A HANDMAKERS’ TALE

Wits engineers earn a high five

Prosthetic hands that use brain signals to control movement sell for up to R150 000, but a team of engineering students from the University of Witwatersrand have made a prototype that will cost less than R2 000.

Armed with a 3-D printer, some simple sensors and motors, and a lot of brain power, six electrical and information engineering students have been working on the robotic hand for three years. They hope that, once perfected, it will be an option for South Africans who cannot afford prostheses.

“The problem with the normal prosthetic hands is that they’re very expensive and too cumbersome, too heavy or have limited functionality,” said Abdul-Khaaliq Mohamed, a lecturer and PhD candidate in the School of Electrical and Information Engineering at Wits, who is co-ordinating the students.

“We’re trying to create a hand that’s relatively cheap but has sufficient functionality that allows users to do basic daily movements. That’s why we’ve gone with the 3-D printing approach and we’ve used very simple sensors and motors to reduce the cost. That’s what is different about this hand in relation to other hands.”

Charl Beukes, trustee of the Amputee Club of South Africa, a nonprofit organisation that raises funds for those who can’t afford prosthetics, said: “It’s estimated there are 2.1 million amputees in South Africa based on the 2011 census, but we reckon there are a lot more. Around 80% don’t have any medical aids or funds to cover [prosthetics].”

A reason for the high cost was that components were made overseas.

Another issue was that prosthetic arms supplied by the government were basic models that were so cumbersome and heavy that the person might choose to cope without it, Beukes said.

He said that in Gauteng more than 300 people had been waiting over two years for various prosthetics procedures and in the Eastern Cape, the province with the biggest burden, there was a waiting time of six to 10 years.

“We do see the battles of people who can’t afford prosthetics and many will never get it,” he said.

Mohamed said their prototype hand was made from assembled plastic parts printed on a 3-D printer and weighed less than 1kg including all the motors and electronics.

“What it doesn’t have, which will be the heavier part, is the battery. We’re still getting to that. But that could sit on the forearm, depending on the level of amputation.”

Mohamed’s research began in 2008 and work on the prototype hand in 2014.

“Normally, with this kind of project, you’re looking at 10 to 20 years to get it functional and I’m not even sure that includes the rigorous medical testing that would be required to get this into a commercial product. So we’re in for the long run.”

Development is happening in stages. Last year the group perfected a tripod pinch, which is used to hold a pen. The bicep and tricep are hooked up to the hand and as the person moves the muscles, the hand closes or opens. Sensors were then added to the fin- gertips to give the hand an ability to sense force and how hard or soft to grasp.

“This year we are trying to integrate the sensors to some sort of vibration feedback on the body. Instead of you feeding the sensors into the brain, which will interpret some sort of sensory feedback, we’ve got motors that vibrate, similar to a cellphone. We attach that to another part of the body and it will vibrate and give you an indication of how strong the hand is grasping.”

Next on the list was an exoskeleton for people who had suffered strokes or had a neuromuscular diseases.

“The exoskeleton hand would be [used] to strengthen the hand of someone who can’t really use the hand properly but has some sort of movement. We might start that next year, depending on resources,” said Mohamed.