March 4, 2021

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Soft robot swims in the Mariana Trench

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A team of researchers affiliated with multiple institutions in China has developed a soft robot that can successfully swim in the Mariana Trench. In their paper published in the journal Nature,, the group describes their soft robot and its capabilities. Cecilia Laschi and Marcello Calisti with the National University of Singapore and the University of Lincoln, respectively, have published a News & Views piece in the same journal issue outlining the work by the team in China.

One of the problems with deep sea submersible craft, whether manned or operated remotely, is dealing with the immense pressure involved. Hulls have to be designed and constructed that are capable of withstanding the crushing pressure found in the deepest parts of the sea—a very expensive way to go. In this new effort, the researchers have taken a new approach to the problem: emulating soft fish.

Prior research has shown that it is possible to make soft robots out of pliable materials such as silicone and other polymers. Soft robots have been constructed from such materials to emulate squid and other soft-body sea creatures. In this new effort, the researchers built their robot using soft polymers in the shape of a flying-type fish—one that swims by flapping its "wings" like a ray. The wings flap via a well-known assembly of fabricated muscle in a silicone body. An applied electrical current forces the muscle to contract, pulling the up. Relaxing the current allowed the wing to relax to its natural state.

Free swimming of soft robot in deep sea at the depth of 3,224 m. This video shows the deep-sea free swimming of soft robot in the South China Sea. The soft robot was grasped by a robotic arm on ‘HAIMA’ ROV and reached the bottom of the South China Sea (depth of 3,224 m). After the releasing, the soft robot was actuated with an on-board AC voltage of 8 kV at 1 Hz and demonstrated free swimming locomotion with its flapping fins. The front view and side view of swimming process were recorded by the cameras and LED lights on the ROV. This video shows the potential of soft robots in deep-sea exploration. Credit: Li et al.
The free swimming tests of soft robot. This video shows free swimming experiment in of the soft robot under hydrostatic pressures of 0 MPa (in a pool) and 110 MPa (in a chamber). The soft was attached on a time-controlled electromagnet and released. After the releasing, the soft robot was actuated with an on-board AC voltage of 7 kV at 1Hz and demonstrated a free swimming locomotion. Credit: Li et al.

The researchers had to overcome a problem others had experienced in the past: adding electronics to control of the robot. They found that simulating the architecture of snailfish bones worked very well—instead of trying to pack the electronics into as small of a packet as possible, they spaced them out and embedded them in silicone. This resulted in greatly reduced stress on the components.

The researchers tested their robot first in the laboratory, then at a nearby lake, and following that, in the South China Sea. Finding success at all of the depth levels they tested, the team then hooked the up to a traditional submersible and sent it down into the depths of the Marina Trench and found it worked just as well down there.

Soft robot free swimming in deep lake. This video shows field exploration of the robot in a deep lake (depth ~70 m). The soft robot was carried by a gripper on ‘Blue ROV’ and released at depth of 8 m and 70 m. After the releasing, the soft robot was actuated with an on-board AC voltage of 8 kV at 1Hz. The free swimming of soft robot was recorded by the internal camera and lights on the ROV, which further confirms the robustness of the robot in field exploration. Credit: Li et al.
Flapping actuation of soft robot in the Mariana Trench at the depth of 10,900 m. This video shows deep sea field test of soft robot in the Mariana Trench. Mounted on a deep sea lander, the soft robot reached the bottom of Mariana Trench. At the depth of 10,900m in the Mariana Trench, the DE driven soft robot kept flapping its fins. The front view and side view of the soft robot were recorded by the deep sea cameras and LED lights in anti-pressure shells. Credit: Li et al.

More information: Guorui Li et al. Self-powered soft robot in the Mariana Trench, Nature (2021). DOI: 10.1038/s41586-020-03153-z

Journal information: Nature

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