Mar.28, 2012

If you have ever heard of Hoberman sphere or Hoberman Twist-O, you can skip the video below - one of Chuck Hoberman's best-known museum pieces, the original Hoberman Sphere was installed in 1992 as the central exhibit in the Liberty Science Center's atrium.

A Hoberman sphere is a structure invented by Chuck Hoberman that resembles a geodesic dome, but is capable of folding down to a fraction of its normal size by the scissor-like action of its joints.

Inspired by the Hoberman Twist-O, a group of engineers at MIT and Harvard University created the "buckliball," a 3D-printed hollow and spherical object. Made of soft rubber, the buckliball contains no moving parts but covered with 24 carefully spaced dimples.

When the air in the buckliball is sucked out the spaces between lateral dimples collapse. Actually when the buckliball's thin ligaments buckle, the thicker ligaments move simultaneously - some rotate clockwise, others counterclockwise. When it is closed entirely the buckliball has only about half the size of the original sphere.

The name buckliball comes from its use of buckling and its resemblance to buckyballs, spherical all-carbon molecules whose name was inspired by the geodesic domes created by architect-inventor Buckminster Fuller.

"In civil engineering, buckling is commonly associated with failure that must be avoided. For example, one typically wants to calculate the buckling criterion for columns and apply an additional safety factor, to ensure that a building stands, says Pedro Reis, the Esther and Harold E. Edgerton Assistant Professor of Civil and Environmental Engineering and Mechanical Engineering at MIT. "We are trying to change this paradigm by turning failure into functionality in soft mechanical structures. For us, the buckliball is the first such object, but there will be many others."

The buckliball is the first morphable structure can be used in engineering design. The awesome part of this design is that the sphere is fully reversible and can revert back to its original exploded state without a degradation in structural integrity. It is possible to use the buckliball for a widespread applications, such as to design large buildings with collapsible roofs or walls, or to make tiny drug-delivery capsules, not to mention many applications to design a new kind of Transformer toy.

Our nature has already used a similar design. Viruses inject their nucleic acids into a host through a reversible structural transformation in which 60 holes open or close based on changes in the acidity of the cell's environment, a different mechanism that achieves a similar reversible collapse at the nanoscale.

"The buckliball not only opens avenues for the design of foldable structures over a wide range of length scales, but may also be used as a building block for creating new materials with unusual properties, capable of dramatic contraction in all directions," says Katia Bertoldi, an assistant professor in applied mechanics at Harvard.

The findings were published in the journal Proceedings of the National Academy of Sciences.

Source MIT

Posted in 3D Printing Applications



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