University of Washington researchers develops tiny sensors that can spread like dandelions

battery-free sensor-carrying device with petal-like form
The dandelion-inspired, battery-free tiny devices will be released via drones in the air for quick distribution.

Nature is always the perfect inspiration for new technological innovations, and it is proven once again with the project developed by a team from the University of Washington. Amazed by how dandelions propagate through their featherlike pappuses and the wind, the group decided to inject the approach in the dispersion of wireless sensors across vast areas like farms and forests.

According to the team, conducting environmental condition monitoring in broad lands by manually placing the sensors can take months. This, however, will change with the tiny sensor system that is carefully placed in a lightweight material with petal-like forms. They will be released via drones in the air, where the wind will do the job of spreading them.

“We show that you can use off-the-shelf components to create tiny things. Our prototype suggests that you could use a drone to release thousands of these devices in a single drop. They’ll all be carried by the wind a little differently, and basically you can create a 1,000-device network with this one drop,” said senior author Shyam Gollakota, a UW professor in the Paul G. Allen School of Computer Science & Engineering. “This is amazing and transformational for the field of deploying sensors, because right now it could take months to manually deploy this many sensors.”

Despite the promising capability of the devices, there’s a challenge about them: the weight of the system (each device can hold at least four sensors) itself is about 30 times as heavy as a 1-milligram dandelion seed. With this, the team had to find the perfect design for the material that would serve as the parachute of the sensors. They needed the one that would allow the sensors to take more time to float in the air while being tossed by the wind. This will result in the broader dispersal of the sensors.

“The way dandelion seed structures work is that they have a central point and these little bristles sticking out to slow down their fall. We took a 2D projection of that to create the base design for our structures,” said the lead author and UW assistant professor in the Allen School, Vikram Iyer. “As we added weight, our bristles started to bend inwards. We added a ring structure to make it more stiff and take up more area to help slow it down.”

The team tested 75 designs in total, and after finding the one, they produced the designs in different sizes. According to the researchers, the variety of sizes will let the sensors fall at different rates.

“This is mimicking biology, where variation is actually a feature, rather than a bug,” said co-author and UW professor of biology, Thomas Daniel. “Plants can’t guarantee that where they grew up this year is going to be good next year, so they have some seeds that can travel farther away to hedge their bets.”

Despite the variation in sizes, the design will ensure that the system can reach up to 100 meters with a moderate breeze. Once placed, the devices can send data up to 60 meters away.

The shape will also help the devices land upright 95% of the time, which is needed since they use a solar panel instead of batteries. This means that they will only work during the day and stop without sufficient sunlight or nighttime. Nonetheless, the researchers included a capacitor in the system’s build, so each device can store some charge overnight.

“Then we’ve got this little circuit that will measure how much energy we’ve stored up and, once the sun is up and there is more energy coming in, it will trigger the rest of the system to turn on because it senses that it’s above some threshold,” Iyer said.

With no battery to get empty, the sustainable system can last a long time until it gets physically destroyed by different elements. There’s still one challenge about it, though: the non-biodegradable electronics they would leave in the environment. This pushes the team to find more ways to further develop the project to make its parts more biodegradable, environmentally friendly, and adaptive.

“This is just the first step, which is why it’s so exciting,” Iyer said. “There are so many other directions we can take now—such as developing larger-scale deployments, creating devices that can change shape as they fall, or even adding some more mobility so that the devices can move around once they are on the ground to get closer to an area we’re curious about.”

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