Melt‐Extruded Thermoplastic Liquid Crystal Elastomer Rotating Fiber Actuators

Untethered soft fiber actuators are advancing toward next‐generation artificial muscles, with rotating polymer fibers allowing controlled rotational deformations and contractions accompanied by torque and longitudinal forces. Current approaches, however, are based either on non‐recyclable and non‐reprogrammable thermosets, exhibit rotational deformations and torques with inadequate actuation performance, or involve intricate multistep processing and photopolymerization impeding scalable fabrication and manufacturing of millimeter‐thick fibers. Here, the melt‐extrusion and drawing of a 50 m long thermoplastic liquid crystal elastomer fiber with a ≈1.3 mm diameter on a large scale is reported. With the responsive thermoplastic material, rotating actuators are fabricated via easily exploited programming freedom resulting in large, reversible rotational deformations and torques. The actuation performance of the twisted fibers may be controlled by the programmed twisting density without complicated preparation steps or photocuring being required. The thermoplastic behavior enables fabrication of plied fibers, demonstrated as a triple helical twisted rope constructed from individual rotating fibers delivering up to three times as great rotational and longitudinal forces capable of reversibly opening and lifting a screw cap vial. Besides the programmability, the thermoplastic material employed lends itself to be completely reprocessed into other configurations with self‐healing properties in contrast to thermosets.


Introduction
Inspired by the abundant shape-morphing materials found in nature, [1] untethered fiber actuators have paved their way to possible applications including soft robotics, [2][3][4] smart clothing, [5,6] DOI: 10.1002/adfm.202306853biomimetic systems, [7][8][9] and prosthetic limbs, [10,11] demonstrating their potential for the development of nextgeneration intelligent materials.[19][20] Once obtained, however, the rotating fibers are tethered or loaded with a fixed weight to maintain the introduced twists showing rotation and contraction during actuation.[23][24] When heated, the polymer muscles reversibly contract and untwist since the highly oriented polymer fibers exhibit thermally induced anisotropic expansion.While highlighting the versatility of the rotating fiber actuators as artificial muscles, the attainable level of contraction and torque is generally low, and neither recycling nor reprogramming has been demonstrated.
[27] The external stimulus creates local disruption in the liquid crystalline (LC) order resulting in actuation of the material through local contraction and expansion.[30][31][32][33][34][35] Among the LCE thermosets, rotating fiber actuators have rarely been reported. [36,37]Fabrication of LCE fibers requires an intricate two-step crosslinking process using a mold, prohibiting reshaping of the fiber actuator due to the permanently crosslinked network.In addition, the achievable fiber diameter is relatively small (i.e., micrometer-scale) due to the preparation methods and further limited by the penetration depth of light during photopolymerization.Thicker fiber actuators might enable generation of larger actuation forces, desirable for applications such as artificial muscles.
What has been unavailable so far is combined control over the response and reprogramming/reprocessing of actuator fibers.One obvious alternative for chemically crosslinked thermosets is thermoplastic elastomers that are based on physical crosslinks.It would be appealing to fabricate thermoplastic fibers, as they allow melt-processing and thermal (re)programming, promising for developing soft fiber actuators.We recently reported on thermoplastic polythiourethane LCE actuator films consisting of alternating thermally dynamic hydrogen-bonding (H-bonding) hard segments as physical crosslinks and temperature-responsive LC soft segments as actuation units (Figure 1a). [38,39]Given that the labile H-bond system affords well-defined microphase-separated domains allowing processing capabilities and reversible actuation, we hypothesize that this material is well-suited for fabricating thermoplastic LCE rotating fiber actuators.
In this work, we present the large-scale fabrication of thermoplastic ≈1.3 mm diameter fiber actuators through melt-extrusion and drawing of a polythiourethane LCE.This material combines straightforward melt-processing and easy-to-exploit freedom in programming with large, reversible deformations accompanied by high actuation forces.In the as-obtained fiber, the H-bonding, crystalline domains and generated molecular order allow reversible uniaxial thermal actuation of the LCE.The fiber may be reprogrammed into a spiral coil or twisted actuator, demonstrating reversible rotational actuation motions.It is shown that the synergistic rotational deformation and contraction with accompanying forces of the twisted fibers are controllable by altering the twisting density, allowing the actuation performance to be varied and optimized toward the desired function.We use the thermoplastic behavior to highlight the potential of this H-bonding LCE material by constructing a shape-changing twisted rope object with enhanced actuation performance capable of reversibly opening and lifting a screw cap vial.Finally, the material may be completely reconfigured into different actuator shapes with potential self-healing capabilities.

