Mechanical Engineering FRM-2 (YOU NEED THE SESSION )
FRM-2
Paper #
Self-Healing Materials
Roland Beard (rkb15@pitt.edu), Callaghan Bradley(cab205@pitt.edu)
producing sustainable technologies is the greatest
engineering challenge today.
Nanotechnology is the answer to the search for
a way to make current technologies more
environmentally friendly. Nanotechnology can be
seen as a performance enhancer for current
technologies. Technologies produced on the nanoscale have the ability to inexpensively reduce
power consumption, increase life expectancy, and
decrease overall negative impact on the
environment. More specifically, nanotechnology
can be used to impart human-like characteristics
upon various technologies. Within the realm of
biological attributes, the creation of a synthetic
self-healing coating for mechanical devices would
allow a device to heal itself with little to no human
interaction. The synthetic self-healing coating is
actually a self-healing polymer. Two primary
methods of implementing the regenerative
characteristic
upon
materials
utilize
supramolecular assembly and microcapsules.
Though the supramolecular method already exists
in the form of a paint coating called the Nissan
Scratch Guard, it has no yet been perfected. Once
perfected, the self-healing coating will have the
potential to increase the sustainability and
efficiency of a multitude of technologies and
mechanical processes.
Abstract The repair-and-go microcapsules mimic
leukocytes in two main ways. They have similar
methods of delivering healing materials and
similar structures. Leukocytes entrap themselves
in the damaged area in order to release the
healing agents into the damaged area. The
microcapsules also do this to release nanoparticles into the damaged area. Microcapsules
also pass the nano-particles through a permeable
barrier, and can be filled and emptied repeatedly,
much like a cell. According to -----[1], “In the
present work, such biological interactions are
replaced with surface energies.” This refers to the
main difference between the leukocytes and the
microcapsule system, where the active biological
work done by the cells is replaced with passive
“surface
energies”
such
as
hydrophilic/hydrophobic preferences.
According to Balazs’, “In our synthetic system the
“leukocyte” is a polymeric microcapsule, the
healing agents are encapsulated solid nanoparticles, and the “wound” is a microscopic crack
on a surface. While in this technology can be
adapted to work with different compounds, we will
be analyzing the research done at the University
of Pittsburgh and University of Massachusetts.
Key
Words—
Supramolecular
Assembly,
Microcapsule, Polymer, Substrate, ScratchGuard.
ENGINEERING GRAND CHALLENGE:
SUSTAINABILITY
THE IMPLICATIONS OF REGENERATIVE
MATERIALS
The most pressing concern in our world today is
the preservation of our future. In response to the
trepidation concerning the world’s future, the
unofficial “green” movement has been created.
The “green” movement refers to the increase in
the desire and production of “green” or sustainable
technologies. Engineers have been tasked with the
job of protecting our world’s future through the
manufacturing of “green” technologies. In fact,
Though nano-scale defects are seemingly
insignificant, “they can have a substantial impact
on the mechanical properties of a system. For
example, “significant stress concentrations at the
tip of notches in the surface; such regions of high
stress can ultimately lead to the propagation of
University of Pittsburgh
Swanson School of Engineering
April 14, 2012
1
Roland Beard, Callaghan Bradley
cracks through the system and degradation of
mechanical behavior”. The imparting of the
regenerative characteristic on devices and
materials would be especially useful in extreme
environments such as aerospace and heavy
industry where nano-scale abrasions are more
common. In addition to extending the lifespan of
the machinery or products, self-healing materials
would significantly extend the lifetime of sensitive
systems as well as lower maintenance costs. For
example, a broken circuit in a fighter plane usually
results in severe injuries or death. Moreover the
plane would have to be stripped in order to find
the technical fault, which is both expensive and
time-consuming. So, self-healing materials have
the potential to save lives as well as money.
Furthermore, faulty or damaged plastic
consumer products negatively effect the
environment. Durable plastics have been
universally accepted as consumer products
ranging from storage containers to computer.
