This press release is quite misleading... the only novel aspect here is "flexible". It's less efficient than the existing rectenna solutions. And it's just as useless unless it's placed directly next to a WiFi router that is experiencing unusually high load.
A single AA battery can deliver 40uW for about 4 years, continuously.
Use a carbon zinc dry cell for things like that, they won't leak like other alkaline battery types. Bit lower capacity so you'll have to replace them more often but they'll not lead to destruction of the device either.
Correct me if I'm wrong here but wouldn't tech like this also sap signal strength like nothing else?
This seems like it would be a potentially nice to have first layer in a secured room/building. Recoup some energy then actually go about blocking unwanted signal leakage.
From a wild speculation side: if a tour bus of the elderly with pacemakers powered by this goes by are they just a traveling dead zone?
If this device is blocking line-of-sight between you and the WiFi access point, then yes it will reduce your signal strength. In this respect it is like a fish tank or any other object that tends to absorb WiFi frequencies.
It cant suck the WiFi out of a large area like some kind of vacuum cleaner, Electromagnetic waves don't work like that.
You can make a Faraday cage out of a lot of stuff but I doubt you could get much in the way of power out of it. Granted you can't get much out of this either but it's measurable.
FWIW, Wi-Fi is generally considered a poor source of harvestable RF for little doodads you might want to power passively. Among other issues, there's a lot of "quiet time" as radios on the same Wi-Fi network negotiate who gets to use the channel at a given moment.
If you are interested in the challenges of harvesting energy from Wi-Fi and some ways to address those challenges, here's a nice paper (originally in CoNEXT 2015) from a team I was fortunate to be on: https://cacm.acm.org/magazines/2017/3/213830-powering-the-ne...
[Edit: the relevance here is that, even with an awesome antenna like the one in the news, the Wi-Fi protocol kinda works against you, which raises a bunch of interesting questions.]
You really just have to assume that the writer of the article is completely ignorant in this case. I hardly think that MIT is claiming to have invented the worlds first antenna connected to a diode but that's the claim that seems to be made in the article. The state of technical reporting is rather sad.
I guess to be fair to the authors. The actual technical achievement is mentioned, albeit briefly,
"To build their rectifier, the researchers used a novel 2-D material called molybdenum disulfide (MoS2)"
It's a novel material that can be used to make planar shoctkey diodes via an unusual process.
The entire rest of the article is just pointless misleading fluff.
The entire rest of the article is just pointless misleading fluff.
No, it's not. It's a press release, which while being pretty technically basic is broadly accurate. It includes some comparisons with existing technology, reasons that this development is different, and possible applications. The point is to make this development known to other people outside the field who have less knowledge about the underlying technology. That's a totally reasonable goal; not every article has to be an in-depth technical review.
This article does commit one unforgivable crime, which is failing to link to the research itself. I absolutely cannot understand why media outlets and press offices are so reticent to do this simple thing.
Let's break it down then.
The first paragraph opens with, "the first fully flexible device that can convert energy from Wi-Fi signals into electricity that could power electronics." This is blatantly false.
The second paragraph is sort of true. They are using their novel diode in an otherwise standard antenna structure.
Third paragraph repeats the second. Mentions that it can be manufactured in sheets?
Fourth paragraph sort of repeats the previous but this time as a quote from someone.
The Quote, " have come up with a new way to power the electronics systems of the future — by harvesting Wi-Fi energy in a way that’s easily integrated in large areas — to bring intelligence to every object around us." It's pure marketing speak. We need more funding, let's throw ai onto this for some reason.
The next 3 paragrpahs are repeats of, This device that provides power can be used to provide power to things. It at least mentions a broad figure of merit, 40 uWatts when exposed to 150 uWatts.
We are now half way through the article when the next paragraph finally mentions rectifiers, giving a brief but not great definition of what they are and their current state of the art. It mentions some problems with modern rectifiers, which are not actually true.
The next paragraph is actually only a single sentence and contains the entirety of the new development that the whole article is supposed to be about!
The next paragraph tries to explain the shortcomings of current Schottky diodes with bad physics.
Another quote about the device but lacking in broader context.
The second to last paragraph gives a better version of the efficiency figure of merit from earlier. Lacks details.
Last paragraph is a list of funders who are paying for the research.
That is a pretty crappy fluff to meat ratio in my book.
It mentions "flexible smartphones" with the obvious intent to mislead the reader that a rectenna would be useful for powering such a device, a truly laughable concept. Which was picked up by other press articles leading to headline claims about "WiFi powered cellphones".
Why is “enough power to charge your phone” your line of practicality? Phones contain an enormous amount of power hungry electronics, bright screens, speakers, multiple GHZ CPUs and radios for transmitting across different spectrum. With 40uW, you’d have to strip most of that away, but you could do something like: power up, take a temperature/CO2/RH/etc reading, transmit to a base station, sleep and repeat every 5 minutes. Sensor networks like these are extremely practical, especially in an industrial setting. Being able to accumulate some power, eg. with an integrated capacitor could also increase your max power draw for when your device is doing work.
Because the first line of the article alludes to using this to power your phone.
It also states. "Promising early applications for the proposed rectenna include powering flexible and wearable electronics, medical devices, and sensors for the “internet of things.” Flexible smartphones, for instance, are a hot new market for major tech firms."
Oh, wow. I had to do a double-take when I read '2-D', because the initial shock of 'converting wi-fi signals to electricity' was already too much for my mortal mind to comprehend.
If this ends up being practical, this is really, really, cool - and that's an understatement.
We're not even going to need to have electrical wiring in homes anymore. 802.11ad 60GHz wifi mesh routers with a lot of coherence and a directional mechanism could power the whole home.
https://en.wikipedia.org/wiki/Foxhole_radio