Mini Review TPNE 2022

Mini-Review

Technological Tattoos
Diogo Pires 93037 and João Machado 111331
A new technology begins to emerge, the tech tattos are here to stay. In a simple way we can measure
a big amount of different things, just like: heart beat , monitor and diagnosis critical health problems,
sleep disorders, brain activity,etc. In this review we analized and discuss two different aproaches. In
one we get the tattos by a graphene-based circuit and in the other by 3D-pritting a composite.

are able to produce some things cheaper provided by nanotech,

Introduction, if we can work and develop this area, we can get a brilliant future.
Tattoos were created in 3337 BC by the Egyptians using sharp Nanocomposites
wooden point and black soot to create the tattoos [1]. In the 19 century
we finally see the first electronic tattoo machine created by Thomas A nanocomposite combines two or more materials – of which at
Edison. We can see that tattoos were always around us since our least one is a nanomaterial – with different physical and chemical
ancients, but only in a way more symbolic, painted and marked in the properties. Nanocomposite materials are designed to exhibit
bodies. Only few years ago we start to hear about Technological properties that exceed, sometimes drastically, the capabilities of
Tattoos and its importance. the sum of their constituent parts.
Unfortunately, nowadays we saw many cases where people died or Nanocomposites are made by embedding materials (called the
get worst for miss or late diagnosis. So, rises the necessity to avoid reinforcing phase) into another material (called the matrix
this situations and detect earlier and faster some problems, even at phase). Either one or both phases can be nanomaterials.
distance. That’s where enters this type of tattoos, with the help and
Typically, reinforcing materials are strong with low densities
development of nanotechnology it’s possible to produce it and give
accessibility to everyone. And that´s why we choose this theme, we while the matrix commonly is a ductile or tough material. If the
want to review something that combine healthcare with composite is designed and fabricated correctly, it combines the
nanotechnology. We believe that’s an area full off application and strength of the reinforcement with the toughness of the matrix to
development potential, after some research we finally found the achieve a combination of desirable properties not available in
perfect theme, Technological Tattoos. any single conventional material.
We found two different and interesting approaches. In one hand we Polymer Nanocomposites- materials incorporating nanosized
have graphene-based tattoos and on the other hand we have a 3D- inclusions into the polymer matrices. The organic origins of
printting tattoo produced with a composite. In the two we can clearly some nanofillers, such as nanocellulose, allow the usage of these
see the contribute of nanotechnology. materials for medical purposes due to their biocompatibility. [3]
Even though there hare some issues to solve like: problems with the
contact with water, skin excessive contraction, the tattoo it’s not
permanent what it some cases could be better…
We believe in the potential of the technological tattoos and in the
future will bey a key to save and help many lives.
Nanotechnology
Nanotechnology is the manipulation of matter on a near-atomic
scale to produce new structures, materials, and devices. The
technology promises scientific advancement in many sectors
such as medicine, consumer products, energy, materials and
manufacturing. Nanotechnology refers to engineered structures,
devices, and systems. Nanomaterials have a length scale between
1 and 100 nanometres. At this size, materials begin to exhibit
unique properties that affect physical, chemical, and biological Figure 1- Examples of Nanocomposites applications

behaviour. Researching, developing, and utilizing these

Graphene-Based Materials
properties is at the heart of new technology. [2]
Nanotechnology represents the future, the amount of stuff we can Graphene, a two-dimensional monoatomic thick building block of a
do its amazing. Improve resistance of material, give materials carbon allotrope, has emerged as an exotic material of the 21st
another proprieties, develop new technology, etc… We already century, and received world-wide attention due to its exceptional
charge transport, thermal, optical, and mechanical properties. [4]

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Mini-Review Universidade de Aveiro

