Experimental Study of a TET System for Implantable Biomedical Devices

Abstract

Time-varying magnetic fields can be used to transfer power across the skin to drive implantable biomedical devices without the use of percutaneous wires. However, the main challenges of a transcutanoues energy transfer (TET) system are the temperature rise caused by power loss in the implanted circuitry and the changes in positioning between the external and internal coils due to fitting and changes in posture. This study presents a TET system with a closed-loop frequency-based power regulation method to deliver the right amount of power to the load under variable coil coupling conditions. After implanting a TET system into adult sheep, the temperature rise in the internal and external coils of a TET system was measured for power delivery in the range of 5 W to 15 W. The sheep was housed in a temperature controlled (16 plusmn1degC, humidity 50plusmn10%) room, in accordance with the standard protocols implemented at the University of Auckland for sheep studies. A power-loss analysis for the overall system was performed. The system was capable of regulating power for axially aligned separations of up to 16 mm. The maximum power efficiency of the overall system was 82.1% and a maximum temperature rise of 2.7degC was observed on the implanted secondary coil.

Improvement of the Coupling Factor of Litz-Wire Coil Pair With Ferrite Substrate for Transcutaneous Energy Transfer System

“…The axial distance between the coil pair would be approximately equal to the thickness of the patient's skin, fatty tissue, and muscle, and it was nominally between 10 to 25 mm [20]. …”

“…The self and mutual inductance of the separate coils (L P i , L Sj , M P,ij , M S,ij and M P S,ij shown in Figure 3(c)) can also be solved by the energy storage which is determined by the magnetic flux density and field intensity in the solution space. The overall self inductance and mutual inductance of this system can also be defined as follows (20) where N Lp and N lS are the primary and secondary number of layer, respectively.…”

Prosthetic Power Supplies

“…This can be provided when the switch current and voltage are kept in phase by adjusting the switching frequency (40), the duty cycle of the gate driver signal (41), the primary inductance (42,43), or the primary capacitance (44,45).…”

An implantable radio-telemetry system for detecting multiple bio-parameters of a small animal based on wireless energy transmission

“…This system can enable the pickup to receive the minimal power up to 20 mW. Dissanayake [15] proposed a transcutaneous energy transmission (TET) system for an implantable biomedical device. Temperature rise was considered in the TET system.…”