For those with amputated forearms, the prospect of having a responsive prosthetic hand and wrist is almost here.
As we’ve previously seen on Bits & Pieces, a number of Makers are increasing the accessibility of bionic devices and assisting amputees regain independence in their daily lives.
A team of Rutgers biomedical engineering seniors — comprised of Mohit Chaudhary, Chris Bargoud, Julian Hsu, James Wong and Rebecca Wenokor — recently sought out to devise what they call a “Brain-Controlled Dexterity Upper Extremity Prosthesis.” The idea of the project, which commenced last September, was to develop a prosthetic hand and wrist that could operate based on brain signals for a fellow classmate.
As one of its creators Chris Bargoud explained, the uniqueness of the project lies within the wrist. The goal was to give the wrist controllable movement that enables various motions, instead of being as static as a majority of wrists on the market today are. He shared, “[Wrists in the market] work like a pin [on the joint between hand and forearm]. You unlock it, rotate your wrist and then lock it. You can’t actually control what you want to do.”
In just a matter of months, the team has already seen tangible results even with a limited amount of time and a budget, thanks in part to the Maker Movement. Using a 3D printer, the students enhanced designs for the hand, constructed its parts, and ultimately, assembled the prosthesis.
The current prototype is attached by strings, along with servo motors in the palm area. By rotating and pulling the cables, the hand’s fingers can move and bend according to its wearer’s needs. The team has its mind set on achieving “three degree-of-freedom,” which are flexion and extension, medial and lateral deviation, and pronation and supination.
“We are focusing on the structure and how to motorize the structure right now. We’ll add on the thumb as well. After our hand is well implemented, we will add on the wrist,” Chaudhary added.
In an effort to have the prosthetic be as anthropomorphic as possible, an OpenBCI open-source device was employed to read a user’s brain and connect with a computer to process the signals. The team plans to program the functions into an Android phone, where Bargoud said the user can click and choose the kinds of motion he wants to perform. Meanwhile, BCI electrodes attached to the brain can pick up a “start this action” command and relay the signal along.
“Even though the name of our project says ‘brain-controlled’, it is more accurately brain initiated,” Julian Hsu suggested.
Both the BCI and the Android phone are connected to an Arduino — a commonality among many of today’s attempts at a next-gen bionic hand like the ATmega32U4 based Youbionic and the ATmega328 powered Bionico Project. The board receives both signals of when to move from BCI and what to do from the Android phone. From there, the Arduino processes the signals and commands the servos to rotate at a specific moment to a certain angle. The servos then drive the gears in the prosthetics to complete the action of the wrist or hand.
“When [the servo] rotates one way, it will pull the string, and when it goes back, we will have rubber bands attached to the back so it will snap it back with the tension,” Bargoud noted.
So what’s next for the team? The Makers plan to continue improving the design, and all agree that the ideal prosthetic hand would be stable, strong, easy to manufacture, user-friendly and as lightweight and realistic as possible.
“Stability is one of our biggest concerns right now… When it is not used at all, we want to make sure it is stable and still, not just flapping around,” Chaudhary concluded, “We also want to make it anthropomorphic, as close to real hand as possible.”
Interested? You can read the entire writeup in the Rutgers campus newspaper here.