Since plastics are utilized in everyday life, they
are highly susceptible to damage, which can result
in loss of function. Once compromised, plastics
are usually disposed of in landfills, or occasionally
repaired. Self-healing polymers offer a solution to
this environmental problem. The implementation
of self-healing coatings would decrease the toll on
the environment that results from consumer waste.
continuity and integrity of the damaged area. [2].
The biological inspiration behind repair-and-go
method was leucocytes, more commonly known
as
white
blood
cells.
The repair-and-go method applies a unique
synthetic imitation for inflammatory response or
triggering/actuation. By using the hydrophobic
and hydrophilic preferences of the capsule, nanoparticles and the scratched material are attracted to
each other throughout the membrane of the
microcapsule.
Supramolecular
self-healing
compounds
focuses on mimicking the matrix remodeling
aspect of biological response to injury. When a bit
of tissue is damaged, the last stage of biological
repair is matrix remodeling. Matrix remodeling
involves the rebuilding of tissue matrices.
Vascular systems are very helpful with this
process by bringing building blocks where they
need to be and getting rid of broken pieces.
Synthetic matrix remodeling is very similar as it
also is the rebuilding of the matrix structure of the
material. However, synthetic materials do not have
a vascular transport system. The synthetic replica
involves the use supramolecular polymers that
have many flexible bonds in their structure. This
gives these polymers the flexibility to reorient
themselves into the proper formation. When the
bonds are reformed, the material has returned to
its
original
structure.
THE BIOLOGY BEHIND THE MECHANICS
The design of self-healing materials is modeled
after biological regenerative systems. According
to [1] “Biological response to injury is threefold:
inflammatory
response
(immediate),
cell
proliferation (secondary), and matrix remodeling
(long-term).” The two different self-healing
methods we will be analyzing focus on imitating
the biological process healing. The repair-and go
method focuses primarily on the emulation of the
initial inflammatory response, while the
supramolecular polymers behave in a manor
analogous
to
matrix
remodeling.
The challenge in re inflammatory response lies
not only in “sensing” the presence of a “wound”
or defect, but then also actively reestablishing the
2
Roland Beard, Callaghan Bradley
Figure 1[2]
blood cell filled with microscopic granules
containing enzymes that digest microorganisms [].
Next, the leukocytes locate and entrap themselves
in regions of damaged tissue. Next the leukocytes
release enzymes through their thin shell into
damaged regions of the body in order to heal the
wound [2]. The microcapsules are designed with
this course of action in mind, along with the
ability to repetitively heal. The repair-and-go
microcapsules mimic leukocytes in two main
ways. They have similar methods of delivering
healing materials and similar structures.
Leukocytes entrap themselves in the damaged area
in order to release the healing agents into the
damaged area. The microcapsules also do this to
release nano-particles into the damaged area.
Microcapsules also pass the nano-particles
through a permeable barrier, and can be filled and
emptied repeatedly, much like a cell. According
to -----[1], “In the present work, such biological
interactions are replaced with surface energies.”
This refers to the main difference between the
leukocytes and the microcapsule system, where
the active biological work done by the cells is
replaced with passive “surface energies” such as
hydrophilic/hydrophobic preferences.
This diagram illustrates the differences between synthetic and biological
repair.
“(Right) In biological systems, wound healing follows three sequential
steps, the first of which is an immediate inflammatory response, including
blood clotting. In the second stage, cell proliferation and matrix deposition
occur and can extend for several days. The long-term response is matrix
remodeling, which sometimes extends for several months. (Left) In
synthetic materials, damage healing proceeds by an immediate response that
actuates (triggers) the healing mechanism (e.g., the rupture of embedded
microcapsules). Once triggered, the second stage involves transport of
chemical species to the site of damage at a relatively rapid rate. During the
final stage of healing, chemical repair takes place and can extend for several
hours or days.” [2]
REPAIR-AND-GO METHOD
In the research done by the University of
Pittsburgh microcapsules were filled with a
polymer surfactant, since the experimental
compromised surface was a polymer. The polymer
surfactant could be replaced with copper nanoparticles suspended in an oil-water mixture. Upon
self-healing, copper particles would be released
into the crack, thus restoring both the integrity and
conductive
property
of
the
material.
