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How to Walk on Water and Climb up Walls

How to Walk on Water and Climb up Walls: Animal Movement and the Robots of the Future

David L. Hu
Princeton University Press
2019
238 pp.
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At the intersection of fluid, solid, and gaseous flow; animal motion and mechanics; applied mathematics; and robotics lies the research of David Hu. Through stories about researchers he has interacted with over the course of his career and a biographical view of his own projects, Hu shows readers that we still have a lot to learn about animal locomotion.

As humans, we are capable of traversing a range of terrain, including mud, sand, and rocky ground. We can move through water or air. There are many animals, however, that excel in environments where we struggle. The indestructible cockroach, for example, not only can survive being squashed to a quarter of its original height, it will alter the shape of its legs so that it can continue to move forward. It also has antennae that it can move at full speed even when surrounded by obstacles. These abilities are reasons why the cockroach is used as a model organism for the development of inexpensive robots that might one day be used in search-and-rescue missions in hazardous environments.

The combination of fluid mechanics and animal physiology helps explain the optimal length of eyelashes for filtering out debris, flying snakes that glide efficiently with no wing or web structure, and how ants form robust collective rafts. However, the study of motion goes beyond the movement itself. Animals such as lamprey reveal how motion can be controlled, not by a brain but by a series of central pattern generators that are sets of small interacting periodic motions. This allows a salamander to change from a walking motion to a swimming one just by altering the speed of the lead oscillations.

Studying animal motion in fine detail may seem wasteful to many, but as Hu convincingly shows, a detailed understanding of the interaction between biology and fluid mechanics is interesting in its own right and a rich source of design and engineering ideas.

About the author

The reviewer is a senior editor at Science.