Ultrasound Wireless Charging To Power Deep Implantable Biomedical Devices

Current wireless charging technologies for implanted biomedical devices like pacemakers and cochlear implants primarily utilize electromagnetic or radio waves. However, these methods often lose considerable power as they travel through tissue, reducing their efficiency for devices implanted deeper within the body. Additionally, they can cause unwanted side effects, such as tissue heating and immune responses. In contrast, ultrasound-based wireless power transfer is emerging as a superior alternative, able to penetrate deeper into tissues with less energy loss and fewer adverse effects. Now, a new study has shown that the shape of the implanted receiver can greatly enhance the effectiveness of power harvesting from an ultrasound beam.

In the study, researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST, Seoul, South Korea) explored how variations in the size, shape, and positioning of the piezoelectric receiver could improve ultrasound energy harvesting. They discovered that placing the receiver within the focal area of a focused ultrasound beam markedly boosts the efficiency of the energy transfer. The piezoelectric receiver produced different phases of electrical signals based on its interaction with various parts of the ultrasound beam, with the most efficient energy transfer occurring within the beam’s main lobe, indicating that larger receivers, which interact with more of the ultrasound beam, are not always more effective.

Image: The wireless power transfer system consists of an ultrasound transmitter outside the body (Photo courtesy of DGIST)

To optimize these findings, the researchers developed an oblong-shaped ultrasound transmitter and receiver. This design allows the transmitter to create a wide main lobe at the focal point, while the receiver, tailored to match the shape of the transmitted beam, maximizes energy output efficiently. The effectiveness of this system was tested both underwater and through 50mm of porcine tissue, demonstrating that the oblong receiver could fully charge a battery through the tissue in just 1.8 hours, a duration that meets the requirements for commercial batteries.

“The combination of a focused beam and a well-matched receiver allows oblong-shaped ultrasound transmitter and receiver to achieve significantly higher energy delivery compared to conventional ultrasound-based wireless power transfer systems,” said DGIST Professor Jin Ho Chang who led the research team. “The combination of a focused beam and a well-matched receiver allows oblong-shaped ultrasound transmitter and receiver to achieve significantly higher energy delivery compared to conventional ultrasound-based wireless power transfer systems.”

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