Real Iron Man

What do you get when you combine a teenager, Lego pieces and the internet?

A functional prosthetic arm and hand, of course.

Easton LaChappelle might only be in his senior year of high school, but the 17-year-old from Colorado, US, has already made strides in science and technology.

LaChappelle - invited to South Africa by the SA Institute of Electrical Engineers - wowed the audience when he spoke at Wits University last night.

His passion for electronics led him to build a hand using Lego pieces, fishing line and servo motors in 2010.

"All I was doing was taking things apart and putting them back together, then putting them elsewhere," he said.

"It was all very cool for me - I did not even think or know that it would work."

The project earned him third prize at the Colorado State Science Fair in 2011 - at which he met a seven-year-old girl wearing a prosthetic arm that cost $80000 (now nearly R800 000).

This, and talking to other paraplegics, motivated him to create a cheaper alternative for about $250 (R2500).

But the self-taught robotics prodigy, who has been described as the "real-life Tony Stark" - after Robert Downey jnr's character in Iron Man - is far from finished.

He is developing a third-generation model of his robotic limb, known as the "Arduino Robotic Arm".

The 2kg arm is being designed to lift as much as 70kg.

His mother, Julia Whelihan, said she was proud of how "normal, mature and balanced" her son had grown up to be.

"He came back from meeting President Barack Obama in Washington DC and headed straight to his prom," she said.

The engineering institute's business director, Stan Bridgens, is fascinated by the ability of LaChappelle to push boundaries .

"It's exciting to meet someone who went beyond the education system by thinking, learning and acting for himself," he said.