Research ArticleBIOMIMETICS

A biorobotic adhesive disc for underwater hitchhiking inspired by the remora suckerfish

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Science Robotics  20 Sep 2017:
Vol. 2, Issue 10, eaan8072
DOI: 10.1126/scirobotics.aan8072
  • Fig. 1 Morphology structure of the remora’s adhesive disc and our biomimetic prototype design with mechanical elements and mechanisms.

    (A) Dorsolateral view of the slender sharksucker, E. naucrates. The arrows indicate the direction of friction and pull-off force. [Photo credit: Klaus M. Stiefel.] (B) 3D reconstructed model of the remora disc based on microCT data (resolution, 35 μm). (Inset) Closer image of the lamellae and rows of spinules. Scale bars, 10 mm. (C) CAD model of the biomimetic remora disc. The principal elements of the disc were assigned multiple materials represented by different colors. The spinules have the greatest stiffness (blue), and the materials in the main body include a fully rigid material [e.g., the ventral process and the lamella plate (green)], a medium rigid material [e.g., the disc base (yellow)], and a flexible material [e.g., the disc lip and soft lamella tissue overlay (orange)]. From the cross-sectional view, the edge of the rigid disc base penetrates into the soft lip and forms a cross-connected anchor-like structure (left inset). (Right inset) The biomimetic lamellae are composed of both a rigid skeleton (green) and a soft lamella tissue overlay (orange). For more data about the stiffness of the materials, refer to table S5. (D) Photograph of the biomimetic remora adhesive disc prototype (disc pad length, 127 mm; width, 62 mm). Scale bars, 10 mm. (Inset) A higher-magnification view showing the rows of composite lamellae embedded with carbon fiber spinules. (E) Drive mechanism for lamella pitch motions, which translates the linear movement of the soft actuators (driven by a pneumatic system) into the rotational movement of the lamellae. Animation of the lamella pitching motion can be seen in movie S3. Lateral view of the actuated disc prototype is provided in movie S4. (F) Pitch angle θ of the three sections of the biomimetic disc lamellae (actuated by three pairs of actuators) versus the input air pressure P. (G) ESEM image of higher-magnification views of a single biological spinule. (H) Optical microscopy image of a single carbon fiber spinule fabricated by laser machining. Scale bars, 100 μm (G and H).

  • Fig. 2 Lamella kinematics of the adhesive disc in a live remora and a biorobotic disc prototype.

    (A) Dorsal view of a live remora’s adhesive disc (LR represents the distance between two adjacent lamellae of the live remora) and (B) the biomimetic remora disc prototype attached to a transparent glass substrate. The representative marker point A on the lamella moves anteriorly when the lamellae are raised up and moves posteriorly when the lamellae are folded down. The displacement profiles of the representative marker points for the lamellae of a live remora (C) and the biomimetic prototype (D) were provided in the raised state (u = Δd/L, where L represents the distance between two adjacent biomimetic lamellae of the prototype and Δd is the displacement of marker point projected in the x axis shown in fig. S1B, which is calculated by instantaneous x value of marker point subtracting the initial x value of marker point). The original point indicates the initial position of the marker point. Profiles for folding down are provided in fig. S8. (E) Statistical analysis of lamella kinematics for the remora and biomimetic disc. The lamella rotational range of the biomimetic disc (u = 0 to 14.8 × 10−2; indicated by black dashed line) is greater than that found in live remoras for both erect and fold motions and can be actively controlled within that range. (F) Dimensionless amplitude u of the disc prototype versus lamella pitch angle (θ). (G) Schematic view of the lamellae interacting with a substrate. α denotes the angle between the disc lamellae (at the initial fold state) and the horizontal plane, whereas θ denotes the lamella dynamic pitch angle. The contact zone between the lamella soft tissue overlay and the substrate is also illustrated. (H) Contact visualization between the biomimetic lamellae and a smooth substrate from side views. Lamellae are composed of both a rigid material (white) and a soft tissue overlay (translucent). Side view of lamellae with the spinules raised from the initial folded state (u = 0; top) to the erected state (u = 14.8 × 10−2, θ = 16°; bottom) while in contact with a smooth surface. When the lamellae are raised, the marker point A moved to A′ with a displacement Δd (1.04 mm) in the direction of the vector arrows.