THE SCIENCE BEHIND THE REPAIR-AND-GO
The “repair-and-go” process defined in Balazs’
work [3] is a selective self-healing process that
utilizes microcapsules for selective deposition of
the healing material. A microcapsule is a microsized hollow container created by means of microencapsulation, which is the process of surrounding
microscopic amounts of a substance with a thin
shell [4]. In this repair-and-go approach, a flexible
microcapsule filled with a solution of nanoparticles rolls across a surface stopping to repair
any defects it encounters by releasing nanoparticles into the defect, then continuing on to the
next defect [2]. This process is very efficient
because the microcapsules as well as their
contents can be reused.
According to Balazs’, “In our synthetic system
the “leukocyte” is a polymeric microcapsule, the
healing agents are encapsulated solid nanoparticles, and the “wound” is a microscopic crack
on a surface. While in this technology can be
adapted to work with different compounds, we
will be analyzing the research done at the
University of Pittsburgh and University of
Massachusetts.
THE AQUEOUS FILLING
The microcapsules are filled with a mixture of oil
and water. Hydrophobic, water repellant, nanoparticles are dispersed throughout the aqueous
mixture of oil and water. This encapsulated
mixture acts as the healing agent, which is
dispersed
by
the
microcapsules.
CdSe (Cadmium Selenide) quantum dots were the
type of nano-particles used as the healing
MANMADE WHITE BLOOD CELLS
The idea of the repair-and-go method of selfhealing with the use of microcapsules is modeled
after a cell in the human body called a granular
leukocyte. A granular leukocyte is a type of white
3
Roland Beard, Callaghan Bradley
particles. “Quantum dots are semiconductors
whose conducting characteristics are closely
related to the size and shape of the individual
crystal.” In this case the quantum dots are similar
in properties to the material that is being
regenerated. Therefore, when the particles fill the
defects, the materials regain most of their original
properties. The CdSe quantum dots were
specifically used because of their inherent
fluorescence, which offers a useful marker to
locate the restored regions of the material. The
CdSe nano-particles are hydrophobic, which
means they do not mix with water or other
hydrophilic substances.
chosen, because of the physical characteristics it
possesses. The polymer, when strained, cracks
randomly. The resulting abrasions are confined to
the outer surface of the substrate, a surface upon
which a different material is deposited or adhered,
usually in a coating or layer [4]. The generated
damage produces cracks analogous to the damage
commonly found in the coatings of materials such
as
rubber.
METHODOLOGY
“Within an oil/water mixture, the amphiphilic
comb copolymers can out-compete the
functionalized quantum dots for an oil-in-water
droplet interface and thus provide an
encapsulating shell for the coated nano-particles,
which are dispersed in the interior oil phase. Upon
cross-linking, the copolymers form a robust micro
carrier for the nano-particles, with a very thin wall
through which the nano-particles can permeate
under
appropriate
conditions.”
In simpler terms, the PCOE-graft-PC
polymers chosen for these “flexible nanocapsules” are specialized surfactants, in the sense
that they have a hydrophobic surface as well as
hydrophilic surface. The hydrophobic CdSe nanoparticles and oil are attracted to the hydrophilic
exterior, thus forming a hydrophobic shell around
the particles. This arrangement causes the aqueous
solution of nano-particles to gravitate toward the
inside of the shell of the surfactant polymers. “The
droplets remain stable for weeks, or longer,
without
substantial
coalescence.”
