July 28, 2015 | By Simon

Without question, the use of 3D printing for creating low-cost and customized prosthetics and other personalized medical aides has been one of the best examples of how the technology can be used for real-world applications.

But for all of the developments that we’ve seen for customized prosthetic arm devices, there are dozens of different ailments that can affect different patients with different symptoms including specifically hands and fingers rather than an entire arm. Among others, a large number of stroke victims are unable to use their fingers effectively and rely on physical therapy in an effort to regain mobility in their hands.

More recently, Daniel Levy, a design engineer, created a 3D printed open-source exoskeleton that is designed to help stroke victims or patients with lack of finger movement regain mobility in their hands.

"I am part of a research team at Lehigh Universities Mountaintop Program." explained Levy to 3Ders. "The program gives us the freedom and space to let us work on whatever we desire for 10 weeks with a $1,500 budget per person, with little to no supervision or regulations."

Levy - along with a team of four other members including Jeff Peisner, Elena Ramirez, Emily Macmillan and Nan He - improved upon the design and ultimately created a device that uses the motion of the wrist to open and close the fingers.

“I was drawn to the project because I have always loved 3D printing and prototyping/designing,” Levy explained.

Levy was inspired to develop the exoskeleton design after the brother of a friend suffered a spinal injury and was unable to regain hand function.

“One of the saddest and most memorable instances, and major motivation for this project, was when I went to give him a friendly handshake to say hello and all he could do was lift up his hand to offer a fist bump,” said Levy.

“That moment, I realized how different his life must be, and how hard it is for him to do simple tasks.”

"The design from the year before was aimed at using the motion of tenodesis and using the motion of the wrist to move/curl the fingers. I wanted to use this idea to design a device that patients can use to actually pick objects up that they otherwise would not have the strength to grasp," said Levy.

Starting by examining how his own wrist moved up and down while simultaneously affecting the finger tendons, Levy began modeling some early stage concepts in SolidWorks and printed them out along the way in an iterative design process to further test his mechanical theories. Once he found the ideal design direction, he centered the design around three parameters that would make the device as useful as possible for as many users as possible: customization, comfort and convenience.

“People suffering from strokes or spinal injuries often recover from the torso-out, meaning they will regain movement in their shoulders, then elbows, then wrists, and then fingers,” explains Levy.

“Many patients never get full use of their fingers back, but they do get full movement of their wrists. There are 2 main uses for the design. The first is functional use, where the device will assist the patient in grasping an object they otherwise did not have the finger strength to pick up. The second is at home rehabilitation use, where the patient will wear the device and repeat the wrist motion many times over. This repetitive rehabilitation uses the idea of neuroplasticity, where repetitive assisted motion will generate new connections in the brain and eventually allow the patient to move their limbs unassisted.”

Throughout the design process, Levy continued to visit his friend’s brother in order to get detailed feedback on the design, which was then used to further refine the design direction.

According to Levy, the Mountaintop Program provided Makerbot Replicator 2 and Ultimaker 2 3D printers for him to test his prints on. While the collars, which were made from Ninjaflex, were made on the MakerBot Replicator 2, the remainder of the pieces were made using Ultimaker 2 3D printers. The majority of the pieces were each made with a 100% infill in order to increase the strength and the total print time for each of the pieces was 18-20 hours max.

Similar to his earliest prototypes, Levy’s final Spiderhand design uses a motion of the wrist to perform an open and close motion of the fingers. Because no two users are the same, the hand has been designed to be customized in two ways: First, the metal rods can be twisted to adjust the length between the forearm piece and the finger piece. They have an adjustable range of 2 inches, making it suitable for almost any hand size, and each finger can be adjusted separately. Second, each of the NinjaFlex collars can be taken out individually and be resized and printed without the need to reprint the entire exoskeleton assembly.

"I am currently working on a few other sizes to put up on thingiverse. A thumb piece has been designed by another teammate (Elena Ramirez). It's job is to keep the thumb rigid to allow the fingers or objects to put pressure on it. It is also adjustable to make the grip wider or smaller, depending on the size of the patient's hand and object they are grasping," added Levy.

“As for how well it works, I can tilt my wrist back to close my fingers, and even as I am trying to spread my fingers open, I can still pick up objects,” says Levy.

“That being said, I have full finger function and have only tested an earlier prototype on my friend. The earlier version was not fitted to his hand and it was only of the index finger, but he could open his finger further, and pick up objects larger than he could have otherwise. I hope to test the newest version on him in the next two weeks or so.”

Currently, Levy’s goal is to get the device into the hands (literally) of as many users as possible so that he can gain even more feedback to make the design more universal for a wider variety of users and needs.

“My vision is to have these open-sourced to everyone, and also have a website/email where people can contact me and I can sell them a custom design if they would prefer.”

Ultimately, Levy would love to establish a line of exoskeleton designs - along with his talented team members - where each of the designs could be custom built for users or downloaded and printed.

With a year left to go at Lehigh University in their Mechanical Engineering and Entrepreneurship (he has even started a beef jerky business) program, Levy is certainly on his way to success.

For those interested in creating their own exoskeleton hand, Levy has uploaded the necessary STL files on a Thingiverse project page. He is also hoping to make an instructional video for assembling the design and how to use in the very near future.

Posted in 3D Printing Applications

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