  • Fig. 3 Adhesive ability of the biorobotic remora disc prototypes.

    (A) Pull-off force time series (Fd) of the biorobotic disc prototype with artificial spinules on a smooth surface (Ra = 0 μm; black), a real shark skin surface (Ra = 120 μm; blue), and a rough surface (Ra = 200 μm; red). (Inset) Vertically directed pull-off forces (Max. Fd) on three surfaces; colors correspond to those in the time history curves. (B) Posteriorly directed backward frictional forces (fxb) of the disc prototype at different lamella pitch angles θ (0°, 8°, and 16°) on the real shark skin versus time during a representative trial. (Inset) Maximum static frictional forces (Max. fxb) at θ = 0°, 8°, and 16° from left to right. (C to E) Backward frictional forces (fxb) of the biorobotic disc prototypes with both lamellae and carbon fiber spinules (red) and lamellae without the artificial spinules (blue) as a function of θ (0° to 16°) on different surfaces. The dashed gray line represents the control prototype without lamellae and spinules. The blue shaded area indicates the contribution of the soft lamella tissue overlay to the frictional force. The red shaded area indicates the contribution of the rigid spinules to the frictional force. (C) Smooth surface. (D) Rough surface (Ra = 200 μm). (E) Real shark skin surface (I. oxyrinchus; Ra ≈ 120 μm). (F) Anisotropic force (fxbfxf) of the disc prototype with carbon fiber spinules versus θ on the rough surface (green) and the shark skin surface (purple).

  • Fig. 4 Attachment of an underwater vehicle using the biorobotic remora disc.

    (A) The remora disc prototype is connected to the ROV via four springs with low stiffness and four soft silicone pneumatic elastomer actuators. The ROV contains three propellers with a motor power rating of 300 W for each. The mass of the robot is 1.46 kg. (B) Frames of attachment of the robot from movie S6 at various time instants. The ROV with the remora disc prototype performs a successful transition from a swimming mode (propelled by rotors) to the attachment mode (4 s) on a smooth glass surface. For demonstration purposes, we also show the remora disc ROV detaching from the surface and transitioning back into the swimming mode (12 s). For simplification, we used a syringe to pump water into the chamber for balancing the pressure difference between the interior and exterior of the disc chamber for detachment. Scale bar, 50 mm. (C) Remora disc ROV after successful attachment to the surface and attachment against propelling, twisting, and pulling. Scale bar, 50 mm. (D) As with the isolated disc prototype studies, the ROV can successfully attach to various surfaces, including smooth (Plexiglas; left), compliant rough (silicone elastomer; middle), and real shark skin (right). Scale bars, 200 μm.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/10/eaan8072/DC1

    Text

    Fig. S1. Experimental setup for remora locomotion observation during attachment and schematic diagrams of lamella kinematic analysis.

    Fig. S2. Design details of the lamella plates and the artificial spinules.

    Fig. S3. Fabrication procedures of the whole remora disc prototype.

    Fig. S4. Design and fabrication of the soft actuators.

    Fig. S5. Two prototypes (disc with lamellae only without spinules and disc with lamellae and with spinules) tested in this study.

    Fig. S6. Experimental setup of forces and pressure measurements.

    Fig. S7. ESEM images of three substrates and setup for the side-view contact visualization.

    Fig. S8. Dimensionless amplitude of the lamellae’s marker point u versus time for the folding down motions of a live remora and the biomimetic remora disc.

    Fig. S9. The fully ambient pressure differential of the prototype chamber versus the lamella pitch angle (θ) when the disc was attached to a smooth substrate.

    Fig. S10. Pressure of the chamber during a complete pull-off process.

    Fig. S11. Forward frictional forces on the (A) shark skin surface and (B) rough surface (Ra = 200 μm).

