Polyphasic Ultrasonic Power transfer for wireless charging of implants

Background:

Wireless power transfer (WPT) for implantable medical devices (IMDs) has become a critical area of research due to the limitations of traditional battery-powered implants. Batteries in IMDs require periodic surgical replacement, posing risks to patients and increasing healthcare costs. As a result, there is a strong demand for reliable, efficient, and minimally invasive power delivery methods. While electromagnetic (EM) wireless power transfer has been explored, it faces significant challenges in biological environments, such as high attenuation in tissue, sensitivity to alignment, and interference from metallic components. Ultrasonic power transfer (UPT) has emerged as a promising alternative, offering deeper tissue penetration, compatibility with metal implants, and the potential for miniaturized transducers suitable for medical use. Despite these advantages, conventional UPT systems, which are typically based on single-phase excitation, suffer from significant drawbacks that limit their effectiveness. The primary issue is the non-uniformity of the acoustic field caused by diffraction, destructive interference, and reflections at tissue interfaces. These phenomena result in spatially varying pressure fields, leading to inefficient and unreliable power delivery to implanted devices. Additionally, the intensity of the transmitted acoustic energy diminishes rapidly with depth due to geometric spreading and tissue absorption, further reducing the amount of usable power at the target site. Current single-phase systems are also highly sensitive to the placement and orientation of the transducer, making consistent power delivery challenging in real-world, dynamic biological environments.

Technology Overview:

This technology is a polyphasic ultrasonic power transfer (UPT) system designed to wirelessly deliver energy to implanted medical devices and other applications where conventional electromagnetic wireless power transfer is ineffective. The system features a linear array of three adjacent piezoelectric transducers. This configuration generates engineered ultrasonic wavefronts, which interact to create a more uniform acoustic pressure field within soft tissue. Simulations demonstrated that this approach significantly increases the time-averaged power delivered by up to 3.4 times at 20 mm depth, compared to traditional single-phase excitation. An embedded energy-harvesting and rectification circuit within the implanted device converts the received acoustic energy into usable electrical power, enabling reliable operation of battery-less implants. What differentiates this technology is its innovative use of controlled phase relationships between multiple transducers to overcome the limitations of single-phase ultrasonic systems. By precisely orchestrating the phase offsets, the system minimizes sensitivity to interference and non-uniformities, resulting in more consistent and efficient power delivery even at greater tissue depths. Unlike electromagnetic wireless power transfer, this ultrasonic approach enables superior penetration due to the physical nature of ultrasound signals and the excellent metal compatibility of acoustic waves. The polyphasic configuration not only increases the total transmitted power but also stabilizes the rectified signal, which is crucial for sensitive medical devices. Its versatility extends to even underwater and industrial applications, where electromagnetic methods are impractical, making it a robust and adaptable solution for challenging wireless power delivery scenarios.

Advantages:

•    Significantly increased power delivery efficiency, achieving up to 3.4x higher acoustic intensity at 20 mm depth compared to single-phase systems
•    More uniform and stable power delivery.
•    Improved reliability and reduced noise in power delivery for implanted medical devices
•    Enables wireless power transfer through biological tissue and metal barriers where electromagnetic methods fail
•    Compact and scalable transducer array design suitable for miniature implantable devices
•    Versatile applications, including biomedical implants, underwater sensors, and industrial environments with electromagnetic shielding
•    Embedded energy harvesting and rectification circuitry for direct powering of implanted devices

Applications:

•    Wireless powering of implanted pacemakers
•    Battery-less neurostimulator energy delivery
•    Underwater sensor power transfer
•    Industrial wireless power in metal enclosures

Intellectual Property Summary:

Patent Pending

Stage of Development:

TRL 3

Licensing Status:

This technology is available for licensing.