[1]
OF
THE
MICROCAPSULES
Through experimentation, Balazs’ discovered the
need for microcapsules to be propelled across the
substrate in order to produce an effective healing
mechanism. A constant flow of water was initially
used to transport the capsules. The results of this
test showed that a constant flow caused the
microcarriers to become entrapped in the surface
scratches. Additionally, the steady flow only
permitted roughly 10-20 percent of particles to be
deposited. To alleviate the problem of permanent
deposition, a pulsatile flow was employed. The
pulsatile flow was found to allow the
microcapsules to repair more effectively,
delivering more nano-particles, as well as continue
moving to other abrasions. Also, the pulse flow
allowed the microcarrier to localize and excrete a
higher concentration of nano-particles along the
interior of the crack. The pulsing of the force in
the water allowed the microcapsules to escape
cracks where it may have become wedged. In fact
the pulsatile flow allowed for between 73% and
90% or the nano-particles to be deposited.
Consequently, the pulse flow increased the healing
rate.
Other than varied water propulsion, there were
two notable contributing factors that promoted the
deposition of nano-particles in compromised
regions of the substrate. The hydrophilic PCsusbstituents of the PCOE-graft-PC, poly
(cyclooctene) and phosphorylcholine grafts,
polymer provided the droplets with antifouling
properties; the ability to prevent undesired
permanent deposition into surface cracks. A graft
is a polymer comprised of molecules in which the
THE MICROCAPSULE EXTERIOR
EXPERIMENTAL RESULTS
GO METHOD
OF
THE REPAIR-AND-
The self-healing technique was tested on
polydimethylsiloxane,
silicon
oxide-coated
siloxane polymer. This particular polymer was
4
Roland Beard, Callaghan Bradley
main chain of atoms is attached at various points
to the side chains containing different atoms or
groups from those in the main chain. The
substituent connected to the main chain in this
polymer is phosphorylcholine [5]. Also, the size of
the nano-particle droplets played a role in
successful delivery of the healing agent. The
larger than average size of the droplets of oil,
water, and nano-particles released into the cracks
prevented irreversible deposition.
potentially be specialized to restore broken
circuits. The microcapsules could be filled with a
material such as copper, which could restore the
conductive traits of a wire. Instead of CdSe
quantum dots, ionic metal quantum dots could be
used
to
fill
the
microcapsules.
SUPRAMOLECULAR
ASSEMBLY
THE SUPRAMOLECULAR STRUCTURE
Supramolecular polymers are large networks of
smaller recurrent molecules, which have been
conjoined into long chains with the use of metal
ions. The metal ions form non-covalent bonds
each of the molecules of the polymer. These noncovalent interactions make supramolecular
polymers unique to the traditional polymers,
which consist of long chain-like, covalently
bonded molecules. The non-covalent bonds can be
repeatedly broken down and restored with
exposure to ultraviolet light. Due to the
reversibility
of
non-covalent
interactions,
supramolecular polymers have the inherent ability
to
self-heal.
Figure 1[6]
This image shows the chemical structure of a PCOE-graft-PC molecule
where the ____side is hydrophobic and the ___side is hydrophilic. Then
when they are added to a solution of oil, water, and nano-particles (NPs),
the PCOE-graft-PC molecules attach themselves to each other, and orient
themselves with the hydrophilic sides toward the water, and the
hydrophobic sides near the hydrophobic NPs.
THE SUPRAMOLECULAR ASSEMBLY AT WORK
When exposed to ultraviolet light, the noncovalent bonds dissociate the metal ionic bonds
causing the polymer to begin to flow. Once the
source of UV light is removed, the polymer will
naturally reassemble into its original state. Due to
the polymer’s ability to regenerate without heat,
the supramolecular assembly proves to be
environmentally and mechanically efficient. The
employment of UV light allows for local healing,
so none of the light is wasted on an unscathed
section of the material. Since UV light is the only
required interaction to start the reversible reaction,
the sun can be utilized as a source of energy for
the self-healing process. So, supramolecular
assembly is highly efficient and cost-effective.
