Nanofiber yarn spinning system
Systems 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 nanofiber spinning system comprising:
a yarn winding device for receiving a false twisted nanofiber yarn;
a first guide for providing a tension to an untwisted nanofiber yarn; and
a first yarn spinner between the yarn winding device and the first guide, the first yarn spinner comprising a first moving surface for a first contact with an exterior surface of the untwisted nanofiber yarn,
wherein the first guide is selected from a hoop, a hook, or a post;
the first contact is configured to provide a friction to a first portion of the untwisted nanofiber yarn;
the first moving surface is configured to cause the first portion of the untwisted nanofiber yarn to twist; and
the first yarn spinner comprises:
a frame with an enclosed circular opening;
a circular bearing mounted to the circular opening, the circular bearing having an outer diameter proximate to the circular opening and an inner diameter opposite the outer diameter; and
a first rotational twist ring having an outer surface mounted to the inner diameter of the circular bearing, an exposed inner surface, and a radius of the first rotational twist ring surface curvature less than 1 centimeter,
wherein the inner surface of the first rotational twist ring is configured to be the first moving surface for the first contact with the exterior surface of the untwisted nanofiber yarn, and an inner diameter of the first rotational twist ring is 100 mm.
2. The nanofiber spinning system of claim 1 , wherein the first rotational twist ring has a silicone rubber surface.
3. The nanofiber spinning system of claim 1 , wherein the inner surface of the first rotational twist ring has a coefficient of friction from 0.25 to 0.75 between the inner surface and the untwisted nanofiber yarn.
4. The nanofiber spinning system of claim 1 , wherein the first rotational twist ring has a surface energy of less than 30 milliNewtons/meter.
5. The nanofiber spinning system of claim 1 , further comprising a substrate cradle for holding a substrate with a nanofiber forest thereon.
6. The nanofiber spinning system of claim 5 , further comprising a densification station between the substrate cradle and the first yarn spinner, wherein the nanofiber sheet drawn from the nanofiber forest at an angle α with respect to the substrate forms the untwisted nanofiber yarn at the densification station.
7. The nanofiber spinning system of claim 6 , wherein the angle a is in a range from 2° to 20°.
8. The nanofiber spinning system of claim 6 , wherein the densification station comprises a container and a solvent within the container.
9. The nanofiber spinning system of claim 8 , further comprising a drier disposed between the densification station and the first guide.
10. The nanofiber spinning system of claim 1 , further comprising a second yarn spinner, wherein the first yarn spinner and the second yarn spinner rotate in a first direction.
11. The nanofiber spinning system of claim 1 , further comprising a second yarn spinner, wherein one of the first yarn spinner and the second yarn spinner rotates in the first direction and the other of the first yarn spinner and the second yarn spinner rotates in a second direction opposite the first direction.