EM radiation behavior upon biological tissues in a radio-frequency power transfer link for a cortical visual implant

Abstract

This paper presents a method to evaluate the interactions between a radio-frequency power transfer link and biological tissues. First we analyze the propagation of a plane wave model at the skin interface to evaluate the frequency that optimize the transfer ratio. We then use the Finite-Difference Time-Domain method to calculate the exact electromagnetic fields propagation in a discrete 3D space and time for a box brain model with an inductive emitting antenna. The results exhibit the electric field pattern in the antenna axis plane and ip the back of the head. They show for an optimize frequency carrier (2OMHz) that the attenuation of electric field strength is 15dB and that most of the energy is reflected at the air-tissue interface.This paper presents a general method to perform the power transfer link investigation. First, the section I1 describes the global visual stimulation system. Section 111 explains the power supply problematic for implanted electronic devices. In section IV, we expose the method to evaluate the optimal power transfer frequency (A) and the Finite-Difference Time-Domain method to calculate the exact electromagnetic propagation in space (B) then the subsection C contains the simulation parameters for a box brain model. Finally, the preliminary results are presented in section V and discussed in section VI.

Power Amplifiers for Electronic Bio-Implants

“…In order to send power to implantable devices, wireless links are usually employed in the form of inductive links. Inductive power transfer is more efficient at lower frequencies (Vaillancourt et al, 1997). However, lower transmission frequencies use larger circuit components, especially transmission coils.…”

“…Typical coupling coefficients for power transfer in air are 0.17 (Ghovanloo and Atluri, 2007). It is more efficient to transmit wireless power at lower frequencies (Vaillancourt et al, 1997), and as the complexity of implants increases, data rates are also required to increase. Wang et al proposed the advantages of biomedical implants operating in dual frequency bands to send power and data, and it has since been the basis of further work in the area .…”

Approaches and Challenges of Engineering Implantable Microelectromechanical Systems (MEMS) Drug Delivery Systems for in Vitro and in Vivo Applications

“…However, since the communication range is limited, devices which are implanted deep within the body may not be able to receive the telemetric signal due to the attenuation of the signal imposed by the tissue. Studies by Vaillancourt et al [51] have demonstrated that telemetric signals such as radio frequency waves experience electric field strength attenuation by up to 15dB as they are passing through the biological tissue. This suggests that wirelessly powered devices have to account for this attenuation loss if a device is implanted deep into the body.…”

Structural Design of CMOS Voltage Regulator for Implantable Devices

“…& Petersen R. C., 2001). This frequency provides a good tradeoff between power level and human tissue penetration (Sauer, 2005;Vaillantcourt, 1997). The ultra high band (typically between 850MHz and 950MHz) offers the largest reading ranges, of up to approximately 3 meters for passive tags and 100 meters for active tags.…”