Scientists have developed insect-sized robots that can flap their wings to fly.

Inspired by bees and other flying insects, the technology means conventional motors and gears are no longer needed to fly the devices.

It could lead to smaller, lighter and more effective micro flying robots, which could be used for environmental measuring, search and rescue, and in dangerous surroundings such as collapsed buildings.

Known as micro air vehicles, the robots are better than other drones at manoeuvring in tight spaces and resisting air turbulence.

Until now, similar machines have used motors, gears and other complicated systems to achieve the up-and-down motion of the wings, which added complexity, weight and other unwanted effects.

Jonathan Rossiter, professor of robotics at the University of Bristol, led the team that successfully demonstrated an artificial muscle system, called the Liquid-amplified Zipping Actuator (Laza).

He said: "Making smaller and better performing, flapping wing, micro robots is a huge challenge.

"Laza is an important step toward autonomous, flying robots that could be as small as insects and perform environmentally critical tasks such as plant pollination and exciting emerging roles such as finding people in collapsed buildings."

In the study, researchers showed how their cost-effective and easy to construct system provided enough power to fly a robot across a room at 18 body lengths per second, which was more than insect muscle of the same weight.

They also demonstrated how Laza could allow the robots to make long-haul flights.