Art is one of the most expressive forms. There are several forms of art that convey a lot of emotions (like music, and videos). In this proposal, I want to make paintings alive, breathe, and react to what is happening around them. I find these subtle movements to be fascinating and very expressive. Now paintings can have a third dimension of expression.
Also nano actuators and other material can be used to change the ambiance of the painting based on the time of the day (or other external factors)
Udayan’s comments: I like the direction. It would be really interesting to come up with more interaction scenarios. You can start by defining the art form you are referring to(need not be just painting), then think about transformation primitives, then pick very specific interaction scenarios. With reference to the leaf itself, see BioLogic and Unimorph from Tangible Media and also this project.