far- and midfield wireless charging of deep-body implantable devices. In addition, fluctuations in the implant position cause a further variation...

Several frequency-dependent mechanisms restrict the maximum achievable efficiency for wireless powering implantable bioelectric devices. Similarly, many mathematical formulations have been proposed to evaluate the effect of these mechanisms as well as predict this maximum efficiency and the corresponding optimum frequency. However, most of these me...

Objective: Numerical modeling of electric fields induced by transcranial alternating current stimulation (tACS) is currently a part of the standard procedure to predict and understand neural response. Quasi-static approximation for electric field calculations is generally applied to reduce the computational cost. This study aims to analyze and quan...

The purpose of this work is to evaluate local power and electric field distributions inside high-resolution 3D anatomical CAD models of cutaneous appendages at 60 GHz upcoming for 5G/6G. The microscale resolution models of cutaneous nerves, lymphatics, pilosebaceous unit, microvasculature, eccrine sweat glands, Meissner corpuscle and Pacinian corpu...

The aim of this study was to investigate quantitatively local sub-cellular power deposition at frequencies upcoming for wireless power transfer (WPT) and millimeter-wave (mmWave) technologies. The study was performed on a realistic two-dimensional keratinocyte cell model, designed based on electron microscopy images and experimental data on surface...

Wireless Power Transfer (WPT) techniques allow significant miniaturisation of implanted medical devices. However, the electromagnetic exposure of the body tissues must be accurately accessed to ensure safe operation. This study, therefore, analyses the exposure induced by the magnetic- and electric-type antenna transmitters over the frequency range...

Objective: Cellular sensitivity to heat is highly variable depending on the cell line. The aim of this paper is to assess the cellular sensitivity of the A375 melanoma cell line to continuous (CW) millimeter-waves (MMW) induced heating at 58.4 GHz, between 37 C and 47 C C to get a deeper insight into optimization of thermal treatment of superficia...

The efficiency of an on-body wireless power transfer system for implant powering is defined by how the electromagnetic energy interacts with the lossy, heterogeneous, and dispersive body tissues. The objective of this study is to discuss the methodology and evaluate the theoretical bounds for the frequency-dependent electromagnetic energy transfer...

With the fast development of 5th generation (5G) mobile networks and prominence of the personal area networks and human-centered communications, people of all ages are increasingly exposed in the upper part of the microwave spectrum. In some exposure scenarios, presence of a textile between the radiating source and skin can affect the power absorpt...

Fundamental limits for implanted antennas should be able to evaluate the bounds on losses with the knowledge of physical limitations from antenna and tissue parameters. In this work, rules of thumb to assess losses of deeply implanted antennas are presented toward improving the radiation efficiency. By means of rigorous and approximate approaches,...

Automated systems based on wearable sensors for livestock monitoring are becoming increasingly popular. Specifically, wireless in-body sensors could yield relevant data such as ruminal temperature. The collection of such data requires an accurate characterization of the in-to-out body wireless channel between the in-body sensor and the gateway. The...

Fundamental in-body limitations on achievable radiation efficiency could provide decision-making assistance to engineers working on antennas for implantable bioelectronics. In this study, proof-of-concept conformal microstrip antennas are proposed based on these theoretical foundations. In particular, maximizing the effective aperture and loading t...

Wireless technologies are essential components of wearable devices for applications ranging from connected healthcare to human-machine interfaces. Their performance, however, is hindered by the human body, which obstructs the propagation of wireless signals over a wide range of directions. Here, we demonstrate conformal propagation and near-omnidir...

Wireless neural interfaces provide major leap capabilities for neurotechnology by removing hazardous and bulky percutaneous links. This study addresses for the first time the radio frequency (RF) electromagnetic (EM) exposure of mm-sized neural implant antennas in the frequency range from 100 MHz to 4 GHz. The results demonstrate the existence of m...

Fundamental limits on radiation performance of implantable antennas serve as the design quality gauge, facilitate the choice of the antenna type, and provide simple design rules to maximize the radiation performance. This study obtains the limits using two formulations: 1) theoretical spherical-wave expansion using elementary magnetic and electric...

Conformal antenna arrays are able to fit seamlessly on curved 3D-shaped surfaces, which are found ubiquitously on vehicles, aircraft, a human body, etc. In addition, conformal structures can overcome the scan loss limitations of conventional planar arrays. Yet, only a few computational analysis methods have been proposed with either performance or...

Fundamental bounds on achievable radiation efficiency serve as the design quality gauge, facilitate the choice of the antenna type considering the available dimensions, and provide simple rules to check the feasibility of a given design. This study quantifies the effect of body-implanted capsule dimensions and materials on achievable radiation effi...

Wireless implantable bioelectronics and accurate in vivo characterization of path loss require efficient and robust in-body antennas. Loading electric antennas with the effective permittivities higher than that of surrounding tissues is a promising solution. In this study, proof-of-concept conformal microstrip antennas are proposed. The antennas ar...

