Ferrofluid GIF

[KickStart]

My intro to something very similar to ferrofluid was via a prosthetic microprocessor knee from Ossur called the Rheo. It uses magnetorheological fluid in a swiveling arrangement (as a knee). It uses electromagnetism, along with the microprocessor to tailor movement resistance similar to muscle movement resistance. RheoKnee has very nice action, and my only issue with it is that it tended to default to freeswing rather than stiff if the battery went dead. But that's a personal comfort level, and there are many above-knee amputees out there successfully walking very well with it. I sent mine to a fellow biker in the Midwest who does construction because his insurance wouldn't pay for one.