SUBMITTED BY

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This report is submitted for the partial fulfillment of the Post Graduate

Diploma in Plastic Processing & Testing (PGD-PPT) course

SUBMITTED BY

SIGN. OF COURSE –IN- CHARGE

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:INTRODUCTION:

Plastic electronics or organic electronics is a branch of electronics that deals with device made from

organic polymer or conductive polymer. Plastics or small molecule, as opposed to Silicon.

Organic electronic because the polymers and small molecules are carbon based, like the molecules of

living things. This is as oppose to traditional electronics which relies on inorganic conductors such as silicon

or copper

Conduction mechanisms involve resonance stabilization and delocalization of pi-electrons along entire

polymers backbones as well as mobility gaps, tunneling and phonon –assisted hopping conductive polymers

are lighter, more flexible and less expensive than inorganic conductors. This makes them a desirable

alternative in many applications. It also creates the possibility of new applications that would be impossible

using copper or silicon.

New application includes small windows and electronic paper. Conductive polymers are expected to

play an important role in the emerging science of molecular computing. In general, organic conductive

polymers have a higher resistance hence therefore conduct electricity poorly and inefficiently, as compared to

inorganic conductors. Researchers currently are exploring way of doping, organic semiconductors like

melanin, with relatively small amount of conductive metals to boost conductivity. However, for many

applications, inorganic conductors will remain the only viable option.

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GENERAL OUTLOOK-

October 10, 2000

We are used to the great impact scientific discoveries have on our ways of thinking. This year's Nobel

Prize in Chemistry is no exception. What we have been taught about plastic is that it is a good

insulator - otherwise we should not use it as insulation in electric wires. But now the time has come

when we have to change our views. Plastic can indeed, under certain circumstances, be made to

behave very like a metal - a discovery for which Alan J. Heeger, Alan G. MacDiarmid and Hideki

Shirakawa are to receive the Nobel Prize in Chemistry 2000.

The men principally credited for the discovery and development of highly-conductive

polymers(at least of the rigid backbone “polyacetelene”)class are Alan J. Heeger, Alan G. macDiramid

and Hideki Shirakawa, who were jointly awarded the noble prize in chemistry in 2000 for

development of oxidized, iodine- doped polyacetelene.

ELECTRICAL CONDUCTION-

We know that the electrical resistance R defined as the ratio of the voltage (V) across a conductor to

the current (I) flowing through it (i.e. R=V/I)

But, the resistance of a conductor depends upon its size and so is not a material property. It is

therefore necessary to use a parameter the resistivity which is a material property and is defined as the

resistance of a conductor of unit length with unit cross-sectional area. Resistivity has unit of ohm

meters (Ωm) in the S.I. system. To compare the properties of conductors it is more convenient to use

conductivity S which is simply the reciprocal of the resistivity i.e.

σ =1/ρ

This is preferred because S is higher for better conductors its S.I. units are reciprocal

ohm meters or siemens per meter (S/M).

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Electrically conductive polymers are mainly derivative of poly acetylene black (the simplest melanin)

Examples include:

PA (more specifically iodine doped Tran’s polyacetylene)

Polyaniline: PANI, when doped with a protonic acid,

Poly (dioctylbi thiophene): PDOT

CHEMICAL BONDING AND CONDUCTIVITY -

The higher no. of free electrons in metals such as copper and iron leafs to higher levels of

conductivity compared with covalently-bonded insulators such as Diamonds where there are none.

The effect of chemical bonding upon conductivity can be seen in fig.1

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EXAMPLES-

POLY ACETELENE-

It is produced in two isomeric forms, cis and Trans polyacetelenes. The particular isomer

obtained depends upon the temperatures at which the polymerization was performed. Reactions at

780C produce mainly the cis-confirmation where as none of the trans-form is also be converted to the

thermodynamically more stable trans-form by heating typically at 170 0C for 20 minutes.

