This High Schooler Invented a Low-Cost, Mind-Controlled Prosthetic Arm

Seventeen-year-old Benjamin Choi put his spare time during the pandemic to good use designing anaccessible device that doesn’t require brain surgery

Ten years ago, when Benjamin Choi was in third grade, he watched a “60Minutes” documentary about a mind-controlled prosthesis.Researchers implanted tiny sensors into the motor cortexof the brain of a patient who moved a robotic arm using only her thoughts. Choiwas fascinated by the concept, likening it to something out of a Star Wars movie.

“I was really, really amazed at the time because this technologywas so impressive,” he says. “But I was also alarmed that they require thisreally risky open brain surgery. And they're so inaccessible, costing in thehundreds of thousands of dollars.” Years later, when the pandemic hit in 2020, Choi—a tenth grader living inVirginia—suddenly found himself with ample free time.

In his makeshift laboratory on the ping-pong table in his basement(where he sometimes worked 16 hours a day!), Choi independently designed thefirst version of his robotic arm using his sister’s $75 3-D printer and somefishing line. The printer couldn’t build pieces over 4.7 inches in length, soChoi printed the arm in tiny pieces and bolted and rubber banded it together.In total, it took about 30 hours to print. This version worked using brain wavedata and head gestures, and Choi posted instructions online for anyone to build theirown.

He had some previous experience building robots and coding fromparticipating in competitive robotics at the elementary, middle school and highschool levels, even going to the world championships several times. Starting inninth grade, he taught himself the computer programming languages Python andC++ by watching videos on Stack Overflow, a website for programmers.

Aftermore than seventy-five design iterations, Choi’s non-invasive, mind-controlledrobotic arm is now made from engineering-grade materials able to withstandweights up to about four tons. It operates using an algorithm driven byartificial intelligence (A.I.) that interprets a user’s brain waves. And itonly costs around $300 to manufacture—a huge savings compared to what’scurrently on the market. A more basic, body-powered upper limb prosthesis costsabout $7,000.As of 2015, the very advanced, full-arm Modular Prosthetic Limb, which has 26joints, hundreds of sensors and can curl up to 45 pounds, cost about $500,000. This prosthesis, paired with a surgeryto reroute nerves that once controlled the arm, allows patients to command thelimb with their thoughts and even feel texture through it.

The invention earned Choi, now a 17-year-old senior at the PotomacSchool in Virginia, a spot in the top 40 finalists of this year’s Regeneron Science TalentSearch, the country’s oldest and most prestigious science and mathcompetition for high school seniors. This year’s first place winner wasChristine Ye from Sammamish, Washington, who developed a way to analyze the gravitational wavesemitted from collisions between neutron stars.

“It means a lot to me to see that my work is recognized likethis,” Choi says. “I'm definitely very grateful to be a finalist.”

An estimated 2 million people are living with the lossof a limb in the United States, and about 185,000 amputations occur every year.The World Health Organization states only onein ten people who need assistive products, including prosthesisand orthoses, have access to them, citing “high cost” and a “lack of awareness,availability, trained personnel, policy and financing.”

Choi’s arm uses electroencephalography, or EEG, to avoid theinvasive techniques of other prostheses. EEG devices record the brain’selectrical activity using sensors placed on the head.

They are often used in medicine to diagnose epilepsy or otherbrain disorders.

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