EXAMPLES OF USES
The two largest advantages of this method of
repairing are efficient delivery of the healing
nano-particles and the ability to repair very tiny
defects in the surface. The first makes this both a
cost effective and green process. The second
makes it very well suited as a surface treatment
method during the production process of sensitive
equipment (especially that which needs to be
under
extreme
conditions.)
The microcapsules could be used to detect damage
on a microscopic level. Filling the microcapsules
with a fluorescent dye would allow the
microcapsules to mark a damaged region of
material. So, microcapsules can be utilized as an
early warning system. The technology could also
5
Roland Beard, Callaghan Bradley
required two consecutive exposures for 30 seconds
at a time to sufficiently heal the cuts. Also, during
the exposure, the surface temperature of the zinc
triflimidate rose to over 220 °C. Using the change
in temperature as evidence, the researchers
concluded that the UV light healing process
occurred as a result of photothermal conversion,
the chemical transformation of light into heat. So,
the supramolecular can reassemble with exposure
to heat, though the addition of heat is not
necessary.
Additionally, the results of the reference
experiments results yielded that the healing
process could only occur in wavelengths inside the
absorption band of the 3·[Zn(NTf2)2]0.7 metalligand complex, range of absorbable light. The
wavelengths between 400 and 500nm did not
cause the polymer to reassemble. However, the
particular range of wavelengths of UV light
necessary to stimulate self-healing lie in the range
of light that the sun produces, between 10 and
400nm. The Nissan Scratch Guard exploits this
ability.
Figure 2 [6]
SUPRAMOLECULAR TESTING
A research team from Case Western Reserve
University has achieved notable results through
experimentation with supramolecular polymers.
The research team used zinc triflimidate
(3·[Zn(NTf2)2]x) , a supramolecular polymer,
throughout their experimentation. To form the
polymer, ~0.025 M zinc triflimidate was mixed
with ~.05M acetonitrile (CH3CN). The solution
of the constituent compounds formed a white
precipitate. Afterward, the precipitate was dried in
a vacuum to produce a supramolecular polymer.
The polymer formed existed in the form of a thin
film.
To measure the self-healing ability of the
polymer, the film of (3·[Zn(NTf2)2]0.7) was
scratched by cutting the film to varied depths
between of ~50–70% of its thickness. Next, the
sample was exposed to a filtered UV light source,
which illuminated the samples with wavelengths
of light ranging from 320 to 390 nanometers at
intensity of 950 mW cm−2. In order to test the
effectiveness of the regenerative technology at
varied wavelengths, reference experiments were
performed with the same lamp system, but with a
filter that illuminated the sample with light of
wavelengths of light between 400 and 500
nanometers.
Under the initial experimental conditions, the
films comprised of 3·[Zn(NTf2)2]0.7 only
NISSAN SCRATCH GUARD
As the maintenance side of products has a much
larger consumer market, it is not surprising that
there is already a self-healing material. This
material is a supramolucar polymer used as a
regenerative
coating.
There is a supramolecular regenerative coating
on the market . The coating exists in the form of
Nissan’s Scratch Guard. The Nissan Scratch
Guard is a protective coating, which Nissan
currently applies to the Nissan Murano, 370Z , XTrail, and Infiniti [7]. The scratch resistant coating
is combined with the standard clearcoat. The
mixture of the two coats acts as a surfactant by
reducing the surface tension of the paint thus
increasing overall flexibility. The regenerative
coating is composed of a highly elastic resin made
of polyrotaxane, which is a supramolecular
polymer. Rotaxane is a mechanically interlocked
molecular structure characterized by the high
freedom and mobility of their components [6].
6
Roland Beard, Callaghan Bradley
Polyrotaxanes are a class of polymeric materials,
which are composed of a network of
interconnected
rotaxane
assemblies.
