A Dual-Band Wireless Power Transmission System for Evaluating mm-Sized Implants

Area of Science:

• Biomedical Engineering
• Neuroscience
• Wireless Power Transfer

Background:

• Distributed neural interfaces using small implantable medical devices (IMDs) are crucial for future brain-computer interfaces, offering reduced tissue damage.
• Wireless evaluation of IMDs in preclinical models faces challenges like weak coupling and limited power delivery within standard environments.
• Existing systems struggle to provide sufficient power to IMDs without exceeding safety limits (specific absorption rate).

Purpose of the Study:

• To develop a wireless power system capable of efficiently powering small implantable medical devices (IMDs) for preclinical neural interface research.
• To address the limitations of power transfer and data connectivity for mm-sized IMDs in a homecage environment.
• To enable robust, closed-loop operation of wirelessly powered implantable optical stimulators (FF-WIOS).

Main Methods:

• A dual-band EnerCage system utilizing two multi-coil inductive links for power transfer at 13.56 MHz and 60 MHz.
• A headstage worn by the animal receives power from the EnerCage and relays it to the implantable medical device (IMD).
• Bluetooth low energy for EnerCage-headstage communication and on-off keying/load-shift-keying for headstage-IMD data transfer; a closed-loop power controller for stability.

Main Results:

• The EnerCage system achieved 14.9%-22.7% power transfer efficiency and delivered 122 mW to the headstage at 7 cm.
• The headstage successfully powered the implantable optical stimulator (FF-WIOS) with 18% efficiency, delivering 2.7 mW at 5 mm depth.
• Bidirectional data connectivity was established, and a closed-loop power controller maintained stable power delivery to both headstage and FF-WIOS.

Conclusions:

• The EnerCage system effectively overcomes wireless powering challenges for small implantable medical devices in preclinical settings.
• This technology facilitates the evaluation of advanced neural interfaces, including wirelessly powered optical stimulators, in realistic environments.
• The dual-band system ensures stable and efficient power and data transfer, crucial for closed-loop brain-computer interface applications.