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A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

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Related in: MedlinePlus

(a) Schematic of the wireless resonant energy transfer system; (b) Packaged implanted receiver coils and IC chip by PDMS.
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f1-sensors-12-10292: (a) Schematic of the wireless resonant energy transfer system; (b) Packaged implanted receiver coils and IC chip by PDMS.

Mentions: Based on the four-coil resonant circuit theory, a wireless energy transfer system (Figure 1(a)) is designed and implemented in this paper. The entire system is composed of the in vitro part, including the energy transmitting circuit (Class-E amplifier) and resonant transmitter coils, which consist of drive coil (coil1) and primary coil (coil2), and the in vivo part including the micro resonant receiver coils which consist of the secondary coil (coil3) and load coil (coil4) and signal shaping chip which includes the rectifier module and LDO voltage regulator module. First the electrical and geometric parameters of the coils are theoretically optimized. Then the energy transfer efficiency is modeled and optimized. The peripheral circuit is composed of Class-E amplifier, low power CMOS rectifier circuit, and capacitor-less low dropout linear voltage regulator (LDO). Finally, an experimental setup is designed to characterize the energy transfer efficiency. Experimental results show that the energy transfer efficiency of resonant four coils is much higher than that of two coils. When the distance between the transmitter coils and the receiver coils is 1.5 cm and the carrier frequency is 742 kHz, the transfer efficiency is 85%. What's more, the power transfer efficiency can be optimized by adding magnetic enhanced resonators. The whole implanted micro system is packaged with polydimethylsiloxane (PDMS) after depositing a layer of Parylene to obtain better seal and biocompatibility as shown in Figure 1(b). The measurement results show that the receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. A power of more than 100 mW can be achieved when the distance is decreased, which can meet the power consumption requirements of most reported biomedical systems such as artificial retinas (power consumption of 42 mW) [13], intraocular pressure sensors (power consumption of μWs or mWs) [14], neural recording systems (power consumption of 5.3 mW) [15], and human body sensor networks [16].


A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

(a) Schematic of the wireless resonant energy transfer system; (b) Packaged implanted receiver coils and IC chip by PDMS.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472828&req=5

f1-sensors-12-10292: (a) Schematic of the wireless resonant energy transfer system; (b) Packaged implanted receiver coils and IC chip by PDMS.
Mentions: Based on the four-coil resonant circuit theory, a wireless energy transfer system (Figure 1(a)) is designed and implemented in this paper. The entire system is composed of the in vitro part, including the energy transmitting circuit (Class-E amplifier) and resonant transmitter coils, which consist of drive coil (coil1) and primary coil (coil2), and the in vivo part including the micro resonant receiver coils which consist of the secondary coil (coil3) and load coil (coil4) and signal shaping chip which includes the rectifier module and LDO voltage regulator module. First the electrical and geometric parameters of the coils are theoretically optimized. Then the energy transfer efficiency is modeled and optimized. The peripheral circuit is composed of Class-E amplifier, low power CMOS rectifier circuit, and capacitor-less low dropout linear voltage regulator (LDO). Finally, an experimental setup is designed to characterize the energy transfer efficiency. Experimental results show that the energy transfer efficiency of resonant four coils is much higher than that of two coils. When the distance between the transmitter coils and the receiver coils is 1.5 cm and the carrier frequency is 742 kHz, the transfer efficiency is 85%. What's more, the power transfer efficiency can be optimized by adding magnetic enhanced resonators. The whole implanted micro system is packaged with polydimethylsiloxane (PDMS) after depositing a layer of Parylene to obtain better seal and biocompatibility as shown in Figure 1(b). The measurement results show that the receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. A power of more than 100 mW can be achieved when the distance is decreased, which can meet the power consumption requirements of most reported biomedical systems such as artificial retinas (power consumption of 42 mW) [13], intraocular pressure sensors (power consumption of μWs or mWs) [14], neural recording systems (power consumption of 5.3 mW) [15], and human body sensor networks [16].

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

Show MeSH
Related in: MedlinePlus