Results and Discussion
To prepare the relatively large amount of material needed for melt-extrusion, the thermoplastic LCE is synthesized by simply scaling up the batch size of our previously reported onepot synthesis method using commercially available building blocks, yielding ≈200 g crude polymer (Figure S1, Supporting Information). [38]The material obtained, containing 10 wt.% Hbonding hard segments, exhibits a high number-average molecular weight (M n ≈ 77 kg mol −1 ) and low polydispersity index (Ð = 2.00; Figure S2, Supporting Information).Absence of thiol (v ˜≈ 2560 cm −1 ) and isocyanate (v ˜≈ 2270 cm −1 ) vibrations from the monomeric precursors as opposed to the presence of amine (3315-3340 cm −1 ) and carbonyl (1638-1677 cm −1 ) vibrations of the polymer is confirmed with Fourier-transform infrared (FTIR) spectroscopy (Figure S3, Supporting Information).The melting temperature is T m = 166 °C, well below the thermal degradation temperature of T d = 252 °C (Figures S4 and S5, Supporting Information).The synthesized LCE exhibits an isotropization temperature of T i ≈ 80 °C, arising from the presence of liquid crystallinity. [39,40]In addition, the material has typical thermoplastic elastomeric properties as it becomes melt-processable at elevated temperatures and solidifies again upon cooling due to the thermoreversible H-bond network.
Using a capillary rheometer, the LCE (195 g) is extruded in the melt at T barrel = 190 °C, where the H-bonds are disrupted and the molecular order vastly diminished, after a wait time t wait = 2 min to obtain the fiber actuators (Figure 1b).This temperature appeared to be crucial since at higher temperatures (T barrel = 200 °C) the viscosity of the polymer decreased such that it could no longer be drawn, whereas at lower temperatures (T barrel = 180 °C), viscosity was too high and extrusion impeded.Extrusion speed was optimized to v piston = 0.8 mm s −1 ; the LCE was processed into a fiber with a relatively large nozzle diameter D nozzle = 2 mm.After extrusion, the fibers are actively cooled with a fan, reforming the LC-ordered state and H-bond network, and drawn with pulling speed v haul-off = 50 mm s −1 , yielding a 50 m long uniaxially aligned, transparent fiber with a ≈1.3 mm diameter collected on a coil (Figure 1c,d; see Table S1 and Figure S6, Supporting Information, for additional details).Even though the drawing leads to a decreased fiber diameter than initially extruded, much thicker fibers with potentially larger actuation forces are obtained than reported before for photopolymerized thermoset LCEs.
Comparing the characterization results of the fiber to the crude polymer shows nearly identical properties before and after processing, suggesting no apparent degradation during extrusion and drawing of the LCE (Figures S2-S5, Supporting Information).The dynamic viscoelastic behavior reveals that the H-bond network is stable up to 130 °C, as indicated by the rubbery plateau, after which the H-bonds start dissociating, and the thermoplastic enters the melt (Figure 1e). [41,42]The mechanical properties of the LCE fibers show a larger elastic modulus and amplified strain hardening compared to an as-molded film: the increased stiffness the result of the uniaxial orientation (vide infra; Figure S7, Supporting Information). [43,44]When the fiber is heated to 110 °C, the LC soft segments in the material are disordered, and the stress-strain curve resembles the non-aligned film with decreased elastic modulus.Typically, however, the elongation at break is significantly lower at elevated temperatures arising from the thermoplastic elastomer character. [45,46]Strain ratedependent tensile tests of the uniaxial fiber show an increase in elastic modulus and overall stress response upon increasing the strain rate at room temperature (RT; Figure S8, Supporting Information).The tensile testing results also show that this thermoplastic LCE provides substantial toughness allowing utilization of the actuating capabilities entirely within the mechanical application limits.
