It seems like electronics-free robots is only the tip of the iceberg:
A chemical gel that can walk like an inchworm, or looper caterpillar has been demonstrated in a Japanese robotics lab.
The video above shows the material in action. It was created in the Shuji Hashimoto applied physics laboratory at Waseda University, Tokyo.
Shingo Maeda and colleagues made the colour-changing, motile gel by combining polymers that change in size depending on their chemical environment. This is based on an oscillating chemical reaction called the Belousov–Zhabotinsky (BZ) reaction. The result is an autonomous material that moves without electronic stimulation.
The BZ reaction is one of a class of chemical systems in which the concentration of one or more compounds periodically increases and decreases. As well as producing stunning patterns (video), it can even be used to perform calculations using a dish containing the pulsing patterns as a chemical brain.