Robert Downey Jr. surprises young disabled boy by giving bionic arm as Iron Man character

The arm was developed by a student who created 3D printed limbs

Robert Downey Jr. and Albert Manero, a #CollectiveProject student who founded Limbitless, surprised a very Alex with a new bionic 3D printed arm. (officevideos/YouTube)

A disabled young boy who loves superheroes was given a shock when Iron Man actor Robert Downey Jr. gave him a bionic arm.

A heart-warming video of the encounter explains that Alex, 7 -who adores superheroes and riding his bike - was born with a partially developed arm.

It then shows an unwitting Alex being lead into a hotel room, where Downey Jr. is waiting in character as Iron Man engineer Tony Stark.

Alex is visibly shocked and can’t stop smiling as the actor introduces himself as a bionic expert.

Asked whether he knows who he’s meeting, he grins and says “Iron Man”. But Downey Jr. is rumbled when Alex declares the man he’s meeting isn’t Tony Stark, but “Robert.”

The actor then unveils Alex’s new bionic arm, as well as an Iron Man-style model for himself.

The arm was created by Alberto Manero, a Fulbright scholar and doctoral student in mechanical engineering at the University of Central Florida, who builds and donates low-cost limbs to children around the world.

The arm cost just £235 ($350) in materials to make, according to Microsoft's The Collective Project which showcases the work of students making positive changes for their communities.

In comparison, traditional false limbs can cost as much as £26,900 ($40,000).

Undeterred by being exposed by the 7-year-old, Downey Jr. continues to act in character, and jokes in the video: “Albert has made it so affordable that I’m going to start farming out a lot of my tech work to Albert too.

"I feel he could cut the price points down on one of my suits by I guess about $1.5billion dollars.”

In a caption alongside the video on his Facebook page, Downey Jr. wrote: “Had the absolute privilege of presenting a brand spanking new 3D-printed bionic Iron Man arm to Alex, the most dapper 7-year-old I’ve ever met."