This bioinspired seed carrier has an 80 percent success rate

Researchers at Carnegie Mellon University have optimized the structure of seeds to develop a robot that can plant seeds efficiently.

Aerial seeding is a widespread technique in remote areas to sow seeds; they are sprayed from an airplane, helicopter, or drone. But the process is inefficient - this is addressed by employing seeds carriers that can improve germination efficiency by helping seeds to penetrate the soil.

And when a seed lies on the surface, it is prone to various risks. It can be either damaged by weather conditions or eaten by wildlife, resulting in low germination rates. Now, some seeds of grass species can bury themselves - an ability that would be highly advantageous for all seeds.

Lining Yao, an assistant Professor of Human-Computer Interaction Institute (HCII) at Carnegie Mellon University, School of Computer Science, and co-authors, were inspired by Erodium seeds, a genus of plants with seeds that unwind coiled tails to act as a drill to plant into the ground. Their self-drilling behavior influenced a new biodegradable seed carrier that is more effective and has a higher implantation success rate than Erodium seeds themselves.

This technology may "improve the effectiveness of aerial seeding to address agricultural and environmental stresses in degraded regions," as per the press release.

The seed carriers are highly efficient and sustainable

The researchers designed a wood-based biodegradable seed system comprising a seed carrier with three coiled tails. These unwind when moistened and can carry seeds as large as those of whitebark pine trees, which are about 11 mm long and weigh about 72 mg.

So, how does it work? A drone will disperse the seed carriers. Once settled on the ground, "moisture causes the cells to swell and the coil to unwind, drilling the payload down; the coil then wound up again as it dried, pushing the payload deeper underground", Naomi Nakayama Imperial College London, London, UK, writes.

The number of unwinding tails has been increased to ensure that the drill bit is more angled to the surface for easy burrowing. The innovative seed carriers have an 80 percent success rate of getting seeds into the ground on flat land, which is the most challenging terrain. It also reduces the risk of them blowing away or being eaten by animals. 

The researchers compared natural Erodium seed's success under the same terrain conditions and found the success rate to be zero percent.

The authors conclude that these carriers can also deploy fertilizers or other materials, like sensors, that could be helpful for agricultural and conservation applications.

The study is published in Nature.

Study Abstract:

Aerial seeding can quickly cover large and physically inaccessible areas1 to improve soil quality and scavenge residual nitrogen in agriculture and for postfire reforestation and wildland restoration. However, it suffers from low germination rates, due to the direct exposure of unburied seeds to harsh sunlight, wind, and granivorous birds, as well as undesirable air humidity and temperature. Here, inspired by Erodium seeds, we design and fabricate self-drilling seed carriers, turning wood veneer into highly stiff (about 4.9 GPa when dry, and about 1.3 GPa when wet) and hygromorphic bending or coiling actuators with an extremely large bending curvature (1,854 m−1), 45 times larger than the values in the literature. Our three-tailed carrier has an 80% drilling success rate on fat land after two triggering cycles, due to the beneficial resting angle (25°–30°) of its tail anchoring, whereas the natural Erodium seed’s success rate is 0%. Our carriers can carry payloads of various sizes and contents including biofertilizers and plant seeds as large as those of whitebark pine, which are about 11 mm in length and about 72 mg. We compare data from experiments and numerical simulation to elucidate the curvature transformation and actuation mechanisms to guide the design and optimization of the seed carriers. Our system will improve the effectiveness of aerial seeding to relieve agricultural and environmental stresses, and has potential applications in energy harvesting, soft robotics, and sustainable buildings.