BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1is an illustration of a twisted fiber, filament, or yarn, showing the fiber bias angle (αfiber).

FIG.2is an illustration of a twisted and coiled fiber or yarn, showing the fiber bias angle (αfiber), coil bias angle (αcoil), coil diameter (D), and fiber diameter (d).

FIGS.3aand3bare illustrations of two example coiled fibers or yarns with different coil bias angles.

FIGS.4aand4bare illustrations of another example of a twisted fiber or yarn generated by removing a sacrificial layer to increase the distance or spacing between the coils.

FIGS.5aand5billustrates a further example of a coiled fiber or yarn produced by wrapping a twisted fiber or yarn around a mandrel or core material, such as another fiber or yarn, and the freed coiled fiber or yarn being produced after removing the mandrel or central core material.

FIGS.6aand6billustrate a still further example of a coiled fiber or yarn produced by wrapping a twisted fiber or yarn around a core material that includes a central core covered in a removable material, and illustrate the example coiled fiber or yarn produced after dissolving or reacting the removable material, leaving behind a central material at the center of the coiled fiber or yarn.

FIGS.7aand7billustrate an example of a twisted fiber or yarn coiled around a mandrel or central core in such a way that the fiber or yarn is not in contact with a nearest neighbor, and further illustrate the coiled fiber or yarn produced after removing the mandrel or central core.

FIGS.8aand8billustrate another example of a twisted fiber or yarn that is coiled around a mandrel or central core alongside a second fiber or yarn that serves as a spacer for the twisted fiber or yarn and illustrate the coiled fiber or yarn that is produced by removing the mandrel or central core and the spacer fiber or yarn.

FIG.9aillustrates two twisted fibers or yarns coiled around a mandrel or central core.

FIG.9billustrates the two coiled fiber or yarn actuators that are produced after removing the mandrel or central core ofFIG.9a. The two coiled actuators are illustrated nested within each other.

FIG.10illustrates an example production process for twisted fibers that includes process monitoring and feedback.

FIG.11aillustrates an example of a fiber coiling system that includes a fiber source spool that feeds a fiber to an uptake spool that receives and winds the fiber.

FIG.11billustrates the fiber coiling system ofFIG.11awhere a coil nucleation region has propagated toward the uptake spool compared toFIG.11a.

FIG.11cillustrates the fiber coiling system ofFIG.11awhere a coil nucleation region has propagated toward the source spool compared toFIG.11a.

FIG.12ais an illustration of kinking or normal snarl that can be produced in a fiber or yarn through the insertion of twist.

FIG.12bis an illustration of a cylindrical snarl that can be produced in a fiber or yarn through the insertion of twist.

FIGS.13and14show two environmentally responsive coiled fiber actuators. The microscope images show coils with similar geometry that were produced by two different methods. The length of the scale bar is 0.5 mm.

FIGS.15a,15b,16a,16b,17a,17band18illustrate example embodiments of bimorphs that include one or more coiled fiber actuator.

FIG.19presents effective linear coefficient of thermal expansion (CTE) data for over 200 example twisted and coiled homochiral fiber actuators with various coil index values (C).

