Seed carriers burrow into the ground when exposed to rain

Some seeds can nest in the soil like tiny borers, and the mechanism of such a genus of plants (erodium) has inspired a new technical seed carrier that can successfully bury itself in the ground 80% of the time.

According to a new study in NatureE-Seed’s three-pronged, corkscrew-like stem twists and turns into the soil when exposed to moisture, burying the seed it carries to take root safely, away from hungry birds and harsh environmental conditions.

Made from a wood veneer, the biodegradable seed carrier could improve germination rates of airborne seeds in hard-to-reach areas that typically suffer from unburied seeds being left exposed to the elements.

The new technology could even be used to deliver nematodes (worms used as natural pesticides), fertilizers and fungi.

“Seed burial has been studied extensively for decades in terms of mechanics, physics and materials science, but until now no one has created a technical equivalent,” says Lining Yao, director of the Morphing Matter Lab at Carnegie Mellon University in the US. and senior author on the paper.

“The seed carrier research has been particularly rewarding because of its potential social impact. We are passionate about things that could have a positive impact on nature.”

Images of an e-seed carrier digging into the soil over time
This time-lapse shows an E-seed carrier burrowing into the soil after exposure to moisture. Photo credit: Carnegie Mellon University

Improving functionality beyond what is found in nature

Some varieties of erodium — a genus of five-petalled flowers native to North Africa, Indomalaya, the Middle East, and Australia — evolved a self-burial mechanism for its seeds as it adapted to arid climates.

The seed sits in a thin, tightly coiled stalk with a long, curved tail at the top. As the stalk begins to uncoil, its twisted tail connects to the ground, causing the seed carrier to erect itself. As it then continues to unwind, it creates torque to bore into the ground and bury the seed.

But the naturally occurring single-tailed version only works well in soil with crevasses, so the team designed their E-seed version with three.

E-Seed greatly improves its ability to right itself and has an 80% success rate when drilling on flat land after two rain cycles (compared to 0% for erodium), making it applicable in a much wider range of environments.

A vegetable plant growing alongside its E seed carrier
A vegetable plant growing alongside its E seed carrier. This seed was planted in a garden on the campus of Carnegie Mellon University in Pittsburgh, Pennsylvania. Photo credit: Carnegie Mellon University

“Geometry can enhance the functionality of materials beyond what nature offers us. It also makes the design versatile for application to other materials,” says Shu Yang, a materials scientist from the University of Pennsylvania and a co-author of the study.

The E-Seed supports consist of wafer-thin veneers of white oak – widely used in furniture – that react to moisture by swelling.

The team developed a five-step process to create the seed carriers in the lab, which involves chemically washing the wood and shaping the veneer strips on a three-dimensional printed mold. The researchers assume that the process will be transferred to an industrial scale in the future.

According to co-author Andreea Danielescu, director of the Future Technologies research and development group at Accenture Labs in the US, E-Seed could be used to improve ecological resilience.

“Technology like E-Seed can help us address real problems — helping us avoid landslides, reduce the impact of invasive species, and improve reforestation of hard-to-reach places,” she says.

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