Shallow penetration of millimeter waves (MMW) and non‐uniform illumination in in vitro experiments result in a non‐uniform distribution of the specific absorption rate (SAR). These SAR gradients trigger convective currents in liquids affecting transient and steady‐state temperature distributions. We analyzed the effect of convection on temperature...

Miniature wireless implantable bioelectronics provide powerful capabilities for biotelemetry, therapeutics, and neural interfacing. These technologies rely on antennas to communicate with external receivers, yet existing systems suffer from poor radiation performance. We address this issue by studying the through-tissue propagation, deriving the op...

This study investigates the impact of convection on temperature dynamics in a typical in vitro exposure scenario during continuous and pulsed millimetre-wave (MMW) induced heating. Results showed that the onset of convection during continuous heating i) is preceded by the appearance of a temperature peak, which occurrence in time depends on SAR (th...

In-body bioelectronics relies on antennas to interface with external on-or off-body equipment. In this paper, we address the impedance detuning of in-body antennas caused by nondeterministic electromagnetic properties of biological tissues. The impedance robustness can be improved in two ways. First, by using wideband and multiresonance antennas wi...

In this Letter, for the first time, the in-to-out-body path loss between an antenna placed inside the cows’ rumen and a distant gateway was characterised at 433 MHz. Measurements were conducted on seven different fistulated cows using a signal generator and a spectrum analyser. Subsequent measurement of the antenna in free space was used to quantif...

Background: Uniform current density electrodes can reduce the risk of electrode corrosion and tissue damage, but existing geometries do not suit thin planar leads. Objectives: This study examines current density distribution (CDD) on low-profile electrode designs and proposes an approach to obtain optimal geometries with near-uniform CDD requiring...

Emerging wireless in-body devices pave the way to many breakthroughs in healthcare and clinical research. This technology enables monitoring of physiological parameters while maintaining mobility and freedom of movement of its user. However, establishing reliable communication between an in-body device and external equipment is still a major challe...

In-body antennas couple strongly to surrounding biological tissues thus resulting in radiation efficiencies well below 1%. Here, we quantify how the permittivity and conductivity, each individually, affect the radiation efficiency of miniature implantable and ingestible antennas. We use a generic pill-sized capsule antenna and a spherical homogeneo...

Long-range in-body biomedical telemetry enables monitoring of physiological parameters while maintaining mobility and freedom of movement. This emerging technology creates new applications in medicine, clinical research, wellness, and defense. Current in-body biotelemetry devices operate within about a meter around a user that limits their applicab...

In-body devices for wireless biotelemetry and neural interfacing could empower many breakthroughs in medicine and clinical research. Despite significant progress in antenna design, improving the radiation performance of miniature in-body devices remains a major challenge because, for the time being, they are able to operate at distances of only up...

We propose a versatile 434 MHz in-body capsule antenna suitable for ingestible and variety of implantable applications. The low profile conformal antenna is synthesized using a hybrid analytical–numerical approach and optimized for robust operation at 434 MHz inside a 17 mm long biocompatible encapsulation (7 mm diameter). The antenna remains match...

When designing a TEM transmission line cell for electromagnetic compatibility susceptibility or immunity tests, its input impedance must be properly defined in order to deliver the maximum power to the device under test. The closed-form solution, relating the cell geometry with the characteristic impedance Zc, is possible only for the simplest “can...

Body-centric wireless networking and communications is an emerging 4G technology for short (1-5 m) and very short (below 1 m) range communications systems, used to connect devices worn on (or in) the body, or between two people in close proximity. It has a great potential for applications in healthcare delivery, entertainment, surveillance, and eme...

The electronic implants for biomedical applications came out in mid-50s with the invention of the first pacemakers. This healthcare innovation exposed the potential and revealed the vast opportunities in the field of implantable electronic devices, enabling new ways of diagnostics and treatments maintaining the patient mobility. So, the idea of wir...

We propose an approach to increase the operating range and matching stability of in-body ingestible or implantable capsule antennas. It involves using high permittivity biocompatible superstrate on a high-Q narrowband microstrip antenna. In this way, the antenna–body coupling can be significantly reduced, resulting in improved detuning immunity, in...

This paper overviews the measurement and simulation of the electric parameters of a small stripline. The stripline was designed and built for electromagnetic compatibility (EMC) testing of small electronic devices with the accent on electromagnetic immunity (EMI) testing. The paper describes the measurement of electric field inside the stripline in...

Two important parameters of triboelectric separation of plastic particles are analyzed: the distribution of their electric charges and their critical velocity (velocity, at which the trajectories of falling particles are not longer significantly influenced by the applied electric field). The analysis is performed by a combination of experimental an...

Electromagnetic field distribution in a phantom is used to calculate SAR values for RF equipment compliance tests. We hypothesized that head structure could act like a dielectric resonator for some frequencies, thus affecting field estimation and measurement by procedures used today. Eigenfrequency problem for a structurally realistic 2D head phant...

RF equipment compliance tests employ electromagnetic field calculation in a head phantom to derive SAR values. We hypothesized that a biological tissue in certain conditions could act like a dielectric resonator hence affecting the field estimation. To study the resonance effects in a human head, we formulated an eigenfrequency problem for a struct...