The properties of the polymer are also affected by this isomerisation. Films of the cis material

are red in transmitted light and the smooth surface has a coppery appearance where as the trans

material is blue in transmission and silvery in reflection. More important the conductivity of the

polymer increase with the cis to Tran’s isomerisation from about 10 -9 S/cm to up to 10-4 S/cm. Hence

pure PA is never more than a semiconductor this is because unlike other unsaturated molecules.

In spite of the lack of intrinsic conductivity in PA the conductivity is greatly increased to

metallic levels by “doping” with certain types of molecules and ions.

Substantial increases are obtained using either electron accepting molecules (oxidizing agent)

such as iodine, bromine and arsenic penta fluoride or electrons doners (reducing agent) such as alkali

metals. It is pointed out however that the term doping in thix context refers to the inclusion of

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substantial quantities of dopant in the polymer. This is to be contrasted with convential

semiconductors technology where dopant concentrate are measure in ppm.

There is a rapid rise more slowly with further addition of dopant. The measured conductivity

for PA treated with different dopant are listed in table-1 with the highest value(S) 1000(S/cm) being

obtained for strong electrons acceptors such as AsF and oriented PA films.

It is possible to tailor the level of conductivity and types of carriers by treating with donor-

doped (n-type) or acceptors doped (p-type) PA.

WHAT EXACTLY HAPPENED IN THE POLYACETYLENE

FILMS?

When we compare some common compounds with regard to conductivity, we see that the

conductivities of the polymers vary considerably. Doped polyacetylene is, e.g., comparable to good

conductors such as copper and silver, whereas in its original form it is a semiconductor.

POLYPYRROLE-

Polypyrrole (ppy) is made by electron polymerization of pyrrole. Blue black, acceptors doped

conducting polymers is produced at the anode when the monomer solution is electrolyst in the

presence of Et4N+BF4. The films have the conductivity of the order of 100 S/cm and for stabilities.

The films are essentially amorphous and it is readily shown by chemical analysis that they are not pure

polymer but contain one BF4 ion for every four pyrrole rings.

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HOW CAN PLASTIC BECOME CONDUCTIVE?

Plastics are polymers, molecules that form long chains, repeating themselves like pearls in a

necklace. In becoming electrically conductive, a polymer has to imitate a metal, that is, its electrons

need to be free to move and not bound to the atoms. The first condition for this is that the polymer

consists of alternating single and double bonds, called conjugated double bonds. Polyacetylene,

prepared through polymerization of the hydrocarbon acetylene, has such a structure:

Polyacetylene

However, it is not enough to have conjugated double bonds. To become electrically

conductive, the plastic has to be disturbed - either by removing electrons from (oxidation), or inserting

them into (reduction), the material. The process is known as doping.

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The game in the illustration to the right offers a simple model of a doped polymer. The pieces

cannot move unless there is at least one empty "hole". In the polymer each piece is an electron that

jumps to a hole vacated by another one. This creates a movement along the molecule - an electric

current. This model is greatly over-simplified, and we shall consider a more "chemical" model later.

Heeger, MacDiarmid and Shirakawa found was that a thin film of polyacetylene could be

oxidised with iodine vapour, increasing its electrical conductivity a billion times. This sensational

finding was the result of their impressive work, but also of coincidences and accidental circumstances.

Let us, shortly, tell the story of one of the great chemical discoveries of our time.

MANUFACTURING PLASTIC ELECTRONICS-

The heart of modern electronics are micro chips circuits and wiring diagrams are designed and

micro miniaturized to the point that thousands or even millions of circuits are contained in a one inch

square chip which is burned on to ultra thin inorganic materials life refined silicon using very high

temperature.

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Plastic electronics, on the other hand, follow a different manufacturing process. The process

starts with the manufacturing of large sheets of PET plastics. The flexible but tough material used in

the production of plastic bottles. Circuits are then printed on these sheets using ink-jet printers or using

techniques much like those used to print magazines and news papers- resulting in a process that is

cheap, easy to do and faster to produce.

The plastic circuit will be used as the active matrix back panes for large but flexible electronic

displays. In an active matrix display, every dot on displays managed by a switching element such as

thin film transistors (TFTs) and the signals on the array of intersecting row and column electrodes.

