Environmental sensors are becoming ubiquitous, for better or worse. As sensors become smaller and cheaper, one key challenge is how to deploy them. People voluntarily carry them in their devices, and so-called “smart” cities and buildings have sensors built in. But many parts of the planet are not conveniently engineeered, so sensors have to be sent there in one way or another. This is one of the killer apps for small UAVs, for example.
This spring researchers at U. Washington report a bioinspired method for dispersing tiny sensors: wind dispersal inspired by dandelion seeds [1]. These small devices are designed to be strewn from a UAV, and float randomly on the wind. The solar powered environmental sensor collect and relay data during the day, and rest at night, so they can persist for quite a while with no need for external power or replacement.
The wind dispersal is inspirited by wind blown seeds, and in keeping with the biological models, each package is slightly different [2]. Between the chaos of wind currents and the variability of the sensors, the group will disperse rather randomly. Like seed dispersal, this strategy achieves coverage and works around ‘hard places’.
This project caught my eye for a slightly different reason. I’ve been watching the development of tiny battery free devices for many years now (OK—probably decades). But I’m more interested in signaling than sensing.
In particular, I have a vision of a cloud of decorative artificial fireflies. Not that natural fireflies aren’t awesome, but I’d like to be able to deploy them at parties, indoors, or on a cityscape. Zillions of tiny lights, emitting charming patterns (and sounds).
I’ve also imagined jewelry that sings softly, just to you. Image earrings that chirp like a bird. Or whisper sweet nothings from a lover.
The dandelion sensors show that power and electronics are getting small enough to begin to realize my visions. Substitute tiny LEDs and speakers, and you’ve got my firefly / earrings.
Now, there are challenges with the dandelion sensors. Networking and data retrieval are certainly a problem. These little guys don’t have much bandwidth, so you need to get a relay station pretty close—another job for a UAV. But still, there are distinct limits to how much data you can actually get out.
Another big problem with the dandelion sensors is that they need to be biodegradable. Spewing these over, say, a farm field, is fine for sensing. But it leaves behind all those sensors which may remain for a long time. They are probably at least a little toxic. And since they are tiny and randomly dispersed, it’s going to be pretty impossible to pick them up one by one. So we really want them to be biodegradable.
I’ll note that my jewelry concept doesn’t suffer from these challenges. The jewelry is intended to last a long time, and doesn’t need to transmit. (In fact, we really don’t want our personal effects spying on us.) And should the jewelry need to be recharged or reprogrammed, it can be done on a table in controlled conditions.
(Why would it need to be reprogrammed? Well, you might need to change the sound recording to erase the voice of a former amour, no?)
Anyway, this is very inspiring, if not quite for the applications highlighted by the researchers.
- Vikram Iyer, Hans Gaensbauer, Thomas L. Daniel, and Shyamnath Gollakota, Wind dispersal of battery-free wireless devices. Nature, 603 (7901):427-433, 2022/03/01 2022. https://doi.org/10.1038/s41586-021-04363-9
- Sarah McQuate, Tiny battery-free devices float in the wind like dandelion seeds, in UW News, March 16, 2022. https://www.washington.edu/news/2022/03/16/battery-free-devices-float-in-wind-like-dandelion-seeds/
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