Figure 2- Graphene-Based Applications

The design of the device can be adjusted within the specifications. The
Recent progress has shown that the graphene-based materials can offered baseline process is a GFET (Fig. 1) consisting of the following
have a profound impact on electronic and optoelectronic devices, fabrication steps:
chemical sensors, nanocomposites and energy storage. We can see
some applications of graphene-based material nowadays in figure 2. • Back Gate & Bottom contact
• Dielectric deposition
[5]The 2D Experimental Pilot Line (2D-EPL), a project grown from
• Wafer scale graphene transfer
the Graphene Flagship, has launched its first customisable wafer run
• Top Contacts and Encapsulation
targeting sensor applications. Companies, universities, and research
• Opening of encapsulation*
institutes can include their designs as dies on joint wafers, to test their
ideas for devices on a larger scale at relatively low costs. The 2D-EPL Electronic skin, a kind of flexible electronic device and system
is a €20 million project aiming to pioneer the fabrication of prototype inspired by human skin, has emerged as a promising candidate for
electronics and sensors based on graphene and related materials wearable personal healthcare applications. Wearable electronic
(GRMs), and at integrating them into established silicon devices with skin-like properties will provide platforms for
semiconductor platforms. While doing so, the project will also refine continuous and real-time monitoring of human physiological signals
and scale up the manufacturing process of graphene-based electronics, such as tissue pressure, body motion, temperature, metabolites,
including developing critical tools, materials and processes. electrolyte balance, and disease-related biomarkers. Transdermal
drug delivery devices can also be integrated into electronic skin to
enhance its non-invasive, real-time dynamic therapy functions.[6]

Drug Delivering
The use of nanotechnology in targeted drug delivery systems
(DDS). A targeted DDS can improve the delivery and local
concentration of drugs. The use of nanoparticles (NPs) and
nanostructured materials for delivering drugs to the targeted zone
of action is preferred owing to their optimal size and drug loading
and releasing characteristics[7]. Example of operation in figure
4.
In the final we can combine this with the technology tattoos in
other to delivery drugs if some value changes from what are
being measure. For example, if the sensor notices a dramatic
Figure 3- Schematic that shows the offered baseline process
change can automatically delivery the drug.

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Figure 4-Drug Delivery System

progression, wound care, general health, fitness monitoring and

more.
Discussion,
Different Body sensors[13]
Electronic skin sensors, also known as the wearable thin film
sensors, can be directly placed on the human body to measure
body parameters such as body temperature, heartbeat, sweat
composition etc. Electronic skin sensors have applications in
many areas such as healthcare, sports, robotics and prosthetics,
etc.
Artificial ionic skin (AI skin):
Scientists at University of Toronto have designed a super-
stretchy, transparent and self-powering sensor that records the
complex sensations of the human skin. The new AI skin could
open doors to skin like fitness products such as fit bits that
Figure 6-Wound monitoring sensor
measure multiple body parameters.
Wearable microfluidic sensor to measure skin pH Levels:
By colleting small amounts of sweat from skin pores, this sensor
can measure the PH from our body. It calculates the rate of
perspiration on the skin’s surface and evaluates skin health
thereby recommending the product for balancing pH and skin
care.

Figure 5- Artificial ionic skin (AI skin)

Wound monitoring sensor:

The sensor works on the principle of biosensor by measuring
important biomarkers such as lactate and oxygen levels in the
skin. Such sensors can provide a better understanding of disease
Figure 7-Wearable microfluidic sensor to measure skin pH Levels

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Figure 8- Experimental of ISDEE

Interactive skin display with epidermal stimuli electrode: E-tattoo:

A novel interactive skin display with epidermal stimuli electrode Graphene-based wearable device that can be placed on the skin
(ISDEE) allow the simultaneous sensing and display of multiple to measure a variety of body responses, from electrical to
epidermal stimulus on a single device, that operates under biomechanical signals. It can take electrocardiograph and
alternating current (AC). This currents depends on the seismocardiography readings simultaneously, sends the data to a
conductance of the skin, this variates with the temperature, sweat smartphone app shows heartbeat in real time.
gland activity, and pressure (figure 8).

BodyNet sensor:
This sensor developed by Scientists from Stanford University,
measures the pulse and rate of respiration through detection of
the expansion and contraction of the skin. Applying in elbows or
knees this sensor can track the movement of the body parts, by
measuring tightening or relaxation of the skin.

Figure 11-Graphene-based tattoo

Electronic Tattoos:
Created in the Coimbra University the electronic tattoos are
another example of a sensor that can measure muscle activity,
breathing, body temperature, brain activity, even emotions.
Printed in 2D using a composite and transferred with water to the
Figure 9- BodyNet sensor skin.

Wearable Skin Sensor:

A non-invasive, flexible and wearable shunt (tube surgically
implemented in the brain that drains excess of fluid to another
part of the body) monitor which monitors the working of shunt
(passage of fluid through the shunt). It uses temperature and
heat transfer measurements and non-invasively shows the
amount of fluid flowing through shunt. This device can
communicate with smartphone through Bluetooth and can
transmit the readings by an Android app. This sensor was Figure 12-Eletronic Tattoos
created to avoid late diagnosis of Hydrocephalus.

