Prosthetics limbs are becoming ever more advanced, comfortable and realistic. But, for someone who has lost a limb, the missing link is being able to feel.
Finding a solution to this problem is the holy grail for engineers working to improve prosthetic technology.
Past attempts to make ‘smart skin’ have proved impractical due to the highly complex wiring required to make hundreds (if not thousands) of independent sensors work together.
Now, researchers at the National University of Singapore (NUS), led by Professor Benjamin Tee, have created an e-skin system that responds 1000 times faster than human touch.
The team’s Asynchronous Coded Electronic Skin (ACES) is a sort of synthetic nervous system that can be integrated into other devices, including prosthetic arms, clothing, and assistive devices.
By having one strong cable rather than relying on multiple ultra-fine ones the ACES skin should be relatively easy to repair if a fault or breakage occurs.
Similarly, this makes it resistant to damage as compared with relying on hundreds of very fine, flimsy wires. These are what previous attempts at e-skin relied on and one of the primary reasons they failed.
With ACES, if the lone cable is broken, it should be pretty easy to find the fault and solder it back together.
As well as being considerably faster to feel than human skin, it has the ability to detect changes across multiple sensors within 60 nanoseconds.
Additionally, when the e-skin is placed over different objects, it can identify their texture, shape, and softness within around 10 milliseconds — nearly instantaneously compared with our reaction time.
This is because the ACES detects signals like the human nervous system and it comprises a network of sensors – each working independently – connected via a single electrical conductor.
“Scalability is a critical consideration as big pieces of high performing electronic skins are required to cover the relatively large surface areas of robots and prosthetic devices,” explained Assistant Professor Tee, one of the research leads. “ACES can be easily paired with any kind of sensor skin layers, for example, those designed to sense temperatures and humidity, to create high-performance ACES-enabled electronic skin with an exceptional sense of touch that can be used for a wide range of purposes,” he added.
The researchers have been working on the skin for around 11 years and last week published their findings in the Science Robotics Journal.
When a human touches something, receptors send the information to the brain which enables us to feel it.
Therefore, for the prosthetic skin to work when attached to a prosthetic hand, a neural implant must be inserted into the patient’s arm so that the brain can detect the sense of touch.
The team in Singapore plan to work with prosthetic experts from overseas to combine their technologies to conduct clinical trials with a patient using an artificial hand.
Interestingly, the technology is not just for humans. It’s for robots too.
“Robots need to have a sense of touch to interact better with humans, but robots today still cannot feel objects very well,” said Prof Tee
According to him ACES will be able to be commercialised for robots within the next few years but could take five to 10 years for prosthetics that sense touch to reach patients.
“Can you imagine if you just have a robot complete with electronic skins, shake his hand and tell you whether you are healthy, whether you need to exercise more?” Prof Tee said to CNN last year.
“These are the things that are possible with electronic skin.”