7/28/2019 nanaogear

1/24

ABSTRACT:

NANOmeans one billionth of one and one third of micro, to be precise

(109 meters). Nanotechnology is simply an emerging frontier and the future

science paving the best way for most of cutting edge technologies. NEMS

technology has been a realm in which machines operate at scales of billionth a

meter. Recent innovations in nanotechnology revealed many potential applications

in fields such as energy, medicine, electronics, computing and many more.The

most advanced innovation in the field of nanotechnology is nanogenerators .These

are futuristic and most advanced technologies which are quiet compact and harvest

mechanical energy from the environment using an array of tiny nanowires. These

nanogenerators find many applications in very small electronic devices; self

powered micro devices and many more practical applications.

These nanogenerators develop energy from body movements, environmental

changes, and even from the rustle of a fiber .these develop power in the range of

nanoamperes and integrating their contributions results in energy which is quiet

sufficient to charge up a mobile phone or an I pod just from body movements

which results in energy conservation .so these nanogenerators are going to play a

key role in the future generations. In recent days these nanogenerators are being

used to drive commercial devices such as LCD (Liquid Crystal Display), LED

7/28/2019 nanaogear

2/24

(Light Emitting Diodes), laser diodes. So focus is held on further improvements of

nano generators.

The paper deals with history, construction, merits, uses, future applications

of nano generators.

7/28/2019 nanaogear

3/24

INTRODUCTION:

Nanogenerator is a technology that converts mechanical/thermal energy as

produced by small-scale physical change into electricity. Nanogenerator has three

typical approaches: piezoelectric, triboelectric, and pyroelectric nanogenerators.

Both the piezoelectric and triboelectric nanogenerators can convert the mechanical

energy into electricity. However, the pyroelectric nanogenertors can be used to

harvest thermal energy from a time-dependent temperature fluctuation.

Nanoscale devices that harvest mechanical energy from the environment

using an array of tiny nanowires are called nano generators. A nanowire is a

nanostructure, with the diameter of the order of a nanometer (109 meters).

Alternatively, nanowires can be defined as structures that have a thickness or

diameter constrained to tens of nanometers or less and an unconstrained length.

A silicon nano generator is an energy harvesting device converting

the external kinetic energy into an electrical energy based on the energy conversion

by nano-structured piezoelectric material.

7/28/2019 nanaogear

4/24

WHAT IS PEIZO ELECTRICITY?

The word piezoelectricity means electricity resulting from pressure.

Piezoelectricity is the charge which accumulates in certain solid materials in

response to applied mechanical strain. Piezoelectricity is the direct result of the

piezoelectric effect, which is understood as the linear electromechanical interaction

between the mechanical and the electrical state in crystalline materials. The

internal generation of electrical charge resulting from an applied mechanical force

is called as piezoelectric effect piezoelectric effect is due to the occurrence of

electric dipole moments in solids.

7/28/2019 nanaogear

5/24

PEIZO-ELECTRIC EFFECT

Nanogenerators may include any types of energy harvesting devices with

nano-structure converting the various types of the ambient energy (e.g. solar power

and thermal energy), it is used in most of times to specifically indicate the kinetic

energy harvesting devices utilizing nano-scaled piezoelectric material. The

mechanical energy from compressing a nanogenerator between two fingers, from a

heart beat, the pounding of a hiker's shoe on a trail, the rustling of a shirt, or the

vibration of a heavy machine is converted into electrical energy by these

generators.

Although nanogenerators will not produce large amounts of electricity

for conventional purposes, they could be used to power nanoscale and micro scale

devices -- and even to recharge pacemakers or iPods.. By simplifying design and

making it more robust and integrating the contributions from many more

nanowires, we can successfully boost the output of a Nanogenerator enough to

drive devices such as commercial liquid-crystal displays, light-emitting diodes and

laser diodes, very small devices which are used in applications of health care,

environmental monitoring and personal electronics "How to power these devices

is a critical issue." And the answer is nanogenerators.