Prior to plastic electronics, these TFTs have been produced using amorphous silicon deposited on a

rigid glass substrate at high temperature through a complex series of production procedures.

It is the collection of switching elements and row-column electrodes which are put together on

a substrate to for the active matrix back pane, which is then combined with different front plate

technologies (LCD screens) to form display.

For many electronic readers the best front plane technology e-paper which looks like paper and

only uses unit’s power when the image shifts or changes.

E-paper however loses its thinness and flexibility when combine with a glass based silicon

back pane. The flexible back pane technology of plastic electronic allows the reader device to become

flexible, light thin and robust enough for a wide range of uses no paper has gone before and to include

large data storage capacities.

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INORGANIC Vs ORGANIC-

Organic electronic or plastic electronic is the branch of electronic that deals with conductive

polymers which are carbon based.

Inorganic electronic, on the other hand, relies on inorganic conductors like copper and silicon.

BENEFITS -

Organic electronics are lighter, more flexible and less expensive than there inorganic

counterparts.

They are also biodegradable (being made from carbon e.g. melanin).

This opens the doors to many exciting and advanced new applications that would be

impossible using copper or silicon.

OBSTACLES-

However conductive polymers have high resistance and therefore are not good conductor of

electricity.

In many cases they also have shorter life time.

Much more dependent on stable environment conditions than inorganic electronics would be.

ORGANIC INORGANIC

$5/ft2 $100/ft2

Low capital $1-$10 billion

Flexible plastic substrate rigid glass or metal

Ambient processing Ultra clean room

Continuous direct printing Multistep photolithography

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Conjugated Polymers: Electronic Conductors

The most important aspect of conjugated polymers from an electrochemical perspective is their

ability to act as electronic conductors. Not surprisingly -electron polymers have been the focus of

extensive research, ranging from applications of ``conventional'' polymers (e.g., polythiophene,

polyaniline, polypyrrole) in charge storage devices such as batteries and super capacitors, to new

polymers with specialized conductivity properties such as low band gap and intrinsically conducting

polymers. Indeed, many successful commercial applications of these polymers have been available for

more than fifteen years, including electrolytic capacitors, "coin'' batteries, magnetic storage media,

electrostatic loudspeakers, and anti-static bags. It has been estimated that the annual global sales of

conducting polymers in the year 2000 will surpass one billion US dollars. Clearly these materials have

considerable commercial potential both from the continued development of well established

technologies and from the generation of new concepts such as those to be presented in this thesis.

Shirakawa can trace the genesis of the field back to the mid 1970s when the first polymer

capable of conducting electricity polyacetylene was reportedly prepared by accident. The subsequent

discovery by Heeger and MacDiarmid that the polymer would undergo an increase in conductivity of

12 orders of magnitude by oxidative doping quickly reverberated around the polymer and

electrochemistry communities, and an intensive search for other conducting polymers soon followed.

The target was (and continues to be) a material, which could combine the processibility,

environmental stability, and weight advantages of a fully organic polymer with the useful electrical

properties of a metal.

The essential structural characteristic of all conjugated polymers is their quasi-infinite

system extending over a large number of recurring monomer units. This feature results in materials

with directional conductivity, strongest along the axis of the chain. The simplest possible form is of

course the archetype polyacetylene (CH) x shown in Figure While polyacetylene itself is too unstable

to be of any practical value, its structure constitutes the core of all conjugated polymers. Owing to its

structural and electronic simplicity, polyacetylene is well suited to ab initio and semi-empirical

calculations and has therefore played a critical role in the elucidation of the theoretical aspects of

conducting polymers.

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a

b C

Figure 1.2: Conjugated polymer structure: (a) trans- and (b) cis-polyacetylene, and (c) polythiophene

Electronically conducting polymers are extensively conjugated molecules, and it is believed

that they possess a spatially delocalized band-like electronic structure. These bands stem from the

splitting of interacting molecular orbital of the constituent monomer units in a manner reminiscent of

the band structure of solid-state semiconductors.

