BEIJING -- A Chinese team has developed a small robot that can operate in the world's deepest sea trench under extremely high pressure.

The robot's operational ability is an engineering marvel that was previously achievable only by large, rigid submersibles weighing several tonnes.

Drawing inspiration from the movement patterns of the batfish, researchers led by Beihang University faculty members designed a 50-centimeter-long robot capable of swimming, gliding and crawling.

While swimming, the robot generates thrust through its tail fin, reaching a maximum speed of 5.5 centimeters per second, and when crawling, it can move at 3 centimeters per second on sandy surfaces using its limbs, according to the study, which was published this week in the Science Robotics journal.

In the 10,600-meter-deep Mariana Trench, pressure can reach 110 million pascals — akin to a 1-tonne weight being placed on a thumbnail. The team crafted a flexible actuation device that exploits the stiffening properties of soft silicone materials under high pressure.

"The material structure transforms external high pressure into enhanced speed and amplitude for the actuator, turning the weakness into an asset," said Pan Fei, the paper's first author from Beihang.

In deep-sea temperatures of 2 to 4 degrees Celsius, the team attached shape-memory alloy springs to the robot's actuator. By heating the springs with periodic currents to force them to alternately contract, they enabled high-frequency, rapid oscillation, according to the study.

Mounted on China's manned submersibles — Shenhai Yongshi (Deep Sea Warrior) and Fendouzhe (Striver) — this compact robot type has completed field tests in the Mariana Trench and other deep-sea locations, and was later retrieved fully intact, said Wen Li, the paper's corresponding author from Beihang.

The team will boost the endurance and efficiency of the small deep-sea robot to support marine resource development, archaeology and environmental monitoring.