7/28/2019 nanaogear

6/24

Mechanism:

The working principle of nanogenerator will be explained for 2 different

cases: the force exerted perpendicular and parallel to the axis of the nanowire.

The working principle for the first case is explained by a vertically grown

nanowire subjected to the laterally moving tip. When a piezoelectric structure is

subjected to the external force by the moving tip, the deformation occurs

throughout the structure.

The piezoelectric effect will create the electrical field inside the

nanostructure; the stretched part with the positive strain will exhibit the positive

electrical potential, whereas the compressed part with the negative strain will show

the negative electrical potential. This is due to the relative displacement of cat ions

with respect to anions in its crystalline structure. As a result, the tip of the

nanowire will have an electrical potential distribution on its surface, while the

bottom of the nanowire is neutralized since it is grounded. The maximum voltage

generated in the nanowire depends on the permittivity in vacuum the dielectric

constant radius and length of the nano wires.

For the second case, a model with a vertically grown nanowire stacked

between the ohmic contact at its bottom and the schottky contact at its top is

considered. When the force is applied toward the tip of the nanowire, the uniaxial

compressive is generated in the nanowire. Due to the piezoelectric effect, the tip of

7/28/2019 nanaogear

7/24

nanowire will have a negative piezoelectric potential, increasing the Fermi level at

the tip. Since the electrons will then flow from the tip to the bottom through the

external circuit as a result, the positive electrical potential will be generated at the

tip. The schottky contact will barricade the electrons being transported through the

interface, therefore maintaining the potential at the tip. As the force is removed, the

effect diminishes, and the electrons will be flowing back to the top in order to

neutralize the positive potential at the tip. The second case will generate alternating

current output signal

7/28/2019 nanaogear

8/24

GEOMETRIC CONFIGURATION

Depending on the configuration of piezoelectric nanostructure, the most of

the nanogenerator can be categorized into 2 types: VING and LING. Still, there is

a configuration that does not fall into the above mentioned categories, as stated in

other type.

7/28/2019 nanaogear

9/24

TRIBOELECTRIC NANOGENERATOR

Triboelectric Nanogenerator is an energy harvesting device that converts the

external the ambient mechanical energy into electricity based on the nano-scale

triboelectric effect. It is another mechanical energy harvesting technology besides

the piezoelectric nanogenerator. This new type of nanogenerator was firstly

demonstrated in Prof. Zhong Lin Wangs group atGeorgia Institute of Technology.

Although it is still in the early stage of the development for triboelectric

nanogenerators, the output voltage has been enhanced to hundreds of volts,[19]and

it has been proven to be a simple, cost-effective, robust and efficient approach to

scavenge mechanical energy.

The typical structure of a triboelectric nanogenerator is the stacking of two

sheets with electrode layers on the back. The inner surfaces of the two sheets are

covered with two different materials respectively, which should have large

difference in their abilities to attract electrons. Also, it is always needed to have an

intrinsic gap existing between the two sheets at strain free condition.

http://en.wikipedia.org/wiki/Energy_harvestinghttp://en.wikipedia.org/wiki/Triboelectric_effecthttp://en.wikipedia.org/wiki/Georgia_Institute_of_Technologyhttp://en.wikipedia.org/wiki/Georgia_Institute_of_Technologyhttp://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlkThis-19http://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlkThis-19http://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlkThis-19http://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Strain_%28chemistry%29http://en.wikipedia.org/wiki/Strain_%28chemistry%29http://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlkThis-19http://en.wikipedia.org/wiki/Georgia_Institute_of_Technologyhttp://en.wikipedia.org/wiki/Triboelectric_effecthttp://en.wikipedia.org/wiki/Energy_harvesting