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Figure 1.3: Band structure in an electronically conducting polymer

It is generally agreed that the mechanism of conductivity in these polymers is based on the

motion of charged defects within the conjugated framework. The charge carriers, either positive p-type

or negative n-type, are the products of oxidizing or reducing the polymer respectively. The following

overview describes these processes in the context of p-type carriers although the concepts are equally

applicable to n-type carriers.

Figure 1.4: Positively charged defects on poly (p-phenylene). A: polaron B: bipolaron

Oxidation of the polymer initially generates a radical cation with both spin and charge.

Borrowing from solid state physics terminology, this species is referred to as a polaron and comprises

both the hole site and the structural distortion which accompanies it. This condition is depicted in

Figure 1.4A. The cation and radical form a bound species, since any increase in the distance between

them would necessitate the creation of additional higher energy quinoid units. Theoretical treatments

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have demonstrated that two nearby polarons combine to form the lower energy bipolaron shown in

Figure 1.4 B. One bipolaron is more stable than two polarons despite the coulombic repulsion of the

two ions. Since the defect is simply a boundary between two moieties of equal energy -- the infinite

conjugation chain on either side -- it can migrate in either direction without affecting the energy of the

backbone, provided that there is no significant energy barrier to the process. It is this charge carrier

mobility that leads to the high conductivity of these polymers.

The conductivity of a conducting polymer is related to the number of charge carriers n and

their mobility :

σ α µn

Because the band gap of conjugated polymers is usually fairly large, n is very small under

ambient conditions. Consequently, conjugated polymers are insulators in their neutral state and no

intrinsically conducting organic polymer is known at this time. A polymer can be made conductive by

oxidation (p-doping) and/or, less frequently, reduction (n-doping) of the polymer either by chemical or

electrochemical means, generating the mobile charge carriers described earlier. The cyclic

voltammetry of electronically conducting polymers is characterized by broad non-Nernstian waves. A

typical example is shown in Figure for an N-substituted pyrrole based conducting polymer.

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Figure 1.5: Cyclic voltammogram of a substituted polypyrrole.

SPECIFYING PLASTICS FOR ELECTRONICS DESIGN

Although not always an easy task, selecting the right plastics can help ensure the safety and

reliability of today's electronics.

Most electronic equipment uses some type of thermoplastic. It is important to understand the

characteristics of plastics used in electronics equipment to determine which plastic is appropriate for a

given application. These characteristics often affect the safety and reliability of the final product. This

article examines many factors surrounding plastics selection that engineers should consider during a

product's design stages.

Underwriters Laboratories (UL) has one of the most comprehensive materials databases

available, and UL 94 ratings are widely accepted flammability performance standards for plastic

materials. The UL 94 standard explains various flammability categories and describes the test methods

used for each rating.

CLASSIFICATION

Each material tested can receive several ratings based on color and thickness. The amount and

type of color additive can vary the flammability rating of a plastic. The UL plastic component

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directory normally specifies four colors: black, white, red, and natural. When specifying a material for

an application, the UL rating should be applicable for the thickness used in the wall section of the

plastic part. It is very important to remember that the thickness must always be reported with the UL

rating to provide meaningful information about the material's characteristics. Ratings are categorized

as follows:

Ratings are differentiated primarily by the testing method. The classification depends on the following

factors:

Sample orientation (horizontal or vertical).

Burn rate.

Time to extinguish.

Resistance to dripping.

Drip flammability.

These parameters affect the end results, and hence the classification. With this in mind, each

material tested could receive several ratings, depending on its color and thickness. Some ratings apply

to specific product types. VTM, for example, refers to very thin material. HBF, HF-1, and HF-2 refer

to foamed materials. These ratings, therefore, should not be compared to those in other categories. In

other words, a vertically rated plastic material is better than a plastic that simply meets the HB

requirements. In addition, a material accepted for a 5V rating must first comply with the vertical test

requirements for V-0, V-1, or V-2. Depending on the end-product application, a designer could specify

one or more ratings for a product.

