Compensating for Tissue Changes in an Ultrasonic Power Link for Implanted Medical Devices

Area of Science:

• Biomedical Engineering
• Acoustics
• Wireless Power Transfer

Background:

• Ultrasonic power transfer is a key wireless technology for biomedical implants.
• Sub-dermal implants face efficiency challenges due to distance-sensitive ultrasonic power transfer efficiency (PTE).
• Variations in tissue properties and implant depth significantly impact PTE.

Purpose of the Study:

• To develop and demonstrate a method for compensating acoustic separation distance in ultrasonic transcutaneous energy transfer (UTET) systems.
• To maintain consistent and high power transfer efficiency for sub-dermal implants.
• To address limitations in battery life and performance caused by PTE fluctuations.

Main Methods:

• A frequency compensation method was implemented by varying the transmit (Tx) frequency in a UTET system.
• Benchtop experiments used porcine tissue samples to simulate in situ implant conditions.
• The system was tested with and without active frequency compensation.

Main Results:

• Without compensation, PTE varied widely from 9% to 25% with simulated tissue changes.
• Active frequency compensation maintained high PTE, ranging from 20% to 27%.
• The proposed compensation strategy is low-power and non-invasive, utilizing transmit-side measurements.

Conclusions:

• Varying transmit frequency effectively compensates for acoustic separation distance in UTET systems.
• This active frequency compensation method significantly improves and stabilizes PTE for biomedical implants.
• The approach is practical for active implanted medical devices, offering improved reliability and performance.