Volume 37
Issue 2

Though the character behind Batmans cowl is just an everyday human, his techie tools elevate his abilities to the heroic. Jack Nicholsons cinematic Joker said it best: Where does he get such wonderful toys?

But bats, it seems, are born with true superpowersfrom the ability to nab airborne insects at night using only echolocation, to their capacity to avoid collision even when navigating amidst thousands of fellow flyersa veritable army of scientists and technologists are hard at work unraveling chiropterans many finely tuned adaptations.

The goal: to further translate bats biological gifts into mathematical algorithms, models and principles that are already being used to advance the frontiers of technology.

Talk about a tech-head! This biomimetic robotic sonor head was inspired
by the distinct facial features of horseshoe bats.
Courtesy of Logan Wallace/ Virginia Tech

From Biology to Engineering

Three steps comprise that process, according to neuroecologist Yossi Yovel. First, characterize an animals behavior and movements. Second, describe that behavior as a mechanical or mathematical principle. Third, mimic it.

Mexican fishing bats (Myotis vivesi) have inspired Yovel, based in Tel Aviv, Israel, to work toward developing a series of swarming robots that use sound to communicate and coordinate the location of each member of the group. Mexican fishing bats, which work together in small groups over open water in the Gulf of California, eavesdrop on each other to listen for good fishing spots. Yovel hopes to have a group of working prototypes to demonstrate in a years time.

The idea of designing robots to communicate with one another in such a fashion enables greater autonomy: no base stations to relay or report to, only a mission, achieved with the help of the rest of the group. It makes them very efficient and able to take advantage of many different environments, Yovel says.

Yovel has also used bat sonar research to develop algorithms for an agricultural robot designed to predict crop yields. Based on how bats distinguish between different types of foliage-rows of corn “sound” different from apple trees, for instance-the robot can detect amounts of developing fruit more accurately than a camera-based system. By allowing farmers to assess their yields with greater accuracy, it gives them more information to use when planning for harvest and sale of the final product.

Ironically, Yovel found the need to develop new tools to gather the necessary data from the bats he studies, all in the pursuit of developing other new technologies. For example, his lab built an ultra lightweight GPS tagonly 2 gramscapable of recording sound, velocity and bearing, heart rate, body temperature and other environmental data.

Bats have these amazing abilities, and now were able to quantify what they do, based on equations of sound and physics, Yovel says. So we develop technology to study bats, and we study bats to develop technology.

Laura Kloepper and her team used trained hawks outfitted with special cameras to better
understand how bats fly en masse without collision.
Courtesy of Laura Kloepper

Sorting Out Sensing

CalTechs Bat Bot, a semi-autonomous drone modeled after a bats many-jointed wings, came from close study of how each joint works to change the wing shape during flight. Watching it flap at a distance leaves no doubt about the source of its inspiration.

Impressive as it is, however, the Bat Bot isnt quite ready for market. Truly autonomous flighted vehicles will require even more sophisticated sensing and feedback systems than the Bat Bot is currently equipped with in order to see and process the features of the environment theyre navigating.

At Virginia Tech, mechanical engineer Rolf Mueller is investigating that very idea, hoping to build a drone that can navigate a forest as blithely as a bat. Mueller has been recording video of wrinkle-lipped bats emerging from their roost in Deer Cave in Gunung Mulu National Park on the island of Borneo. He plans to use the video to characterize mathematically how the bats change their flight path from a long, streaming ribbon into a donut-like torus as they evade hungry hawks on the hunt.

When we look at what can flyinsects, birds, bats and airplanesbats have the most degrees of freedom, Mueller says. They are able to rapidly change direction and speed without significantly compromising function. Several species of birds and many types of insects approach bat-like levels of dexterity, but only bats use echolocation to determine their flight path.

Sound of Sonar

Though sound-based range finding and imaging instruments came into use in the early 1900s, bats evolved the ability to use sonar millions of years ago. From a technological standpoint, says biosonar researcher Laura Kloepper, our tools only approximate what bats can do, but we still havent been able to build anything as small and powerful as those that exist in nature.

Practically speaking, sonar is a very simple tactic, says Kloepper, an assistant professor of biology at St. Marys College in Notre Dame, Indiana. Send a sound wave out, then adjust your trajectory based on the sound that bounces back to you. The engineering challenge lies in understanding how bats process and use that information so well.

Bats defy what we can do with our technology, Kloepper says. Their mouth, the emitter, is tiny, but they can tell objects apart with incredible resolution. We cant quite explain why yet.

Using drones, a camera on a zip line and even a hawk fitted with a recording device, Kloepper records swarming bats to understand how individuals emit and receive their own signals amid thousands of others. Her work could help self-driving cars better discern their own signals from a noisy world.

Yossi Yovel studies how bats use echolocation when flying through narrow corridors.
Courtesy of Yossi Yovel

That could require a device that can use feedback to adjust its sonar signals. Wu-Jung Lee, an acoustics researcher at the University of Washington, worked with Cynthia Moss at Johns Hopkins University to discover the mechanism for how Egyptian fruit bats adjust their sonar on the wing: The bat produces a unique double click with its tongue, and adjusts the angle and frequency of sound between each click of a pair as it homes in on a target.

Thats a very adaptive behavior, and something our systems currently dont do, Lee says. Current sonar systems cant adjust any characteristic of the sound beam based on feedback received from the environmentone reason why our self-driving vehicles turn so slowly.

But even a basic understanding of how bats echolocate is already helping people in a very real way, specifically those without the sense of sight. In Kenya, bats echolocating abilities inspired engineer Brian Mwiti to build a handheld device for the visually impaired to help them navigate their surroundings.

Outfitted with three ultrasonic emitters, Mwitis Sixth Sense device alerts the user to obstacles overhead, directly ahead or on the ground with directional buzzes. The vibrations grow in intensity as the user gets nearer to the obstacle, or as people or objects approach the user.

Were building all this cool technology and moving forward in the technology revolution, and people are still using sticks to walk, Mwiti says. Bats perceive their environments so well. I thought we could borrow from them to help people who cant see.