The
polyrotaxanes are ideal for supramolecular
assembly because of their durability that results
from the cross linking, the bonding of polymeric
chains, of each rotaxane structure. These polymers
dissociate quickly when exposed to UV light.
Though the specifics of the experimental results
are not publicly released, the Scratch Shield coat
had a fifth of the number of scratches compared
with a conventional clearcoat [8]. Furthermore, the
experimental findings show that the time for selfrepair is dependent upon surrounding temperature
as well as the depth of the scratch, and the
material was nearly restored to its original state.
The time required to regenerate damaged material
ranged from a matter of minutes to a week. Also,
the coating was found to be ineffective when
dealing with scratches that are deep enough to
sever the bonds within the clearcoat or if the
clearcoat
has
been
peeled
off
[7,9].
This image illustrates how the “high-density
bonding” in Nissan Scratch Guard. “-The paint
does not self-repair if scratches are deep enough to
sever the bonds within the clearcoat or if the
clearcoat
has
been
peeled
off.
The amount of time required for self-repair
depends on the surrounding temperature and the
depth of the scratch. In some cases, restoration
may
take
up
to
one
week.’
SELF-HEALING MATERIALS: The Good and
the Bad
These two self-healing materials are good
examples of how diverse the applications of selfhealing materials can be. Supramolecular
materials have the advantage of using energy from
its surroundings, making it a good choice for
products that need low levels of protection as well
as for machinery that is exposed to ultraviolet light
daily.
The repair-and-go method has the
advantage of efficiently repairing very small
defects on surfaces. Even though they are both
self-healing technologies, they have very different
applications. While the repair-and-go method is
better suited as a surface treatment method,
supramolecular material makes a very effective
self-healing sealant. They can also both be
adapted for similar uses. Currently, both of these
technologies are in the process of being adapted to
employed in the form of an I-phone case.
Presently, the supramolecular Nissan paint is
being modified to self-heal at lower temperatures
and levels of exposure to UV light to fit consumer
needs, while the repair-and-go method is still in its
experimental phase.
In contrast, there are issues concerning the
implementation of these self-healing methods.
While considering real-world applications of the
repair-and-go technique, there are issues to be
pondered even though it is still in the experimental
phase. The primary concern we see with the usage
of the repair-and-go method is the need to create a
pulsatile flow to allow the microcapsules to exit
the cracks. The supramolecular assembly has a
fault as well. The supramolecular coating could
not be employed in an industrial setting, because
currently, the coating can only repair cosmetic
damage. So, supramolecular polymers would be
most efficient in consumer products.
Figure 3 [8]
This image illustrates how the “high-density bonding” in Nissan Scratch
Guard. “-The paint does not self-repair if scratches are deep enough to sever
the bonds within the clearcoat or if the clearcoat has been peeled off.
-The amount of time required for self-repair depends on the surrounding
temperature and the depth of the scratch. In some cases, restoration may
take up to one week.’ [10,11]
ECONOMICS AND EFFICIENCY
7
Roland Beard, Callaghan Bradley
Supramolecular polymers materials and repairand-go healing are in many ways more efficient
the current alternatives, though they do pose some
practical problems.
The repair and go method requires not only the
application of the microcapsule solution to the
defective surface, but the solution must be
propelled with a pulsating flow. This requirement
is not convenient for application to consumer and
industrial technologies. So, the capsules must be
adapted as to propel themselves.
However,
the
fabrication
of
these
microcapsules as well as the repair-and-go
delivery method of the healing nano-particle
solution is a very efficient process. The “special”
hydrophobic/hydrophilic
structure
of
the
microcapsules makes their formation very
efficient. Traditionally, microcapsule based
technologies have required complex chemical
fabrication processes to process and fill the
microcapsules, which requires energy and money.
The repair- and-go microcapsules do not require
external energy to be created. The PCOE-graft-PC
molecules are simply mixed in a solution of oil,
water, and nano-particles. The mixture naturally
arranges the constituents into microcapsules. So,
the production of these microcapsules is an energy
efficient and sustainable process.