OPERATING TEMPERATURE

Some engineers make the erroneous assumption that there is a direct correlation between a

material's UL rating and its operating temperature. UL ratings relate only to a material's behavior when

introduced to a flame source. How a material reacts when the flames come in direct contact with it

determines its UL rating. For example, for a rating of 94V-0, a material must be self-extinguishing and

must not drip or run while burning.

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In the test, a sample of the material is held over a Bunsen burner, ignited, and allowed to burn.

When the sample is removed from the flame, the fire must go out within 10 seconds, and the material

must not have dripped from the burning sample. If the material continues to burn or if it drips and

runs, it cannot be rated 94V-0. For this rating, operating temperature never comes into play.

ComponentFlammability

Requirements

Enclosure 94V-1 or better

Printed circuit board 94V-1 or better

Integrated circuit,

transistor, optocoupler

package, capacitor, and

other small parts

94HB or better

Cord anchorage bushing 94HB or better

Operating temperature is determined by establishing the point at which temperature causes an

end product to cease to perform as it was intended. This premise applies to minimum as well as

maximum temperatures. Most nylon materials, for example, have a maximum operating temperature

of 250°F (120°C). However, the actual operating temperatures of finished goods vary depending on

the mass (volume of material), temperature variations over time, and mold factor. A 94V-0 rating for a

material does not necessarily mean that a finished product can withstand a high temperature.

SAFETY STANDARDS AND PLASTICS

Almost all product safety standards have clauses concerning flammability requirements for

plastics in electronics. Requirements normally cover plastics that support live parts, such as a

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transformer's bobbin; enclosure of live parts, such as a monitor cover; and decorative parts, such as a

lamp cover. EN 60950, for example, has guidelines specifying minimum requirements for plastic

parts.

Most electrical and electronic equipment has some type of enclosure. Enclosures are normally

evaluated to meet one or more of the following requirements:

A fire enclosure must prevent the spread of fire and flames.

An electrical enclosure must prevent access to hazardous voltages or parts that carry hazardous

energy.

A mechanical enclosure must prevent injury from physical or mechanical hazards.

A product can have one or more enclosure types. Section 4 of EN 60950 requires that fire and

electrical enclosures meet certain parameters in order to be considered effective. A summary of these

requirements is presented here, but it is essential that designers refer to the standard for complete

details.

The top and side openings of the enclosure must satisfy one of the following conditions: do not

exceed 5 mm in any dimension; do not exceed 1 mm in width regardless of length; are constructed

with louvers shaped so that they deflect external, vertically falling objects outward; are located so that

objects, upon entering the enclosure, are unlikely to fall on bare parts at hazardous voltages.

If the end product is a stationary or movable equipment with a mass of 18 kg or greater, fire

enclosures are considered to comply without test if, in the smallest thickness used, the material is of

flammability class 5V.

The bottom of a fire enclosure—or individual barriers—must provide protection underneath all

internal parts, including partially enclosed components or assemblies that could emit, under fault

conditions, material likely to ignite the supporting surface.

If a hole is cut to fit a plastic window or a screen in a fire enclosure, then the window or screen

must have a flammability rating of 5V. However, if a hole is cut to accommodate a fuse holder, a

switch, or similar components, then there is no need for these components to meet 5V flammability

requirements, provided that such components have appropriate approvals.

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DESIGN TIPS

Resources.

One source of valuable information is the UL Recognized Component Directory, also known

as the UL Yellow Book. This directory provides names of companies authorized by UL to provide

plastic components bearing a UL mark. It also provides technical information about various plastics.

The book uses some important abbreviations and terms (see sidebar below).

The UL Directory: Key Terms and Abbreviations

ALL: All Color.

Any possible color has been recognized.

Col: Color.

This indicates the specific color of the plastic material onto which the recognition (UL mark) is

applied.

CTI: Comparative Tracking Index.

CTI is expressed as the voltage that causes tracking after 50 drops of 0.1% ammonium chloride

solution have fallen on the material. The results of testing the nominal 3-mm thickness are considered

representative of the material's performance in any thickness.

D-495: Arc Resistance.