The molecular and segmental orientation of the obtained thermoplastic LCE fiber were monitored by X-ray scattering spectroscopy.In the wide-angle diffractogram (WAXS), characteristic orientationally arranged diffraction patterns orthogonal to the drawing direction were observed for the fiber due to the scattering of short-range ordered LC and H-bonding moieties with corresponding order parameter S = 0.46 (Figure 1f; Figure S9, Supporting Information).This contrasts with the crude polymer, which only shows a diffuse ring-shaped pattern arising from isotropic/random orientation of the material (S ≈ 0; Figure S10, Supporting Information).The formation of well-defined, microphase-separated domains in the fiber is confirmed by medium-angle X-ray spectroscopy (MAXS), where two peaks are observed resulting from the interdomain spacing of distinct LC and H-bonding domains (Figure S11, Supporting Information). [47,48]From this spectral data, it was found the domain spacings between the H-bonding moieties slightly increased upon stretching, and an additional peak appeared, originating from the scattering between LC moieties.The 2D medium-angle diffractogram of the fiber shows double two-point scattering patterns suggesting the orientation of both distinct domains is along the stretching direction (Figure S12, Supporting Information).In case of the crude polymer, long-range correlation resulting from microphase separation with random orientation was observed, as revealed by the ring-shaped pattern (Figure S12, Supporting Information).Microphase-separation was further confirmed by FTIR spectroscopy: C = O H-bond (1638 cm −1 ) and minor C = O free (1677 cm −1 ) stretching bands were observed, reflected by a sharp N-H H-bond (3315 cm −1 ) and weak N-H free (3340 cm −1 ) vibration, indicating the formation of distinct Hbonded domains (Figure S13, Supporting Information). [49,50]The interdomain spacing and strong hydrogen bonding interactions indicate the formation of well-defined microphase-separated domains, as observed for thermoplastic polythiourethane LCE actuator films. [38]These results suggest excellent uniaxial molecular alignment of the fiber due to shear and elongational flow associated with the extrusion and drawing process, as well as the presence of microphase-separated H-bonding domains acting as physical crosslinks: both are required for reversible actuation.
The thermal actuation behavior of the fiber obtained was monitored between 25 and 110 °C (Figure 2a); the maximum contraction was 27% in length and expansion of 20% in width parallel and perpendicular to the alignment, respectively (Figure 2b).Increasing the temperature results in large deformation of the fiber, which levels off when the T i is passed. [26,38]The fiber actuator demonstrates fully reversible actuation over at least 50 heating/cooling cycles (Figure S14, Supporting Information).Interestingly, when the fiber is initially placed on a heated surface of 110 °C, it instantly bends and commences rolling in one direction, eventually straightening and slowing down but continuing to roll at reduced speed (v average = 1.68 mm s −1 ; Figure S15, Supporting Information): such autonomous fiber rolling has been described earlier for LCE thermosets. [51,52]o demonstrate the reprogramming capabilities of this thermoplastic system, spiral coil actuators are fabricated that expand upon heating.First, a single coiled object is formed by wrapping the pliable fiber around a cylindrical support at 130 °C for 30 min, during which the H-bond system becomes dynamic and reorganizes, thereby fixing the coil conformation upon cooling (Figure 2c).As can be seen from scanning electron microscopy (SEM), the surface of the spiral coil exhibits a slightly slanted texture along the fiber axis (Figure S16, Supporting Information).The sample was heated to 110 °C and shows atypical actuation by expanding and uncoiling into a looser and longer spiral coil (Figure 2d).Interestingly, the total length of the fiber forming the coil actually decreased in the actuated state by 28%, matching the uniaxial fiber (Supporting Information for calculation details).Similarly, a second spiral coil actuator with opposing handedness was formed to avoid overall rotational actuation by wrapping either end around a support in opposite directions while fixing the middle.The double-handed coil object responded by expanding and uncoiling upon heating as well, showing torsion-neutral deformations (Figure 2e).When the coiled objects are placed on a heated surface of 110 °C, it begins rolling, but the direction is less controlled.
