Tutku Karacolak

Design of a Dual-Band Implantable Antenna and Development of Skin Mimicking Gels for Continuous Glucose Monitoring

In this study, we present a small-size dual medical implant communications service (MICS) (402-405 MHz) and industrial, scientific, and medical (ISM) (2.4-2.48 GHz) band implantable antenna for continuous glucose-monitoring applications. The antenna is optimized for dual-band operation by combining an in-house finite-element boundary integral electromagnetic simulation code and particle swarm optimization algorithm. In order to test the designed antenna in vitro, gels mimicking the electrical properties of human skin are also developed. The optimized antenna is fabricated and measured in the gel. The simulated and measured bandwidths are found to be 20.4% MICS, 4.2% ISM, and 35.3% MICS, and 7.1% ISM, respectively. Although we have emphasized continuous glucose monitoring throughout this paper, the antenna and skin mimicking gels presented here can be used for many other wireless telemetry applications.

A Small Antipodal Vivaldi Antenna for Ultrawide-Band Applications

A compact antipodal Vivaldi antenna for ultrawide-band (UWB) applications is proposed. The antenna operates across the entire UWB spectrum from 3.1 to 10.6 GHz, and also has low cross-polarization levels and reasonable gain values over the same frequency band. Two different substrates, Rogers RO3006 and FR4, are considered, and results regarding return loss, far field pattern, phase response, group delay, and gain are presented.

Electrical Properties of Rat Skin and Design of Implantable Antennas for Medical Wireless Telemetry

The design and test is described of a small size dual band implantable antenna operating in Medical Implant Communications Service (MICS) (402 MHz-405 MHz) and Industrial, Scientific and Medical (ISM) (2.4 GHz-2.48 GHz) bands to be used in animal studies for medical research. The antenna is intended for wireless medical monitoring of the physiological parameters such as glucose, pressure, temperature, etc. First, the electrical properties (epsivr and sigma) of skin samples from donor rats are measured at Mississippi State Universitys (MSU) College of Veterinary Medicine. A dual band antenna is then designed using an in-house finite element boundary integral solver in conjunction with particle swarm optimization algorithm. Finally, the antenna is tested using both skin-mimicking materials and real skin samples. The development details of the skin-mimicking materials are also given. Results regarding the S11 and gain of the designed antenna are given and discussed in detail.

In Vivo Verification of Implantable Antennas Using Rats as Model Animals

The main objective of this study is to test in vivo a small-size dual-band implantable antenna operating in Medical Implant Communications Service (MICS) (402405 MHz) and Industrial, Scientific, and Medical (ISM) (2.42.48 GHz) bands and to investigate the effects of live tissue on the antenna performance. To do so, we have designed and fabricated three identical antennas that were surgically implanted into rats at Mississippi State Universitys (MSU) College of Veterinary Medicine. X-ray images are also taken to ensure the proper placement of the antenna within the body. Results regarding return loss measurements and the performance change of the antenna are presented. We have also investigated possible candidate materials that can be used for encasing of the antenna for biocompatibility.

A Double-Sided Rounded Bow-Tie Antenna (DSRBA) for UWB Communication

A double-sided rounded bow-tie antenna (DSRBA) for ultrawideband (UWB) communication is proposed. The antenna covers the UWB spectrum from 3.1 to 10.6 GHz, and has return loss below -10 dB throughout the entire band. The antenna has also omnidirectional radiation characteristics and reasonable gain values over the same frequency band. Two different substrates, Rogers RO3006 and Liquid Crystal Polymer (LCP), are considered. Both materials have very low loss tangent. Results regarding return loss, far-field pattern, and gain are presented

Characterization and Testing of a Skin Mimicking Material for Implantable Antennas Operating at ISM Band (2.4 GHz-2.48 GHz)

In this study, we present a simple recipe for a skin mimicking material intended for in vitro testing of implantable antennas operating at Industrial, Scientific, and Medical (ISM) (2.4 GHz2.48 GHz) band. The material is composed of de-ionized water, Triton X-100, and Diethylene Glycol Butyl Ether (DGBE). The relative dielectric constant and conductivity of the proposed material are within 0.5% and 3.4% of the properties of the reference human skin from the literature in the entire ISM band. In order to test the transmission characteristics of the material, in vitro measurements of a dual-band antenna are performed.

Glucose-dependent dielectric properties of blood plasma

In this study, we show a correlation between electrical properties (relative permittivity-εr and conductivity-σ) of blood plasma and plasma glucose concentration. In order to formulate that correlation, we performed electrical property measurements on blood samples collected from 10 adults between the ages of 18 and 40 at University of Alabama Birmingham (UAB) Childrens hospital. The measurements are conducted between 500 MHz and 20 GHz band. Using the data obtained from measurements, we developed a single-pole Cole-Cole model for εr and σ as a function of plasma blood glucose concentration. To provide an application, we designed a microstrip patch antenna that can be used to predict the glucose concentration within a given plasma sample. Simulation results regarding antenna design and its performance are also presented.

Dielectric Properties of Porcine Skin Tissue and In Vivo Testing of Implantable Antennas Using Pigs as Model Animals

The development of most medical systems depends on the accurate characterization of the dielectric properties [relative permittivity (εr) and conductivity (σ)] of biological tissues. The main objective of this study is to measure the dielectric properties of porcine skin tissue in the frequency range of 300 MHz-3 GHz. The skin samples were provided from three pigs of same age, sex, and breed. The measured data was similar to the dielectric properties of human skin tissue. A three-pole Cole-Cole model is also used to fit the dielectric properties as a function of frequency for future studies. To show porcine skin tissue may be used as a substitute for human skin, implantable antennas designed using human-skin electrical properties are fabricated. The antennas are surgically implanted into two porcine test subjects at the Mississippi State University (MSU) College of Veterinary Medicine, and return loss measurements are carried out. In vivo studies are performed over the course of two weeks to verify the proper vaibility of the antennas. Antenna measurements show that porcine and human skin tissues give similar responses.

A Wideband Implantable Antenna for Continuous Health Monitoring in the MedRadio and ISM Bands

The main objective of this letter is to present a small-size, dual-wideband implantable antenna operating in the Medical Device Radiocommunications Service (MedRadio) (401-406 MHz) and Industrial, Scientific, and Medical (ISM) (2.4-2.48 GHz) bands. The proposed antenna has a 71.6% reduction in size with respect to the previous similar dual-band implantable antenna. The measured -10-dB bandwidths are 56% (278 MHz) for the MedRadio and 33% (870 MHz) for the ISM bands, respectively. The antenna is in vitro tested in a tissue-mimicking gel approximating the electrical properties of human skin tissue. Results are compared to simulations.

Electrical properties of nude rat skin and design of implantable antennas for wireless data telemetry

The main objective of this study is to design and testing of a small size dual band implantable antenna operating in Medical Implant Communications Service (MICS) (402 MHz–405 MHz) and Industrial, Scientific and Medical (ISM) (2.4 GHz–2.48 GHz) bands. The antenna is intended for wireless medical monitoring of the physiological parameters such as glucose, pressure, temperature etc. First, the electrical properties (εr and σ) of skin samples from donor rats were measured at MSU’s College of Veterinary Medicine and then a computer model was created. The dual band antenna was then designed using an in-house Finite Element Boundary Integral solvers in conjunction with Particle Swarm Optimization (PSO) algorithm. In vitro tests are performed using skin mimicking materials. Results regarding the return loss and gain of the designed antenna were given and discussed in detail.