Resonance-based Wireless Power Transfer System Research Articles

A frequency-tuned magnetic resonance-based wireless power transfer system with near-constant efficiency up to 24 cm distance

A frequency-tuned magnetic resonance-based wireless power transfer system with near-constant efficiency up to 24 cm distance

A remotely operated drug delivery system with dose control

“On demand” implantable drug delivery systems can provide optimized treatments, due to their ability to provide targeted, flexible and precise dose release. However, two important issues that need to be carefully considered in a mature device include an effective actuation stimulus and a controllable dose release mechanism. This work focuses on remotely powering an implantable drug delivery system and providing a high degree of control over the released dose. This is accomplished by integration of a resonance-based wireless power transfer system, a constant voltage control circuit and an electrolytic pump. Upon the activation of the wireless power transfer system, the electrolytic actuator is remotely powered by a constant voltage regardless of movements of the device within an effective range of translation and rotation. This in turn contributes to a predictable dose release rate and greater flexibility in the positioning of external powering source. We have conducted proof-of-concept drug delivery studies using the liquid drug in reservoir approach and the solid drug in reservoir approach, respectively. Our experimental results demonstrate that the range of flow rate is mainly determined by the voltage controlled with a Zener diode and the resistance of the implantable device. The latter can be adjusted by connecting different resistors, providing control over the flow rate to meet different clinical needs. The flow rate can be maintained at a constant level within the effective movement range. When using a solid drug substitute with a low solubility, solvent blue 38, the dose release can be kept at 2.36μg/cycle within the effective movement range by using an input voltage of 10Vpp and a load of 1.5kΩ, which indicates the feasibility and controllability of our system without any complicated closed-loop sensor.

Stable and High-Efficiency Wireless Power Transfer System for Robotic Capsule Using a Modified Helmholtz Coil

Magnetic resonance-based wireless power transfer system offers a promising solution to overcome power limitations typically encountered by capsule endoscopy. Despite of much attention in this area, aspects such as power stability and power transfer efficiency remain suboptimal and therefore investigation for further improvement is still required. This paper presents a method to improve power stability as well as power transfer efficiency for wireless capsule endoscopy. A new power transmission coil capable of producing uniform magnetic field is proposed to improve power stability through uniform field that at the same time minimizes the unnecessary peak electromagnetic exposure. To improve power transfer efficiency, a mixed resonance scheme is employed. Our experimental results show improvement over existing methods where the proposed system attained power stability of 94.62% and power transfer efficiency of 4.9% under worst position of the receiving coil. Furthermore, the proposed transmitting coil provides additional advantage, where it minimized the unnecessary peak electromagnetic exposure by 26% as compared to the conventional Helmholtz coil-based system. We believe the proposed system will open new direction for future wireless capsule endoscopy and can also be useful in other industrial applications.

Impedance matching control method for an underwater magnetic resonance-based wireless power transfer system with metamaterials

In this paper, a new method of improving the efficiency of the underwater magnetic resonance-based wireless power transfer (MRWPT) system is proposed. A kind of the negative permeability (MNG) metamaterials with low megahertz frequency is designed, which can be adjusted to work well in the system. The S-parameters, resonant frequency, and permeability of metamaterials are worked out for analysis. A new impedance matching control method was also proposed for reducing the reflection loss in a way to help the sea water MRWPT system to achieve the maximum efficiency. This method is also able to reduce the unnecessary power loss caused by power fluctuation. The measured results show that the performance of the proposed metamaterials and the proposed control method are perfect in improving its efficiency in sea water.