Twisted fiber actuators were obtained by rotating one end of the fiber while fixing the other, heating it to 130 °C for 30 min, and then leaving it at RT overnight (Figure 3a).During cooling, the twisted fiber's length increases due to the intrinsic anisotropic expansion of the LCs while the initial number of introduced twists is maintained, resulting in lower twisting densities in the eventual programmed twisted fiber (Table S2, Supporting Information).As apparent from SEM, the surface of the twisted fibers exhibits a slanted texture along the fiber axis arising from the programmed twists in the fiber (Figure 3b).Tensile tests revealed similar mechanical properties for the programmed twisted fiber actuator and the as-obtained fiber, although the strength and modulus are somewhat reduced (Figure S17, Supporting Information).Now reprogrammed into a twisted configuration, the material acts as a reversible rotating actuator in response to temperature (Figure 3c).
The actuation performance of the twisted fiber is systematically characterized by monitoring the shape change over a temperature range of 30 to 110 °C.The rotations (untwisting) and contraction of the rotating fiber actuator both increase with heating up to the T i , after which it gradually reaches its maximum (Figure 3d).The programmed LCE fiber with twisting density  0 = 75.9°mm−1 contracts up to 19.5% and reaches a rotational deformation of 48.1°mm −1 upon heating to 110 °C, for example.The thermal-responsive curve closely resembles that of thermoset rotating fibers previously reported. [36]During cooling, the fiber reversibly recovers by retwisting and expanding into its initial configuration with negligible hysteresis.Accompanying the completely reversible shape changes, the fibers deliver rotational (torque) and longitudinal forces, and following from this, shear and longitudinal stresses are calculated by the appropriate normalizations based on geometry as described in the "Experimental Section" (Figure 3e; Figures S18 and S19, Supporting Information).Upon increasing the temperature, the torque and longitudinal force increase as the fibers are untwisting and contracting, matching the behavior of the rotation and length changes (Figure 3d).Cooling follows a similar trajectory, with fully reversible actuation and only a small thermal hysteresis, suggesting excellent elastic behavior and thermal stability of the twisted fibers when heated up to 110 °C.
The twisting density may be controlled by selectively deforming the fibers with a specific number of twists followed by thermal reprogramming: a series of five twisted fibers are prepared with twisting densities  0 = 0, 11.4, 27.2, 50.9, and 75.9°mm −1 (see Table S2, Supporting Information, for additional details).Attempts to obtain even higher twisting densities resulted in the generation of coiled structures, minimizing the introduced strain energy. [53]SEM imaging confirms that a twisted configuration is obtained after programming, as apparent from the tilted surface texture compared to the uniaxial programmed fiber (Figure S20, Supporting Information).In addition, the angle of the twisted textures with respect to the drawing direction increases with the twisting density and resembles the theoretically calculated bias angle.Furthermore, it is assumed that the azimuthal component of the director increases further from the center because the material experiences larger shear on the outside of the fiber during twisting. [54]he rotation and contraction both depend on the fibers' programmed twisting density: all twisted fibers rotate and contract during heating, while the non-twisted fiber ( 0 = 0) only contracts without rotational deformation, as expected (Figure 3f).Untwisting causes the individual fibers to expand simultaneously, thereby partially counteracting the intrinsic contracting behavior of the LCE actuator.Hence, increasing the programmed twist density resulted in more significant rotating deformations since more twists are stored while the contraction is reduced.Juxtaposing the torque and longitudinal force of the prepared rotating fibers shows the clear twisting density dependence on the actuation performance (Figure 3g).The torque exhibits a clear trend as it greatly increases with the twisting density and then levels off, reaching 75.5 μN m, resembling the actuation behavior of the rotational deformation (Figure 3f), whereas, in contrast, the longitudinal force generally decreases with a maximum of 0.42 N.These melt-extruded thermoplastic LCE fibers exceed the previously reported thermosets in terms of attainable torques and forces since we were able to obtain much thicker fibers. [15,19,36]imilarly, as discussed earlier for the coils, a double-handed twisted fiber ( 0 = 72.0°mm−1 ) with both left-and righthandedness can be fabricated, showing torsion-neutral contraction upon actuation instead since both ends of the twisted fiber untwist in opposite directions due to the programmed countertwists (a video of the single-and double-handed twisted fiber actuators can be seen in Video S1, Supporting Information).
