Optimal frequency for powering millimeter-sized biomedical implants inside an inductively-powered homecage

Area of Science:

• Biomedical Engineering
• Neuroscience Technology
• Implantable Devices

Background:

• Longitudinal studies in freely-behaving animals require efficient wireless power for implanted devices.
• Existing inductive powering methods face challenges with miniaturized implants and transmission efficiency.
• Millimeter-sized implants present unique design constraints for power delivery.

Purpose of the Study:

• To determine the optimal design and operating frequency for an inductively-powered homecage system.
• To enhance power transmission efficiency (PTE) for millimeter (mm)-sized biomedical implants.
• To facilitate long-term behavioral neuroscience and electrophysiology experiments using wirelessly powered implants.

Main Methods:

• Derivation of a simplified equation for the PTE of 3-coil inductive links.
• Co-optimization of multi-coil inductive link geometry (3- and 4-coil) and operating frequency (fp).
• Utilizing a commercial field solver (HFSS) for simulation and optimization of 3-coil link designs.

Main Results:

• Achieved a significant PTE of 2.56% for a 1 mm3 implant coil at a 7 cm distance.
• Identified an optimal operating frequency (fp) of 40 MHz for the inductive link.
• Demonstrated the effectiveness of an intermediate receiver coil (18 mm diameter) in enhancing PTE.

Conclusions:

• The co-optimization of inductive link geometry and operating frequency is crucial for efficient mm-sized implant powering.
• The proposed 3-coil inductive link design offers a viable solution for powering implants in freely-behaving small animals.
• This technology advancement supports advanced longitudinal studies in neuroscience and electrophysiology.