Research ArticleSOFT ROBOTS

Self-healing soft pneumatic robots

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Science Robotics  16 Aug 2017:
Vol. 2, Issue 9, eaan4268
DOI: 10.1126/scirobotics.aan4268
  • Fig. 1 SH soft pneumatic actuators.

    (A and D) SH soft pneumatic hand. (B) SH soft pneumatic gripper. (C) SH PPAM.

  • Fig. 2 The thermoreversible network formed by the DA cross-links.

    (A) The equilibrium DA reaction: At low temperatures, the network is formed due to high conversion to the DA bonds. At high temperatures, these DA bonds fall apart, and the mobility of the polymer chains increases. (B) Thermoreversible elastomeric network formed by cross-links of the reversible DA bond.

  • Fig. 3 Schematic of the SH cycle of DA polymers.

    The SH procedure contains five steps: the damage, a heating step, an isothermal step, a controlled cooling, and a recovery at room temperature. The pictures illustrate the self-healing of a damaged DA polymer sample (DPBM-FGE-J4000) during the different stages (movie S1).

  • Fig. 4 Design and manufacturing of the SH BSPA.

    (A) Dimensions (in millimeters) (detailed data sheets in fig. S10). (B) Illustration of the bending motion caused by an overpressure in the air chambers. (C) Abaqus simulation for large deformations at 30 kPa (fig. S9 and movie S2). (D) Building the BSPA: Through folding and self-healing procedures (<78°C globally and <110°C locally), connections are made between the different parts, and the actuator is made airtight (fig. S12).

  • Fig. 5 DA sheets with completely different mechanical properties can be seamlessly healed together.

    (A) Using different Jeffamines (J400, J2000, and J4000), furan-functionalized building blocks (FGE-Jx) with different spacer lengths can be synthesized. (B) Because the J4000 and J2000 DA polymers differ only in furan spacer length, the materials can be self-healed together using an SH procedure with a maximum temperature of 95°C (movie S3). The initial gap between the sheets was 0.3 mm.

  • Fig. 6 Mechanical characteristics of the four BSPAs and their functionality in a soft gripper and a soft hand.

    The experimental measurements are compared to the numerical simulations using static elastic models in Abaqus. (A) Vertical and horizontal displacement of the actuator tip for different overpressures. (B) Bending angle as a function of the overpressure. (C) Force exerted by the tip of the BSPA. (D) Operating the four BSPAs in a soft pneumatic gripper. The overpressure in the actuators can be regulated individually. This allows simultaneously exerting the same force on the object with each actuator to create smooth, controlled grasping motions. Soft objects, such as an orange (92.8 g), can be grasped, picked up, and moved (movie S4). (E) The four BSPAs were also integrated as fingers in a soft pneumatic hand, together with a six-cell prototype acting as a thumb. All actuators are controlled individually (movie S5).

  • Fig. 7 Experimental deformations and contractions forces of the two PPAM designs.

    (A) Shape of the PPAM at ambient pressure and near-maximum overpressure tested (movie S6). The experiments (Exp) are compared with the results of the numerical simulations using the static elastic model (MDL) in Abaqus (movie S2). (B) Relative width increase and contraction as a function of the overpressure. (C) Contraction force as a function of the overpressure.

  • Fig. 8 Validating the SH ability in practice and recovery of the mechanical properties of the actuators after healing cuts.

    Cuts with lengths of 8 to 9.5 mm made with a scalpel blade. (A) Cutting the finger actuator (BSPA) with a scalpel blade with a thickness of 0.39 mm (movie S7). The macroscopic cuts (length of 9.4 mm and all the way through) can be healed entirely using an SH procedure, after which the actuator is again completely airtight. The asterisk indicates the location of failure due to overpressure. (B) Macroscopic cuts (8.6 mm) in the self-healing membrane of the PPAM can be healed entirely using an SH procedure (movie S8). After this, the muscle is again airtight and recovers its functionality. (C) The bending angle as a function of overpressure and the trajectory of the tip of the BSPA are measured after 1 and 2 damage SH cycles and are compared with the initial characteristics. (D) Contraction force of the PPAM 1 as a function of overpressure as measured after 1, 2, and 3 damage SH cycles and compared with the initial characteristics. (E) Influence of the heating procedure (4 hours at 80°C followed by at least 3 days at 25°C) on the viscoelastic properties expressed in equivalent SH cycles.

  • Table 1 Thermal and mechanical properties of DA materials synthesized using different Jeffamine Jx spacers.
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Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/9/eaan4268/DC1

    Fig. S1. Synthesis of the thermoreversible covalent networks.

    Fig. S2. The thermoreversible DA reaction.

