NOVELTY - A pre-primary assembly comprising parallel array of nanofibers is formed by dispersing nanofibers in liquid. The drawing operation is performed at an angle of 60-90degrees from the pre-primary assembly to provide a primary assembly of nanofibers having alignment axis about which twisting can occur. The primary assembly is selected from aligned array, and an array that is converging toward alignment about the alignment axis. A twisted yarn is provided by twisting about the alignment axis of the primary assembly.    USE - For textile comprising electrically conducting wires, electronic switch, electrical transformer and electromagnet, scaffold for tissue growth, electronic field emission source of flat panel display, lamp, gas discharge tube providing surge protection, x-ray generator, microwave generator, transparent conductor for LCD, light emitting display, solar cell, switchable transparency window, laser, optical modulator, electron field emission device, electronic switch, optical polarizer, electrochemical device such as battery, supercapacitor, electromechanical actuator, fuel cell, optoelectronic device such as solar cell, photovoltaic detector, photovoltaic transistor, LED, OLED, PLED and photosensitive FET (all claimed).    ADVANTAGE - Provides unique properties and property combinations such as extreme toughness, resistance to failure at knots, high electrical and thermal conductivities, high absorption of energy that occurs reversibly, up to 13% strain-to-failure, very high resistance to creep, retention of strength even when heated in air at 450degreesC for one hour, and very high radiation and UV resistance, even when irradiated in air.    DETAILED DESCRIPTION - The significant component of the nanofibers have a maximum thickness orthogonal to the nanofiber axis of 341nm. The nanofibers have a minimum length-to-thickness ratio in the thinnest lateral thickness direction of 100. The minimum ratio of nanofiber length to twisted yarn circumference is 5. The maximum introduced twist in one direction per twisted yarn length for the twisted yarn of diameter (D) is 0.06/D turns. The twisted yarn has a weight-averaged nanofiber length approximately 2 times the length of one turn of twist of the twisted yarn. The primary preassembly is a forest of multiwalled carbon nanotubes having diameter of 10nm. The density of the forest at the forest base is 20 billion nanotubes/cm2. The percentage of the area of the forest base that is occupied by the carbon nanotubes is about 4%. The drawing and twisting are conducted at temperature between 20-500degreesC. INDEPENDENT CLAIMS are included for the following:    (1) yarn production apparatus;    (2) textile;    (3) composite material;    (4) scaffold;    (5) thermochromic material system;    (6) electrochemical device;    (7) electronic field emission source;    (8) electrically conducting wire;    (9) fuel cell;    (10) microfluidic circuit device;    (11) nanofiber article;    (12) microfluidic-self repair structure;    (13) incandescent electrically powered light source;    (14) optoelectronic device; and    (15) optoelectronic device manufacturing method.    DESCRIPTION OF DRAWING(S) - The figure shows the engineering stress-strain curves up to fracture for carbon MWNT singles yarn, twofold MWNT carbon nanotube yarn and PVA-infiltrated MWNT singles yarn.