(Source: LucasFilm)
Material has a broad pressure sensing range; could be used to coat prosthetic limbs

It stretches like skin and has tiny embedded points of sensation.  It's called electronic skin, or e-skin for short.

I. A New Skin

The latest e-skin comes courtesy of Professor Hossam Haick at the Technion-Israel Institute of Technology and his team of biomedical researchers who pushed the boundaries of e-skin, creating a flexible sensor that offers similar capabilities to the real biological construct.

The new flexible sensor can "simultaneously sense touch, humidity, and temperature, as real skin can do" and is "at least 10 times more sensitive in touch than the currently existing touch-based e-skin systems."

Creating e-skin is a seemingly daunting task.  The eventual goal is to coat prosthetic limbs with the sensor layer and then wire it up to the nervous system, restoring patients' sense of touch (or alternatively wire it up to robots to make them more humanlike).  However, that's easier said that done.

artificial skin
[Image Source: ATS]

Real skin can sense with great detail a broad array of physical inputs -- humidity, temperature, pressure, and the presence of chemicals.  That would generally make for one pricey, power-hungry sensor.  But e-skin's requirements force researchers to try to preserve all that sensitivity and multi-sensory inputs in a layer that is relatively cheap and must be able to operate on low voltages.

II. Nanoparticle PET layer Improves Sensitivity

The tiny embedded nanosensors in Prof. Haick's e-skin are beautiful capped nanoparticles.  The nanoparticle itself is made of gold and is topped with sensory "prong" molecules called ligands.  Prof. Haick describes, "Monolayer-capped nanoparticles can be thought of as flowers, where the center of the flower is the gold or metal nanoparticle and the petals are the monolayer of organic ligands that generally protect it."

Artificial skin
[Image Source: ACS/Prof. Haick]

The researchers deposited to the monolayer-capped nanoparticles atop a thin film of polyethylene terephthalate (PET), the same flexible plastic that is formed into soda bottles.  The result is a conductive layer that responds to bending by bring particles to the surface, which in turn alters the electric properties, creating sensation.  The sensor has a broad range sensing from "tens of milligrams to tens of grams".

The team says that the PET/nanoparticle layer will be embeddable within a variety of more complex multi-layer e-skin constructs, which in turn will be used to coat future artificial limbs.  The sensors could also be repurposed by civil and mechanical engineers to create failure warnings to detect cracks in parts, buildings, or bridges.

Artificial Skin
[Image Source: ATS]

Dr. Nir Peled, Head of the Thoracic Cancer Research and Detection Center at Israel's Sheba Medical Center -- was not affiliated with the work, but praised it in a university press release, stating, "The development of the artificial skin as biosensor by Professor Haick and his team is another breakthrough that puts nanotechnology at the front of the diagnostic era."

The work has been published [abstract] in the peer-reviewed journal ACS Applied Materials & Interfaces.  Co-authors include Meital Segev-Bar and Gregory Shuster, graduate students in the Technion's Russell Berrie Nanotechnology Institute, as well as Avigail Landman and Maayan Nir-Shapira, undergraduate students in the Technion's Chemical Engineering Department.

Sources: ACS Applied Materials & Interfaces, ATS

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