As I have said many times, I love biomimetic and bioinspired design, and biomimetic robots. Aside from the beauty and romance, bioinspired design is a path to elegant and superior engineering.
Researchers at The Wyss Institute for Biologically Inspired Engineering (Harvard) have been walking this walk in a big way.
First of all, natural systems have a lot of squishy parts, and some, like octopuses have no rigid structure at all. Yet they function and move as well or better than human engineered machinery. There is much to learn.
A second thing about biological systems is that they are self-fueling. Most biological systems spend most of their time foraging and processing fuel, as well as related efforts at storage and waste removal. Furthermore, fuels are transformed into action via molecular and biological paths that are efficient and self-regenerating.
Enter “soft robots”.
Michael Wehner and colleagues published a description of “octobot”, which is “an entirely soft, autonomous robot”. 
The robot is fabricated by a combination of methods to produce a squishy body with reservoirs and network of channels for fluids. These are organized to control the motion of the “tentacles” through selected pressure, i.e., pumping fluid into various channels to push the flesh around.
The “microfluidic” network is embodies (literally) the control logic, which enables autonomous (i.e., untethered) operation. It is powered entirely by hydrogen peroxide which decomposes to produce gas in the presence of a catalyst. Basically, as long as octobot can “drink” some hydrogen peroxide now and again, it can continue to “digest” it and operate.
(OK, ocotbot doesn’t forage in this way, and “starves” in a few minutes—but it is believable that it could in the future.)
This cool work demonstrates a complete working system that “may serve as a foundation for a new generation of completely soft, autonomous robots”. Foundation? It’s an inspiration.
Very nice work.
- Michael Wehner, Ryan L. Truby, Daniel J. Fitzgerald, Bobak Mosadegh, George M. Whitesides, Jennifer A. Lewis, and Robert J. Wood, An integrated design and fabrication strategy for entirely soft, autonomous robots. Nature, 536 (7617):451-455, 08/25/print 2016. http://dx.doi.org/10.1038/nature19100