A nanotube assembly including a nanotube layer, a first layer and a second layer. The nanotube layer comprises a vertically aligned nanotube array. The nanotube array includes a plurality of nanotubes. The first layer of a first conductive material is disposed on one surface of the nanotube layer. The second layer of a second conductive material is disposed on an opposite surface of the nanotube layer. The nanotube of the nanotube layer includes a first end against the first layer and a second end against the second layer. The resistance from the first end to the first layer is lower than a resistance from the second end to the second layer. One or more nano-particles are placed within the nanotube. At least one of the nano-particles is electrically charged, and can move along the nanotube under influence of an electric field.

A process of producing a yarn, ribbon or sheet comprising nanofibers that includes infiltrating a liquid into the yarn, ribbon or sheet and evaporating the liquid from the yarn, ribbon, or sheet to strengthen the yarn, ribbon or sheet. The yarn, ribbon, or sheet can be formed by solid-state draw from a carbon nanotube forest.