Bent out of shape

Engineers at MIT have brought Professor Pat Pending’s Covert-a-Car from Wacky Races a step closer to reality by developing materials for vehicles that can morph to suit their environment.



The researchers have looked to the properties of rechargeable batteries to develop a new material that can change shape according to requirements. Aeroplane wings could adjust mid-flight to use thermals to increase fuel efficiency and boat hulls could change shape for different water conditions.



Yet-Ming Chiang, the Kyocera professor in the Department of Materials Science and Engineering (MSE) noticed that lithium rechargeable batteries expand and contract as they are charged and recharged. “”This has generally been thought to be something detrimental to batteries. But I thought we could use this behavior to another end – the actuation, or movement, of large-scale structures,” he said.



Chiang realised that ion flow through the solid compounds in batteries could be made to behave in a similar way to plants, which use fluid mechanics to move towards light. He and his team designed their own moving batteries out of graphite posts surrounded by a lithium source.



The result is a battery-based actuator that can pull and push with great force, but which operates at low voltages. The components are also very light and can work under tremendous stresses, essential for use in aircraft.



Later this year, Chiang’s team hopes to demonstrate shape-morphing helicopter rotor blades. These could allow for a more efficient design and ultimately carry heavier loads.