Yasmeen ChahalWRIT 340, Elisa Warford

CYBORG YOU: ELECTRONIC SKIN

E-skin is a mesh of electronic sensors that are placed on a thin plastic film to mimic the behavior of

actual skin. It was originally developed to make robots and prosthetics more life like. However, today it is

extensively being used on humans. Many different researchers have been working on e-skin for decades, but

it was only recently that e-skin became a true reality. This can be attributed to the use of flexible carbon

nano fiber to make the electronic circuits of e-skin. This gives the skin great flexibility and the ability to

conform the shape of the part of the body it is applied to .It can be applied to skin as easily as a temporary

tattoo yet it can do wonders. It can monitor a person’s heart rate, temperature, voice signals and much

more. Researchers discover a new possibility for e-skin everyday. It is anticipated that e-skin will allow

doctors to monitor brain activity and also help heal wounds faster with the use of photo sensors in e-skin.

INTRODUCTION:

Who wouldn’t like the convenience of knowing if something is wrong with their body without

having to make a trip to the doctor’s office? This is now possible with the development of e-skin

(electronic skin). E-skin is a network of sensors with a thickness one tenth that of plastic kitchen wrap

and can conform to any shape. E-skin is the first user-interactive “electronic skin” that can respond to

pressure by instantly transmitting light. It can be used to monitor a variety of medical conditions by

accounting for the pressure, heart rate and other changes in the body [2]. Formerly heart patients would

have to undergo extensive testing to monitor their heart function. However, with e-skin heart patients

can find out the condition of their heart without leaving the comfort of their home. E-skin is the triumph

of many different researchers who have been working on it for over a decade.

The most advanced version of the E-skin has been developed by a team of researchers at the

University of California, Berkeley who claim that this new skin would enable humans to interact with the

environment in new ways [1]. However, many versions of the skin have been seen previously, such as

the one being developed at the University of Tokyo, and John Rogers electrical epidermis at the

University of Illinois, Urbana Champagne [2]. It started off as an electronic mesh that could be wrapped

around the mechanical body of a robot to control the temperature and pressure of the robot. If the robot

shook hands with a human, the e-skin would be able to tell the change in pressure and light up to signal

this change [1]. After robots, researchers developed e-skin for prosthetics. The application of e-skin on

the surface of prosthetics would make prosthetics more sensitive to temperature and pressure changes.

As can be seen in Figure 1a, e-skin is extensively used to make prosthetics more life like. However, once

successful with robots, researchers began to develop it for human use. With its intricate design it can

monitor pressure and other significant changes in the human body. The main challenge in doing so is to

make flexible circuit boards as opposed to the rigid ones made out of silicon and glass. Many

manufacturers have already developed flexible circuit boards for some components such as wiring, but

silicon chips are still attached to it. Nevertheless, the developers of e-skin found a way to make all

components of e-skin flexible, enabling it to be bend around a joint or conform the shape of the object it

is being used on.

Figure 1. (a) Prosthetic Hand covered in electronic skin.

(http://spectrum.ieee.org/biomedical/bionics/bionic-skin-for-a-cyborg-you)

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HOW DOES IT WORK?

As can be seen in Figure 2, electronic skin is made up of a network of sensors that are placed on

thin plastic substrates that are less than 40 micrometers thick. It can spatially and temporarily map

pressure, detect heartbeat and a variety of other things. It is a network of 16 by 16 pixels, each one

equipped with a carbon nanotube thin-film transistor, a pressure sensor and a light emitting diode [2].

All of these components are placed together on a thin plastic film. The plastic film is not only flexible but

it can also hold up well against mechanical strain. This property of plastic film allows carbon nanotube

conductors to be placed on it without tearing it apart.

A carbon nanotube is a recently developed thin conducting tube made out of carbon polymers

with high elasticity [3]. Carbon nanotubes make the electronics used in e-skin completely flexible, so that

e-skin can be applied to any part of the body without any damage to its electronic components. Initially,

many different substances such as amorphous silicon, low temperature silicon and organic

semiconductors were experimented with to make the electronics for e-skin. But all of these materials are

rigid and break upon bending; thus, rendering them unsuitable for use in e-skin. The carbon nanotube

thin film transistor not only gives e-skin flexibility but also helps it mimic the sensitivity of real skin. The

skin has about 2 million sensors over the entire body. It is physically impossible to wire 2 million sensors

directly onto skin, which is why it is necessary to use an ultra-sensitive material that will be able to

recreate sensitivity of the skin effectively [2]. Carbon nanotubes are highly sensitive and can detect the

slightest change in temperature, pressure or any other quantity that is being monitored. Since, e-skin

does not display any numerical results, the lighting up of the diode informs the user of any change in the

quantity being measured from its normal value. So, how does e-skin light up? When the sensor detects

touch, the thin film transistor powers the organic light emitting diode, which then emits red, green or

blue light [1]. The greater the magnitude of the pressure the brighter the light will be. E-skin has also

been equipped with many features to transmit information to other devices.

