Continuous production of nanoforests

A method for continuous production of nanoforests, the method comprising:

• unrolling a flexible substrate from a feed roll into a first furnace;
• growing a first nanoforest comprising first nanotubes or first nanowires on a surface of the substrate as it passes through a first growth zone in the first furnace, wherein the first nanotubes or first nanowires are oriented substantially perpendicular to the surface of the substrate;
• cooling the first nanoforest in a first cooling zone;
• rolling the first nanoforest through rollers to form a collapsed layer comprising the first nanotubes or first nanowires, wherein in the collapsed layer the first nanotubes or first nanowires are oriented substantially parallel to the surface of the substrate;
• growing a second nanoforest comprising second nanotubes or second nanowires on the collapsed layer as it passes through a second growth zone, the second nanotubes or second nanowires oriented substantially perpendicular to the surface of the substrate;
• cooling the second nanoforest in a second cooling zone;
• and
• rolling the substrate comprising the first nanoforest and the second nanoforest onto a first take-up roll.