Flying fish inspired robot

‘Flying fish’ robot can leap out of water to glide through air

Image credit: Aerial Robotics Lab/Imperial College London

Researchers from Imperial College London have developed a bio-inspired bot that uses water from the environment to create a gas, which enables the system to launch itself from the water’s surface.

According to the team, the robot, which is capable of travelling up to 26m through the air after take-off, could be used to collect water samples in hazardous and cluttered environments: for example, during flooding or when monitoring ocean pollution.

Robots that can transition from water to air are desirable in such situations. However, the launch requires a lot of power and has been seen as a challenge to achieve in smaller robots, explains lead researcher Dr Mirko Kovac, director of the Aerial Robotics Laboratory at Imperial.

“Water-to-air transition is a power-intensive process, which is difficult to achieve on a small-scale flying vehicle that needs to be lightweight for flight,” he said.

To tackle this challenge, the researchers at Imperial have invented a system that requires as little as 0.2g of calcium carbide powder in a combustion chamber, with the only moving part being a small pump that brings in water from the environment the robot is floating in, such as a lake or ocean.

The water and the calcium-carbide powder then combine in a reaction chamber, producing burnable acetylene gas (C2H2, the simplest alkyne). As the gas ignites and expands, it pushes the water out like a jet, which propels the robot clear of the water and into a glide of up to 26m.

“We have used water-reactive chemicals to reduce the materials that the robot needs to carry,” said Kovac. “Since the chamber fills passively and the environmental water acts as a piston, we can create a full combustion cycle with only one moving part, which is the pump that mixes the water with the fuel.”

The team tested the robot in a lab, in a lake, and in a wave tank, showing that it can escape from the water’s surface even under relatively rough conditions. While similar robots often require calm conditions to leap from the water, the team’s invention generates a force 25 times the robot’s weight, giving it a greater chance of overcoming the waves.

Weighing just 160g, the bot can ‘jump’ multiple times after refilling its water tank. This could allow it to float on water and take samples at multiple points without additional power, therefore saving energy over longer distances compared to an electrically-powered robot.

Stages of flying fish-inspire robot

The different stages of flight

Image credit: Aerial Robotics Lab/Imperial College London

The researchers are now collaborating with the Swiss Federal Laboratories for Materials Science and Technology (Empa) to build new vehicles using advanced materials. Furthermore, they will begin field trials of the robot in a range of environments, including monitoring the oceans around coral reefs and offshore energy platforms.

Raphael Zufferey, first author on the paper said: “These kinds of low-power, tether-free robots could be really useful in environments that are normally time- and resource-intensive to monitor, including after disasters such as floods or nuclear accidents.”

The details of the robot are published in Science Robotics.

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