There are many other possible applications. For example, research is being conducted on sensors embedded in socket liners, which hold the prosthesis to the residual limb, that will automatically adapt to fluctuation in body volume. Self-adjusting sockets would make the device more comfortable and prevent sores, bruises and other complications. Similar sensor technology could also enable artificial feet to stiffen or relax to adapt to changing resistance and speed, making it possible to use the same device for a variety of activities.

The biggest obstacle yet to be overcome is replicating the complexity of the entire range of limb movement with existing technology. While great strides have been made, there are a number of inter-related factors, such as power, response speed, range of motion, weight and durability, that still must be resolved. The ultimate goal in solving these problems is the complete integration of mind, body and machine.

The Ghost in the Machine

In 2000, Dr. Miguel Nicolelis, a neurobiologist at Duke University Medical Center, trained a monkey to move a robotic arm using thoughts transmitted through electrodes implanted in its brain. Recent experiments show the technique may work in humans as well. The key is to identify the neurons that are activated when someone consciously thinks about a movement and then performs it. Studies show that these brain cells remain active even in amputees.