Stanford researchers create tiny, wirelessly powered cardiac device
One big problem we have with bio-implantable devices, like cardiac implants, is that they require a battery–and batteries need to be changed once in a while. This means more surgery.
In this day and age of wireless devices, it seems like
It turns out, the existing models told researchers that radio waves couldn’t penetrate deeply enough into human tissue to be useful for power delivery. The human body is a poor conductor of electricity. Ultimately, it took someone willing to question the accepted models, to show that it could, in fact, be done.
By ignoring the currently held ideas of “that isn’t possible”, Ada Poon and her team showed that radio waves can travel in a different way– and by doing so, they can be used as a wireless source for power delivery; in fact, using this method, it is actually advantageous that human tissue is such a poor electrical conductor.
“In this high-frequency range, we can increase power transfer by about 10 times over earlier devices,” said Ho, who honed the mathematical models.
Two hurdles remained:
1) how to use this wireless delivery safely to avoid unnecessary tissue heating
2) how to orient the antennas for maximum efficiency in the constantly moving environment of a human body.
Differences in alignment of just a few degrees could produce troubling drops in power.
“This can’t happen medical devices,” said Poon. “As the human heart and body are in constant motion, solving this issue was critical to the success of our research.” The team responded by designing an innovative slotted transmitting antenna structure. It delivers consistent power efficiency regardless of orientation of the two antennas.
The new design serves additionally to focus the radio waves precisely at the point inside the body where the implanted device rests on the surface of the heart – increasing the electric field where it is needed most, but canceling it elsewhere. This helps reduce overall tissue heating to levels well within the IEEE standards. Poon has applied for a patent on the antenna structure.”