The programmability of the thermoplastic LCE system lends itself to realize more versatile and thicker fibers, and to demonstrate this, a three-ply twisted rope construct was fabricated, integrating all the functionalities of this material.In the first step, the fibers were formed by twisting them at 130 °C, forming three individual pre-programmed fibers ( 0 = 72.0°mm−1 ) with a right-handed twisted configuration (Figure 4a).Then, three of these fibers are bundled and intertwisted in the same direction at 130 °C to obtain a right-handed rope construct ( 0 = 72.0°mm−1 ) with complementary twists promoting the rotating behavior during actuation (Figure 4b).It should be noted that during programming, physical H-bonding crosslinks may form between the individual fibers in the construct, potentially affecting the actuation performance while at the same time preventing the bundle from loosening and maintaining its functionalities.The angle of the slanted surface textures on the individual fibers increased upon fabricating the construct, as observed from SEM, indicating the twisting is slightly enhanced (Figure 4c).Actuating the construct by heating led up to three times as great of a torque and longitudinal force compared to the individual rotating fibers (Figure 4d), while the shape changes remained similar, as expected (Figure S21, Supporting Information).Shear and longitudinal stresses are calculated by normalizing to the effective cross-sectional area of the rope construct (Figure S22, Supporting Information), which are comparable with thermoset rotating fibers previously reported. [36]he combination of reversible torsional motion and contraction with the enhanced rotational and longitudinal forces obtained in the construct allows us to convert thermal energy into mechanical work, as demonstrated by opening/closing a vial screw cap and reversibly lifting the closed vial.Heating the rope construct to around 110 °C with a heat gun while the vial is fixed leads to unscrewing the cap that completely screws back on by itself when the rope construct is cooled (Figure 4e).Now, when the base of the closed vial is released, the construct lifts the vial and its cargo (12.3 g) upon heating and reversibly drops it afterward (a video of the thermal actuation cycle can be seen in Video S2, Supporting Information).
By making use of the thermoplastic behavior, it is possible to reprocess and reprogram this material in its entirety, generating a completely reconfigured and repurposed temperatureresponsive LCE.To highlight this, the fiber actuator is cut into pieces, remolded into a film, and sequentially programmed into an oriented twisted ribbon that may then be used as an actuator or again turned into any other desired structure (Figure S23, Supporting Information).The second feature facilitated by the dynamic H-bond system is the self-healing/welding ability enabling damage recovery of the material and formation of more complex shapes.For the former, a molded film was cut into two pieces and then rejoined at 150 °C for 2 min recovering the initial seamless film, demonstrating the potential self-healing capabilities of this material (Figure S24, Supporting Information).The healed film exhibits similar mechanical properties as the pristine film, indicating excellent self-healing performance (Figure S25, Supporting Information).

Conclusion
We have demonstrated the scalable fabrication of a thermoplastic LCE fiber enabling soft actuators for reprocessable and reprogrammable materials, retaining the intrinsic actuating properties with mechanical integrity, yet being completely reconfigurable.Fabrication of a 50 m long, 1.3 mm thick single fiber with a high level of molecular order and well-defined microphaseseparated domains was achieved by extruding and drawing the material in the thermoplastic melt without photopolymerization being needed.Despite being physically crosslinked, the LCE fiber shows not only thermal relaxation of the H-bond network in the viscoelastic region at elevated temperatures, but also excellent thermal actuation and elasticity at the service temperature allowing for reversible deformation.We have shown that rotating fiber actuators can be fabricated by using this reprogrammable H-bond system, affording synergistically contracting and rotating actuators with large, controllable actuation performance.Finally, to highlight the adaptability of this thermoplastic LCE, the individual twisted fibers may be easily reconfigured by temperature into a shape-morphing construct able to deliver greater forces, and completely reprocessed and reformed into any desired structure with potential self-healing capabilities.Our work lays a foundation for artificial muscles with larger diameters than LCE thermosets and the processability, scalability, and recyclability of thermoplastic elastomers.
