When you think about how to power a distributed network of environmental sensors, the kind we'll want to have in order to connect the entirety of our physical world to the Internet of Things, the answer is obvious: solar power. Most of these sensors are by nature too tiny to have access to much of a temperature gradient, and a steady supply of vibrations isn't always available. Batteries have limited lifespans and add bulk and expense.
That's one of the reason that organic and polymer-based solar cells are so interesting. In particular, the latest development: A polymer-based (i.e. plastic) solar cell thinner than spider silk that can be bent and crumpled and still produces power.
(c) Stretchable solar cells made by attaching the ultrathin solar cell to a pre-stretched elastomer
From the abstract of the paper announcing their development:
This solar plastic only converts 4.2 percent of the sun's energy into electricity, which is awful by the standards of conventional polycrystaline solar cells, but absolutely miraculous when you consider how thin and versatile this material could be.
These ultrathin organic solar cells are over ten times thinner, lighter and more flexible than any other solar cell of any technology to date.