Are there any scientists trying to change string theory to a principal?
Dr. Michio Kaku is working on String Theory and Membrane Theory, but I don't know if he's trying to change it into principle. I bet Lior could give you a better answer.
There are no scientists who are working to change the string theory. No one has tried to come up with an idea that suggests changing the theory. For more information, go to http://en.wikipedia.org/wiki/String_theory.