Video of the week: tether-free robot takes flight from water

This week’s video comes from Imperial College London where water-reactive chemicals are helping to propel a robot 26m through the air, an advance that could see the ‘bot taking water samples from hazardous environments.


Making the transition from water to air requires a lot of power, so the team at Imperial developed a system that requires 0.2g of calcium carbide powder in the bio-inspired robot’s combustion chamber. The university added that the only moving part is a small pump that brings in water from the environment the robot is in.

The water and the calcium-carbide combine in a reaction chamber, producing combustible acetylene gas. As the gas ignites and expands, it pushes the water out as a jet, which propels the robot from the water and into a glide. Details of the robot are published in Science Robotics.

In a statement, lead researcher Dr Mirko Kovac, director of the Aerial Robotics Laboratory at Imperial, said: “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.

“We have used water-reactive chemicals to reduce the materials that the robot needs to carry. 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.”

tether-free robot
A bio-inspired bot uses water from the environment to create a gas and launch itself from the water’s surface (Credit: Aerial Robotics Lab/Imperial College London)

Tests took place in a lab, lake and wave tank. They demonstrated it could escape from the water’s surface even under relatively rough conditions, unlike similar robots that often require calm conditions to take off from water. The team’s invention generates a force 25 times the robot’s weight, giving it a greater chance of overcoming choppy waves.

The 160g robot can reportedly ‘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, saving energy over longer distances compared to an electrically powered robot.

The team are now working with the Swiss Federal Laboratories for Materials Science and Technology (Empa) to build new vehicles using advanced materials and 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.”