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Tiny muscles let bats control wing shape and stiffness as they fly, a new study claims.

They appear to fine tune their flight a little like Batman in the Dark Knight, whose wings almost 'solidify' when he starts to fly.

Bats use the network of hair-thin muscles embedded in the delicate membrane of their 'floppy' wing skin to adjust the curvature while they fly and the discovery could lead to engineering innovations for aeroplanes.

Fine tuning flight: Hair-thin muscles embedded in the skin of their wings allow bats like this Jamaican fruit bat to change the stiffness and curvature of their wings at different points of the wing stroke. That observation could help improve design of mechanical flight surfaces

'Aerodynamic performance depends upon wing shape,' Jorn Cheney, a biology graduate student from Brown University said.

'The shape of a membrane wing might initially begin flat but as soon as it starts producing lift it's not going to remain flat because it has to deform in response to that aerodynamic load.

'The shape it adopts could be a terrible one – it could make the animal crash – or it could be beneficial. But they are not locked into that shape.

'Because bats have these muscles in their wings and also bones that can control the general shape as well, they can adopt any number of profiles,' he explained.

Nature's superheroes: Bats appear to fine tune their flight a little like Batman in the Dark Knight (pictured), whose wings almost 'solidify' when he starts to fly

The tiny muscles called plagiopatagiales were discovered over 100 years ago but their function has never been demonstrated until now, Mr Cheney said.

This illustration and close-up shows tiny muscles that work together to stiffen or reshape an area of the bat's wing during flight

At first he thought that each individual muscle would be too weak to reshape the wing, so to find out whether the muscles would work together to enhance force, he attached electrode sensors to a few muscles on the wings of Jamaican fruit bats.

He then filmed them as they flew in the lab's wind tunnel and discovered that all three key findings pointed towards modulating skin stiffness.

The study, published in the journal Bioinspiration and Biomimetics, revealed that the muscles tense on the downstroke and relax on the upstroke.

'This is the first study showing that bats turn these muscles on and off during a typical wingbeat cycle,' said co-author Sharon Swartz, professor of biology at Brown.

Another finding was that the muscles don't act individually. Instead they exert their force in a synchronised fashion, providing enough collective strength to stiffen the wing.

Finally they revealed that the muscles appeared to activate at different times at different flight speeds.

As the bats flew faster, they tensed the muscles sooner in the upstroke-downstroke cycle, suggesting that the muscles behave actively in keeping with conditions of flight.

The team is using the findings to build a robotic bat wing, which could give them data about wingbeat frequency and the degree of wing folding during flapping. The data collected could help to improve the design of mechanical flight surfaces.