- DNA molecules, roots and tendrils of plant often assume shape of a helix by twisting in a left or right hand direction, but when scientists conducted an experiment on a pair of rubber ribbon, it started twisting in one direction and then reversed its direction (perversion) to form a hemihelix.
- Researchers at Harvard University have found out that occurs due to elastic instabilities. They used 2 strips of an elastic polymer of equal lengths, stretched the shorter one to the same length as the other. When these two strips were joined side-by-side while maintaining the stretching force, the bi-strip twisted to form either a helix or a hemihelix.
- The strip twists to reduce the load it bears and imperfections in the material world cause it to buckle at certain places resulting to perversions at these points.
- The shape formed is not a function of the materials preferred mode of deformation, but determined by its aspect ratio: ratio of its length to width, with hemi helices preferred for lower aspect ratios when buckling loads increase. The number of perversions increased when the ratios were around or under 1, and helices were formed for ratios above 3.
- This indicates that complex 3D shapes can deterministically be manufactures from flat structures by application of simple forces, as seen in industries where sheet metal is beat into the chassis of a car.
- Potential applications include 3D electromagnetic wave-guides and mechanical, thermal and chemical sensors.
- Read at: http://www.thehindu.com/todays-paper/tp-features/tp-sci-tech-and-agri/engineers-find-the-helixs-twisted-cousin/article5941923.ece
Exams Perspective:
- DNA
- Hemi helix
- Watson & Crick Model
- Double helix
- Electromagnetic Waves
- 3D