Research ArticleUNDERSEA ROBOTS

Ultragentle manipulation of delicate structures using a soft robotic gripper

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Science Robotics  28 Aug 2019:
Vol. 4, Issue 33, eaax5425
DOI: 10.1126/scirobotics.aax5425
  • Fig. 1 Soft robotic actuators are a promising approach to grasping fragile marine organisms.

    (A) Illustration demonstrating the envisioned application of soft robotic actuators (green) attached to an ROV. These actuators were designed for ultragentle manipulation of delicate tissues, such as jellyfish and other gelatinous marine species. The target species for our soft gripper are (B) A. aurita, (C) C. mosaicus (photo credit: Peter Campbell; www.greenlivingpedia.org/Image:Blue_Blubber_Jellyfish_IMGP2102.JPG), and (D) M. papua.

  • Fig. 2 Fabricating nanofiber-reinforced soft robotic actuators.

    (A) Actuators were manufactured using molding and cobonding (cross-sectional view shown). (B) Six soft actuators connected to a 3D-printed hub. (C) As an actuator is pressurized, the internal channel inflates and the device bends toward the strain-limiting nanofiber layer.

  • Fig. 3 We evaluated the effect of actuator geometry on burst pressure and percentage of defects.

    (A) Cobonding cured actuator section to uncured silicone layer. (B) Actuator burst pressure as a function of internal channel height, with a constant membrane thickness of 0.25 mm (mean ± SD, n = 4 actuators). (C) Burst pressure as a function of membrane thickness (mean ± SD, n = 4 actuators). *P < 0.05. (D) % pristine actuators and burst pressure as a function of adhesion layer thickness (mean ± SD, n = 5 actuators). (E) Scanning electron micrographs of actuators with 30- and 50-μm adhesion layers (cross section).

  • Fig. 4 We mapped the region of acquisition of our soft gripper using our water tank testing setup.

    (A) A coarse estimate (n = 2) of the region indicates a roughly diamond shape, and (B) various grasp types were observed, including cage grasps, bell hooks, and tentacle wraps. A higher-fidelity investigation along (C) the vertical axis, (D) the y axis, and (E) the x axis behind the target was performed with n = 5 grasps for each condition. Error bars in (C) to (E) represent the 95% Agresti-Coull confidence interval.

  • Fig. 5 We evaluated the robustness of our gripper to external forces on a target object.

    (A) The target was grasped by our soft actuators and pulled out at an angle. (B) The maximal external force before failure increased as a function of the angle applied while the grasp success rate decreased. Error bars represent the SD for pull force measurements, and the 95% Agresti-Coull confidence interval for grasp success rate estimates. n = 5 successful grasps per condition, except 75° and 90°, where n = 5 attempts were made.

  • Fig. 6 A handheld grasping device was developed to test our soft actuators outside the laboratory.

    (A) Design of soft robotic gripping device, shown with a four-actuator hub. Inset: Different hubs, including this six-actuator palm, can be attached modularly. Soft fiber-reinforced actuators grasping (B) A. aurita, (C) C. mosaicus, and (D) M. papua. (C and D) Photos courtesy of Anand Varma.

  • Fig. 7 Gentle grasping of A. aurita.

    (A) Actuators approach the jellyfish, un-inflated. (B) Actuators begin to hydraulically pressurize. (C) Actuator pressurization continues until the jellyfish is gently and securely grasped. Photos courtesy of Anand Varma.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/4/33/eaax5425/DC1

    Text

    Fig. S1. Schematic of grasp quality testing procedure.

    Fig. S2. Contact pressure of soft actuators.

    Fig. S3. Characterizing the shear strength of wet adhesion between soft actuators.

    Fig. S4. Destructive grasp attempt of gelatinous acorn worm.

    Fig. S5. Drag force versus soft gripper speed.

    Fig. S6. Comparative failure pressure of fiber-reinforced and pure elastomer actuators.

    Fig. S7. Caging grasps using soft robotic actuators.

    Movie S1. Empirical evaluation of ultrasoft gripper performance using a custom-designed underwater testing platform.

    Movie S2. Field testing of soft robotic gripper.

    References (6067)

  • Supplementary Materials

    The PDF file includes:

    • Text
    • Fig. S1. Schematic of grasp quality testing procedure.
    • Fig. S2. Contact pressure of soft actuators.
    • Fig. S3. Characterizing the shear strength of wet adhesion between soft actuators.
    • Fig. S4. Destructive grasp attempt of gelatinous acorn worm.
    • Fig. S5. Drag force versus soft gripper speed.
    • Fig. S6. Comparative failure pressure of fiber-reinforced and pure elastomer actuators.
    • Fig. S7. Caging grasps using soft robotic actuators.
    • References (6067)

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Empirical evaluation of ultrasoft gripper performance using a custom-designed underwater testing platform.
    • Movie S2 (.mp4 format). Field testing of soft robotic gripper.

    Files in this Data Supplement:

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