Autonomous Self-Drilling Seed Carriers for Aerial Seeding with Superior Success Rates

Abstract Aerial seeding can quickly cover large and physically inaccessible areas to improve soil quality and scavenge residual nitrogen in agriculture, for postfire reforestation3–6 and wildland restoration. However, it suffers from low germination rates due to the direct exposure of unburied seeds to harsh sunlight, wind, granivorous birds, and undesirable air humidity and temperature1. Inspired by Erodium seeds, we design and fabricate self-drilling seed carriers, turning wood veneer into highly stiff (7.2 GPa when dry, and 1.2 GPa when wet) and hygromorphic bending or coiling actuators with an extremely large bending curvature (1854 m-1), 45 times larger than the literature values. Our three-tailed carrier has an 80% drilling success rate on flat 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 different sizes and contents including biofertilizers and plant seeds as large as those of whitebark pine, which are 11 mm in length. We compare experiments with numerical simulation to elucidate the curvature transformation and actuation mechanisms to guide the design and optimization of the seed carriers. Our system will significantly improve the effectiveness of aerial seeding to relieve agricultural and environmental stresses, and has potential applications in energy harvesting, soft robotics and sustainable buildings.