Apr 14, 2016 | By Tess

Perhaps one of the most inspirational recent uses of 3D printing has been the development and creation of a number of custom fitted 3D printed prosthetic hands for children with disabilities. The global community of makers who have dedicated themselves, through the e-NABLE network, to designing and 3D printing prosthetic hands, have changed a number of young lives for the better, including that of fourth grader Peyton Andry, who recently received a 3D printed hand from the organization. To help further advance the quality of the 3D printed prosthetic hands that are being made by maker volunteers and to ensure their usability for those wearing them, a team of students from the Rice University in Houston, Texas have developed a force-testing device that is capable of measuring how efficient the 3D printed hand is.

The research team, which has appropriately dubbed itself “Carpel Diem”, is made up of two mechanical engineers, Rachel Sterling and Amber Wang, two bioengineering majors, Nicolette Chamberlain-Simon and Michaela Dimoff, and computer engineering major Nirali Desai. Together, they initially set out to design their own 3D printed hand prosthetic but soon realized that what was maybe more necessary was a way to test existing designs, to determine their efficacy and usability.

As Amber Wong explains, “Children born without full hands are forced to adapt to the world and figure out how to go about their daily routines. If a prosthetic hand is not absolutely perfect in its function, the child will probably discard it and return to his or her own adaptive ways.”

To test the 3D printed prosthetics, the team from Rice University came up with a novel device that can test how efficiently force exerted by the wearer is transferred to the artificial hand’s own movement. Typically, the 3D printed hands are attached to the wearer who can control the prosthetic finger movements, instructing them to grab or hold objects by moving their wrist in a certain way. How much effort is necessary to get a 3D printed hand to grip or hold, however, depends entirely on its design.

“If a kid has to put in five pounds of force to only get one pound of grip, that’s a lot of lost efficiency because of how these hands are designed,” says Rachel Sterling. “Until we reach a force efficiency of 100 percent, the hands aren’t going to be useful.”

The force-testing device consists of a motorized wrist and palm rig which is capable of moving up to 60 degrees in any direction, a number of objects, such as a cylinder, a sphere, and a rectangular prism which are equipped with force sensors, and a user-friendly control program. Using the control program, the movement of the mechanical wrist can be set which in turn moves the hand and fingers of the 3D printed prosthetic hand. By moving the wrist rig, the 3D printed hand can pick up the sensor embedded objects, which can then determine details about force strength and distribution.

These types of testing devices are not common fare within the 3D printed prosthetic hand industry, as Nirali Desai explains, “The industry standards for testing these kinds of devices are not very well established. We had to get very creative about how we were going to test the accuracy and precision of our device.”

Carpal Diem is hoping that their force-testing device will continue to be developed and ultimately be made available to volunteers at e-NABLE so that they can easily 3D print and test prototypes for different prosthetic hand designs. Eventually, they are even hoping to provide makers with the specifications necessary to create their very own testing devices, so that no 3D printed prosthetic hand will be unsuitable.

The testing device, which was developed as part of a senior capstone design project, will be on display at the University’s Engineering Design Showcase, and might even have the chance to win a prize of up to $5,000.



Posted in 3D Printing Application



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Johnny Zhu wrote at 4/22/2016 5:17:43 PM:

I think it is really cool that this group made this force testing device because it can test force of a prosthetic hand. I agree with Rachel Sterling, who is in the team, “ Carpel Diem”. She said that the prosthetic hands will be useless if they have to use 5 pounds of force to pick up a 1 pound of grip. I think it was amazing that a few college kids actually thought of this! The device got put in the University’s Engineering Design Showcase and they have a chance to win up to $5,000!

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