7/28/2019 nanaogear

10/24

The scheme view of the typical structure of a triboelectric nanogenerator

Mechanism

The scheme showing the mechanism of triboelectric nanogenerators

The working mechanism of the triboelectric nanogenerator can be described

as the periodic change of the potential difference induced by the cycled separation

and re-contact of the opposite triboelectric charges on the inner surfaces of the two

sheets. When a mechanical agitation is applied onto the device to bend or press it,

http://en.wikipedia.org/wiki/Potentialhttp://en.wikipedia.org/wiki/File:The_scheme_showing_the_mechanism_of_triboelectric_nanogenerators.tifhttp://en.wikipedia.org/wiki/File:The_scheme_view_of_the_typical_structure_of_a_triboelectric_nanogenerator.tifhttp://en.wikipedia.org/wiki/File:The_scheme_showing_the_mechanism_of_triboelectric_nanogenerators.tifhttp://en.wikipedia.org/wiki/File:The_scheme_view_of_the_typical_structure_of_a_triboelectric_nanogenerator.tifhttp://en.wikipedia.org/wiki/Potentialhttp://en.wikipedia.org/wiki/File:The_scheme_showing_the_mechanism_of_triboelectric_nanogenerators.tifhttp://en.wikipedia.org/wiki/File:The_scheme_view_of_the_typical_structure_of_a_triboelectric_nanogenerator.tif

7/28/2019 nanaogear

11/24

the inners surfaces of the two sheets will get into close contact and the charge

transfer will begin, leaving one side of the surface with positive charges and the

other with negative charges. This is just the triboelectric effect. When the

deformation is released, the two surfaces with opposite charges will separate

automatically, so that these opposite triboelectrc charges will generate an electric

field in between and thus induce a potential difference across the top and bottom

electrodes. In order to screen this potential difference, the electrons will be driven

to flow from one electrode to the other through the external load. The electricity

generated in this process will continue until the potentials of the two electrodes get

back to even again. Subsequently, when the two sheets are pressed towards each

other again, the triboelectric-charge-induced potential difference will begin to

decrease to zero, so that the transferred charges will flow back through the external

load, to generate anothercurrentpulse in the opposite direction. When this periodic

mechanical deformation lasts, the alternating current (AC) signals will be

continuously generated.

As for the pair of materials getting in contact and generating triboelectric

charges, at least one of them need to be an insulator, so that the triboelectric

charges cannot be conducted away but will remain on the inner surface of the

sheet. Then, these immobile triboelectric charges can induce AC electricity flow in

the external load under the periodic distance change.

http://en.wikipedia.org/wiki/Triboelectric_effecthttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Insulator_%28electricity%29http://en.wikipedia.org/wiki/Insulator_%28electricity%29http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Triboelectric_effect

7/28/2019 nanaogear

12/24

APPLICATIONS

The power generated by triboelectric nanogenrators under mechanical

agitation can be used in a number of applications where there exists the mechanical

motion. These applications will include, but not limited to, the following aspects:

SELF-POWERED SYSTEMS

One of the most important applications is to use the triboelectric

nanogenerator as the power source for the independent and maintenance-free

operation of electronic device and systems. The triboelectric nanogenerator can

directly power the portable devices all by itself in some case; or the AC current

pulses produced could be regulated by a rectifier and a storage unit in the first

place, and then the stored energy will be able to power the regular electronics such

as LED

THE POWERING OF PERSONAL ELECTRONICS

Since there is abundant mechanical energy generated on human bodies in

peoples everyday life, we can make use of the triboelectric nanogenerator to

convert this amount of mechanical energy into electricity, to charge-up the

personal mobile electronics such as cell phones and laptops. This will help to

7/28/2019 nanaogear

13/24

greatly improve the convenience of peoples life and expand the application of the

personal electronics.

THE POWER SOURCE FOR ELECTROCHEMICAL PROCESSES

The triboelectric nanogenerator can be used as a direct power source to

facilitate electrochemical process, such as pollution degradation, electrodeposition,

water splitting and so on.

