Research ArticleSOFT ROBOTS

MXene artificial muscles based on ionically cross-linked Ti3C2Tx electrode for kinetic soft robotics

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Science Robotics  21 Aug 2019:
Vol. 4, Issue 33, eaaw7797
DOI: 10.1126/scirobotics.aaw7797
  • Fig. 1 Synthesis and characterization of ionically cross-linked Ti3C2Tx MXene.

    (A) Schematic representation of the synthesis of ionically cross-linked Ti3C2Tx MXene. (B) SEM image of Ti3C2Tx (scale bar, 500 nm). (C) SEM image of Ti3C2Tx-PP (scale bar, 2 μm). (D) Raman spectra of Ti3C2Tx, PP, and Ti3C2Tx-PP. a.u., arbitrary units. (E) Representation of the phase change of benzoid PEDOT into quinoid PEDOT.

  • Fig. 2 Morphological, electrical, and electrochemical characterization of all AWIS actuators.

    (A to C) Cross-sectional SEM images of PP, T1PP4, and T1PP2 electrodes, respectively. Scale bar, ~15 μm. Insets: SEM images of electrode surface. Scale bars, ~2 μm. (D) Optical image of ionic soft actuators with the pristine Ti3C2Tx MXene–based electrode, showing flaking of few MXene sheets under bending. (E) Optical image of ionic soft actuators with the Ti3C2Tx-PP–based electrode, indicating good adhesion and flexibility. (F) CV curves of four actuators at a scan rate of 10 mV s−1. (G) EIS curve of all AWIS actuators. Inset: The magnified high-frequency region. (H) The volumetric capacitance value of all AWIS actuators at a scan rate of 10 mV s−1 and electrical conductivity of all electrodes. (I) Stress-strain curves of PP, T1PP2, and T1PP4 electrode materials.

  • Fig. 3 Actuation performances of AWIS actuators.

    (A) Peak-to-peak bending strain of actuators under sinusoidal input voltage of 1 V at the excitation frequency of 0.1 Hz. (B) Peak-to-peak amplitudes of bending strain at a range of frequencies from 0.1 to 20 Hz under sinusoidal input voltage of 1 V. (C) Peak-to-peak amplitudes of bending strain with a range of applied voltage from 0.1 to 1 V at 0.1 Hz. (D) Phase delay comparison plot of actuator response under sinusoidal input voltage of 0.5 V with varying of frequency from 0.1 to 3 Hz. (E) Time-related to actuation performance of AWIS actuators under DC voltage of 0.5 and 1 V. (F) Actuation retention test of AWIS actuators for 18,000 cycles under sinusoidal input voltage of 1 V at the excitation frequency of 1 Hz, showing high durability for 5 hours. Inset curves show the first four cycles and the last four cycles of actuation performance.

  • Fig. 4 Demonstration of origami-inspired narcissus flower robot.

    The total weight of the flower is 375 mg. (A) Schematic illustration of the origami-inspired narcissus flower robot: Initially, the robot was in closed position; after applying 3-V DC input, the robot “blooms” like a narcissus flower. (B) Optical photographs of the original and the postbloom flower robot, which could serve as a fashion brooch. The flower robot was placed on a black coat worn by our lab secretary J.-Y. Lim. (C) Optical images of a real narcissus flower in different stages of blooming taken from www.youtube.com/watch?v=smJmfgaQAR4&t=2s (copyright permission by the owner). (D) Optical images of AWIS actuator–based narcissus flower robot in various stages of blooming.

  • Fig. 5 Demonstration of kinetic art: “Dancing” butterflies on a tree.

    The weight of each butterfly is 310 mg. (A to E) Optical images of AWIS actuator–based butterfly robots on tree branches with different wing positions. Initially, the butterflies were in dead position; after applying 2 V of AC input with frequency of 0.2 Hz, butterflies behaved like live butterflies.

  • Fig. 6 Demonstration of kinetic art: A tree with dancing leaves.

    The weight of each leaf is 38 mg. (A to F) Optical images of AWIS actuator–based kinetic soft sculpture tree with a theme of dancing leaf robot under 1.5-V and 0.2-Hz input stimulation.

  • Fig. 7 Schematic analysis of mechanism and performance of MXene AWIS actuators.

    (A) Schematic representation of a mechanism for high and fast actuation of MXene-based AWIS actuators. (B and C) Visual curves comparing results obtained in this study with results reported in the literature regarding response times and bending strains of ionic soft actuators, respectively.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/4/33/eaaw7797/DC1

    Fig. S1. Schematic representation for synthesis of Ti3C2Tx and morphological images.

    Fig. S2. Ionically cross-linked MXene-PP electrode.

    Fig. S3. FTIR spectra of all MXene materials.

    Fig. S4. Chemical and structural characterization of all AWIS actuator electrodes.

    Fig. S5. Fabrication of actuators and electrochemical CV results.

    Fig. S6. Actuation performance of neat Ti3C2Tx MXene–based ionic soft actuator under various input voltages at a frequency of 0.1 Hz.

    Fig. S7. Actuation performances of T1PP2 and T1PP4 AWIS actuators.

    Fig. S8. Comparison graph for power consumption–strain dependency of MXene-based actuator compared with other soft actuators.

    Fig. S9. Durability results of all actuators.

    Table S1. Mechanical properties of PP, T1PP4, and T1PP2 electrodes.

    Table S2. Comparison of blocking force for ionic soft actuators.

    Table S3. Comparison of bending strain for ionic soft actuators.

    Movie S1. Kinetic art demonstration of origami-inspired narcissus flower robot.

    Movie S2. Kinetic art demonstration of dancing butterfly robots.

    Movie S3. Kinetic art demonstration of dancing leaves.

    References (4952)

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Schematic representation for synthesis of Ti3C2Tx and morphological images.
    • Fig. S2. Ionically cross-linked MXene-PP electrode.
    • Fig. S3. FTIR spectra of all MXene materials.
    • Fig. S4. Chemical and structural characterization of all AWIS actuator electrodes.
    • Fig. S5. Fabrication of actuators and electrochemical CV results.
    • Fig. S6. Actuation performance of neat Ti3C2Tx MXene–based ionic soft actuator under various input voltages at a frequency of 0.1 Hz.
    • Fig. S7. Actuation performances of T1PP2 and T1PP4 AWIS actuators.
    • Fig. S8. Comparison graph for power consumption–strain dependency of MXene-based actuator compared with other soft actuators.
    • Fig. S9. Durability results of all actuators.
    • Table S1. Mechanical properties of PP, T1PP4, and T1PP2 electrodes.
    • Table S2. Comparison of blocking force for ionic soft actuators.
    • Table S3. Comparison of bending strain for ionic soft actuators.
    • References (4952)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Kinetic art demonstration of origami-inspired narcissus flower robot.
    • Movie S2 (.mp4 format). Kinetic art demonstration of dancing butterfly robots .
    • Movie S3 (.mp4 format). Kinetic art demonstration of dancing leaves.

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