Measured in accordance with ASTM D-495, arc resistance is expressed as the number of seconds that

a material resists the formation of a surface conducting path when subjected to an intermittently

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occurring arc of high-voltage, low-current characteristics. The results of testing the nominal 3-mm

thickness are considered representative of the material's performance in any thickness.

HAI: High Amp Arc Ignition.

Ignition performance is expressed as the number of arc rupture exposures (standardized as to

electrode type and shape, and electric circuit) necessary to ignite a material when applied at a standard

rate on the materials surface.

HVTR: High Voltage Arc Tracking Rate.

Measured in mm/min, HVTR is denoted as the rate that a tracking path can be produced on the

surface of the material under standardized test conditions. A note is made if the material ignites. The

results of testing the nominal 3-mm thickness are considered representative of the material's

performance in any thickness.

HWI: Hot Wire Ignition.

Ignition performance is also expressed as the mean number of seconds needed to either ignite

standard specimens or to burn through specimens without ignition. Specimens are wrapped with

resistance wire that dissipates a specified level of electrical energy to determine the ignition rate.

Min Thk mm: Minimum Thickness (mm).

This represents the thickness of the specimen subjected to tests. This designation is important because

a number of properties are strictly dependent on the specimen thickness.

NC: Natural Color.

NC indicates that only the unpigmented material is covered by the recognition.

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RTI: Relative Temperature Index.

RTI is an investigation of a material with respect to its retention of certain critical properties (e.g.,

dielectric, tensile, impact) as part of a long-term thermal-aging program, conducted according to UL

746B. The temperature index indicates the temperature (°C) above which the material is likely to

degrade prematurely. The printed value refers to the extrapolation to approximately 100,000 hours

with the retention of at least 50% of its original value after the aging test. Depending on the property

requirements for a given application, three different RTI expressions are possible: electrical (Elec),

mechanical with impact (Mech with imp), or mechanical without impact (Mech w/o imp).

UL 94: Flame Class.

This classification of the material is based on burning tests conducted in accordance with UL 94 (a

gas-burner test on a small-scale specimen).

MATERIALS

Selecting the appropriate plastic material for a particular design is often the most difficult task

a designer must face. Many factors-

1. Such as ability to mold or machine, weight, cost, thermal behavior,

2. Flammability rating- affects the final decision.

Because no plastic is likely to meet all of a designer's requirements for a particular application,

some degree of compromise is almost always necessary in designing plastic parts for electronics.

Selecting a material cannot be based simply on a comparison of numbers from published data

sheets. Values from data sheets often represent laboratory tests that may not duplicate real-life

molding conditions. For example, it is a mistake to choose the most economical material for a part by

comparing the cost per pound of various plastics. Some plastics weigh twice as much per cubic inch as

others, and so it would then require twice as much material to fill a given cavity-and cost twice as

much to ship.

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The choice of any material should be based on the best combination of required properties. An

ideal material will have a value for each required property just sufficient to perform properly and

safely in a given application. A molded plastic part is significantly affected by processing factors such

as direction of flow, pressure during molding, melting temperature, thermal degradation, cooling rate,

and stress concentrations. A high value provided in a data sheet could be reduced considerably by

processing conditions.

There is no simple procedure for selecting the best plastic for a new application. Understanding

the behavior of a plastic under real-life conditions is critical to determining how the material will

perform after it is molded. Successfully designing plastic parts that demonstrate optimal cost and

performance characteristics requires learning as much as possible about many different plastics, and

understanding the peculiarities of their processing.

COMPOUND SELECTION

One of the first design considerations to establish is whether thermosetting materials or

thermoplastics are appropriate. Thermosetting materials are initially soft but change irreversibly hard

upon heating. Thermoplastics can be repeatedly softened by heating and hardened again by cooling.

Designers must study the generic properties of different compounds to become familiar with their

differences.

To make this determination, it is often helpful to consult molders and plastics manufacturers.

However, such advice should be taken cautiously because these sources do not have access to internal

factors such as production, engineering, purchasing, and marketing considerations. Molders can often

detect and correct visible problems or readily measured factors such as color, surface condition, and

dimensions. However, without extensive testing and quality control, less-apparent property changes

may not show up until the molded parts are in service. Properties such as impact strength, toughness,

and chemical resistance can be diminished by improper control of processing parameters. Molding

processes can alter the published data-sheet properties, reducing strength as well as creating areas of

stress concentrations.