Furthermore, the conventional microcapsule
based self-healing systems involve the rupturing
of a capsule to release the contents into the
damaged area. In addition to this process lacking
precision, a damaged region can only be
regenerated once. Also, the debris resulting from
the broken capsules can alter the mechanical
properties of the material [quote]. repair- and-go
microcapsules do not deposit debris from broken
shells, thus preserving the mechanical properties
of the material. Also, the repair-and-go
microcapsules can be “refilled” by simply
remixing them in an oil, water, and nano-particle
solution [7]. The capsules absorb the solution
through their porous shells. The recyclability of
the capsules causes the microcapsules to be
exceptionally economical and efficient. In Balazs’
experiments, she simply rinsed the substrate with
water to remove the microcapsules in order to save
them for future testing [8]. Accordingly, these
microcapsules are low maintenance and have
extensive life spans.
The evaluation of each self-healing process’
economical efficiently shows the high level of
sustainability of the regenerative materials. Both
regenerative polymers do not require added energy
in their respective formations. Also, since each
substance is capable of regeneration, there are no
associated maintenance costs to date. Evidencing
the low costs of production and proven
regenerative abilities, we believe the self-healing
technology to be the answer to the current
engineering challenge of increasing sustainability.
CONCLUSION
Nature accomplishes a lot of work with very
little dangerous waste. It grows large trees with
only O2, nitrogen , and fertilizer as byproducts. So
it is a very good idea to look to natural biological
systems for inspiration. The “green” movement
will likely become a bigger and bigger part of our
professional and political environment in the
future. However, one of its biggest setbacks is
when its proponents try to be too ambitious. Our
entire culture is not going to change of overnight
into some “green” utopia for any reason.
However, we can make a big difference by
refining our current technologies to make them
more sustainable.
Instead of asking people to change, offer to
make what the have stronger, last longer, run
cheaper, and be generally “greener”. For example,
instead of trying to redesign expensive, sensitive
electrical systems for a space probe, we can treat
the parts with the repair-and-go method. This will
make it last longer under strenuous conditions,
thus save money and resources. Nissan’s Scratch
Guard is already making the maintenance of their
cars more efficient by repairs cosmetic scratches
before they can corrode the body of the car. Selfhealing nanotechnologies are a great way to
8
Roland Beard, Callaghan Bradley
Available:http://www.gizmag.com/worlds-first-self-healing-iphonecase/21127/
accomplish this. As illustrated in this paper, this
technology can improve our current products in
both the manufacturing stage and maintenance.
The most productive way to promote the
“green” cause is to start with what we already
have. While one day entirely preconceived
“green” technologies will be very important., it is
equally important to find ways to improve and
adjust what the technology machinery and
equipment we already have. Self-healing materials
are a great way that we can refine our current
technologies to make them cleaner, cheaper,
stronger, and more efficient.
ADDITIONAL RESOURCES
Kolmakov, G. V., Revanur, R., Tangirala, R., Emrick, T., Russell, T. P.,
Crosby, A. J., and Balazs, A. B., Using nanoparticle-filled microcapsules
for site-specific healing of damaged substrates: creating a "repair-and-go"
system", ACS Nano 2010, 4, 1115-1123.
Katrina Kratz, Amrit Narasimhan, Ravisubhash Tangirala, SungCheal
Moon, Ravindra Revanur, Santanu Kundu, Hyun Suk Kim, Alfred J.
Crosby, Thomas P. Russell, Todd Emrick, German Kolmakov, Anna C.
Balazs. Probing and repairing damaged surfaces with nanoparticlecontaining microcapsules. Nature Nanotechnology, 2012; DOI:
10.1038/nnano.2011.235
ACKNOWLEGEMENTS
I would like to thank Kenechi Agbim for aiding us
in our writing process.
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