Shaping nanomaterials by short electrical pulses.

We report a new dry-state technique for non-contact patterning of nanostructured conducting materials, and demonstrate its use for carbon nanotube forests and freestanding sheets of carbon nanotubes, graphene, graphene sponge, and MXene. This method uses self-generated electron-emission pulses (∼20 ns) in air. On a substrate-tip separation scale of 10 to 20 nm, the few molecules of gas at atmospheric pressure enables electron-emission-based interaction between a sharp tungsten tip and elements of nanostructured materials. Using the advantages of field enhancement at sharp ends of nanostructured materials, the discharge voltage is reduced to 25-30 V, depending upon the materials density. This method causes largely non-oxidative sequential decomposition of nanostructure elements neighboring the tungsten tip. The main decomposition mechanism is thermal dissociation facilitated by Joule heating and electrostatic removal of debris. The non-contact-based patterning of nanomaterials can be as fast as 10 cm s. The resulting precisely patterned structures (<200 nm) are largely free of foreign contaminants, thermal impact and sub-surface structural changes.