Engineer invents safe way to transfer energy to medical chips in the body | Hacker News Reader

Engineer invents safe way to transfer energy to medical chips in the body

news.stanford.edu

41 pointsgivan14 comments

Caveat - It has been more than decade since I worked in an optics lab, and I haven't looked behind the pay wall at the paper.

---

-I'm pretty sure this works in a way analogous to "frustrated total internal reflection," which powers many fingerprint readers. (look up total internal reflection on Wikipedia)

-By placing three mediums with different impedances in sequence, you can promote an "evanescent" (non-propagating) nearfield wave to partially couple into the the third medium.

-The wave will propagate in the third medium if it has the correct impedance relationship to the other two, and if it supports a propagation mode of the incident wave. In this case it appears that the skin is being used as the third medium, based on the wording in the promo blurb from Stanford.

Paper" "Wireless power transfer to deep-tissue microimplants" from "Proceedings of the National Academy of Sciences" (PNAS) is pay-walled here:

http://www.pnas.org/content/early/2014/05/14/1403002111

Summary:-

Far-field electromagnetic waves are reflected/absorbed by the body therefore are not useful for energy transfer. Near-field waves do not reach far enough to be useful (1/r^3 law). The discovery: Mid-field waves, waves which propagate well in biological tissue.

The near field 1/r^3 is defined by r and the starting point for how you define r is the radius of the coil used to generate the magnetic field. The average human body isn't much more than a foot thick. Putting a 12" diameter and thus 6" radius coil in a bit of padding and wearing it like a backpack isn't out of the question especially if it's only for a few hours to charge up every day. Or built in to your bed.

That's not to say that what's been discovered here isn't a lot better than a big-ass coil. Just that the idea you couldn't get wireless power into the body is wrong. People have been using subdermal inductive charging for insulin pumps for years.

>Just that the idea you couldn't get wireless power into the body is wrong.

Agreed! But like you said this might make this thing a little less unwieldy.

Yeah I guess I was disagreeing with the notion in the article that the researcher "invented" a way to get wireless power into the body. That's already done. It works. It's not great, but it works. So what was cooked up was a huge improvement, not the original invention.

Slightly off-topic, but are humans the only animal that communicate electromagnetically? There's a bunch of obvious advantages to it, and there are already animals that can generate sufficient current. Is it because you can't build antennae from organic material?

Fireflies. Could be that there's a bacteria involved somewhere, but bioluminescence for communication is a thing.

To be fair, any animals that use body language (i.e. dogs wagging tails) or sight are communicating electromagnetically (reflected light) in the same we humans communicate electromagnetically. We're not generating our own EM signals, but using tools.

I had a discussion about this a while ago with a friend. There's a really interesting video of a HAM guy who has built a system such that he yells into a microphone which then uses the audio energy to generate an RF pulse that travels out the antenna. All RF energy is generated by the vocal energy. By yelling in pulses, Morse (or whatever) coding can be generated. I think he had used to the communicate between Massachusetts and somewhere in Florida.

Our conclusion as to why don't animals communicate with their own RF energy was your answer that you can't build good antennas from organic material. Evolutionarily, though, it seems like a great advantage!

>There's a really interesting video of a HAM guy who has built a system such that he yells into a microphone which then uses the audio energy to generate an RF pulse that travels out the antenna.

Fascinating, would love to see that in some distopian sci-fi story. Link for those that are curious: http://hackaday.com/2013/11/26/amateur-radio-transmits-1000-...

This is the future of "Wearables"! Combining them with implants to provide truly valuable data about your body and allowing them to deliver targeted medical treatment. So very exciting.

Conveniently packaging data regarding heart, liver and kidney function to be easily parsed and stored by advertisers/insurance/NSA

One step closer towards the borg :)

A very, very EMP-sensitive borg.

Reply on news.ycombinator.com