a carbon tube containing a carbonized tube wall . the tube wall is consisted of carbonized coating material and trace of fiber residue , and the carbonized coating material is prepared according to a process including the steps of : coating a fiber structure with a carbon - containing coating material to form a coating layer over the fiber structure ; removing the fiber structure ; and carbonizing the coating layer to form the carbonized tube wall . the fiber structure can be either a two - dimensional or three - dimensional object , and a two - dimensional or three - dimensional device can be prepared accordingly . the carbon - containing coating material can be made of repeating units of substituted polyacrylonitriles , unsubstituted polyacrylonitriles , substituted poly , unsubstituted poly , substituted poly , or unsubstituted poly , or it can be made of conjugated polymers including doped and undoped conjugated homopolymers , doped and undoped conjugated copolymers .