In-body path loss models for implants in heterogeneous human tissues using implantable slot dipole conformal flexible antennas

A wireless body area network (WBAN) consists of a wireless network with devices placed close to, attached on, or implanted into the human body. Wireless communication within a human body experiences loss in the form of attenuation and absorption. A path loss model is necessary to account for these losses. In this article, path loss is studied in the heterogeneous anatomical model of a 6-year male child from the Virtual Family using an implantable slot dipole conformal flexible antenna and an in-body path loss model is proposed at 2.45 GHz with application to implants in a human body. The model is based on 3D electromagnetic simulations and is compared to models in a homogeneous muscle tissue medium

Evaluation of electric and magnetic fields distribution and SAR induced in 3D models of water containers by radiofrequency radiation using FDTD and FEM simulation techniques

In this study, two software packages using different numerical techniques FEKO 6.3 with Finite-Element Method (FEM) and XFDTD 7 with Finite Difference Time Domain Method (FDTD) were used to assess exposure of 3D models of square, rectangular, and pyramidal shaped water containers to electromagnetic waves at 300, 900, and 2400 MHz frequencies. Using the FEM simulation technique, the peak electric field of 25, 4.5, and 2 V/m at 300 MHz and 15.75, 1.5, and 1.75 V/m at 900 MHz were observed in pyramidal, rectangular, and square shaped 3D container models, respectively. The FDTD simulation method confirmed a peak electric field of 12.782, 10.907, and 10.625 V/m at 2400 MHz in the pyramidal, square, and rectangular shaped 3D models, respectively. The study demonstrated an exceptionally high level of electric field in the water in the two identical pyramid shaped 3D models analyzed using the two different simulation techniques. Both FEM and FDTD simulation techniques indicated variations in the distribution of electric, magnetic fields, and specific absorption rate of water stored inside the 3D container models. The study successfully demonstrated that shape and dimensions of 3D models significantly influence the electric and magnetic fields inside packaged materials; thus, specific absorption rates in the stored water vary according to the shape and dimensions of the packaging materials.Comment: 22 pages, 30 figures and 2 table

Modelling of the dielectric properties of trabecular bone samples at microwave frequency

In this paper the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity (conductivity): the higher the BV/TV the lower the permittivity (conductivity). This is in agreement with the recently published in vivo data. Keywords: Bone dielectric properties, Microwave tomography, Finite difference time domain.Comment: 10 pages, 5 figures, 4 table

Multiple Antenna Techniques for Terahertz Nano-Bio Communication

Using higher frequency bands becomes an essential demand resulting from the explosive wireless traffic needs and the spectrum shortage of the currently used bands. This paper presents an overview on the terahertz technology and its application in the area of multi-input multi-output antenna system and in-vivo nano-communication. In addition, it presents a preliminary study on applying multiple input-single output (MISO) antenna technique to investigate the signal propagation and antenna diversity techniques inside the human skin tissues, which is represented by three layers: stratum corneum (SC), epidermis, and dermis layers, in the terahertz (THz) frequency range (0.8-1.2) THz. The spatial antenna diversity is investigated in this study to understand MISO system performance for two different in-vivo channels resulting from the signal propagation between two transmitting antennas, located at the dermis layer, and one receiving antenna, located at epidermis layer. Three techniques are investigated: selection combining (SC), equal-gain combing (EGC), and maximum-ratio combining (MRC). The initial study indicates that using multiple antenna technique with THz might be not useful for in-vivo nano-communication

HF-VHF帯における生体等価ファントムを用いた電磁波と人体相互作用の検証

研究科: 千葉大学大学院工学研究科学位:千大院工博甲第工185号博士(工学)千葉大

Preparation of bioactive surface via gel oxidation on titanium for biomedical application (hip joint replacement)

Titanium and its alloys are widely used as implant in biomedical applications. They have good mechanical and chemical properties, biocompatibility and biointegration with human body, but they have no ability to bond directly to natural bone. Therefore, alkali and heat treatments (gel oxidation) were introduced to improve the bioactivity of titanium by forming a mixture of sodium titanate and rutile on the surface of titanium. This method enables titanium to possess a bioactive surface which is essential to induce the apatite formation. This study aims to investigate the effects of alkali, sodium removal and heat treatments on in vitro bioactivity of titanium. UV light irradiation was used to study the effect on in vitro bioactivity of titanium. Alkalitreated titanium subjected to heat treatment in air have shown better overall in vitro performance than those treated in argon atmosphere. Therefore, the sodium removal treatment (dilute hydrochloric acid (HCl) treatment) was introduced to convert sodium titanate into anatase to improve the bioactivity of titanium treated in argon atmosphere. Thus, four samples (AT-0.5-HT500R, AT-0.5-HT600R, AT-5-HT500R and AT-5- HT600R) with different ratios of anatase to rutile were produced by varying the concentration of HCl acid treatment and heating temperature in argon atmosphere. It was found that the incorporation of sodium removal treatment has reduced two times the duration of apatite formation as compared with the conventional alkali and heat treatments. In order to further enhance the bioactivity, these samples were subjected to six different conditions of ultraviolet light irradiation and followed by in vitro bioactivity test. As a result, AT-5-HT500R (82.2% anatase and 17.8% rutile) was proven to deliver the best performance. It was confirmed that UV light irradiation enhances the bioactivity by removing hydrocarbon, inducing superhydrophilicity and forming OH groups. It was discovered that the duration of apatite formation was shortened to 7 days. Furthermore, the continuous UVA irradiation during in vitro test resulted in the acceleration of bonelike apatite formation in 3 days. It can be concluded that the sodium removal treatment and UV light irradiation give very significant impact to the formation of bonelike apatite on the titanium surfaces for biomedical applications