Procedure and Production

All these technologies have something in common, they are
made almost in the same way. We have two different ways to do
it.

Figure 10-Wearable Skin Sensor

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Firstly, the goal of these two different methods of production is

to create an ultra-thin patch by using circuits in a serpentine
shape with the mechanical properties of skin, so they can still
work properly even if bent, twisted, or stretched.[14]
These paths can include transistors, many types of sensors as
mentioned before, radio frequency capacitors, and LEDs, as well
as solar cells and conductive coils which act as a power source.
In order to build this, was integrated inorganic semiconductor
nanomaterials into devices and circuits that combine with soft,
organic substrates to offer a ‘tissue-like’ class of electronics
technology.[14]
When the size of semiconductor materials is reduced to
nanoscale, their physical and chemical properties change
drastically, resulting in unique properties due to their large
surface area or quantum size effect.[14]
The quantum size effect occurs when the material is so small that
averaging the properties no longer works and is needed to deal Figure 14 – Components of an electronic tattoo.[17]
with the specific behaviour of individual atoms or molecules.
This behaviour can be very different to when these atoms are
aggregated into a bulk material. This effect starts in nanoscale, There are many kinds of components in this ultra-thin patch used to
particularly at the lower end (single digit and low tens of monitor the health of an individual. Let see what function of each
nanometres). Materials reduced to the nanoscale can suddenly component has
show very different properties compared to what they show on a • EEG/EMG sensors - With these sensors is possible to track
macroscale. For instance, opaque substances become transparent the electrical brain activity through brain wave patterns.[18]
(copper); inert materials become catalysts (platinum); stable • ECH sensors - The ECG sensors are used to determine heart
materials turn combustible (aluminium); solids turn into liquids rate, heart rhythm, and other information regarding the heart's
at room temperature (gold); insulators become conductors condition.[18]
(silicon).[15]
As surface area of a material increases, a greater amount of the • Photo detectors - These sensors convert light photons into
material can come into contact with surrounding materials, thus electric current.
affecting reactivity and facilitating chemical processes.[16] On • Strain gauges - The strain gauge is a sensor whose measured
the figure 13, shows the proportion of surface area between a electrical resistance varies with changes in strain. In this case the
bulk material and a nanomaterial. strain comes from the movement of the individual.
• Temperature sensors – Like the name says, it measures the
temperature of the skin of the individual.
• Wireless antenna - The wireless antenna acts as a radiator and
transmits waves through the air. Also receive the waves from the
air.[18]
• Wireless communication oscillator – It is an essential building
block in modern wireless radios.
• Wireless power coil - It is essential for wireless charging. The
wireless charging coils generate an alternating electromagnetic field
used to inductively transfer energy to other coils
• LED – LED stands for light-emitting diode. It is a
semiconductor light source that emits light when current flows
through it.
Figure 13 – Proportions of surface area of a bulk material and a nanomaterial.[16]
Now, will be analysed two ways how to manufacture and to implant
on the skin this technology.
After knowing why, the properties of semiconductor in nanoscale The first method shows the procedure to manufacture a graphene
change, it is time to analyse what kind of sensors exist on this kind of electronic tattoo. There are many steps in this process, so to be easier
technology. On the figure 14 shows every type of component to understand, the figure 15 shows a scheme of this method.
integrated on this ultra-thin patch.

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Thus, APCVD is a chemical synthesis process at atmosphere pressure