HOW POLYMER CONDUCTIVITY WAS REAVEALED?

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The leading actor in this story is the hydrocarbon polyacetylene, a flat molecule with an angle

of 120° between the bonds and hence existing in two different forms, the isomers cis-polyacetylene

and trans-polyacetylene. At the beginning of the 1970s, the Japanese chemist Shirakawa found that it

was possible to synthetisize polyacetylene in a new way, in which he could control the proportions of

cis- and trans-isomers in the black polyacetylene film that appeared on the inside of the reaction

vessel. Once - by mistake - a thousand-fold too much catalyst was added. To Shirakawa's surprise, this

time a beautiful silvery film appeared.

Shirakawa was stimulated by this discovery. The silvery film was trans-polyacetylene, and the

corresponding reaction at another temperature gave a copper-coloured film instead. The latter film

appeared to consist of almost pure cis-polyacetylene. This way of varying temperature and

concentration of catalyst was to become decisive for the development ahead.

In another part of the world, chemist MacDiarmid and physicist Heeger were experimenting with a

metallic-looking film of the inorganic polymer sulphur nitride, (SN)x. MacDiarmid referred to this at a

seminar in Tokyo. Here the story could have come to a sudden end, had not Shirakawa and

MacDiarmid happened to meet, accidentally, during a coffee-break.

When MacDiarmid heard about Shirakawa's discovery of an organic polymer that also gleamed like

silver, he invited Shirakawa to the University of Pennsylvania in Philadelphia. They set about

modifying polyacetylene by oxidation with iodine vapour. Shirakawa knew that the optical properties

changed in the oxidation process and MacDiarmid suggested that they ask Heeger to have a look at the

films. One of Heeger's students measured the conductivity of the iodine-doped trans-polyacetylene and

- eureka! The conductivity had increased ten million times!

In the summer of 1977, Heeger, MacDiarmid, Shirakawa, and co-workers, published their discovery in

the article "Synthesis of electrically conducting organic polymers: Halogen derivatives of

polyacetylene (CH)n" in The Journal of Chemical Society, Chemical Communications. The discovery

was considered a major breakthrough. Since then the field has grown immensely, and also given rise

to many new and exciting applications. We shall return to some of them.

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DOPING- FOR BETTER MOLECULE PERFORMANCE

A metal wire conducts electric current because the electrons in the metal are free to move.

The higher no. of free electrons in metals such as copper and iron leafs to higher levels of

conductivity compared with covalently-bonded insulators such as Diamonds where there are none.

When describing polymer molecules we distinguish between (sigma) bonds and (pi) bonds. The

bonds are fixed and immobile. They form the covalent bonds between the carbon atoms. The

electrons in a conjugated double bond system are also relatively localised, though not as strongly

bound as the electrons. Before a current can flow along the molecule one or more electrons have to

be removed or inserted. If an electrical field is then applied, the electrons constituting the bonds can

move rapidly along the molecule chain. The conductivity of the plastic material, which consists of

many polymer chains, will be limited by the fact that the electrons have to "jump" from one molecule

to the next. Hence, the chains have to be well packed in ordered rows.

As mentioned earlier, there are two types of doping, oxidation or reduction. In the case of

polyacetylene the reactions are written like this:

Oxidation with halogen (p-doping): [CH]n + 3x/2 I2 --> [CH]nx+ + x I3

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Reduction with alkali metal (n-doping): [CH]n + x Na --> [CH]nx- + x Na+

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The doped polymer is a salt. However, it is not the iodide or sodium ions that move to create the

current, but the electrons from the conjugated double bonds. Furthermore, if a strong enough electrical

field is applied, the iodide and sodium ions can move either towards or away from the polymer. This

means that the direction of the doping reaction can be controlled and the conductive polymer can

easily be switched on or off.

