4. Conclusion

We have presented a DH coil as the WPT receiver in implantable medical devices. This new coil has several attractive properties that it can be made conveniently at high precision on a flexible PCB along with other electronic components, forming a complete flexible sheet. This sheet, after being hermetically sealed, can be wrapped around a tubular biological structure, such as a blood vessel or a nerve bundle, to perform diagnostic, monitoring and therapeutic functions. The DH coil has been mathematically analyzed, and expressions for both mutual inductance and self-inductance have been derived. We have found that the DH coil provides a

### Wireless Power Transfer for Miniature Implantable Biomedical Devices DOI: http://dx.doi.org/10.5772/intechopen.89120

higher coupling factor than the conventional solenoid coil when a lateral or angular misalignment exists. In addition, the DH coil achieves the largest coupling factor and energy transfer efficiency when the axis of the DH coil is in parallel with the plane of the planar spiral transmitter coil. Our computer simulation and experiments under lateral and angular misalignments have been conducted and their results have verified our analytical results.

In order to support biomedical studies using the animal model, we have designed a new power mat, enabling wireless power delivery to miniaturized moving targets. The power mat contains a single or multiple transmitter cells and each cell consists of seven hexagonally packed PSCs. We have conducted theoretical, computational and experimental studies on the special WPT system to meet the challenge of distributing the electromagnetic field evenly over the power mat. We have analyzed the HPT cell using the CMT. Formulas have been derived relating the received power to the inputs and system parameters. Then, we utilize computer simulation to study the evenness of the magnetic field distribution over the power mat at different distances between the power mat and the floor of the animal cage. Finally, we constructed a prototype system, measured its magnetic field distribution and verified that our design has met the challenge. We have also presented a new design of the receiver coil consisting of three serially connected sub-coils. This new design of the receiver coil allows it to capture the most magnetic flux produced by the transmitter, facilitates a match of resonant frequencies of the transmitter and receiver, and reduces the volume of the implant.
