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    Biomimicry – The Burr and the Invention of Velcro

    3D Burr - Color 3D Velcro - Gray
    Figure 1. Biomimicry of a burr (Left) for the invention of Velcro (Right).

    Nature has had billions of years to refine itself and develop a plethora of unique structures and functions. Scientists and engineers use what nature shows us to develop some of the most innovative technologies, such as a seahorse tail for a mechanical arm or kingfisher’s bill for a bullet train design. One of the older biomimicry examples is Velcro.®

    About Velcro

    Velcro was invented by George de Mestral in 1941 and was inspired by the burrs he found on himself and on his dog. Being an engineer and entrepreneur, Mr. de Mestral examined the burr under a microscope and realized the small hooks of the burr and loops of the fur/fabric allowed the burr to adhere exceedingly well. This sparked his idea to mimic the structure as a potential fastener. The words velours (French for loop) and crochet (French for hook) were combined to start the Velcro company in 1959. Since then, Velcro has become integrated into daily life and has revolutionized the fastener industry.1

    Micro-CT of a Burr and Velcro

    Here at Micro Photonics, we decided to replicate this investigation of a burr through Micro-CT imaging. Our story begins with some hunting dogs, much in the way George de Mestral began his study. Ann Bagnell at Micro Photonics is an avid dog trainer, and after time in the field one of her Italian Spinone came back with burrs in its coat. Through carefully cutting out the burr, most of the hair remained attached. This is where Micro-CT excels, because we are able to see the internal hooks underneath all the fur. In addition to the burr, we scanned a piece of Velcro to show a comparison.

    The structures that makes a burr so useful are its fine, hook-shaped spikes (See Figure 2). With this high resolution scan at 6.3 microns we can easily see the curved spikes and how well they grasp the dog hair. Comparing this close-up image of the burr to the Velcro sample (Figure 3), you can see the resemblance to the design.

    Close-up of Burr
    Figure 2. Close-up of hook-shaped spikes & entrapped dog hair on a burr.

    Close-up of Velcro
    Figure 3. Close-up of Velcro showing the hook-shaped design.

    Even with the shape being similar there are other aspects of the burr that Mr. Mestral may not have looked at, such as the internal structure of the spike. Using a virtual cut with the CTVox software we were able to see that the spikes are actually hollow (Figure 4). Could this be an improvement to future designs of Velcro? If so, it may provide reduced material cost or possibly strength benefits due to being a hollow rod. Obviously, more research would need to be done but we will leave that to the experts in Velcro.

    Burr - Hollow Spikes
    Figure 4. CTVox virtual cut showing that the spikes are hollow, as noted by the shadow on the inside.

    We hope you enjoyed learning about how Velcro was developed. This example is one of many biomimicry applications that can be investigated with micro-CT to solve some of industries’ toughest problems. If you have an application you would like tested, or are interested in providing a sample for the next image of the month, please e-mail: brandon@microphotonics.com.

    Brasch
    Figure 5: Brasch

    ……………….
    SCAN SPECIFICATIONS

    System
    SkyScan 1272 Micro-CT

    Voltage
    50kV

    Current
    200µA

    Pixel Size
    6.3um

    Rotation Step
    0.2

    Scan Time
    01:27:23 (HH:MM:SS)

    Software
    NRecon, DataViewer, CTVox

    Location
    Micro Photonics Imaging Laboratory, Allentown, PA

    Works Cited
    1. Hooked on Innovation. (2016). WIPO.
    Retrieved from: http://www.wipo.int/ipadvantage/en/details.jsp?id=2658

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