Synthetic Procedure: The thermoplastic LCE was synthesized using a previously reported method with minor adaptations. [38]A double jacketed reaction vessel (2 L) connected to a heated water circulator (Lauda M3) was charged with diacrylate mesogens 1 (71.06 g, 105.62 mmol) and 2 (62.17 g, 105.62 mmol) in DMAc (300 mL).After completely dissolving the monomers, dithiol 3 (46.21g, 253.49mmol) and catalyst 4 (0.18 g, 1.30 mmol, 0.1 wt.%) in DMAc (59 mL) were added sequentially, and the reaction mixture was stirred under argon atmosphere at RT.After 2 h reaction time, diisocyanate 5 (14.21 g, 84.50 mmol) and catalyst 6 (0.20 g, 1.98 mmol, 0.1 wt.%) were added to the mixture in DMAc (29 mL) and stirred at RT for 15 min.Additional DMAc (387 mL) was added, and the reaction was continued by adding dithiol 7 (6.35g, 42.25 mmol) in DMAc (25 mL) dropwise, after which the reaction mixture was allowed to stir at 60 °C overnight.The crude mixture was cooled to RT the next day, followed by precipitation into Et 2 O (16 L) under continuous stirring.Afterward, the product was transferred into fresh Et 2 O (4 L) and stirred overnight.The final product was obtained by decanting the solvent and drying the polymer under a vacuum at 40 °C for 24 h yielding a white solid (≥98.5% recovery).
General Characterizations: GPC was carried out using a Waters HPLC system equipped with a PSS PFG (8 × 50 mm 2 , 7 μm) and two PFG linear XL columns (8 × 300 mm 2 , 7 μm) in series, and a refractive index detector calibrated with poly(methyl methacrylate) standards.HFIP and potassium trifluoroacetate (0.02 м) were used as mobile phase with a flow rate of 0.8 mL min −1 at 35 °C, and the samples were prepared in HFIP with toluene (0.02 м) and potassium trifluoroacetate (0.02 м).Attenuated total reflectance (ATR) FTIR spectra were recorded on a Varian 670 IR spectrometer equipped with an ATR sampling accessory.All spectra were taken over a range of 4000-650 cm −1 with 50 scans and a spectral resolution of 4 cm −1 at RT and processed with Varian Resolutions.Differential scanning calorimetry (DSC) scans were collected using a TA Instruments Q2000 DSC instrument equipped with a cooling accessory between −50 to 210 °C at 10 °C min −1 under nitrogen and hermetic T-zero aluminum sample pans with 10 mg product.Transition temperatures were determined from the second cycle.Thermal gravimetric analysis (TGA) was performed on a TA instruments Q50 instrument between 28 to 800 °C at 5 °C min −1 with 5 mg product.The T d was determined by 1% weight loss.Dynamic mechanical analysis (DMA) was carried out using a TA Instruments Q800 apparatus in vertical tension mode on as-obtained fibers (D = 1.3 mm).Thermographs were obtained between −50 and 200 °C at a heating rate of 5 °C min −1 with 0.01 N preload force, 20 μm amplitude, and a 1 Hz oscillating frequency.Tensile testing was performed using a Zwick Z010 universal testing machine equipped with a 100 N load cell and Zwick air-circulated oven on compression-molded dog-bone specimens (2 × 0.35 mm 2 ) or as-obtained fibers (D = 1.3 mm) with a 20 mm gauge length and 500 mm min −1 elongation rate until failure unless stated otherwise.The strain is defined as  = (L−L 0 )/L 0 , where L 0 is the initial length and L at a certain time.WAXS and MAXS measurements were performed on a Ganesha lab instrument equipped with a Pilatus 300 K silicon pixel detector (487 × 619 pixels, 172 μm 2 in size) and a Genix-Cu ultralow divergence source (Cu K,  = 0.154 nm, Φ = 1 × 10 8 photons s −1 ).Diffraction patterns were collected with an exposure time of 30 min (WAXS) or 60 min (MAXS), placed at a sample-to-detector distance of 89 mm (WAXS) or 440 mm (MAXS), and analyzed using a custom Python script with the PyFAI software package.Silver behenate was used as the calibration standard, and the orientational order parameter S was determined using the Kratky method. [55]The order parameter is measured of the whole material because the observed signals of the LC and H-bonding domains are overlapping.SEM imaging was performed with an FEI Quanta 3D FEG instrument in secondary electron mode operating at 5 kV beam current on gold sputter-coated samples (T = 12.5 nm; Q150T, Quorum).Photographs and videos were taken with a camera (Olympus OM-D E-M10 Mark III) in manual mode, and LEDs in a photo box provided lighting.
