A vegetable plant growing next to its E-seed carrier. This seed was planted in a lab at Carnegie Mellon University to observe the effect on the seed of helpful fungus also carried in the E-seed. (Credit: Carnegie Mellon)
Engineers have developed wooden seed carriers that mimic the behavior of self-burying seeds.
Before a seed can grow into a tree, flower, or plant, it needs to successfully implant itself in soil—a delicate and complex process.
For the Erodium flower to implant a seed, its stalk forms a tightly wound, seed-carrying body with a long, curved tail at the top. When it begins to unwind, the twisting tail engages with the ground, causing the seed carrier to push itself upright. Further unwinding creates torque to drill down into the ground, burying the seed.
Inspired by Erodium’s magic, Teng Zhang, professor of mechanical and aerospace engineering at Syracuse University, Lining Yao from Carnegie Mellon University, and a team of collaborators worked to engineer a biodegradable seed carrier called E-seed.
Their seed carrier, fashioned from wood veneer, could enable aerial seeding of difficult-to-access areas, and could work for a variety of seeds or fertilizers and adapt to many different environments. The carriers also could be used to implant sensors for environmental monitoring. They might also assist in energy harvesting by implanting devices that create current based on temperature fluctuations.
“This is a perfect example demonstrating the beauty and power of bioinspired design. We learn from nature and eventually achieve superior performance by leveraging the freedom of engineering design,” says Zhang.
“Seed burial has been heavily studied for decades in terms of mechanics, physics, and materials science, but until now, no one has created an engineering equivalent,” says Yao, director of the Morphing Matter Lab in the School of Computer Science’s Human-Computer Interaction Institute at Carnegie Mellon.
“The seed carrier research has been particularly rewarding because of its potential social impact. We get excited about things that could have a beneficial effect on nature.”
Additional collaborators are from Carnegie Mellon, the University of Pennsylvania, Zhejiang University, and Accenture Labs.
Inspired by how dandelions use the wind to distribute their seeds, researchers have developed a tiny sensor-carrying device that can be blown by the wind as it tumbles toward the ground.
Wireless sensors can monitor how temperature, humidity, or other environmental conditions vary across large swaths of land, such as farms or forests.
These tools could provide unique insights for a variety of applications, including digital agriculture and monitoring climate change. One problem, however, is that it is currently time-consuming and expensive to physically place hundreds of sensors across a large area.
The new sensor is about 30 times as heavy as a 1 milligram dandelion seed but can still travel up to 100 meters in a moderate breeze, about the length of a football field, from where it was released by a drone. Once on the ground, the device, which can hold at least four sensors, uses solar panels to power its onboard electronics and can share sensor data up to 60 meters away.
The researchers tested 75 designs, some of which are shown here in yellow. (Credit: Mark Stone/U. Washington)
“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,” says senior author Shyam Gollakota, professor in the Paul G. Allen School of Computer Science & Engineering at the University of Washington.
“This is amazing and transformational for the field of deploying sensors, because right now it could take months to manually deploy this many sensors.”
Because the devices have electronics on board, it’s challenging to make the whole system as light as an actual dandelion seed. The first step was to develop a shape that would allow the system to take its time falling to the ground so that it could be tossed around by a breeze. The researchers tested 75 designs to determine what would lead to the smallest “terminal velocity,” or the maximum speed a device would have as it fell through the air.
“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,” says Vikram Iyer, an assistant professor in the Allen School and lead author of the paper.
“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.”
To keep things light, the team used solar panels instead of a heavy battery to power the electronics. The devices landed with the solar panels facing upright 95% of the time. Their shape and structure allow them to flip over and fall in a consistently upright orientation similar to a dandelion seed.
Without a battery, however, the system can’t store a charge, which means that after the sun goes down, the sensors stop working. And then when the sun comes up the next morning, the system needs a bit of energy to get started.
