First Man to Control Bionic Leg with Thoughts
Recently, a 32-year-old man who lost his leg below the knee after a motorcycle accident four years ago now has a robotic prosthesis that he can control with his mind.
Similar technology has allowed amputees to control bionic arms with their thoughts i.e. Zac Vawter is the first amputee with a thought-controlled bionic leg.
This robotic leg which decodes the electrical signals traveling through Vawter's remaining leg muscle not only interprets the patient's intended movements but also has a motor in the knee and ankle, which helps him push himself up stairs and perform other activities. This robotic leg allows Vawter to seamlessly transition between walking, sitting and ascending, descending stairs and ramps.
Technology that uses lower-leg prosthetics today are passive like a spring which means people with those devices have to use their intact limb to pull the prosthetics behind them and the lower leg prosthetics that do have motors are either controlled by a remote or require the patient to perform exaggerated movements (like kicking their leg very far back) before changing activities.
How it works?
According to Vawter his thought-controlled robotic leg and responds much more appropriately to the environment and where he wants to go and how he wants to walk, for example: when wearing a conventional prosthetic and walking up stairs he has to put the same foot first on each step he climbs whereas with this leg it's more so that he just interact with my environment how a normal person would and can walk up stairs foot over foot. As soon as a person thinks about moving their lower limb a signal from the brain is sent down the spinal cord and through nerves to muscles in the leg.
When an amputation occur nerve signals that would have gone to the knee or ankle for instance aren't able to deliver their message to muscle. So, to overcome this problem the researchers first performed a surgery on Vawter to redirect his nerve signals so that signals that would have gone to the lower leg instead go to the healthy hamstring muscle in the top part of his leg.
The electrodes were placed on leg to detect electrical signals from the muscle contractions. Computer program decodes the signals to interpret the patient's movement; mechanical sensors on the robotic leg (including an accelerometer and a gyroscope) also collect data to help with control.
By using the robotic leg Vawter was able to walk on level ground or go up ramps and stairs and transition between these activities without stopping, he was also able to use his thoughts to change the position of his lower leg while sitting down something that cannot be done with current motorized leg prosthetics.
Researchers want to make the robotic leg quieter, smaller and stronger and reduce the error rate further. This study was funded by an $8 million grant from the U.S Army and the goal is to make this technology available to servicemen and women as well as civilians.