Electroplated helical conductors and methods for making the electroplated helical conductors are provided. The electroplated helical conductors are made from pre-formed thermally and electrically conducting nanomembrane ribbons having non-helical or helical configurations. The dimensions and shapes of the pre-formed nanomembrane ribbons are altered and controlled by the electrodeposition of a metal film onto the surfaces of the nanomembrane ribbons.

Electroplated helical conductors and methods for making the electroplated helical conductors are provided. The electroplated helical conductors are made from pre-formed thermally and electrically conducting nanomembrane ribbons having non-helical or helical configurations. The dimensions and shapes of the pre-formed nanomembrane ribbons are altered and controlled by the electrodeposition of a metal film onto the surfaces of the nanomembrane ribbons.

A slow-wave structure, a traveling wave tube, an electronic device, and a communication system are provided. The slow-wave structure includes a folded waveguide structure, where the waveguide structure has a cycle in a longitudinal direction and an amplitude in a transverse direction perpendicular to the longitudinal direction, and at least one of an amplitude of a first part of the waveguide structure and a cycle of the first part gradually changes in the longitudinal direction. Therefore, reflection of the slow-wave structure can be reduced, backward wave oscillation can be effectively suppressed, and a wider operating bandwidth can be obtained.