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Figure 2. What does E-skin look like?

(http://spectrum.ieee.org/biomedical/bionics/bionic-skin-for-a-cyborg-you)

Electronic skins have been linked with radio- frequency communication modules with the

integrated electronic circuit allowing it to transmit information wirelessly, specifically to other e-skinned

people or computers. John Roger’s team at the university of Illinois, Urbana Champaign has developed

the most advanced version of e-skin known as the “electrical epidermis” which is fitted with an antenna

[2]. This will now allow surgeons to make more life like prosthetics and have finer control over tools

used for minimally invasive surgery. This can revolutionize the field of surgery. Although many skeptics

labeled e-skin as an unfeasible product, the invention of flexible electronics has made the dream of e-

skin come to reality.

FLEXIBLE ELECTRONICS:

Flexible electronics, also known as flex circuits are complex circuits assembled on flexible plastic

substrates. Flexible electronics have been developed since the early 1900s. Initially Dr. Ken Gilleo

developed a flexible circuit, which was further disclosed in an English patent by Albert Hansen in 1903

where he described his flex circuit as metal conductors on paraffin coated paper [3]. The diaries of

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Thomas Edison also suggest that he was working on creating flexible circuit using graphite [3]. However,

he was not able to complete his project. Flexible electronic circuits are not a recent development, but this

technology has only recently been perfected for use in e-skin. In the past, electronic circuits have been

used in cameras, solar cells and for powering satellites. E-skin is only one of the multivariate things that

flexible circuits can be used for.

This technology gives the otherwise stiff components of an electrical circuit such as chips and

transistors flexibility. Takao Someya at the University of Tokyo ,used flexible organic transistors to act as

pressure sensors [4]. However, the use of these sensors was limited because they changed configuration

when pressure was applied to them. It was Zhenan Bao, another developer of e-skin who addressed this

issue by patterning various polymer materials into thin sheets to find the most suitable material for

embedding flexible electronic in. He said his goal was to mimic the human skin, which would require

extremely sensitive and flexible electronics [4]. There is a range of materials today that can serve as

flexible substrates for electronic components to be embedded in such as ultra thin glass, stainless steel

foils and plastic films [2]. The most popular out of the range is plastic films. The popularity of plastic films

can be attributed to the manufacturing process for electronic circuits: inkjet printing. The total area of

the human skin is about two square meters, about twice as big as the biggest LCD TV screen that can be

purchased in the market. The only way to manufacture something that large and flexible is by inkjet

printing. Inkjet printing can deliver the exact amount of a substance that needs to be applied to precisely

targeted positions [2]. Printing processes can also apply coating of thin-film materials which otherwise

takes a long time and wastes huge amounts of raw material. Plastic films are also a popular substrate for

e-skin manufacturing as it makes the application of e-skin on human skin facile.

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Figure 3. Flexible electronics, they are manufactured on thin sheets of plastics

(http://www.popsci.com/science/article/2011-08/epidermal-electronics-paste-peelable-circuitry-your-

skin-just-temporary-tattoo)

HOW IS IT USED?

E-skin has a number of applications, and can be applied to the skin as easily as a temporary tattoo

as shown in Figure 4a. The circuit is first transferred onto a water-soluble plastic, which is used to

transfer the circuit onto the skin. Once the circuit has been applied onto the skin, the water-soluble sheet

washes away, leaving just the circuit behind [5]. For such a complex device, this is a rather easy way to

apply it. Doctors can use these tiny devices to monitor a patient’s vital signs without the need for wires

and bulky contact pads. E-skin can also be worn by patients outside the bounds of the hospital, without

the device being visible. It can be concealed under a band aid or even the patient’s clothing (see figure

4b). Roger and his colleagues tried out a number of applications for this, the most astonishing one being

the use of electronic skin to detect muscular activity of a person’s throat [5]. The electronic skin circuit is

applied to the patient’s throat, which then relays the signal to a computer, allowing researchers to

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differentiate between words spoken by the patients. This application was even used by patients to

control a voice-activated video game.

