New research into burrowing seeds could inform the next generation of drilling robots, according to a new study from scientists in South Korea.
Published in the journal Physics of Fluids, the new study described how seeds from the flowering species Pelargonium responded to a sufficient degree of humidity by rotationally burrowing deeper into soil through the use of a corkscrew appendage known as an awn.
The study team noted how the awn reacted to humidity by hygrosopic expansion, causing it to straighten out. If the seed was secured within the soil, this deformation was seen to generate thrust, with the unwinding coil digging down and sending the seed deeper into the ground.
The research team said they were inspired by a documentary on plants, particularly a scene that showed how a plant’s seed can move without the use of muscles. Before settling on the Pelargonium species for their paper, the research team also investigated seeds from a number of other species. They noted that the seeds of some plants, like some wild wheats, have curved awns that produce only bending motions.
"Our work illuminates the surprising functionality and beauty of natural design," study author Wonjung Kim, a professor at Sogang University, said in a press release. "Although plants cannot generally produce active motions due to their lack of muscle, some seeds have evolved to create burrowing toward a better germination environment. More surprisingly, when a helical shape awn is exploited, the burial strategy is remarkably good for drag reduction."
In addition to showcasing another mechanical development courtesy of countless years of evolution, the study team was also able to develop mathematical models that have direct uses in contemporary and next-generation robotics. Comprehending the movement of these seeds and how their design cuts down on the drag caused by soil helps robotics engineers in the development of soil-drilling machines.
"To obtain environmental information such as soil pollution in inaccessible areas such as space planets, battlefields, or disaster areas, small robots are needed," Kim said. "Our research has demonstrated a reduction in particle drag by rotation, which informs an efficient intruder design method for digging robots. Furthermore, self-burrowing awns provide inspiration for designing non-motorized robots that respond to various stimuli such as heat, light, and humidity."
Those robots could find a use on other planets as NASA is currently looking into ways to autonomously drill beneath the icy surfaces of distant worlds like Jupiter’s moon Europa. According to a news story from the American space agency, NASA has been busy developing an underground probe capable of digging through miles of ice while transporting samples for later testing.
The technology is being developed to gather specimens from under the exterior of an icy moon like Europa. The probe and other systems being developed under the same NASA project would experience a wide variety of demanding environments. Temperatures can get to hundreds of degrees below freezing. Wheels might have to traverse ice that acts more like sand. On Europa in particular, the exterior is constantly being bombarded with radiation.
To drill deep into ice, NASA scientists are developing a heat probe that uses a vacuum for extremely efficient insulation, which is the same method used to insulate a typical Thermos bottle. Rather than radiating heat in an outward direction, it would keep that energy, generated from a hunk of plutonium, as the probe drops farther into the ice.
NASA has said a spinning blade on the bottom of the drill would cut through the ice, throwing ice bits back into the body of the probe, where they would melt and be pumped out the back of the machine.
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