– His arms paralyzed by a rare virus three years ago, Max Ng has struggled to push, pull and poke his way through the world with the gleeful ease that most 5-year-olds enjoy.

But a device built by four University of California, San Diego, engineering students delivers just the help he needs.

At Rady Children’s Hospital, Max was strapped into a pair of motor-assisted orthotic braces, his fingers sliding into sensor-loaded gloves. Once the contraption was in place, tilting his wrist up caused his arm to raise, bending at the elbow. Tilting down accomplished the opposite motion, and Max was quick to start roughhousing with his father, Dr. Ted Ng. “One of the things I missed the most is him just grabbing me for a hug,” Ted Ng said.

Max is one of more than 500 kids who have experienced such symptoms since 2014. His condition, called acute flaccid myelitis, is thought to be caused by infection from viruses in the same family as the germ that causes polio.

Dr. Andrew Skalsky, a rehabilitation medicine physician, said Max is rare among AMF patients. He retained full control of the muscles in his wrists and hands even as loss of the motor nerves attached to the major muscles in his arms and shoulders have atrophied. Wrist and finger dexterity intact, Max has developed clever ways to raise his arms, pushing them up with his knees to bring his hands close to what he wants to grasp. But certain tasks, such has hugging his parents or young sister, were still out of reach.

Existing braces, with beefy frames and large motors, have been too heavy. Because no two AMF patients experience exactly the same issues, there was no real incentive for a company to invent the right product. A custom solution was needed, and Skalsky thought he knew just how to get the job done.

In September, he submitted an application to UCSD’s engineering school, which requires all mechanical and aerospace engineering seniors to complete a capstone course, teaming up to solve real-world problems. Through rapid prototyping, using 3-D printers and computer simulation, a team of four students was able to make prototype after prototype until they had something that worked well enough to be machined in lightweight aluminum and sewed together by a professional seamstress.

The team used ultralight motors capable of generating enough force to lift more than a pound while weighing only about as much as a ballpoint pen.

“This is what is called human-centered design,” student Marcos Serrano said. “It was very important not just for it to work, but he had to be able to get it on and off easily, and he had to be able to actually use it.”