Scientists invent robot that can swim under sand like sea turtle hatchlings •
Shivam Chopra holds a robot that can swim under sand, similar to sea turtle hatchlings. Credit: David Baillot

Scientists invent robot that can swim under sand like sea turtle hatchlings

Welcome to the innovative world of robotics, where one innovative creation is making waves…under the sand. This unique robot, created by a team of scientists at the University of California San Diego, can “swim” under the sand’s surface and dig itself back out when needed, similar to a sea turtle hatchling.

This new robot can swim under sand thanks to a pair of front limbs modeled after the oversized flippers of sea turtle hatchlings. In an awe-inspiring feat of engineering, this robot is the first of its kind able to navigate sand at a depth of five inches.

While it may seem slow, traversing at a speed of 1.2 millimeters per second or around 13 feet per hour, it’s worth noting that this is on par with the speed of other subterranean creatures such as worms and clams.

Apart from its turtle-inspired limbs, the robot is furnished with force sensors at the ends of these flippers, empowering it to detect obstacles while moving. Furthermore, you can operate it without physical constraints and control it remotely via WiFi.

Sand robots have significant hurdles

Robots designed to swim under sand encounter numerous hurdles. The forces they face are much greater than those met by robots navigating air or water, and they can sustain damage more readily.

Nonetheless, overcoming these challenges could offer significant advantages such as inspecting grain silos, taking soil contaminant measurements, engaging in seafloor digging, assisting in extraterrestrial exploration, and aiding in search and rescue operations.

Devising this sand-swimming robot involved a series of meticulous experiments aimed at better understanding the complex nature of sand and how to enable robotic locomotion through it.

Sand presents a particular challenge due to the large forces caused by the friction between grains, difficulty in sensing obstacles, and its variable behavior. Sand can act like a liquid or a solid depending on the situation.

Biomimicry — copying sea turtle hatchlings

The team found inspiration in nature, studying the movement of various animals to develop their sand-swimming robot. They found their solution in the sea turtle hatchlings, whose large front fins enable them to surface after hatching.

Replicating these flippers in the robot not only generates large propulsive forces but also enables the robot to steer and potentially detect obstacles.

Yet, the mystery of how robots equipped with flipper-like appendages move in sand persists. “We needed to build a robot that is both strong and streamlined,” said Shivam Chopra, the lead author of the paper describing the robot, published in the journal Advanced Intelligent Systems.

Extensive simulations and testing by the UC San Diego team resulted in the adoption of a tapered body design and a shovel-shaped nose.

By monitoring torque changes caused by its flipper movement, the robot can identify obstacles above it as it swims under sand. However, it cannot yet detect obstacles below or directly in front of it.

To counterbalance this, the robot features a unique design addition: two foil-like surfaces, dubbed “terrafoils,” mounted on the sides of the bot’s nose, enabling it to maintain a consistent depth in the sand and avoid always heading upwards.

Researchers tested this revolutionary robot in a lab setting and at La Jolla Shores, a beach close to the UC San Diego campus. The trials showed that the robot’s speed reduced in wet sand due to the greater resistance it offered.

Future advancements will focus on increasing the robot’s speed and enhancing its burrowing capabilities, allowing it to dig into the sand as well as dig itself out. This study marks an exciting step forward in robotic locomotion through challenging terrains.

More about sea turtle hatchlings

Sea turtle hatchlings are young sea turtles that have recently emerged from their eggs. They represent an important life stage of all seven existing species of sea turtles: the Loggerhead, Green, Hawksbill, Flatback, Olive Ridley, Kemp’s Ridley, and Leatherback.

Here’s an overview of their life, their challenges, and their role in the larger ecosystem.

Life cycle

The mother turtle typically lays sea turtle eggs in clutches on sandy beaches.She will come ashore during the night, dig a hole with her flippers, lay her eggs, cover the hole with sand, and then return to the sea. The number of eggs in a clutch varies by species, but it can be anywhere from 50 to 200 eggs.

After being laid, the eggs incubate in the warmth of the sand for about 60 days, though this can vary depending on the species and the temperature. Warmer sands tend to speed up the incubation process, and interestingly, they also influence the sex of the hatchlings. Warmer conditions generally produce more female hatchlings, while cooler conditions result in more males, a phenomenon known as temperature-dependent sex determination.

Emergence and journey to the sea

When the hatchlings finally emerge from their eggs, they dig their way up through the sand in a group effort, usually at night when the temperatures are cooler and predators are less active. This emergence is known as a “boil.” Once they reach the surface, they use visual cues to find the sea, often navigating by the natural light on the ocean horizon.

This journey from the nest to the sea is fraught with danger. Predators such as birds, crabs, and other animals are a major threat. Human-made obstacles and artificial lights can also confuse or misdirect hatchlings, leading them away from the sea.

The lost years

Once they reach the ocean, the hatchlings begin what is often referred to as the “lost years” — a period ranging from a few years to a decade where they live in the open ocean.

During this time, their whereabouts and habits are largely unknown to scientists due to tracking difficulties. They drift with the currents and forage for food, growing until they reach a certain size and maturity.

Sea turtle hatchling survival

Survival rates for sea turtle hatchlings are tragically low. It’s estimated that only about one in 1,000 to 10,000 hatchlings survive to adulthood. Natural predators, human activities, marine pollution, habitat loss, and climate change all contribute to the high mortality rate.

Significance in the ecosystem

Despite their small size and vulnerable status, sea turtle hatchlings play a crucial role in marine ecosystems. They are a part of the food web, serving as a food source for various predators. They contribute to the nutrient cycle, both on land and in the sea.

For example, unhatched eggs and hatchlings that don’t make it to the sea provide nutrients that enrich coastal vegetation.

Furthermore, their journey from nest to sea helps aerate the sand. This can benefit beach ecosystems.

By adulthood, depending on the species, sea turtles also play roles in controlling jellyfish populations, grazing on sea grass and keeping it healthy, and even helping to shape the physical environment in the case of species that use sponges or corals as food.

Protection and conservation efforts worldwide are continuously working towards ensuring the survival and health of sea turtle hatchlings, and thus, the continuance of these vital marine creatures.

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