PITTSBURGH (AP) — Giving a high-five. Rubbing his girlfriend’s hand. Such ordinary acts — but a milestone for a paralysed man.

True, a robotic arm parked next to his wheelchair did the touching, painstakingly, palm to palm. But Tim Hemmes made that arm move just by thinking about it.

Emotions surged. For the first time in the seven years since a motorcycle accident left him a quadriplegic, Hemmes was reaching out to someone — even if it was only temporary, part of a monthlong science experiment at the University of Pittsburgh.

“It wasn’t my arm but it was my brain, my thoughts. I was moving something,” Hemmes says. “I don’t have one single word to give you what I felt at that moment. That word doesn’t exist.”

The Pennsylvania man is among the pioneers in an ambitious quest for thought-controlled prosthetics to give the paralysed more independence — the ability to feed themselves, turn a doorknob, hug a loved one.

The goal is a Star Trek-like melding of mind and machine, combining what’s considered the most humanlike bionic arm to date — even the fingers bend like real ones — with tiny chips implanted in the brain. Those electrodes tap into electrical signals from brain cells that command movement. Bypassing a broken spinal cord, they relay those signals to the robotic third arm.

This research is years away from commercial use, but numerous teams are investigating different methods.