HRL Laboratories has figured out how to replicate the rapid stiffening and softening of human muscle in metal. The technology could be used to create the ultimate automotive suspension, or give a robot the strength and sensitivity of a person.

Principal Investigator Christopher Churchill breaks down how the company’s “tunable variable stiffness” tech works:

HRL says their setup can change from stiff to soft by a factor of 100 in milliseconds, independent of the load it’s carrying.


Now of course variable stiffness already exists in your car’s shock absorbers; they’re firm while stopped but bendy when you go over bumps. Adjustability also exists already in this space; car shocks can be set to “hard” or “soft” depending on what sort of performance is desired.

Newer tech like GM’s magnetic ride suspension takes that even further; controlling the stiffness of a hydraulic shock with magnetized flakes of metal.

HRL’s concept is interesting because it’s mechanical, and simple.


It’s really just strips of metal that are precisely balanced in series. That gives it a huge potential range of applications; cars, trains, robot arms that could pet a kitten gently and then pick up an engine.

“Advanced lightweight materials are increasingly finding their way into transportation platforms to achieve low mass and high stiffness,” Churchill said in a press release. “Utilizing adaptive negative stiffness to soften stiff systems on demand has the potential to solve shock and vibration problems that only get more difficult with these next-generation platforms.”


It will be interesting to see this tested outside the laboratory. I’m imagining the ultimate on-road/off-road vehicle fitted with something like this.


Images via HRL Laboratories

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