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Skin-like Prosthetic Coverings Becoming Closer to Reality

Pixelated electronics built with skin-like materials conform to the complex curves of a hand.

Image by L.A. Cicero courtesy of Stanford University.

Restoring
lost sense of touch with stretchable, electronically-sensitive
synthetic materials has been the focus of research conducted by Stanford
University chemical engineer Zhenan Bao, PhD for more than 20 years. In
research published February 19 in the journal Nature, Bao and a
team of researchers described their development of stretchable,
touch-sensitive circuitry and a mass-production manufacturing process
for it. The new polymer circuitry with integrated touch sensors may one
day lead to coverings for prosthetic devices that have skin-like
sensitivity. 

The research describes the two technical
firsts: the material’s ability to detect the light pressure of an
artificial ladybug footprint and the method to mass produce the new
class of flexible, stretchable electronics—a critical step on the path
to commercialization, Bao said.

“Research into synthetic skin and
flexible electronics has come a long way, but until now no one had
demonstrated a process to reliably manufacture stretchable circuits,”
she said.

Bao’s hope is that manufacturers might one day be able
to make sheets of polymer-based electronics embedded with a broad
variety of sensors, and eventually connect these flexible, multipurpose
circuits with a person’s nervous system. Such a product would be similar
to human skin, a more complex biochemical sensory network. Before it
leads to artificial skin, the process will enable the creation of
foldable, stretchable touchscreens, electronic clothing, or skin-like
patches for medical applications.

Bao said their production
process involves several layers of new polymers, some that provide the
material’s elasticity and others with intricately patterned electronic
meshes. Other layers serve as insulators to isolate the electronically
sensitive material. One step in the production process involves the use
of an inkjet printer to paint on certain layers.

The research team
has successfully fashioned its material in squares about two inches on a
side and containing more than 6,000 individual signal-processing
devices that act like synthetic nerve endings. All this is encapsulated
in a waterproof protective layer.

The prototype can be stretched
to double its original dimensions while maintaining its ability to
conduct electricity without cracks, delamination, or wrinkles and return
to its original size and shape. To test durability, the team stretched a
sample more than one thousand times without significant damage or loss
of sensitivity. The sample was also tested while adhered to a human
hand.

Bao said much work lies ahead before the new materials and
processes are as ubiquitous and capable as rigid silicon circuitry.
First, she said, her team must improve the electronic speed and
performance of their prototype but calls this development a promising
step.

“I believe we’re on the verge of a whole new world of electronics,” she said.

Editor’s note: This story was adapted from materials provided by Stanford University.

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