Late last year, Harvard University chemists and materials scientists introduced a robot whose rubbery appendages fly—or, more accurately, crawl—in the face of conventional automatons. These invertebrate-inspired albino bots relied on elastic polymers and pneumatic pumps to imitate the movements of worms, squid and starfish. Now these squishy quadrupeds can be pumped with a variety of dyes, enabling them to either blend in or stand out from their environments.

In addition to stretching the boundaries of how robots are designed, built and operated, adding color could help scientists better understand why certain creatures may have evolved to their current shape, color and capabilities, according to the researchers, led by chemist and materials scientist George Whitesides. In the August 17 issue of Science, the researchers describe using 3-D printers to create silicone robots whose different layers contain microchannels through which liquids can flow in a variety of patterns. Heated or cooled solutions pumped into these channels enabled the researchers to create thermal camouflage, while fluorescent fluids produced glow-in-the-dark robots.

These five-centimeter-thick bots, each of which looks like a pair of Ys joined at the stem, mimic natural movement without the need for complex mechanical components and assembly. They also demonstrate the value of considering simple animals when looking for inspiration for robots and machines, the researchers say.

The shape-shifting robot features an upper, flexible layer designed with a system of channels through which air can pass. A second layer is made of a more rigid polymer. The researchers place the top, actuating layer onto the bottom, strain limiting/sealing layer with a thin coating of silicone adhesive. Air pumped into different valves in the upper layer causes them to inflate and bend the robot into different positions. For example, the robot can lift any one of its four legs off the ground and leave the other three legs planted to provide stability, depending on which channels are inflated.