Animal cells can change their shape as result of their metabolisms, the chemical reaction going on in the cytoplasm. This allows them to move around, like in the case of an amoeba, or to create forces, like in the case of muscle cells.
Engineers have been able to create shape change and induce movement with a variety of mechanical tricks that are very effective but requires bulky settings.
At Pittsburgh's Swanson School of Engineering a team of researchers is trying to mimic cells to dramatically reduce the bulkiness needed today for movements by creating a smart material that can change its shape in a very precise way internally transforming available energy into mechanical energy.
To do so they are experimenting with a special polymer they have first designed and simulated at the computer (yet another example on the paradigm shift in material design, first create the material in cyberspace and then produce it).
They started with a gel containing spirobenzopyran, SP, that can be morphed into different shapes by hitting them with a beam of light, and then with a Belousov-Zhabotinsky gel having the property of pulsating in presence of light and worked on a computer to find the best mix of the two.
The result is a material that can change its shape in a controlled way and that they feel can be used to create squishy robots, much lighter than the ones we have today.