Theory of carbomorph cycles.

We present a theory of a reversibly deforming sp2-carbon-based system controlled by competing strain, surface, and electrostatic energies, a carbomorph. For example, external forces (such as electrostatic, chemical, interfacial) could convert a bistable carbon nanotube between the collapsed and inflated states. Such a system could operate as a voltage-controlled constant-force spring, a charge-controlled harmonic spring, or an electromechanical engine or generator (with linear stroke up to few microns) driven across a propagating quasi-one-dimensional structural phase transition.