A tangled web: Hydroentangling, a simple, high-speed, low-cost, environmentally benign textile technology is used to assemble individual carbon nanotubes (CNTs) into strong, electrical-conducting, multifunctional CNT nonwoven membranes. Hydroentangled CNT membranes with thicknesses ranging from 80 nm to 1.5 mm can be fabricated in as quick as 5 s per batch or up to 400 m min(-1)