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Embedded with sensory receptors, skin is the largest organ on the human body. But what happens when a limb is lost, or the skin is left ruined to the point where those receptors can no longer transmit tactile or thermal information from the environment to our brains?

Stepping in to solve that conundrum is a team of researchers from South Korea's Seoul National University, who have come up with the idea of attaching "smart skin" to prosthetics in order to restore a sense of touch to people with artificial limbs.


In a study, entitled "Stretchable silicon nanoribbon electronics for skin prosthesis", published in the journal Nature Communications, the researchers assert that while progress has been made in "understanding the neural circuits underlying mechanical and thermal sensation, replicating these capabilities in artificial skin and prosthetics remains challenging."

The difficulty of imitating the special functions of skin on prosthetic limbs has meant that amputee patients use prosthetic limbs for functional or cosmetic purposes, as opposed to sensory ones.

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The South Korean researchers assert that stretchable prosthetic skin -- which can be stretched out over the whole prosthesis -- equipped with "ultrathin single crystalline silicon nanoribbon (SiNR) strain, pressure and temperature arrays", may one day solve some of these issues.

The SiNR sensor arrays have "geometries" that are designed to stretch. This component along with the integration of "stretchable humidity sensors and heaters" enables, according to the researchers, the person in question to feel the sensation of skin moistures and to regulate body temperatures. Furthermore, ultrathin stretchable nanowire-based electrodes transmit electrical stimuli from the prosthetic skin to the body.

Recognising that our sense of touch varies throughout the body, the researchers note the importance of "location specific optimization of sensors and actuators in artificial skin and prosthetics". That would mean that the tactile and thermal sensing abilities of this "smart skin" would vary depending on which body part it replicated.

Throughout our hectic daily lives, our skin comes into contact with a massive amount of external data that must be processed.


Clued up on this fact, the researchers in South Korea mention that their prosthetic hand and laminated electronic skin might have to shake hands, tap keyboards, touch dry and wet surfaces, and hold hot and cold things.

For the moment, this "smart skin" equipped prosthetic hand comes with humidity sensors that allow it to detect dampness. Thermal actuators also bring the smart skin a temperature profile that matches real human skin.

The researchers in South Korea are ultimately aiming to restore sensitivity to external stimuli for people with prosthetic limbs, and their "smart skin" looks like a logical contribution to the emerging field of smart prosthetics.