“The challenge is that most chips will draw slightly more power for a short time when you first turn them on,” Iyer says. “They’ll check to make sure everything is working properly before they start executing the code that you wrote. This happens when you turn on your phone or your laptop, too, but of course they have a battery.”
The team designed the electronics to include a capacitor, a device that 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 says.
These devices use backscatter, a method that involves sending information by reflecting transmitted signals, to wirelessly send sensor data back to the researchers. Devices carrying sensors—measuring temperature, humidity, pressure, and light—sent data until sunset when they turned off. Data collection resumed when the devices turned themselves back on the next morning.
To measure how far the devices would travel in the wind, the researchers dropped them from different heights, either by hand or by drone on campus. One trick to spread out the devices from a single drop point, the researchers say, is to vary their shapes slightly so they are carried by the breeze differently.
“This is mimicking biology, where variation is actually a feature, rather than a bug,” says coauthor Thomas Daniel, professor of biology. “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.”
Another benefit of the battery-free system is that there’s nothing on the device that will run out of juice—the device will keep going until it physically breaks down. One drawback to this is that electronics will be scattered across the ecosystem of interest. The researchers are studying how to make these systems more biodegradable.
“This is just the first step, which is why it’s so exciting,” Iyer says. “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.”
Hans Gaensbauer, who completed this research as a UW undergraduate majoring in electrical and computer engineering and is now an engineer at Gridware, is also a coauthor. The Moore Inventor Fellow award, the National Science Foundation, and a grant from the US Air Force Office of Scientific Research funded the work.
Researchers have created a sensor system that can ride on the back of a moth.
The system weights 98 milligrams, about one tenth the weight of a jellybean, or less than one hundredth of an ounce.
Once the sensor has reached its destination riding a moth’s back, a researcher can send a Bluetooth command, to release the sensor from its perch. The sensor can fall up to 72 feet—from about the sixth floor of a building—and land without breaking. Once on the ground, the sensor can collect data, such as temperature or humidity, for almost three years.
The sensor system (shown here on top of a penny) was designed with its battery in one corner (shown here as the disc on the left). As the sensor falls, it begins rotating around the corner with the battery, generating additional drag force and slowing its descent. (Credit: Iyer et al./MobiCom 2020)
“We have seen examples of how the military drops food and essential supplies from helicopters in disaster zones. We were inspired by this and asked the question: Can we use a similar method to map out conditions in regions that are too small or too dangerous for a person to go to?” says senior author Shyam Gollakota, an associate professor in the School of Computer Science & Engineering at the University of Washington.
“This is the first time anyone has shown that sensors can be released from tiny drones or insects such as moths, which can traverse through narrow spaces better than any drone and sustain much longer flights.”
While industrial-sized drones use grippers to carry their payloads, the sensor is held on the drone or insect using a magnetic pin surrounded by a thin coil of wire.
The sensor system can also be carried by a small drone. The drone shown here is a commercial quadcopter that was used in the experiments. (Credit: Mark Stone/U. Washington)
To release the sensor, a researcher on the ground sends a wireless command that creates a current through the coil to generate a magnetic field. The magnetic field makes the magnetic pin pop out of place and sends the sensor on its way.
Researchers designed the sensor with its battery, the heaviest part, in one corner. As the sensor falls, it begins rotating around the corner with the battery, generating additional drag force and slowing its descent. That, combined with the sensor’s low weight, keeps its maximum fall speed at around 11 miles per hour, allowing the sensor to hit the ground safely.
The researchers envision using this system to create a sensor network within a study area. For example, researchers could use drones or insects to scatter sensors across a forest or farm that they want to monitor.
Once a mechanism is developed to recover sensors after their batteries have died, the team expects their system could be used in a wide variety of locations, including environmentally sensitive areas. The researchers plan to replace the battery with a solar cell and automate sensor deployment in industrial settings.
The researchers presented the work, which the National Science Foundation funded, at the MobiCom 2020.
