Electronic SKIN can ‘feel’ heat and pressure at the same time: Film is so sensitive it can tell when a human hair is placed on it
- Human skin contains unique microstructures and sensory receptors
- Researchers have mimicked these structures in an electronic film
- The grooved surface is made from plastic and graphene oxide and can detect touch and temperature using electric charges
- It is so sensitive it can detect the weight of a human hair being placed on it
The unique way in which our fingertips can detect changes in both temperature and pressure have been reproduced in an electronic ‘skin’.
In tests, the grooves in the e-skin were able to respond to water droplets running across them and could detect when a human hair was placed on their surface.
The breakthrough could be used to make more life-like prostheses or improve the accuracy of wearable sensors and medical diagnostic devices.
The electronic skin was developed by researchers at the Ulsan National Institute of Science and Technology, led by Professor Jonghwa Park.
Human skin contains unique epidermal and dermal microstructures and sensory receptors.
The microridges on the fingertip are especially designed to fine-tune perception of surface texture and transfer sensory information to the brain.
Existing electronic skin technology lets robots and robotic prostheses grasp and manipulate objects, discern the surface texture and hardness, and feel the warmth of objects.
However, electronic skins that can simultaneously detect both heat and different types of pressure with a level of high sensitivity have been a difficult to develop, until now.
Professor Park and his colleagues have designed ferroelectric films that mimic the grooved, microscopically ‘mountainous’ structure of human fingertip skin.
By adding composites made of a polymer and reduced graphene oxide, the films are able to detect touch and temperature using sensing electric charges.
The authors tested the e-skin’s response to sensory changes created by water droplets and found that the skins can detect water falling at different pressures and temperatures.
They also found that the artificial fingertip skin could detect a tiny amount of pressure created by a human hair.
And when attached to a human wrist, Professor Park and colleagues said their e-skin can be used to monitor pulse pressure by detecting the changes in skin temperature that occur when blood vessels dilate or constrict.
Last month, researchers from Stanford University developed touch-sensitive artificial skin that not only detects pressure, but can transmit signals to nerve cells.
They hope the proof-of-concept experiment will lead to artificial hands that allow the wearer to feel different textures and distinguish between hot and cold.
The two-ply ‘skin’ has a springy top layer that reacts to pressure and a bottom layer which produces biochemical signals suitable for transmission to neurons.
In the tests, pressure signals from the skin generated light pulses that activated a line of light-sensitive nerve cells.
Other methods of stimulating nerves were likely to be used in real prosthetic devices, said the researchers writing in the journal Science.
Professor Zhenan Bao, from Stanford University in the US, said: ‘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.
‘We have a lot of work to take this from experimental to practical applications. But I now see a clear path where we can take our artificial skin.’
Attached to a robot hand, the skin was able to detect pressure over the same range as its human counterpart, from a light finger tap to a firm handshake.
The secret of its design is a scattering of billions of carbon ‘nanotubes’ – microscopic hollow carbon rods.
Putting pressure on the skin squeezes the nanotubes closer together and enables them to conduct electricity.
Real skin transmits pressure information as short pulses of electrical signals that are sent to the brain. In a similar way, the artificial skin produces signal pulses that vary in intensity according to the pressure level.
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