• New soft robot material to morph from gr

    From ScienceDaily@1:317/3 to All on Wed Feb 9 21:30:36 2022
    New soft robot material to morph from ground to air vehicle using liquid
    metal

    Date:
    February 9, 2022
    Source:
    Virginia Tech
    Summary:
    Researchers have developed a new approach for shape changing at
    the material level. They use rubber, metal, and temperature to
    morph materials and fix them into place with no motors or pulleys.



    FULL STORY ========================================================================== Imagine a small autonomous vehicle that could drive over land, stop,
    and flatten itself into a quadcopter. The rotors start spinning, and the vehicle flies away. Looking at it more closely, what do you think you
    would see? What mechanisms have caused it to morph from a land vehicle
    into a flying quadcopter? You might imagine gears and belts, perhaps a
    series of tiny servo motors that pulled all its pieces into place.


    ==========================================================================
    If this mechanism was designed by a team at Virginia Tech led by Michael Bartlett, assistant professor in mechanical engineering, you would see a
    new approach for shape changing at the material level. These researchers
    use rubber, metal, and temperature to morph materials and fix them into
    place with no motors or pulleys. The team's work has been published in
    Science Robotics.

    Co-authors of the paper include graduate students Dohgyu Hwang and
    Edward J.

    Barron III and postdoctoral researcher A. B. M. Tahidul Haque.

    Getting into shape Nature is rich with organisms that change shape to
    perform different functions.

    The octopus dramatically reshapes to move, eat, and interact with its environment; humans flex muscles to support loads and hold shape;
    and plants move to capture sunlight throughout the day. How do you
    create a material that achieves these functions to enable new types
    of multifunctional, morphing robots? "When we started the project, we
    wanted a material that could do three things: change shape, hold that
    shape, and then return to the original configuration, and to do this
    over many cycles," said Bartlett. "One of the challenges was to create
    a material that was soft enough to dramatically change shape, yet rigid
    enough to create adaptable machines that can perform different functions."
    To create a structure that could be morphed, the team turned to kirigami,
    the Japanese art of making shapes out of paper by cutting. (This method
    differs from origami, which uses folding.) By observing the strength of
    those kirigami patterns in rubbers and composites, the team was able to
    create a material architecture of a repeating geometric pattern.



    ========================================================================== Next, they needed a material that would hold shape but allow for that
    shape to be erased on demand. Here they introduced an endoskeleton made of
    a low melting point alloy (LMPA) embedded inside a rubber skin. Normally,
    when a metal is stretched too far, the metal becomes permanently bent,
    cracked, or stretched into a fixed, unusable shape. However, with this
    special metal embedded in rubber, the researchers turned this typical
    failure mechanism into a strength.

    When stretched, this composite would now hold a desired shape rapidly,
    perfect for soft morphing materials that can become instantly load
    bearing.

    Finally, the material had to return the structure back to its original
    shape.

    Here, the team incorporated soft, tendril-like heaters next to the
    LMPA mesh.

    The heaters cause the metal to be converted to a liquid at 60 degrees
    Celsius (140 degrees Fahrenheit), or 10 percent of the melting temperature
    of aluminum.

    The elastomer skin keeps the melted metal contained and in place, and
    then pulls the material back into the original shape, reversing the
    stretching, giving the composite what the researchers call "reversible plasticity." After the metal cools, it again contributes to holding the structure's shape.

    "These composites have a metal endoskeleton embedded into a rubber with
    soft heaters, where the kirigami-inspired cuts define an array of metal
    beams. These cuts combined with the unique properties of the materials
    were really important to morph, fix into shape rapidly, then return to
    the original shape," Hwang said.

    The researchers found that this kirigami-inspired composite design could
    create complex shapes, from cylinders to balls to the bumpy shape of
    the bottom of a pepper. Shape change could also be achieved quickly:
    After impact with a ball, the shape changed and fixed into place in less
    than 1/10 of a second. Also, if the material broke, it could be healed
    multiple times by melting and reforming the metal endoskeleton.

    One drone for land and air, one for sea The applications for this
    technology are only starting to unfold. By combining this material with
    onboard power, control, and motors, the team created a functional drone
    that autonomously morphs from a ground to air vehicle. The team also
    created a small, deployable submarine, using the morphing and returning
    of the material to retrieve objects from an aquarium by scraping the
    belly of the sub along the bottom.

    "We're excited about the opportunities this material presents for multifunctional robots. These composites are strong enough to withstand
    the forces from motors or propulsion systems, yet can readily shape morph, which allows machines to adapt to their environment," said Barron.

    Looking forward, the researchers envision the morphing composites playing
    a role in the emerging field of soft robotics to create machines that
    can perform diverse functions, self-heal after being damaged to increase resilience, and spur different ideas in human-machine interfaces and
    wearable devices.

    This project was funded through Bartlett's DARPA Young Faculty Award
    and Director's Fellowship.

    ========================================================================== Story Source: Materials provided by Virginia_Tech. Original written by
    Alex Parrish. Note: Content may be edited for style and length.


    ========================================================================== Related Multimedia:
    * Video_and_images_of_morphing_material ========================================================================== Journal Reference:
    1. Dohgyu Hwang, Edward J. Barron, A. B. M. Tahidul Haque, Michael D.

    Bartlett. Shape morphing mechanical metamaterials through
    reversible plasticity. Science Robotics, 2022; 7 (63) DOI: 10.1126/
    scirobotics.abg2171 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220209154810.htm

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