Technically, the apparatus is an untethered, upper-body exoskeleton; to the layman, it is essentially a battery-powered arm brace attached to a backpack, which can carry an additional 18kg.

Either way, Titan Arm's cost-efficient design has won the team accolades and at least US$75,000 in prize money.

"They built something that people can relate to," said Robert Carpick, chairman of Penn's mechanical engineering department. "And, of course, it appeals clearly to what we've all seen in so many science-fiction movies of superhuman strength being endowed by an exoskeleton."

The project builds on existing studies of such body equipment, sometimes called "wearable robots". Research companies have built lower-body exoskeletons that help paralysed people walk, though current models are not approved for retail and can cost US$50,000 to US$100,000.

The Penn students were moved by the power of the concept - restoring mobility to those who have suffered traumas - as well as the idea of preventing injuries in those who perform repetitive heavy lifting tasks, said team member Nick Parrotta.

"When we started talking to physical therapists and prospective users, or people who have gone through these types of injuries, we just kept on getting more and more motivated," said Parrotta, now in graduate school at the university.

Parrotta and classmates Elizabeth Beattie, Nick McGill and Niko Vladimirov set out to develop an affordable, lightweight suit for the right arm.

The final product cost less than US$2,000 and weighs 8kg - less than the backpack that Beattie usually carries. A handheld joystick controls motorised cables that raise and lower the arm; sensors measure the wearer's range of motion to help track rehab progress.

Since it was unveiled, Titan Arm has won the US$10,000 Intel Cornell Cup USA and US$65,000 James Dyson Award.