
Wireless system can power devices inside the body - tostitos1979
http://news.mit.edu/2018/wireless-system-power-devices-inside-body-0604
======
ffk
The main thing I got from the MIT article is this:

"This system relies on an array of antennas that emit radio waves of slightly
different frequencies. As the radio waves travel, they overlap and combine in
different ways."

This is known as constructive interference, pretty nifty to see it used in
this context. The range has been increased from 10 cm to 1 meter since the
paper I co-authored on this subject. Impressive!

These kinds of applications have also been a long time coming. With IoT
devices and NFC readers looming around the corner, I think it is likely that
we will see some pretty innovative medical inventions. Likewise, as mentioned
by NKosmatos, we need to take the security aspect very seriously. Some of
these NFC devices are programmable, and should defend against attacks that
could lead to events such as withholding life-saving medicine or misreporting
biometrics.

For reference, check out this paper I co-authored:

Suitability of NFC for Medical Device Communication and Power Delivery (2007)

[https://ieeexplore.ieee.org/document/4454171/](https://ieeexplore.ieee.org/document/4454171/)

And if you're interested in an early paper about RFID-delivered viruses, check
out this by Tanenbaum et al.:

[http://www.rfidvirus.org/papers/percom.06.pdf](http://www.rfidvirus.org/papers/percom.06.pdf)

~~~
darkmighty
Isn't this description flawed though? Waves of different frequencies are
independent in power. Thus they don't interfere (when time-averaged) -- at
all. Zero. (this is because signals of different frequencies are orthogonal in
the time-average integral of product sense)

What creates interference is difference is _phase_ among waves of the exact
same frequency.

It's odd that the paper author is making such basic EM theory mistake, and I
wonder what the actual device construction is like. (since it cannot work the
way he describes at steady state)

Maybe he's interpreting phase modulation as frequency modulation? Of course at
steady state all frequencies would be the same, making this a weird/incorrect
interpretation I think.

~~~
ffk
My understanding is all frequencies interfere with all other frequencies. When
averaged, the total power is probably not affected, but the power at any given
point at a small enough time interval should be noticeable.

But then, I'm not an antenna designer, I may have something fundamentally
wrong in my understanding. :)

~~~
darkmighty
The problem is as soon as you're speaking of "frequency" you're already on a
time-scale where the power doesn't interfere with other frequencies (as long
as the medium is linear, etc -- which is almost certainly true here). In the
mathematical/technical sense (in linear system theory)it's quite clear that
different frequencies would interfere, it's a basic entire principle of linear
circuit design that's been used for centuries -- systems have a Frequency
Response where each frequency is independent as a result of the eigenfunction
property. Personally I just think it's a big oversight, maybe they were trying
to give a laymen explanation and confused themselves. What they're doing must
be some form of phase modulation, _maybe_ they're interpreting as short bursts
of frequency modulation (with a stable steady-state frequency), but as I said
this is not an illuminating view imo.

Edit: Actually I think they might have frequency control indeed. That would be
a good idea to find a peak in frequency response (i.e. "resonant power
transfer"), not for any directivity gains through constructive interference.
That might be the source of confusion.

------
fouc
Radio waves are used to power cochlear implants. There is a chip & receiver
unit that is inserted under the skin on the head, with electrodes that go into
the cochlea. Externally there is an antenna that is held on the head next to
the skin, using a magnet to hold it in place. Radio waves are sent across the
skin to power the chip and control the electrodes.

------
excalibur
Plenty of nefarious applications for this. The range alone blows away existing
RFID designs, which will make it the preferred "chipping" technology for
surveillance states everywhere.

~~~
dsfyu404ed
There are positive uses. I can see this being useful for monitoring health in
animals raised for food in addition to the medical applications the article
mentioned.

That said, the potential for abuse is limited by what society will tolerate.
We tolerate tracking and alcohol monitoring bracelets for people who drive
drunk. If we tolerate tracking implants for sex offenders on parole or
something I'm sure it'll filter down routine probation sentences eventually.

~~~
sametmax
We tolerate tracking devices with camera, microphones and banking history in
our pocket. We even pay for it. So i wouldn't count of the public wisdom on
this. Or anything really.

------
trhway
>The implants are powered by radio frequency waves, which can safely pass
through human tissues. In tests in animals

why animals? couldn't the researchers just swallow that "prototype about the
size of a grain of rice" themselves and/or get several paid volunteers?

~~~
dear
Because animals have no say and they don't have to pay the animals. Once it's
done the animals will just be euthanized.

------
ThomPete
One of the first "promises" of nanotechnology I ever read about was that you
could create batteries so small that just calling your cellphone would charge
them I wonder if that is fundamentally the same idea.

------
NKosmatos
Interesting and for sure there are numerous applications for such devices, but
they didn’t mention anything about security and possible interferences. Sounds
very promising but scary at the same time.

------
ghostbrainalpha
I want to power my earbuds without ever removing them. If they can do this I
would be the first human tester.

I'd also love to start my car, without having to remember where i left my
keys.

------
smolder
Can it power tumors?

More seriously, though, nanotech or relatively small implantables/injectables
powered by radio or induction could do a lot for medicine... If anyone could
afford it.

------
JumpCrisscross
How much energy could a device extract from blood sugar?

~~~
Pfhreak
I'm waiting for someone to invent the implantable chip that converts blood
sugar into heat/light purely with the intention of wasting that energy.

Grab enough power to monitor blood sugar, to make sure you aren't putting
someone into a coma, but otherwise just try to burn an extra few hundred
calories a day.

~~~
booleandilemma
Why waste this energy? Couldn’t they devise a way to mine bitcoin with it? :)

~~~
delecti
Oh god, just what the world's food distribution problems need.

------
mclightning
How does the device come out when you need it to?

------
apocalypstyx
Texhnolyze here we come.

