Smart Fluid
From: NASA Tech Briefs

Physical rehabilitation has traditionally consisted of painstakingly
retraining the body on weight machines and other resistance devices, but with
the growing interest in "smart fluids," Northeastern University engineering
professor Constantinos Mavroidis envisions a simple brace that can increase
the resistance on a healing joint with the turn of a dial. 

"Smart fluids" is a generic term for any particle-filled, oil-based
suspension that changes consistence in a magnetic or electric field.
Mavroidis is working with electro-rheological fluids (ERFs) which change from
liquid to solid the instant an electric field is applied; remove the field
and the paste-like substance reverts to liquid form. 

Applications for ERFs include automotive technology and industrial uses, and
Mavroidis and his co-researchers have developed prototypes for a leg brace
that could increase pressure on a joint simply by increasing the voltage from
a small battery. Plans are underway to begin human trials this fall in
association with Spaulding Rehabilitation Hospital in Boston. 

For more information, visit: http://link.abpi.net/l.php?20040603A6