THE ACTIVE (SELF-POWERED) PRESSURE SENSOR

Since the triboelectric nanogenerators can efficiently produce electricity in

response to external motion and vibration induced by pressure change, they can be

used as an active sensor to detect the subtle pressure change with very high

sensitivity. They will not rely on external power source to work.[20]

http://en.wikipedia.org/wiki/Electrophoretic_depositionhttp://en.wikipedia.org/wiki/Water_splittinghttp://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlzThis-20http://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlzThis-20http://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlzThis-20http://en.wikipedia.org/wiki/Nanogenerator#cite_note-DoinlzThis-20http://en.wikipedia.org/wiki/Water_splittinghttp://en.wikipedia.org/wiki/Electrophoretic_deposition

7/28/2019 nanaogear

14/24

PYROELECTRIC NANOGENERATOR

Pyroelectric Nanogenerator is an energy harvesting device converting the

external thermal energy into an electrical energy by using nano-structured

pyroelectric materials. Usually, harvesting thermoelectric energy mainly relies on

the Seebeck effect that utilizes a temperature difference between two ends of the

device for driving the diffusion of charge carriers.[21]However, in an environment

that the temperature is spatially uniform without a gradient, such as in outdoor in

our daily life, the Seebeck effect can not be used to to harvest thermal energy from

a time-dependent temperature fluctuation. In this case, the pyroelectric effect has to

be the choice, which is about the spontaneous polarization in certain anisotropic

solids as a result of temperature fluctuation.[22]

The first pyroelectric nanogenerator

was introduced by Prof. Zhong Lin Wang at Georgia Institute of Technology in

2012.[23]By harvesting the waste heat energy, this new type of nanogenerator has

the potential applications such as wireless sensors, temperature imaging, medical

diagnostics, and personal electronics.

Mechanism

The mechanism of the pyroelectric nanogenerator based on a composite

structure of pyroelectric nanowries.(a-c) Schematic diagrams of the pyroelectric

nanogenerator with negative electric dipoles under room temperature (a), heated

http://en.wikipedia.org/wiki/Nanogenerator#cite_note-21http://en.wikipedia.org/wiki/Nanogenerator#cite_note-21http://en.wikipedia.org/wiki/Nanogenerator#cite_note-21http://en.wikipedia.org/wiki/Nanogenerator#cite_note-22http://en.wikipedia.org/wiki/Nanogenerator#cite_note-22http://en.wikipedia.org/wiki/Nanogenerator#cite_note-22http://en.wikipedia.org/wiki/Nanogenerator#cite_note-23http://en.wikipedia.org/wiki/Nanogenerator#cite_note-23http://en.wikipedia.org/wiki/Nanogenerator#cite_note-23http://en.wikipedia.org/wiki/File:1The_mechanism_of_the_pyroelectric_nanogenerator_based_on_a_composite_structure_of_pyroelectric_nanowries..jpghttp://en.wikipedia.org/wiki/Nanogenerator#cite_note-23http://en.wikipedia.org/wiki/Nanogenerator#cite_note-22http://en.wikipedia.org/wiki/Nanogenerator#cite_note-21

7/28/2019 nanaogear

15/24

(b) and cooled (c) conditions. The angles marked in the diagrams represent the

degrees to which the dipole would oscillate as driven by statistical thermal

fluctuations.

The working principle of pyroelectric nanogenerator will be explained for 2

different cases: the primary pyroelectric effect and the secondary pyroelectric

effect.

The working principle for the first case is explained by the primary

pyroelectric effect, which describes the charge produced in a strain-free case. The

primary pyroelectric effect dominates the pyroelectric response in PZT, BTO, and

some other ferroelectric materials.[24] The mechanism is based on the thermally

induced random wobbling of the electric dipole around its equilibrium axis, the

magnitude of which increases with increasing temperature.[25] Due to thermal

fluctuations under room temperature, the electric dipoles will randomly oscillate

within a degree from their respective aligning axes. Under a fixed temperature, the

total average strength of the spontaneous polarization form the electric dipoles is

constant, resulting in no output of the pyroelectric nanogenerator. If we apply a

change in temperature in the nanogenerator form room temperature to a higher

temperature, the increase in temperature will result in that the electric dipoles

oscillate within a larger degree of spread around their respective aligning axes. The

http://en.wikipedia.org/wiki/Nanogenerator#cite_note-24http://en.wikipedia.org/wiki/Nanogenerator#cite_note-24http://en.wikipedia.org/wiki/Nanogenerator#cite_note-24http://en.wikipedia.org/wiki/Nanogenerator#cite_note-25http://en.wikipedia.org/wiki/Nanogenerator#cite_note-25http://en.wikipedia.org/wiki/Nanogenerator#cite_note-25http://en.wikipedia.org/wiki/Nanogenerator#cite_note-25http://en.wikipedia.org/wiki/Nanogenerator#cite_note-24

