Based on first-principles calculation, the electronic transport properties of two–one–two dimensional carbon structures, graphene(benzene)–chain–graphene(benzene), are investigated. Switching behavior induced by conformational changes is observed, even for the systems with curved and quite long carbon chains. The spatial asymmetry of transmission channels between one- and two-dimensional carbon structures is found to be the physical mechanism behind this behavior, and it can be extended to metal systems. It is also found that the orientation of a transmission channel is able to be rotated by a nanotube (or curved graphene) through the non-planar π-conjugated orbitals to modulate the switching behavior. Based on these structures, a kind of extremely-small pure-carbon logic operators and some other devices are proposed. As atomic motion could process information directly, the switching behavior and those devices would be very useful in nanomechanics.