Extruding and Drawing of Thermoplastic LCE Fibers: Extrusion and drawing of the thermoplastic LCE were done using a rheometer equipped with a capillary die (L capillary = 10 mm and D capillary = 2 mm).To extrude the material, regions of the barrel were set to specific temperatures ranging from T barrel = 180-190 °C with a melting time of t wait = 2 min and a constant piston speed v piston = 0.8 mm s −1 .After the material left the capillary, it was actively cooled by a fan and drawn using a haul-off unit with a pulling speed v haul-off = 50 mm s −1 , after which it was collected and stored on a coil (Table S1, Supporting Information).
Preparation of the Rotating Actuators and Rope Construct: The singlehanded coiled actuator was obtained by wrapping the fiber around a cylindrical support (D = 0.8 mm) and heating it to 130 °C for 30 min, after which the support was removed, and the sample was stored at RT overnight.A double-handed coiled object was prepared similarly by fixing the fiber in the middle and wrapping each side around the support in opposite direction.Twisted fiber actuators were obtained by rotating one end around the longitudinal axis while the other end was fixed and subsequently heating it to 130 °C for 30 min and left at RT overnight.The twisting density  0 was controlled during programming by introducing a certain amount of twists (0, 6, 12, 18, or 24), which is given by  0 = ∆/L 0 , where ∆ is the angle of rotation (360°× twists) and L 0 the initial length of the fiber. [36]Subsequently, the theoretical bias angle can be calculated as  = tan −1 (r 0  0 ), where r 0 is the radius of the fiber.The rope construct was fabricated by first programming three individual right-handed twisted fibers ( 0 = 72.0°mm −1 ) as discussed above.Next, these programmed fibers were bundled together along their longitudinal axis and intertwisted in the same direction by right-handed twisting one end of the fiber bundle while fixing the other side and heated to 130 °C for 30 min, after which the obtained construct ( rope = 72.0°mm−1 ) was left at RT overnight.
Thermal Actuation: Actuation of the as-obtained fiber was monitored by heating and cooling the samples between 25 and 110 °C with temperature intervals of 10 °C (the first step being 5 °C) using a hotplate.The measured contraction and expansion as a function of temperature were averaged over seven different fibers.Autonomous rolling of the fiber was obtained by placing it on a preheated hotplate of 110 °C.The spiral coil actuators were placed on a hotplate and gradually heated from 25 to 110 °C with 10 °C intervals.Thermal actuation of the twisted fibers was obtained by vertically hanging the samples with a small load (6 g) and using a heat gun with a wide flare nozzle set to 110 °C.For the rope construct, one side was fixed with a paper clamp while the other was connected to a screw eye attached to the vial's cap containing a load (12.3 g) and heated using a heat gun with a wide flare nozzle set to 110 °C.The cargo in the vial was a fluorescent pigment (PF-38 tropical sunlight orange, Risk Reactor) in CHCl 3 (1 mg mL −1 ).Prior to all the actuation measurements, the thermal history was erased by subjecting all samples to a full heating/cooling cycle.Images were analyzed using the open-source software ImageJ.