7/28/2019 nanaogear

16/24

total average spontaneous polarization is decreased due to the spread of the

oscillation angles. The quantity of induced charges in the electrodes are thus

reduced, resulting in a flow of electrons. If the nanogenerator is cooled instead of

heated, the spontaneous polarization will be enhanced since the electric dipoles

oscillate within a smaller degree of spread angles due to the lower thermal activity.

The total magnitude of the polarization is increased and the amount of induced

charges in the electrodes are increased. The electrons will then flow in an opposite

direction.

For the second case, the obtained pyroelectric response is explained by the

secondary pyroelectric effect, which describes the charge produced by the strain

induced by thermal expansion. The secondary pyroelectric effect dominates the

pyroelectric response in ZnO, CdS, and some other wurzite-type materials. The

thermal deformation can induce a piezoelectric potential difference across the

material, which can drive the electrons to flow in the external circuit. The output of

the nanogenerator is associated with the piezoelectric coefficient and the thermal

deformation of the materials.The output current I of the pyroelectric

nanogenerators can be determined by the equation of I=p(dT/dt), where p is the

pyroelectric coefficient, A is the effective area of the NG, dT/dt is the rate of

change in temperature.

7/28/2019 nanaogear

17/24

VERTICAL NANOWIRE INTEGRATED NANOGENERATOR (VING):

VING is a 3-dimensional configuration consisting of a stack of 3 layers in

general, which are the base electrode, the vertically grown piezoelectric

nanostructure and the counterelectrode.The piezoelectric nanostructure is usually

grown from the base electrode by various synthesizing techniques, which are then

integrated with the counter electrode in full or partial mechanical contact with its

tip.

Motion in-plane or out-of-plane occurred by the external vibration induces

the deformationofthe piezoelectric nanostructure, leading to the generation of the

electrical potential distribution inside each individual nanowire. It should be noted

that the counter electrode is coated with the metal forming the schottky contact

with the tip of the nanowire, where only the compressed portion of piezoelectric

nanowire would allow the accumulated electrons pass through the barrier between

its tip and the counter electrode, in case of n-type nanowire. The switch-on and

off characteristic of this configuration shows its capability of generating direct

current generation without any requirement for the external rectifier.

7/28/2019 nanaogear

18/24

LATERAL NANOWIRE INTEGRATED NANOGENERATOR (LING):

LING is a 2-dimensional configuration consisting of three parts: the base

electrode, the laterally grown piezoelectric nanostructure and the metal electrode

for schottky contact. In most of cases, the thickness of the substrate film is much

thicker than the diameter of the piezoelectric nanostructure, so the individual

nanostructure is subjected to the pure tensile strain.

7/28/2019 nanaogear

19/24

MATERIALS:

Among various piezoelectric materials studied for the nanogenerator, many

of the researches have been focused on the materials with quartzite structure such

as ZnO, CdS and GaN. The greatest advantage of theses material arises from the

facile and cost-effective fabrication technique, hydrothermal synthesis. Since the

hydrothermal synthesis can be conducted in a low temperature environment under

100C in addition to vertical and crystalline growth, these materials can be

integrated in various substrates with reduced concern for its physical

characteristics such as a melting temperature.

7/28/2019 nanaogear

20/24

APPLICATIONS:

Nanogenerator is expected to be applied for various applications where the

periodic kinetic energy exists, such as wind and ocean waves in a large scale to the

muscle movement by the beat of a heart or inhalation of lung in a small scale.

