Nanofiber yarn spinning system
Methods, systems, and apparatus for fabricating nanofiber yarn at rates of at least 30 m/min (1.8 kilometers (km)/hour (hr)) using a “false twist” nanofiber yarn spinner and a false twist spinning technique are disclosed. In a false twist spinning technique, a twist is introduced to nanofibers in a strand by twisting the nanofibers at points between ends of the strand. This is in contrast to the “true twist” technique where one end of a strand is fixed and the opposing end of the strand is rotated to introduce the twist to intervening portions of yarn.
1. A method for spinning nanofiber yarn comprising:
providing a nanofiber forest on a substrate;
drawing the nanofiber forest from the substrate at an angle α to form a nanofiber sheet;
infiltrating the nanofiber sheet with a fluid to form an untwisted nanofiber strand having an exterior surface and a longitudinal axis;
passing the nanofiber strand through a twist ring, the twist ring having an inner diameter, a minor radius, an inner surface and an outer surface;
applying a force between the inner surface of the twist ring and the untwisted nanofiber strand between endpoints of the untwisted nanofiber strand, the force applied by the twist ring, the nanofiber strand having an angle of entry β from 10° to 70°, thus forming a false twist nanofiber yarn having a twist angle from 5° to 30° and an exit angle; and
winding the false twist nanofiber yarn.
2. The method of claim 1 , wherein applying the force comprises contact between the untwisted nanofiber strand and a surface of the twist ring while the twist ring is rotating.
3. The method of claim 2 , wherein the contact between the untwisted nanofiber strand and the surface of the rotating twist ring is less than 5 milliseconds.
4. The method of claim 2 , wherein the contact between the untwisted nanofiber strand and the surface of the rotating twist ring is less than 0.5 milliseconds.
5. The method of claim 2 , wherein applying the force comprises using a silicone rubber surface as the surface of the rotating twist ring.
6. The method of claim 2 , wherein applying the force comprises using a surface with a coefficient of friction from 0.25 to 0.75 between the surface of the rotating twist ring and at least one of the untwisted nanofiber strands and the nanofiber yarn.
7. The method of claim 2 , wherein applying the force comprises using a surface with a surface energy of less than 30 milliNewtons/meter.
8. The method of claim 1 , wherein infiltrating the nanofiber sheet further comprises infiltrating the nanofiber sheet with at least one of a polymer and a nanoparticle.
9. The method of claim 1 , further comprising drying the untwisted nanofiber strand to remove the fluid.
10. The method of claim 1 , wherein the angle α is in a range from 2° to 20°.