In the past few years, we have covered plenty of clever soft actuators. This one shared by Michael Dickey on YouTube shows a soft actuator using bubbles. Here is how it works:
the gas is created by electrochemical reactions that are controlled by electrochemistry. Rather than rubber, the chamber is made of hydrogel, which is a polymer network swollen with water. The water is the reactant that converts to gas. The resulting bubbles inflate the chamber within the hydrogel.
This approach can potentially used to make soft actuators that can operate underwater.
[paper]