Insects walk on water, snakes slither, and fish swim. Animals move with astounding grace, speed, and versatility: how do they do it, and what can we learn from them? In How to Walk on Water and Climb up Walls, David Hu takes readers on an accessible, wondrous journey into the world of animal motion. From basement labs at MIT to the rain forests of Panama, Hu shows how animals have adapted and evolved to traverse their environments, taking advantage of physical laws with results that are startling and ingenious. In turn, the latest discoveries about animal mechanics are inspiring scientists to invent robots and devices that move with similar elegance and efficiency.
In the second part of our Q+A with David Hu, he describes what we know (and don’t know) about animal motion, and what the future of robots will look like. Check out the first part of our Q+A here.
Don’t we already know everything about animal motion?
From cave paintings to today’s videos of cats on YouTube, the movement of animals has always fascinated people. The thesis of my book is that there is an explosion of new interest and progress in understanding animal motion. Recent technological developments and the teamwork of biologists, computer scientists, physicists, and engineers, are leading to changes in the way animal motion is now studied.
What can we learn from studying animal motion?
Animals have existed for millions of years. As a result, they have evolved a huge diversity, inhabiting nearly every part of the planet, across terrains from desert to forest to sea. This range of environments, combined with their intense competition to eat or be eaten has led to the evolution of ingenious methods of locomotion. Their varying locomotion mechanisms can inspire new ways of propulsion for humans, from robots that walk across the clutter in our homes to tracked vehicles that move across the dusty surface of Mars. But before we robots are improved sufficiently to enter our everyday lives, an understanding how animals movement is of great benefit.
What kind of approach is needed to study animal motion?
We already have many of the tools to understand the movement of animals. Because animals move through air and water, the same tools that engineers use to design boats and airplanes can be applied to animals. The brains of animals can be studied in a similar way. To react quickly to their surroundings, animals rely on a system of nerves that can act autonomously, similar to the cruise control in your car, and the motion of an autonomous robot. Since animals share things in common with boats, airplanes, and robots—the same tools to study these human-made systems can be used to reverse-engineer systems in nature.
How did you become interested in studying animals and insects?
My PhD was on the physics of insects that walk on water. People who study the motion of fluids have often looked to birds and fish for inspiration. During my PhD, I realized that while we often see insects as annoying, they are the dominant non-microscopic life form on earth, and their small size gives them an even greater versatility to move. After my PhD study on water striders and a postdoctoral study on snakes, I founded my own laboratory for studying animal movement.
What are the applications of your work, whether it’s a shaking wet dog or animals waving their tails?
In the course of my work, I often design and build new devices based on animal movement. My work on water striders led to a collaborator building a palm-sized water-walking robot. My work on cat tongues led to a cat-tongue inspired brush that combs with lower force and is easier to clean. From this book, I hope to show curiosity-based research on animal motion can lead to useful new inventions.
What are the robots of the future going to be like?
Many robots rely on wheels and are tested on linoleum floors. Robots built for such structured environments often do poorly in nature. A grassy field, a moss-covered stream, even a living room littered with children’s toys. These are terrain that is impassible by most robots. To traverse these cluttered areas, robots will likely need multiple legs, or no legs at all, resembling insects or snakes. I bet that robots that successfully traverse outdoor environments will show some resemblance to the animals that make this place their home. This is because the laws of physics provide immutable constraints that have influenced the shape and kind of motion that is most effective on these terrain.
David L. Hu is associate professor of mechanical engineering and biology and adjunct professor of physics at Georgia Institute of Technology. He lives in Atlanta.