Wirelessly powered implants suit miniature cardiac pacing

22nd March 2017

Enaie Azambuja

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As implantable devices continue to shrink, the race is on for similarly-sized reliable power sources. Current state-of-the art implantables often depend on chunky batteries that suffer from limited lifetimes, with a typical pacemaker battery lasting around eight years. While some techniques have successfully harvested power from biological processes such as heart beats or from body heat, most devices require significantly more energy.

A report on work pioneered by scientists at the National University of Singapore describes a newly designed device that allows for wireless transmission of power into the body, demonstrating this technology’s potential by powering a miniature cardiac pacemaker implanted in a pig model.

Building on the principles used in microwave focusing for heat ablation of deep-tissue tumors, the team designed a flexible antenna that easily fits in one’s palm and enables the transmission of electromagnetic power to a defined focal point deep inside the body.

While the distinct aspects of their design are not novel, the innovative combination of phased arrays and conformal surfaces resulted in a clear improvement in energy transfer efficiency by radio frequency radiation.

Using a transvenous catheter to implant a miniature cardiac stimulator at various locations in the heart, and ensuring they are within the generated focal spot, the team was able to modulate pig cardiac rates in an efficient and reversible manner.

The team’s use of electromagnetic waves ensures better penetration through bone, compared to ultrasound, while holding the possibility of coupled data transmission for telemetry applications. Additionally, typical methods used for electromagnetic energy supplies depend on inductive coupling, which is incompatible with tiny devices implanted deep within the body.

While there is still room for improvement, particularly for reliable long-term usage, the technology holds immediate and promising implications for biosensors, neuromodulation, and cancer therapy.