I would expect stimuli-responsive polymers to have what you're looking for, and the keyword "stimuli-responsive" may be a useful search term. The stimuli-responsive polymers undergo conformational changes in response to changes in their environment. The primary environmental control variables people use are temperature, pH, and ionic strength. But people have also looked at glucose, visible light, and electric and magnetic fields. Usually this happens in solution, but you can also make hydrogels out of these polymers. In that case, the hydrogels swell or deswell when you hit them with the stimulus.
I just found this paper, so I haven't read it, but it appears to describe exactly what you are looking for, by using stimuli-responsive polymers. The full citation is J. Mater. Chem., 2012,22, 19482-19487. I've heard of Sergiy Minko in the context of stimuli-responsive polymers, so he's probably a good person to look for.
This post imported from StackExchange Physics at 2014-03-24 04:43 (UCT), posted by SE-user Colin McFaul