Nanogenerators are now close to producing enough current for a self-powered

system that might monitor the environment for a toxic gas, for instance, and then

broadcast a warning. The system would include capacitors able to store up the

small charges until enough power was available to send out a burst of data. If we

can sustain this rate of improvement, we will reach some true applications in

healthcare devices, personal electronics, or environmental monitoring recent

improvements in the nanogenerators, including a simpler fabrication technique.

The further feasible applications are as follows

Self-powered nano/micro devices.

One of the feasible applications of nanogenerator is an independent or a

supplementary energy source to nano/micro devices consuming relatively low

amount of energy in a condition where the kinetic energy is supplied continuously.

One of example is the self-powered pH or UV sensor integrated VING with an

output voltage of 20~40 mV onto the sensor.

Still, the converted electrical energy is relatively small for operating

nano/micro devices; therefore the range of its application is still bounded as a

7/28/2019 nanaogear

21/24

supplementary energy source to the battery. The breakthrough is being sought by

combining the nanogenerator with the other types of energy harvesting devices,

such as solar cell or biochemical energy harvester this approach is expected to

contribute to the development of the energy source suitable for the application

where the independent operation is crucial, such as Smartdust.

Smart Wearable Systems:The outfit integrated or made of the textiles with

the piezoelectric fiber is one of the feasible applications of the nanogenerator. The

kinetic energy from the human body is converted to the electrical energy through

the piezoelectric fibers, and it can be possibly applied to supply the portable

electronic devices such as health-monitoring system attached with the Smart

Wearable Systems. The nanogenerator such as VING can be also easily integrated

in the shoe employing the walking motion of human body.

Another similar application is a power-generating artificial skin. There is a

possibility of generating AC voltage of up to 100 mV from the flexible SWG

attached to the running hamster.

Transparent and Flexible Devices

Some of the piezoelectric nanostructure can be formed in various kinds of

substrates, such as flexible and transparent organic substrate. The recent

researchers have developed the transparent and flexible nanogenerator which can

be possibly used for self-powered tactile sensor and anticipated that the

7/28/2019 nanaogear

22/24

development may be extended to the energy-efficient touch screen devices. Their

research focus is being extended to enhance the transparency of the device and the

cost-effectiveness by substituting Indium-Tin-Oxide (ITO) electrode with a

graphene layer.

Implantable Telemetric Energy Receiver:

The nanogenerator based on ZnO nanowire can be applied for implantable

devices since ZnO not only is bio-compatible but also can be synthesized upon the

organic substrate, rendering the nanogenerator bio-compatible in overall. The

implantable device integrated with the nanogenerator can be operated by receiving

the external ultrasonic vibration outside the human body, which is converted to the

electrical energy by the piezoelectric nanostructure.

7/28/2019 nanaogear

23/24

CONCLUSION:

In future a day may come when nanogenerators power the entire globe.

The nanogenerators would certainly bring up a new industrial revolution in the

power generation .With the application of nanotechnology in every sphere of the

life many compact designs can be expected which constitute for the

technological development .With their size, precision and accuracy nanogenerators

are definitely going to be an un-avoidable part of our future.

7/28/2019 nanaogear

24/24

REFERENCES

Wang, Zhong Lin; Song, Jinhui (June 2006). "Piezoelectric NanogeneratorsBased on Zinc Oxide Nanowire Arrays".Science312 (5771): 242246.

doi:10.1126/science.1124005. PMID 16614215. edit

Wang, Zhong Lin; Wang, Xudong; Song, Jinhui; Liu, Jin; Gao, Yifan(2008). "Piezoelectric Nanogenerators for Self-Powered Nanodevices".

