- Smorph ball (Image: Denis Terwagne and Pedro Reis (MIT))
- dn25809-1_300[1].jpg (5.71 KiB) Viewed 2680 times
The surface, dubbed Smorph for Smart Morphable Surface, relies on simple mechanics to achieve this effect. "We use wrinkling," says Pedro Reis of the Massachusetts Institute of Technology, who leads the project.
The team has created a prototype out of silicon (see photo). The hollow ball is wrapped in a very thin, stiff layer of polystyrene. Lowering the pressure inside the ball causes the outer skin to wrinkle as the ball contracts, in the same way the skin of a prune does as the inner flesh dries and contracts.
Reis found that these wrinkles could be made into a dimple pattern, similar to those placed on golf balls to decrease their drag. As dimple depth on the material changes with the internal pressure, this means it can be altered to give the best aerodynamics for the conditions. At some wind speeds, Reis's altered dimples reduced drag by a factor of two.
So far, the researchers have only created a spherical Smorph, but Reis says he is working on creating the same effect in different shapes – the wing of an aeroplane or the bonnet of a car, for instance.
Jonathan Morrison, who studies aerodynamics at Imperial College London, says the aerospace industry is already looking into adaptive surfaces to reduce drag. A crude form already exists in the form of flaps and slats on an aeroplane's wing. "The idea with adaptive tech is that rather than all these moving surfaces, you just change the shape of the wing," he says.
Journal reference: Advanced Materials, doi.org/tf6