Go bury yourself: Engineers design wooden seed carriers that drill down in the soil when exposed to rainfall

Some seeds can implant themselves in soil like tiny drills and the mechanism of one such genus of plant (Erodium) has inspired a new engineered seed carrier that can successfully bury itself down in the soil 80% of the time.

According to a new study in Nature, E-seed’s three pronged corkscrew-like stalk unwinds and twists into the ground when exposed to moisture, burying the seed it carries to take root safely away from hungry birds and harsh environmental conditions.

Made from a wooden veneer, the biodegradable seed carrier could improve the germination rates of aerial seeding in difficult to access areas, which usually suffers due to unburied seeds being left exposed to the elements.

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

“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 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 get excited about things that could have a beneficial effect on nature.”

Improving functionality beyond what’s 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-burying mechanism for its seeds as it adapted to arid climates.

The seed sits inside a thin, tightly wound stalk with a long, curved tail at the top. As the stalk begins to unwind, its twisting tail connects with the ground and causes the seed carrier to push itself upright. Then, as it continues to unwind, it creates torque to drill down into the soil and bury the seed.

But the one-tailed version found in nature only works well in soils with crevices, so the team designed their E-seed version with three.

Enhancing its ability to push itself upright significantly, E-seed has an 80% drilling success rate on flat land after two rain cycles (compared to 0% for Erodium), making it applicable in a much broader range of environments.

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

The E-seed carriers are made of paper thin veneers of white oak – widely used in furniture – which respond to moisture by swelling.

The team developed a five-step process for manufacturing the seed carriers in the lab which involves treating the wood through chemical washing and moulding the veneer strips on a three-dimensionally printed mould. The researchers anticipate adapting the process to an industrial scale in the future.

According to co-author Andreea Danielescu, director of the Future Technologies R&D group at Accenture Labs in the US, E-seed could be used to improve ecological resilience.

“Technologies like E-seed can help us address real-world problems — helping us avoid landslides, reducing the impact of invasive species and improving reforestation of hard-to-reach places,” she says.