for the formation of single layer for example graphene on an arbitrary
substrate by exposing the substrate to the gas-phase precursors at
controlled reaction conditions.[19]
In this process has mixed homogeneous gas-phase and heterogeneous
surface reactions. In general, as the partial pressure or temperature in
the reaction substances are increased, homogeneous gas-phase
reactions and the resulting homogeneous nucleation became
significant. To grow a high-quality graphene layer, this homogeneous
nucleation needs to be minimized.[19] A general mechanism for
APCVD, in this case to grow a graphene layer on catalytic metal
substrates includes eight steps as follow on this order:
1- Mass transport of the reactant,
2- Reaction of the film precursor,
3- Diffusion of gas molecules,
4- Adsorption of the precursor,
5- Diffusion of the precursor into substrate,
Figure 15 – Fabrication process of graphene electronic tattoo.[11]
6- Surface reaction,
7- Desorption of the product, and
The steps are:
8- Removal of the by-product.
• Firstly, is needed to grow graphene on copper foil using
In the figure 16, shows a scheme how to produce a layer of graphene
atmospheric pressure chemical vapor deposition system
by using the process APCVD.
(APCVD).[11]
• Next, sub-micrometre-thick poly(methyl methacrylate)
(PMMA) is spun coated onto the as-grown graphene in
order to remove it from the copper.[11]
• The following step is the etching process. In this way, the
large-area graphene produced on copper foil maintains its
excellent continuity.[11]
• Then, graphene/PMMA is transferred onto tattoo paper with
PMMA touching the paper and graphene facing up.[11]
• Next step, graphene/PMMA is cut by a mechanical cutter
plotter. In this way, is possible to carve out the intended
filamentary serpentine designs on the graphene.[11]
• Then, the extraneous areas of the graphene/PMMA are
peeled off from the tattoo paper manually, leaving a
completed graphene electronic tattoo (GET) sensor on
tattoo paper.[11]
• The created GET sensor can then be applied to any area of
Figure 16 – Scheme of the process of growth of graphene using APCVD.[19]
the glabrous or less hairy skin, regardless of its curvature or
shape, by bringing the graphene side into contact with the The second method consists of using a low cost-cost printer circuits
skin and moistening the tattoo paper's reverse side to to manufacture an ultra-thin patch.[10] It is possible to modify an
separate the GET from the paper just like a temporary average inkjet printer to be able to print electrically conductive
transfer tattoo. The ultrathin GET may adhere to the skin circuits. However, how to change an inkjet printer to a printer of
using only van der Waals interactions; no skin preparation conductive circuits?
or glue is needed.[11] The techniques for printing electronics are still largely being
• Finally, the GET is on the skin.[11] developed. Some of the main techniques include screen printing,
rotogravure, and inkjet. Howsoever, in this report will focus the inkjet
printing method because it is the cheapest and easiest method, just
One detail was not explained of this process of manufacture was how need some modifications to be able to print circuits. There are
APCVD works. primarily two ways that inkjet printers operate.[20]

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The first type is called a "Thermal Bubble," and it involves sending a

current first through minuscule resistors in the print head. These
resistors produce heat, which causes some of the adjacent ink to
evaporate. As the ink vaporizes, a gas bubble is formed, and as it
expands, it forces tiny droplets of ink into the nozzle. The ink nozzle
is refilled with air when the bubble eventually explodes, creating a
vacuum in its place.[20] On the figure 17 is displayed a diagram of
this method.

Figure 19 – Example of modified “Piezoelectric” printer capable to print conductive

circuits.[21]

Figure 17 – Diagram of the method “Thermal Bubble” of the inkjet printer.[20]

After knowing how these printers works, is needed to describe this

type of ink.
The second method is known as a “Piezoelectric” printer.
Piezoelectricity is a material property where if a mechanical stress is The material used to build this ink is nanoparticles of silver. But first,
applied, an electric potential is created. The opposite is also true, if a why silver used on conductive inks? Due to the fact that it is a noble
piezoelectric material is exposed to a change in electric potential metal with unquestionable benefits in terms of electrical conductivity,
energy, then its volume will change. Piezoelectric printers utilize this oxidation resistance, and fascinating plasmonic and antibacterial
property by having piezoelectric crystals in the print head’s ink properties. At least for some essential systems that cannot lose
reservoir. When a voltage is applied to these crystals they deform and efficiency, it is difficult to picture a time without the usage of silver.
expel tiny ink droplets out of the nozzle.[20] On the figure 18 is Now why nanoparticles? The key characteristic is related to their size,
displayed a diagram of this method. which elevates surface tension and ionic forces to a degree of
significance that enables a play against gravity and stabilizes a
suspension. [22]
Thus, conductive inks are typically dispersions of nanoparticles of
silver in aqueous or organic solvents that are stabilized by surfactants
and polymers. In this method, the ink is a nanocomposite which the
matrix is a polymer and nanoparticles of silver as a filler.
Nanoparticles of silver used for these types of inks generally have
spherical shape with diameters ranging from 5 to approximately 100
nm with narrow dimensional distribution.[22]
Now, raises the question how these nanoparticles of silver are
Figure 18 – Diagram of the method “Piezoelectric” of the inkjet printer.[20] manufactured? There are many ways to produce these kinds of
materials but will focus only on the physical and chemical methods.

