Artificial skin and medical bionics are restoring the sense of touch

By Steve Brachmann
November 4, 2015

bionic-skin-335The science behind the sense of touch is very complex and research on how sensory afferent receptors like slowly adapting type 1 (SA1), rapidly adapting (RA) and other receptors work in concert to stimulate the sensation we take for granted as the sense of touch. A human’s sense of touch also conveys all kinds of emotional communication, making it much more than a tool to let the brain know that the body is in contact with an object.

We’ve covered an array of bionic technologies in recent months here on IPWatchdog. Last December we profiled Dr. Hugh Herr, inventor of the world’s first bionic foot and calf system and the Intellectual Property Owners Educational Foundation’s 2014 Inventor of the Year. Bionic prostheses for upper body amputations spurred on by research at the Defense Advanced Research Projects Agency (DARPA), in conjunction with Segway inventor Dean Kamen, were covered in a July profile of bionic arm tech. Even the complex engineering of the human eye is possible to duplicate and early bionic prosthetics that restore at least some pixelated form of vision to the blind have been developed.

Now it appears that we’re on the way towards the creation of an artificial skin product for bionic prostheses that would be able to restore the sense of touch in a person who has lost an appendage. An electronic artificial skin developed by researchers working at Stanford University is capable of transmitting pressure changes through nerve cells, triggering a response from the brain that the artificial skin is in contact with something or someone.

The research project, funded by the U.S. Department of Defense and led by head researcher Zhenan Bao, has developed a new type of pressure sensor made from a thin, flexible material that can be laid over existing prostheses. Within the plastic material are embedded a series of pure carbon nanotubes for conducting electricity. When the material is squeezed or otherwise deformed, pulses of energy from the carbon nanotubes are transmitted and those pulses grow more rapid as the pressure is increased. In vitro tests with a mouse brain showed that the sensors were capable of interacting with neurons.

This bionics innovation, which can be implemented in a diverse range of prosthetic devices, goes beyond some of the more limited applications of previous bionic touch systems. An article published in the February 2014 edition of the research journal Science Translational Medicine reported on a Dutch man receiving an arm prosthetic which sensory-stimulating electrodes. The device’s artificial tendons had sensors for tracking finger movement and tension data used to send translated signals to nerve electrodes implanted in a subject’s upper arm. According to reports, the man receiving the prosthetic device was able to sense touch in his left hand for the first time in nine years since losing the appendage in a fireworks accident.


The complexity of the human central nervous system is such that a person’s sense of touch can be lost at the source, through amputation, or at points throughout the spinal cord and brain caused by injury or health disorders. Whereas the bionic hand described above relied on a sensor array installed in a person’s arm, a different DARPA project produced recently by the defense research agency sought to restore touch in a paralyzed individual by installing an electrode array into that person’s motor cortex and sensory cortex, the regions of the human brain which are responsible for recognizing tactile stimulation. Scientists were able to connect a bionic hand prosthesis to the electrode array and the individual was able to detect pressure on the bionic fingertips, even when blindfolded.

A different bionics research project conducted at Case Western Reserve University successfully grafted electronics to nerve cells in the upper arm of a man who lost his hand in an accident. The electronic cuffs provide a stimulation to nerve cells in response to signals from a series of 19 sensor locations. The sensors and the nerve stimulation system are designed so that a person can even detect the texture of the material which they’re holding or touching.

The ability to tell temperature through touch is another aspect of the sense of touch that we often take for granted. A team of researchers collected together from a group of British universities have developed bionic limb electrodes to wrap around nerve endings in a person’s arm. Reports on the work of those medical scientists indicate that both temperature and shear force information can be transmitted to the brain in real-time through this system. The bionic limb is also expected to improve proprioception, or a person’s innate sense of the relative position of his or her limbs in whatever position they’re being held.

The continuing miniaturization of computing chips and semiconductor devices has been supporting recent developments in bionic fields. Reports out of Gisborne, NZ, indicate that a doctor and an engineer were able to construct a prosthetic hand outfitted with fingertip touch sensors using a Raspberry Pi computing unit. The small form factor computer was installed in the forearm of the device to process the sensor information. The credit card-sized Raspberry Pi, which is available for about $40 USD, provides the computational processing required by bionics while costing a fraction of the specialized electronics used in other prostheses. This May, we noted the 50th anniversary of Moore’s Law, the prediction made by semiconductor engineer Gordon Moore that computing power would essentially double every two years while becoming less to produce. Smaller, cheaper computing products like the Raspberry Pi reinforce the notion that technological innovation is still trending in this way. Future developments in miniaturized sensors that could be contained within a flexible material have definite implications for more robust bionic touch systems.

An increase in activity for the bionics market could invite more investment in the field, unlocking developments in bionic touch and beyond. A report released by global analysis firm Transparency Market Research indicates that the global market for artificial vital organs and medical bionics is expected to almost double from $17.5 billion USD in 2011 up to $32.3 billion in 2018. This market sector covers bionic limbs and specialized bionics for the brain, heart, eyes or ears.

The Author

Steve Brachmann

Steve Brachmann is a freelance journalist located in Buffalo, New York. He has worked professionally as a freelancer for more than a decade. He writes about technology and innovation. His work has been published by The Buffalo News, The Hamburg Sun, USAToday.com, Chron.com, Motley Fool and OpenLettersMonthly.com. Steve also provides website copy and documents for various business clients and is available for research projects and freelance work.

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