Born armless, the 11-year-old's prosthetic arms are activated when she flexes her back and chest muscles.
Diamond Excell was born without arms and without full use of muscles where her shoulders would have connected to them.
So she learned how to brush her teeth, write and pick up small objects with her feet.
But on Wednesday, the 11-year-old girl used newly fitted "bionic" arms to give her mother something that had been out of reach until recently: a hug.
"It felt so good," said Delia Excell. "Words can't even express the way I felt when she hugged me with those arms."
After a few test fittings, Diamond went home Wednesday with her new electronic limbs, after showing them off to the media and supporters, who helped raise about $60,000 toward their $70,000 cost. The arms will require retoolings as Diamond grows.
Ivan Yaeger, 33, who once designed an artificial limb in junior high school for a science project, used existing electronics and off-the-shelf parts to design Diamond's arms.
He then teamed up with Eugene Silva, a board-certified prosthetist at Advanced Motion Control Inc., to build and test the arms.
The hands are covered with molded latex textured to simulate a real hand, with fingernails and tone that match Diamond's skin color.
The rest of the arm is covered with stocking net material and has some padding underneath to protect the electronics and cables inside.
Yaeger said that once Diamond masters the use of the arms, he will give them a more lifelike covering.
Diamond was born without some of the muscles that connect arms to shoulders, so Yaeger and Silva had to devise ways for the girl to operate the arms with other muscles in her body.
Each arm has three motors to open and close three joints. The motors are activated by signals that the brain generates when a muscle is flexed.
By twitching a group of back muscles, Diamond can open the joints. She closes them by flexing her chest muscles. Two sensors mounted on the harness that holds the arms to her torso allow her to switch between each joint.
She demonstrated her new dexterity to reporters by hooking her thumb through the handle of a small bag, closing her hand and picking it up.
"It . . . was easy," she said.
When prompted to hug her mother before the cameras Wednesday, Diamond attempted to trigger a motion with her arms as she joined in the embrace. Her wrists moved, oddly turning the palms of her hands outward.
"Time will tell, when she gets therapy in the future, what she can do with her arms," her mother said. "She's strong and determined, and she has given me strength."
Yaeger said he planned to approach manufacturers to further develop the arms' design.