Characterization of the Twisted Rotating Fibers: The contraction and rotational deformation of the twisted fibers with different twisting densities were monitored between 30 and 110 °C with a temperature ramp of 5 °C min −1 using a precision-controlled heating and cooling stage (Instec HCP204).Photographs were taken at 5 °C temperature intervals using a digital camera, and the resulting images were analyzed using the opensource software ImageJ.The length changes were measured from the endto-end distance of the fiber.For the rotational deformations, a dot is drawn on the fiber's base from which the change in angle of rotation was used to calculate rotations upon actuation:  = ∆/L 0 .The torque and longitudinal force of the fibers were gauged by a rheometer (ARES, TA instruments) equipped with torsion DMA clamps in strain-controlled mode where both the rotational and longitudinal displacement are set to zero.The samples (L ≈ 25 mm) were heated and cooled between 30 and 110 °C with a temperature ramp of 5 °C min −1 and a soak time of 3 min after each ramp.The shear stress was calculated by using a plate-plate geometry as given by  = (2T)/(r 0 3 ), where T is the experimentally measured torque and r 0 is the radius of the fiber, assuming linear elastic behavior and provides the maximum shear stress at the outer radius of the fiber.The longitudinal stress was calculated by  = F / A, where F is the experimentally measured force, and A is the cross-sectional area of the fiber.Prior to all the measurements, the thermal history was erased by subjecting all samples to a full heating and cooling cycle.
Reprocessing and Self-Healing of the Thermoplastic LCE: The asobtained fiber was chopped into pieces and remolded at 200 °C and 0.5 bar for 2 min (Tribotrak, DACA instruments) into a circular LCE film.Next, a twisted ribbon actuator was obtained by cutting a rectangular shape from the reprocessed film, stretching it to 200% elongation, twisting one end while the other end is fixed, heating it to 130 °C for 2 min, and cooling it to RT.Finally, the twisted ribbon actuator was cut into small pieces.For self-healing, a pristine LCE film was prepared by compression molding the crude material at 200 °C and 0.5 bar for 2 min.Then, the pristine film was cut in the middle, rejoined at RT, and heated to 150 °C for 2 min, yielding a healed film.

Figure 1 .
Figure 1.a) Molecular representation of the thermoplastic LCE.b) Schematic melt-extrusion and drawing process of the fibers.Photographs of the fiber obtained on a c) coil (scale bar = 15 mm) and d) magnified image of the fiber showing details of a segment of the strand (scale bar = 1.5 mm).e) DMA measurements of the storage modulus (gray line) and loss tangent profiles (red line) of the melt-extruded fiber.f) 2D X-ray diffractogram of the as-obtained fiber.The arrow denotes the alignment direction (n).

Figure 2 .
Figure 2. a) Thermal actuation of the as-obtained thermoplastic LCE fiber (scale bar = 5 mm).b) Width expansion (black squares) and length contraction (red dots) as a function of temperature.c) Schematic representation of reprogramming spiral coil actuators.Thermal actuation of the d) single-handed and e) double-handed spiral fiber actuators (scale bar = 5 mm).

Figure 3 .
Figure 3. a) Schematic preparation of twisted fiber actuators and the corresponding actuation behavior showing the accompanying deformations and forces.b) SEM image of the programmed twisted LCE fiber with twisting density  0 = 75.9°mm −1 (scale bar = 0.3 mm).c) Thermal actuation of the programmed twisted LCE fiber ( 0 = 72.0°mm −1 ) by heating to 110 °C and cooling back to 30 °C (scale bar = 15 mm).d) Rotation and length changes, and e) torque and longitudinal force of a twisted fiber ( 0 = 75.9°mm −1 ) upon heating (filled symbols) and cooling (open symbols).Maximum f) rotations and length changes, and g) torque and longitudinal force of the fibers with different twisting densities at 110 °C.

Figure 4 .
Figure 4. a) Schematic preparation of the rope construct actuator and the corresponding actuation behavior.b) Photograph (scale bar = 2 mm) and c) SEM image of the obtained twisted rope construct actuator with corresponding bias angle  (scale bar = 0.25 mm).d) Torque and longitudinal force of the rope object ( 0 = 72.0°mm−1 ) upon heating (filled symbols) and cooling (open symbols).e) Thermal actuation of the rope construct actuator opening and closing a screw cap and subsequently lifting the closed vial (scale bar = 15 mm).