Figure 4. (a) E-skin is easy to put on just like a temporary tattoo. (b) Electronic skin can be easily

camouflaged under a band-aid, allowing patients to wear it outside the hospital.

(http://www.sciencedaily.com/releases/2013/05/130516105702.htm)

E-skin can be used to monitor muscle and nerve activity. Patients with neurological disorders

such as amyotrophic lateral sclerosis, a disease that affects a person’s nerves, which are responsible for

controlling voluntary muscle movements, can use e-skin as an interface for communication with

computers [2]. E-skin can transmit information to the computer allowing doctors or patients to monitor

their body activities. Rogers and his colleague demonstrated that e-skin can not only monitor the activity

of the nervous system but it can also control the nervous system by simulating nerves with electrical

signals [2]. This will allow patients to simulate their nerves when required and perform most of the

functions of a normal person. E-skin can be used to heal wounds faster, monitor heart activity and detect

the vital signs of the patient. Most of the prosthetics being used currently are aesthetically like real limbs,

but they still lack most of the functions of the human limbs. E-skin would allow the prosthetics to be

more sensitive and enable them to function like real limbs.

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FUTURE OF E-SKIN:

E-skins are already being used for a variety of applications in the medical industry. It has

anticipated that it can be used for many different applications in the future. It has already conquered the

world of robotics by making prosthetic limbs more sensitive and life like. In the medical field it has

already been used for monitoring pressure, temperature and heart rate. However, the applications of e-

skin are boundless. Currently it is impossible to study the brain function in a normal environment. To use

an EEG, a device that measures brain function, the patient has to go to a lab and be entangled in a maze of

wires for an extended period of time. E-skin patched can eliminate this inconvenience and allow

neurologists to monitor brain function easily with the use of a skin patch [6]. It also predicted that E-skin

could revolutionize the field of phototherapy. Currently light is being used to treat pain, skin conditions

and fatal neonatal diseases. But the use of light therapy requires the patient to be immobile and isolated

for hours [6]. E-skin will allow phototherapy to be transmitted while allowing the patients to go on with

their regular life. Photo sensors can be directly put on the skin without being attached to wires and

machines. Parents will be able to touch their new born without worrying about damaging any medical

equipment attached to their baby. Parents can hold their baby while phototherapy: a form of therapy

using light to cure diseases, is being transmitted to their child. New applications for e-skin are emerging

all the time. Researchers hope to merge e-skin with drug delivery systems to deliver drugs directly at the

site of the tumor, use it to heal wounds faster and reduce the side effects of treating skin cancer [6]. Skin

that understands its user, skin that can communicate back, skin that can extend the medical field in

directions never imagined before, the possibilities of e-skin development are endless.

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REFERENCES:

[1] M. Feldman (2013, August 12). Electronic Skin Lights Up When Touched [Online]. Available:

http://spectrum.ieee.org/biomedical/devices/electronic-skin-lights-up-when-touched .

[2] T. Someya (2013, August 26). Bionic skin for a Cyborg You [Online]. Available:

http://spectrum.ieee.org/biomedical/bionics/bionic-skin-for-a-cyborg-you .

[3] E. Stoye (2013, July 18). Flexible electronics boost with stretchiest conductor ever made [Online].

Available: http://www.rsc.org/chemistryworld/2013/07/flexible-electronics-super-stretchy-conductor-

ever.

[4] K. Bourzac (2010, September 13). Electrical Skin that Rivals the Real Thing [Online]. Available:

http://www.technologyreview.com/news/420755/electric-skin-that-rivals-the-real-thing/

[5] L. Ahlberg (2011, August 11). Smart skin: Electronics that stick and stretch like a temporary tattoo

[Online]. Available: http://news.illinois.edu/news/11/0811skin_electronics_JohnRogers.html

[6] S. Cherry (2013, September 13). What could flexible electronics ever do for us? [Online]. Available:

http://www.pyramidion.be/index.php?option=com_content&view=article&id=123:what-could-flexible-

electronics-ever-do-for-us&catid=34:storybook&Itemid=69

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