Some researchers suggest that a “Piezoelectric” printer is preferable The two most significant physical methods are evaporation-
to a “Thermal Bubble” printer to print conductive circuits because it condensation and laser ablation. The benefits of physical methods
is less likely to change the composition and characteristics of the over chemical processes are the absence of solvent contamination in
conductive ink.[20] the generated thin films and the uniformity of nanoparticles
distribution. On the other hand, the physical methods consume a great
In order to change a “Piezoelectric” printer is needed to add the ink
amount of energy while raising the environmental temperature around
cartridges which will extend beyond the printer chassis. Also is
the source material and requires a lot of time to achieve thermal
needed to install air filters on the top of the cartridges because, in this
stability.[22]
way, a vacuum is not formed inside of the container when ink is being
drawn out. The final step is to fill the cartridges with conductive ink. Condensation-evaporation method involves the use of tube furnace. A
In this way, is possible to change a “Piezoelectric” printer to a printer solution mixture of silver nitrate and sodium acetate is heated in tube
of conductive circuits. On the figure 19 shows a example of a furnace, and it converts the liquid into gas. Then there will be the
“Piezoelectric” printer modified which is capable print conductive formation of silver nanoparticles after cooling process. On the figure
circuits.[20] 20 shows this kind of process.[23]

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From these manufacture processes is possible to obtain silver

nanoparticles. As already mentioned, silver nanoparticles have
distinctive physical properties such as electrical, optical and thermal
properties. Also, silver nanoparticles have high electrical
conductivity, low sintering temperature and great stability. With these
properties, is possible to create a conductive ink. In conclusion, this
second method, basically modifies an inkjet printer to conductive of
circuits printer which uses this conductive ink in order to manufacture
these ultra-thin patches. These ultra-thin patches are easily
transferable with water to the skin, in the same way that a temporary
tattoo.[10]
Advantages:
Figure 20 - Synthesis of Silver nanoparticles by Evaporation-condensation method.[23]
• Measurements of heartbeat, monitor and diagnose
In the case of laser ablation, this method is more efficient, and it critical health, sleep disorders, brain activity, monitor
depends upon the different parameters for example duration of laser new-borns, etc. (figure13) [9]
pulses, wavelength of laser, and presence or absence of surfactants.
Because metallic nanoparticles are produced without the use of
chemicals, unadulterated product is produced, so the laser ablation
approach offers an advantage over other techniques.[23]
Laser ablation is basically a method of breaking down one part of
material to create a microfeature using a laser beam. On the figure 21
shows this process of manufacturing of nanoparticles of silver.

Figure 23 - Measurements from Tech Tattoos

• Transmit information about the patient to smartphones or

other connected devices. They could allow healthcare
experts to monitor them at distance and quickly.
• Don’t need a charger.
• Significantly more time- and cost-effective.
Figure 21 – Laser ablation method.[23]
• No skin preparation or skin adhesive is required.[11]
In the case of chemical methods, they are mostly used for the synthesis • Stretchability of almost 50% without losing connectivity.
of silver nanoparticles. The samples of silver nanocubes are
• Being produced in 2D its easier to produce and in big
synthesized by reducing silver nitrate with glycol and treated with quantities. Until now the existing alternatives to produce
PVP. This process is known as polyol process. On the figure 22 is this type of ultra-thin circuits required an intensive labor,
displayed this process.[24] high production costs and were exclusively manufactured in
laboratory rooms.

Disadvantages:
• Still need to be more accurate with skin contract
• Because the human epidermis naturally eliminates dead
skin cells, further research is needed to find materials
that can adhere to the skin without sloughing off or
wiping off in the presence of sweat.[12]
• There may be still have some issues between contact
with water and the tattoo.
• After some hours starts to fracture or delaminate, if you
Figure 22 – Chemical method for synthesis of silver nanoparticles.[23]
want to keep for some days you have to apply liquid
bandage coverage.

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• It is not yet possible to insert these tattoos into the skin

and human body. To stimulate some body part to
recover faster. For example, create a way to get these
tattoos applied to the spinal cord in order to stimulate it
and reactivate the nerves to work again.
• Loss of freedom

Figure 11-Improving football performance

• diabetic sensors to measure glucose levels.

