Omnidirectional Ultrasonic Powering for Millimeter-Scale Implantable Devices.

Area of Science:

• Biomedical Engineering
• Acoustic Energy Transfer
• Implantable Medical Devices

Background:

• Traditional inductive powering has limitations in penetration depth and directionality for deep-seated medical implants.
• Ultrasonic wireless powering offers superior energy-conversion efficiency, deeper penetration, and omnidirectionality.
• Millimeter-scale devices require efficient and reliable wireless power solutions for medical applications.

Purpose of the Study:

• To investigate the feasibility of ultrasonic wireless powering for millimeter-scale implantable medical devices.
• To evaluate output power levels, efficiency, range, and omnidirectionality of ultrasonic powering.
• To assess the performance of piezoelectric receivers at various frequencies and sizes.

Main Methods:

• Utilized piezoelectric receivers of sizes 1x5x1 mm³, 2x2x2 mm³, and 2x4x2 mm³.
• Irradiated receivers at 1.15 and 2.3 MHz within FDA limits for medical imaging.
• Measured electrical power output, efficiency, and power stability across varying angular positions.

Main Results:

• Piezoelectric receivers generated 2.48 mW, 8.7 mW, and 12.0 mW of electrical power.
• Achieved efficiencies of 0.4%, 1.7%, and 2.7% at a 20-cm powering distance.
• Output power remained stable within 92% despite angular variations, demonstrating robustness.

Conclusions:

• Ultrasonic wireless powering is a viable solution for deep-seated millimeter-scale implantable medical devices.
• The investigated piezoelectric receivers demonstrate promising power output and efficiency for medical applications.
• The omnidirectional nature and power stability of ultrasonic powering are advantageous for implantable systems.