Smart fluids for the knee

Strengthening a knee after injury often require hours on the machines of a hospital or gym. But Constantinos Mavroidis, a mechanical engineer at Northeastern University, has devised a portable device that people can strap onto their knees to rehabilitate them as they walk around.

It’s basically an off-the-shelf knee brace with small, tightly sealed containers added to either side of the brace at the knee.

The containers are filled with small plates and a “smart” fluid that changes from liquid to gel when it is zapped by electricity.


When a computer-controlled voltage is sent to the plates, an electric field is created and the fluid grows viscous. As the knee flexes and the plates rotate relative to one another, resistance is created.

“It’s basically a weight-lifting machine that you can slap on your leg,” said Jason Nikitczuk who worked on the project. “You can adjust how much weight you are applying, just like you change weights on a machine.”

Mavroidis hopes that his invention may one day find use for long trips in space which cause significant loss in the bone and muscle mass of astronauts, and they might wear his device during their daily activities to strengthen their legs.

Via Globe and Mail.