Coiled, twisted nanofiber yarn and polymer fiber torsional actuators
Actuators (artificial muscles) comprising twist-spun nanofiber yarn or twist-inserted polymer fibers generate torsional actuation when powered electrically, photonically, chemically, thermally, by absorption, or by other means. These artificial muscles utilize coiled yarns/polymer fibers and can be either neat or comprising a guest. In some embodiments, the torsional fiber actuator includes a first polymer fiber (exhibiting a first polymer fiber diameter) and a torsional return spring in communication with the first polymer fiber. The first polymer fiber is configured to include a first plurality of twists in a first direction to produce a twisted polymer fiber. The first polymer fiber is further configured to include a plurality of coils in the twisted polymer fiber in a second direction each coil having a mean coil diameter. In some embodiments, the torsional nanofiber actuator includes a first carbon nanofiber yarn (having a yarn diameter) and a torsional return spring in communication with the first carbon nanofiber yarn. The first carbon nanofiber yarn includes a plurality of twists in a first direction to produce a twisted carbon nanofiber yarn. The first carbon nanofiber yarn further includes a plurality of coils in the twisted carbon nanofiber yarn, with each coil having a mean coil diameter greater than the yarn diameter.
1. A torsional fiber actuator comprising:
(a) a first polymer fiber exhibiting a first polymer fiber diameter, the first polymer fiber configured to include
(i) a first plurality of twists in a first direction to produce a twisted polymer fiber, and
(ii) a plurality of coils in the twisted polymer fiber in a second direction each coil having a mean coil diameter, wherein
(A) the first plurality of twists and the plurality of coils in the first polymer fibers comprise a reversible torsional fiber actuating element; and
(b) a torsional return spring in communication with the first polymer fiber.
2. The torsional fiber actuator of claim 1 , wherein the first direction and the second direction are the same.
3. The torsional fiber actuator of claim 1 , wherein the first direction and the second direction are in opposite directions.
4. The torsional fiber actuator of claim 1 , wherein each coil of the plurality of coils has a mean coil diameter that is a mean of an inner coil diameter and an outer coil diameter that is no more than 1.7 times greater than the first polymer fiber diameter.
5. The torsional fiber actuator of claim 1 , wherein the torsional return spring comprises a second fiber plied with the first polymer fiber in a third direction opposite the first direction.
6. The torsional fiber actuator of claim 1 further comprising:
(a) a second polymer fiber configured to include a second plurality of twists in the first direction, the second polymer fiber plied with the first polymer fiber in a third direction opposite the first direction to form a heterochiral plied yarn, and
(b) wherein the second polymer fiber is the torsional return spring.
7. The torsional fiber actuator of claim 1 further comprising a conductor in contact with the first polymer fiber.
8. The torsional fiber actuator of claim 1 further comprising a rotor connected to at least one of the first polymer fiber and the torsional return spring.
9. A torsional nanofiber actuator comprising:
(a) a first carbon nanofiber yarn having a yarn diameter and comprising
(i) a plurality of twists in a first direction to produce a twisted carbon nanofiber yarn, and
(ii) a plurality of coils in the twisted carbon nanofiber yarn, each coil having a mean coil diameter greater than the yarn diameter, wherein
(A) the first plurality of twists and the plurality of coils in the first polymer fibers comprise a reversible torsional fiber actuating element; and
(b) a torsional return spring in communication with the first carbon nanofiber yarn.
10. The torsional nanofiber actuator of claim 9 further comprising a guest in the first carbon nanofiber yard, the guest and the first carbon nanofiber yard forming a first hybrid yard.
11. The torsional nanofiber actuator of claim 10 , wherein
(a) the guest is capable of a volume change causing the first carbon nanofiber yarn to change from a non-actuated state to an actuated state,
(b) the volume change of the guest is at least 7.7%, and
(c) the volume change results in rotational torque of the first carbon nanofiber yarn.
12. The torsional nanofiber actuator of claim 10 , wherein the first hybrid yarn has a torsional actuation of from 71°/mm to 100°/mm.
13. The torsional nanofiber actuator of claim 10 , wherein the guest is wax.
14. The torsional nanofiber actuator of claim 10 , wherein the guest is polydiacetylene.
15. The torsional nanofiber actuator of claim 9 , wherein the torsional return spring comprises a segment of the carbon nanofiber yarn infiltrated with wax.
16. The torsional nanofiber actuator of claim 15 , wherein the torsional actuation comprises up to 30°/mm.
17. The torsional nanofiber actuator of claim 9 further comprising a second yarn plied with the first carbon nanofiber yarn to form a two-ply heterochiral yarn.
18. The torsional nanofiber actuator of claim 17 , wherein the two-ply heterochiral yarn further comprises a wax infiltrant throughout the two-ply heterochiral yarn.
19. The torsional nanofiber actuator of claim 18 , wherein the torsional actuation is up to 30°/mm.
20. The torsional nanofiber actuator of claim 17 , wherein the two-ply heterochiral yarn further comprises a wax infiltrant within half of the two-ply heterochiral yarn.
21. The torsional nanofiber actuator of claim 20 , wherein the torsional actuation is up to 12.6°/mm.
22. The torsional nanofiber actuator of claim 9 , wherein the first carbon nanofiber yarn comprises a homochiral carbon nanofiber yarn, wherein a first half of the homochiral carbon nanofiber yarn comprises the plurality of twists and a second half of the homochiral carbon yarn is unactuated and comprises the torsional return spring.