Chemical gel walks like a worm

TOKYO – A Japanese robotics lab has created a chemical gel that can crawl around like an inchworm.

Shingo Maeda and colleagues at the Shuji Hashimoto applied physics laboratory at Waseda University made the colour-changing, itchy-footed gel by combining polymers that change in size depending on their chemical environment.

It’s based on an oscillating chemical reaction called the Belousov–Zhabotinsky (BZ) reaction, in which the concentration of one or more compounds periodically increases and decreases. The result is an autonomous material that can go walkies without electronic stimulation.

Polymers used in the gel shrink and grow in response to ruthenium bipyridine ions, alternately losing and gaining electrons in the cyclical reaction. That effect has been known for some time, but hasn’t been used to make a self-locomoting material on such a scale before.

Maeda and colleagues created a gel that magnifies the small changes in size by building tension into it. That produces its curved shape as well as amplifying the material’s response to the oscillating reaction inside itself.

The gel can currently only crawl if it’s on a notched surface. But the lab is now working on a version that will be able to lie flat on a normal surface and move using a peristaltic motion, like an earthworm or snail.

The stuff has implications for electronics engineers, say its developers. While mechanical systems need complex fabricated circuits or external control devices because the mechanical motion is driven by on-off switching of external signals, chemical systems can be “self organised” and generate their own control and mechanical signals from within. It means the gel could be used to make components of a robot, with more conventional engineering used for the parts for which only electronics will do.

As well as producing stunning patterns, it can even be used to perform calculations like a chemical brain, say the developers.

A report appears in New Scientist. There’s a great video.