Digital ‘skin’ could give artificial limbs feeling

19 Oct 2015

Scientists have developed a ‘skin-inspired organic digital mechanoreceptor’ that could give people with prosthetic limbs a type of feeling that is otherwise, obviously, lacking.

Advancements in prosthetic manufacturing, tailoring and distributing have completely revolutionised the industry in the past couple of years, from ‘mind-controlled’ robotic arms, to 3D printing prosthetics overnight.

But there is one glaring omission from all these massive steps forward: tactile feedback.

Tactile feedback (or feeling, to you and me) is one of the (several) major roles skin plays in the make-up of a human. Bulging with receptors, our skin is like a sensor funfair, allowing us to just graze surfaces and establish what they are.

With prosthetic limbs, hands, feet, we’ve got nothing like that. Popping on the odd sensor here and there is as far as we have gotten.

So, when word gets out about scientists working out how to change this, a lot of people take notice.

Scientists at Stanford University in the US have developed a flexible material to replicate skin – filled with organic circuits and pressure sensors – that can be put onto a robotic hand.

In a report published in Science, Zhenan Bao and 16 colleagues describe an approach to simulate the mechanoreceptors of human skin, using pressure-sensitive foils and printed ring oscillators.

“The sensor successfully converted pressure into a digital response in a pressure range comparable to that found in a human grip,” reads the research, led by Bao.

“This is the first time a flexible, skin-like material has been able to detect pressure and also transmit a signal to a component of the nervous system,” added Bao.

It works by using a layered plastic construct, the outer housing the sensing mechanism and the inner becoming a circuit to translate and send signals to the brain.

The process required proof that an electronic signal could be recognised by a biological neuron.

It did this by adapting a technique called optogenetics, a combination of optics and genetics.

“A number of companies and clinical trials are already exploring optogenetics as an alternative to electrical stimulation,” said Polina Anikeeva, who wrote a complementary piece in Science.

“As the efficacy and safety of the method becomes better understood, it is not unrealistic to envision more applications of optogenetic neural stimulation in prosthetic interfaces — but it is going to take time and effort.”

Obviously someway short of human skin, this could still prove quite revolutionary and, if anything, inevitable.

The world has seen an explosion in sensors and sensor technology. Not just installed on everything from street lamps to game controllers, they are getting smaller, more focused and, ultimately, more adaptable.

It is from this, you would assume, that fake skin will quickly evolve.

“We have a lot of work to take this from experimental to practical applications,” Bao said. “But after spending many years in this work, I now see a clear path where we can take our artificial skin.”

Main image via Shutterstock

Gordon Hunt was a journalist with Silicon Republic