    Fig. S3. Simulation for the DA series: DPBM-FGE-J400, DPBM-FGE-J2000, and DPBM-FGE-J4000.

    Fig. S4. Temperature profile of the SH procedure.

    Fig. S5. Temperature-dependent viscoelastic behavior for the DA polymer series measured by DMA.

    Fig. S6. Stress-strain curves for the DA polymer series.

    Fig. S7. Young’s modulus determination of the DPBM-FGE-Jx.

    Fig. S8. Measuring the gel temperature (Tgel) through dynamic rheometry.

    Fig. S9. Simulating different designs for the SH soft robotic demonstrators using a static elastic model in Abaqus.

    Fig. S10. Dimensions of the two BSPA designs in millimeters.

    Fig. S11. Dimensions of the two PPAM prototypes in millimeters.

    Fig. S12. Constructing a BSPA using shaping through folding and self-healing.

    Fig. S13. Shaping through folding and self-healing to manufacture the PPAMs.

    Fig. S14. Pressure control system scheme.

    Fig. S15. Images of the pressure control system.

    Fig. S16. Irreversible cross-linking of bismaleimide networks.

    Fig. S17. DA polymer waste of the manufacturing process of the prototypes can be recycled.

    Fig. S18. Recovery of the material properties after the recycling procedure.

    Movie S1. Visualization of the SH process of the DA elastomers using optical microscopy.

    Movie S2. Healing DA polymers together with different mechanical properties; DPBM-FGE-J4000 and DPBM-FGE-J2000.

    Movie S3. Simulating large deformations using static elastic models in Abaqus.

    Movie S4. The soft pneumatic gripper handling a 92-g mandarin orange.

    Movie S5. The soft pneumatic hand in which all the fingers are controlled individually.

    Movie S6. Actuation of the PPAM.

    Movie S7. Damaging the soft pneumatic hand.

    Movie S8. Damaging the PPAMs.

  • Supplementary Materials

    Supplementary Material for:

    Self-healing soft pneumatic robots

    Seppe Terryn, Joost Brancart, Dirk Lefeber, Guy Van Assche, Bram Vanderborght*

    *Corresponding author. Email: bram.vanderborght{at}vub.ac.be

    Published 16 August 2017, Sci. Robot. 2, eaan4268 (2017)
    DOI: 10.1126/scirobotics.aan4268

    This PDF file includes:

    • Fig. S1. Synthesis of the thermoreversible covalent networks.
    • Fig. S2. The thermoreversible DA reaction.
    • Fig. S3. Simulation for the DA series: DPBM-FGE-J400, DPBM-FGE-J2000, and DPBM-FGE-J4000.
    • Fig. S4. Temperature profile of the SH procedure.
    • Fig. S5. Temperature-dependent viscoelastic behavior for the DA polymer series measured by DMA.
    • Fig. S6. Stress-strain curves for the DA polymer series.
    • Fig. S7. Young’s modulus determination of the DPBM-FGE-Jx.
    • Fig. S8. Measuring the gel temperature (Tgel) through dynamic rheometry.
    • Fig. S9. Simulating different designs for the SH soft robotic demonstrators using a static elastic model in Abaqus.
    • Fig. S10. Dimensions of the two BSPA designs in millimeters.
    • Fig. S11. Dimensions of the two PPAM prototypes in millimeters.
    • Fig. S12. Constructing a BSPA using shaping through folding and self-healing.
    • Fig. S13. Shaping through folding and self-healing to manufacture the PPAMs.
    • Fig. S14. Pressure control system scheme.
    • Fig. S15. Images of the pressure control system.
    • Fig. S16. Irreversible cross-linking of bismaleimide networks.
    • Fig. S17. DA polymer waste of the manufacturing process of the prototypes can be recycled.
    • Fig. S18. Recovery of the material properties after the recycling procedure.

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Visualization of the SH process of the DA elastomers using optical microscopy.
    • Movie S2 (.mp4 format). Healing DA polymers together with different mechanical properties; DPBM-FGE-J4000 and DPBM-FGE-J2000.
    • Movie S3 (.mp4 format). Simulating large deformations using static elastic models in Abaqus.
    • Movie S4 (.mp4 format). The soft pneumatic gripper handling a 92-g mandarin orange.
    • Movie S5 (.mp4 format). The soft pneumatic hand in which all the fingers are controlled individually.
    • Movie S6 (.mp4 format). Actuation of the PPAM.
    • Movie S7 (.mp4 format). Damaging the soft pneumatic hand.
    • Movie S8 (.mp4 format). Damaging the PPAMs.

    Files in this Data Supplement:

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