US military engineers are looking to bats for inspiration.

Video footage of bats in flight has revealed extreme aerodynamic flexibility of the creature's wings. Bats' wings are made of highly jointed skeletons and elastic membranes, which allow them to generate and manipulate lift in unusual ways.

For their study, researchers Kenneth Breuer and Sharon Swartz at Brown University in Providence, US, used high -speed video cameras to record the 3D wing and body movements of flying lesser short-nosed fruit bats, Cynopterus brachyotis.

They found that while the down stroke looked similar to that of birds, but with more sweeping and billowing, during the upstroke, the bat completely collapsed its wings.

To better understand how these differences affected flight performance, the team studied the patterns of air movement during the creature's flight. They filled the flight cage with a mist of particles and tracked their movement and speed with lasers and another set of cameras.

They found that the stretchy skin on a bat's wings interacted with air differently compared to the firmer wings of birds and insects, deforming in ways that gave more lift at higher angles of attack (the angle at which the wing meets the air on its down stroke).

This could allow the bats to fly more efficiently and reduce the risk of stalling at low speeds, the researchers said in their study in the journal Bioinspiration and Biomimetics.

"The resulting wake pattern is really the footprint of the bat. It's a physical record of the how the aerodynamic forces are generated," said Swartz, a biologist who studies the mechanical performance of vertebrate skeletons.

According to the duo, the wings' elasticity, combined with dozens of joints, allow bats to generate unusual shapes and motions, such as folding the wings very close to the body to reduce drag.

"It's pretty clear the bats are taking advantage of these stretchy, flexible wings," New Scientist quoted Swartz as saying.

The researchers now aim to study bats' wakes using higher-resolution cameras provided by the US Air Force Office of Scientific Research.

The information could help design tiny flying vehicles, such as those being developed for military reconnaissance, they said.

"The knowledge of the aerodynamics in that size range is very limited. Here's a system that works so it's a good idea to take a look at it. Standard wing shapes do not work well at small scales," said Geoffrey Spedding, a mechanical engineer who studies tiny aircraft at the University of Southern California in Los Angeles, US. (ANI)