Bats are known for their bony wings and fast flight. Researchers at Brown University in Rhode Island are studying these characteristics to determine how bats can advance human technology.
Bats can advancing human technology
Bats are known for their bony wings and fast flight.
Researchers at Brown University in Rhode Island are studying these characteristics to determine how bats can advance human technology.
Our partner 'Science Friday' has the story.
Before we had high-speed video, people had this view that bat flight was just kind of a minor variant of bird flight.
But what we've found over and over again is how unbelievably maneuverable these animals are.
Being able to manipulate their wings and their bodies in such a way that they can adjust and they can maneuver really boggles the mind.
A bat wing, framed by the skeleton, allows bats to have a kind of control over a three-dimensional shape that would be impossible for any other kind of flying animal.
I'm Sharon Swartz.
I study bats, how they fly, and the structure of their wings.
And I'm Kenny Breuer.
I'm a professor of engineering, and I study animal flight and fluid mechanics.
So, the collaboration between Sharon's lab and my lab allows us to approach the same problem from two different perspectives.
We really find that we can do much more interesting things together than either of us can do by ourselves.
Because we're able to combine aerodynamics with the study of the morphology of the wings.
There's a lot of really fundamental differences between the flight of birds and bats.
So, a bird wing is a relatively stiff airfoil.
Bats have a whole hand in their wing, and that allows them to change the conformation and shape of the wing with incredible dexterity and precision.
So, the bones of the part of the wing that's closest to the shoulder, the humerus and the radius, have the kind of geometry that we see in birds.
But once you cross the wrist joint, we see bones that are less mineralized, and that makes that bone itself less stiff.
It actually promotes bending.
We don't usually think of skin as being a muscular organ, but the skin of the wing membranes of bats is invested with a whole series of muscles.
And what we observe is that the muscles turn on and off in every wingbeat cycle.
And so these muscles can change the stiffness of the skin in the wing membrane.
And so that means the muscles change the aerodynamic properties of the airfoil.
And that's completely different from a bird in the way in which it operates.
It bends, it flexes, it puffs out.
So, they're able to continue to generate lift even as they're moving more slowly.
So, when we first started, really very little was known about the precise nature of bat flight.
We're really interested now in how the animal has evolved to generate these kinds of forces and motions.
What can we learn about thrust, about lift, about unsteady flight mechanisms, about muscle activity?
And we design these experiments at each stage just to move ourselves forward.
So, when we do our tests, we use two facilities.
One is a flight corridor, which is just a room, and we have our cameras set up in there.
Just being able to see in detail how bats move their wings has turned out to give us a lot of insight.
The other one is this wind tunnel.
The equivalent of a treadmill for a flying animal.
We take high-resolution, high-frequency motion of the wings from multiple angles, and we reconstruct the kinematics of the motion that way.
And then we fill the wind tunnel with a cloud, and we record the motion of the particles of that cloud, and from that, we can reconstruct the wake.
And that lets us learn a lot about how it uses the wings to produce aerodynamic forces.
Once we've taken measurements with the animals, we can re-create aspects of that using engineered robotic flapping wings that we test in the wind tunnel.
And there, we can do things that we can't ask the animals to do, and it does provide a lot of inspiration and ideas of things that we might try for building robotic flying vehicles.
So, one of the things that bats do extremely well is landing.
They have to slow down, they have to flip themselves upside down and land, hanging on to the ceiling or hanging on to a tree roost.
It's like doing a high dive backwards.
What we've found is that, during the last two wingbeats of a bat preparing to land, there's almost no aerodynamic force produced.
They also use the mass in their wings to manipulate their body, and that controls their rotation in the same way that a high diver controls her rotation when they dive.
The bats are incredibly agile and maneuverable, and they're very resistant to perturbations in the air -- to gusts.
If we want to understand how bats are able to do this so well, we have to have some way of providing a gust to the animal in the lab and then seeing what it does in detail.
We have two sets of laser crossbeams here so that when the bat flies through, the bat breaks the laser beams.
That sends a trigger signal.
The air jet delivers a puff of air, and we can capture all of that in high-speed video from above and below using an array of high-speed cameras.
We find that, even really strong gusts of wind, they recover stability in less than a single wingbeat.
And so what we're trying to understand now is, what are the mechanisms that they use to recover so quickly?
What is it about the properties of the body and the wing that might return control passively, and how much is active?
The ability to do these experiments really gives us a unique insight as to how these animals move and maneuver, and also just how they evolved.
I mean, what is the evolution of flight in mammals?
I think that we understand enough now about how flight works where we can look at the origin and diversification of that flight.
It's a beautiful evolutionary laboratory.
I love those moments where you've recorded something that no one has seen before.
A moment of insight into the natural world.
It doesn't matter how tiny it is.
There's nothing like that.