IEEE Pervasive Computing7 (1): 4955. hdl:1853.2F25449. Retrieved

2012-06-15. edit

Wang, Xudong; Song, Jinhui; Liu, Jin; Wang, Zhong Lin (2007). "Direct-Current Nanogenerator Driven by Ultrasonic Waves".Science316 (5821):

102105. doi:10.1126/science.1139366. PMID 17412957. edit

Choi, Min-Yeol; Choi, Dukhyun; Jin, Mi-Jin; Kim, Insoo; Kim, Sang-Hyeob; Choi, Jae-Young; Lee, Sang Yoon; Kim, Jong Min et al. (5 June

2009). "Mechanically Powered Transparent Flexible Charge-Generating

Nanodevices with Piezoelectric ZnO Nanorods".Advanced Materials21

(21): 21852189. doi:10.1002/adma.200803605. edit

http://www.nanoscience.gatech.edu/zlwang/paper/2006/06_SCIENCE_1.pdfhttp://www.nanoscience.gatech.edu/zlwang/paper/2006/06_SCIENCE_1.pdfhttp://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1126%2Fscience.1124005http://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/16614215http://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1126.2Fscience.1124005&action=edit&editintro=Template:Cite_doi/editintro2http://www.nanoscience.gatech.edu/zlwang/paper/2008/08_PVC_1.pdfhttp://en.wikipedia.org/wiki/Handle_Systemhttp://hdl.handle.net/1853.2F25449http://en.wikipedia.org/w/index.php?title=Template:Cite_hdl/1853.2F25449&action=edit&editintro=Template:Cite_hdl/editintro2http://www.nanoscience.gatech.edu/zlwang/paper/2007/07_SCI_1.pdfhttp://www.nanoscience.gatech.edu/zlwang/paper/2007/07_SCI_1.pdfhttp://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Science_%28journal%29http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1126%2Fscience.1139366http://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/17412957http://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1126.2Fscience.1139366&action=edit&editintro=Template:Cite_doi/editintro2http://home.skku.edu/~nesel/bbs/paper%20files/68.pdfhttp://home.skku.edu/~nesel/bbs/paper%20files/68.pdfhttp://en.wikipedia.org/wiki/Advanced_Materialshttp://en.wikipedia.org/wiki/Advanced_Materialshttp://en.wikipedia.org/wiki/Advanced_Materialshttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1002%2Fadma.200803605http://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1002.2Fadma.200803605&action=edit&editintro=Template:Cite_doi/editintro2http://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1002.2Fadma.200803605&action=edit&editintro=Template:Cite_doi/editintro2http://dx.doi.org/10.1002%2Fadma.200803605http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Advanced_Materialshttp://home.skku.edu/~nesel/bbs/paper%20files/68.pdfhttp://home.skku.edu/~nesel/bbs/paper%20files/68.pdfhttp://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1126.2Fscience.1139366&action=edit&editintro=Template:Cite_doi/editintro2http://www.ncbi.nlm.nih.gov/pubmed/17412957http://en.wikipedia.org/wiki/PubMed_Identifierhttp://dx.doi.org/10.1126%2Fscience.1139366http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Science_%28journal%29http://www.nanoscience.gatech.edu/zlwang/paper/2007/07_SCI_1.pdfhttp://www.nanoscience.gatech.edu/zlwang/paper/2007/07_SCI_1.pdfhttp://en.wikipedia.org/w/index.php?title=Template:Cite_hdl/1853.2F25449&action=edit&editintro=Template:Cite_hdl/editintro2http://hdl.handle.net/1853.2F25449http://en.wikipedia.org/wiki/Handle_Systemhttp://www.nanoscience.gatech.edu/zlwang/paper/2008/08_PVC_1.pdfhttp://en.wikipedia.org/w/index.php?title=Template:Cite_doi/10.1126.2Fscience.1124005&action=edit&editintro=Template:Cite_doi/editintro2http://www.ncbi.nlm.nih.gov/pubmed/16614215http://en.wikipedia.org/wiki/PubMed_Identifierhttp://dx.doi.org/10.1126%2Fscience.1124005http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Science_%28journal%29http://www.nanoscience.gatech.edu/zlwang/paper/2006/06_SCIENCE_1.pdfhttp://www.nanoscience.gatech.edu/zlwang/paper/2006/06_SCIENCE_1.pdf