    Table S1. Morphological parameters of three individual remoras and their adhesive discs.

    Table S2. Physical parameters of the disc prototype and the lamellae.

    Table S3. Length of the artificial spinule plates of the disc prototype.

    Table S4. Geometry of a single laser-cut biomimetic spinule and the spinule plate.

    Table S5. Stiffness of the components in the biomimetic prototype.

    Movie S1. Demonstration of a remora’s adhesive disc in the microCT data.

    Movie S2. Remora lamella motion recorded by a high-speed camera (erect up and fold down).

    Movie S3. Animation of lamella pitching mechanism.

    Movie S4. Lamella motion of the biomimetic adhesive disc.

    Movie S5. Lamella motion comparison between the biological and biomimetic adhesive disc (erect up and fold down, on the transparent glass surface).

    Movie S6. Demonstration of the underwater attachment of the biorobotic remora disc via an underwater robotic system.

    Movie S7. Demonstration of the biorobotic remora disc gripping a variety of items in air.

    References (4143)

  • Supplementary Materials

    Supplementary Material for:

    A biorobotic adhesive disc for underwater hitchhiking inspired by the remora suckerfish

    Yueping Wang, Xingbang Yang, Yufeng Chen, Dylan K. Wainwright, Christopher P. Kenaley, Zheyuan Gong, Zemin Liu, Huan Liu, Juan Guan, Tianmiao Wang, James C. Weaver, Robert J. Wood,* Li Wen*

    *Corresponding author. Email: liwen{at}buaa.edu.cn (L.W.); rjwood{at}eecs.harvard.edu (R.J.W.)

    Published 20 September 2017, Sci. Robot. 2, eaan8072 (2017)
    DOI: 10.1126/scirobotics.aan8072

    This PDF file includes:

    • Text
    • Fig. S1. Experimental setup for remora locomotion observation during attachment and schematic diagrams of lamella kinematic analysis.
    • Fig. S2. Design details of the lamella plates and the artificial spinules.
    • Fig. S3. Fabrication procedures of the whole remora disc prototype.
    • Fig. S4. Design and fabrication of the soft actuators.
    • Fig. S5. Two prototypes (disc with lamellae only without spinules and disc with lamellae and with spinules) tested in this study.
    • Fig. S6. Experimental setup of forces and pressure measurements.
    • Fig. S7. ESEM images of three substrates and setup for the side-view contact visualization.
    • Fig. S8. Dimensionless amplitude of the lamellae’s marker point u versus time for the folding down motions of a live remora and the biomimetic remora disc.
    • Fig. S9. The fully ambient pressure differential of the prototype chamber versus the lamella pitch angle (θ) when the disc was attached to a smooth substrate.
    • Fig. S10. Pressure of the chamber during a complete pull-off process.
    • Fig. S11. Forward frictional forces on the (A) shark skin surface and (B) rough surface (Ra = 200 μm).
    • Table S1. Morphological parameters of three individual remoras and their adhesive discs.
    • Table S2. Physical parameters of the disc prototype and the lamellae.
    • Table S3. Length of the artificial spinule plates of the disc prototype.
    • Table S4. Geometry of a single laser-cut biomimetic spinule and the spinule plate.
    • Table S5. Stiffness of the components in the biomimetic prototype.
    • References (4143)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Demonstration of a remora's adhesive disc in the microCT data.
    • Movie S2 (.mp4 format). Remora lamella motion recorded by a high-speed camera (erect up and fold down).
    • Movie S3 (.mp4 format). Animation of lamella pitching mechanism.
    • Movie S4 (.mp4 format). Lamella motion of the biomimetic adhesive disc.
    • Movie S5 (.mp4 format). Lamella motion comparison between the biological and biomimetic adhesive disc (erect up and fold down, on the transparent glass surface).
    • Movie S6 (.mp4 format). Demonstration of the underwater attachment of the biorobotic remora disc via an underwater robotic system.
    • Movie S7 (.mp4 format). Demonstration of the biorobotic remora disc gripping a variety of items in air.

    Files in this Data Supplement:

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