Figure 9-Wash Tattoos Conclusions

Like we saw, this type of technology is the future! We can save
many lives with this tattoos and improve many others. The
Applications:
progress on medicine and nanotechnology provides us this
• An electronic tattoo on the forearm of a person with a enormous variety of skin sensors.
hand prosthesis has been shown that it is possible to In one hand we can produce them by 3D printing a composite
control the hand using signs of muscles received by and in the other hand we can produce it by graphene-based
tattoos. By putting the tattoo on the right muscle, the circuit. Both are total painless and being produce in a 2D layer
tattoo lets you see when it is activated and whether the they are truly cheaper than being produce in laboratory. It’s only
hand closes or opens. (Figure 25) [10] possible because the advances in the nanotechnology. We have
infinite applications, also some problems to solve first like the
stretchability and durability of the tattoo.
Unfortunately, with this emerges other philosophical
problematics. According with Catarina- “Now, the body is no
longer an independent and autonomous entity, living almost
anonymously, as it used to be in disciplinary societies.” (Nabais,
2007) She is right, with that much control and vigilance, at
certain point people will lose their independence and freedom.
Being controlled 24h remotely, not only their problems but also
Figure 10- Manipulating prothesis
their position in case of needs to call an ambulance.

In our opinion this is a little price to pay to get a better healthy

• Apply to home appliances in order to monitor their
life. Instead of being in a hospital monetarized, people can be
condition and fault scan.
with their family, at home, and controlled at the same time.
• Outside of the healthcare field, these electronic circuits
We learned a lot with this review and get excited with this theme.
can be used on any 3D surface, such as a car dashboard,
We believe that next step in medicine passes throw technological
to allow touch-activated control of the car's various
tattoos and combination with nanotechnology.
features, such as controlling the radio's volume or
temperature of the car.
• If the values change in a patient can be sent a warning
Acknowledgements
directly to the firefighters in order to call an ambulance
quickly. We would like to acknowledge all the professors in this
• In the future these tattoos could be apply in assignment that made us gain interest in this area. In special do
professional players to measure, during matches or Dr. Gil Gonçalves that show us the potential of nanotechnology
competitions, beats or muscle fatigue. to monetarize people’s health.

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Notes and references 17 The electronic tattoo that can monitor patient
symptoms remotely [Internet] 2018 [cited 25 June
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https://ironinktattoo.com/history-of-tattoos/ monitor-patient-symptoms
2 Nanotechnology [Internet]. 2020 [cited 17 June 2022]. 18 Biomedical Sensors: Types of sensors and How it works
Available from: [Internet] 2005 [cited 26 June 2022]. Available from:
https://www.cdc.gov/niosh/topics/nanotech/default.h https://www.seeedstudio.com/blog/2019/10/14/biom
tml edical-sensors-types-of-sensors-and-how-it-works/
3 Nanocomposites [Internet]. Nanowerk.com. 2022 [cited 19 Pietro Mandracci, “Chemical Vapor Deposition for
17 June 2022]. Available from: Nanotechnology”, 2018, [cited 26 June 2022]. Available
https://www.nanowerk.com/nanocomposites.php from: https://www.intechopen.com/chapters/63774
4 Virendra S. Graphene based materials: Past, present and 20 Print Conductive Circuits with an Inkjet Printer,
future. 56th ed. Progress in Materials Science. 2011. p. remotely [Internet] 2008 [cited 26 June 2022]. Available
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https://doi.org/10.1016/j.pmatsci.2011.03.003 Conductive-Circuits-With-An-Inkjet-Printer/
5 2D-EPL offers developers the chance to test graphene- 21 Inkjet-compatible conductive ink lets users make their
based sensors | Graphene Flagship [Internet]. own electronics at home [Internet] 2015 [cited 26 June
Graphene-flagship.eu. 2022 [cited 20 June 2022]. 2022]. Available from:
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the-chance-to-test-graphene-based-sensors/ own-electronics-at-home/
6 Ma Z, Li S, Wang H, Cheng W, Li Y, Pan L, et al. Advanced 22 Krishna Rajan, ignazio Roppolo. Annalisa Chiappone,
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electronics-can-monitor-your-vital-signs-
040113#Electronic-Tattoos
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10 | D. Pires, J. Machado, 2022 Universidade de

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