POLARONS- DOPED CARBON CHAINS

In the first of the above reactions, oxidation, the iodine molecule attracts an electron from the

polyacetylene chain and becomes I3- . The polyacetylene molecule, now positively charged, is termed a

radical cation, or polaron (fig. b below).

The lonely electron of the double bond, from which an electron was removed, can move easily. As a

consequence, the double bond successively moves along the molecule. The positive charge, on the

other hand, is fixed by electrostatic attraction to the iodide ion, which does not move so readily. If the

polyacetylene chain is heavily oxidised, polarons condense pair-wise into so-called solitons. These

solitons are then responsible, in complicated ways, for the transport of charges along the polymer

chains, as well as from chain to chain on a macroscopic scale.

We have only touched upon the complex theory that explains how polymers can be made electrically

conductive.

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APPLICATION OF PLASTIC ELECTRONICS-

ORGANIC LIGHT EMITTING DIODES (OLEDs)-

An electron and hole pair is generated inside the emissive layer.

When the electron and hole combine, a photon is produced, this will show up as a dot of light

on the screen.

Many OLEDs together on a screen make up a picture.

WHAT IS OLED-

An OLED or Organic Light-Emitting Diode is a light emitting device based on the principle of

electrophosphorescence. Several types of organic material that will glow red, green and blue are

placed between two layers of conductive material and covered with glass or another translucent

protective material. When electric current is applied, the conductive layers act as anode (positively

charged) and cathode (negatively charged), enabling the flow of energy from the negative layer to the

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positive layer and stimulating the organic material to emit a bright light. The two most common types

of OLED:

The two most common types of OLED:

SMOLED or Small Molecular OLED :

Layers of organic material with very small molecular structures are assembled using vacuum vapor

deposition

Poly-OLED or Polymer OLED :

Layers are prepared by spin coating a surface with large molecular structure organic polymers

For the deposition of organic thin film, our group investiagates evaporation techniques such as Vapour

Thermal Evaporation (VTE) and Organic Vapur Phase Deposition (OVPD). In combination with our

experimental lineup, comprising x-ray-diffraction and -reflectometry, atomic-force microscopy,

ellipsometry and electrical characterization methods, we are able to produce multi-layer samples (e.g.

OTFTs as shown in fig. 3) and characterize them with respect to their optical, structural,

morphological and electrical properties.

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OLED vs. LCD

A non-organic LCD display does not emit light; a backlight sits behind the LCD panel and to create

the image you see on screen, individual liquid crystals allow light to pass or block it. OLED computer

displays do not require a backlight since the organic material self-generates light, so they require very

little external power.

1. Active OLED

2. Passive OLED

FIGURE OF PASSIVE OLED

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ORGANIC THIN FILM

Fig. 1: Surface of an organic thin film detected with an AFM (Atomic Force Microscope).

Thin organic films (10-1000nm), that serve as active layers in both electrical (e.g. transistors) and

optical (e.g. light emitting diodes) devices.

In the field of organic transistors (OTFT – Organic Thin-Film Transistors), especially crystalline

materials such as Pentacene and Perylene are of importance. They grow as polycrystalline islands (fig.

1). Such transistors can be employed as control elements for organic displays. The important

advantages of organic over inorganic transistors (e.g. based on silicon or germanium) are the ability of

low-cost production and the prospect of using flexible substrates. This facilitates the development of

elastic displays.

In contrast to the crystalline materials employed for OTFTs, amorphous organic films are used for

organic light emitting diodes (OLEDs). Already today, OLEDs can be found in many products such as

cell phones and digital cameras due to the high level of efficiency and the brilliant colors. Moreover,

organic displays do not exhibt color shifting upon variation of the angel of vision. In addition to

displays also their use as illuminants is of interest (fig. 2). Some of our investigated materials, e.g.

ALq3 and alpha-NPD, are suitable candidates for these applications.

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ORGANIC THIN FILM TRANSISTORS (OTFTs)

Organic transistors are transistors that use organic molecules rather than silicon for their active

material.

DIFFRENCE BETWEEN TFT AND OTFT-

• TFTs :

1. Silicon deposited on glass.

2. The deposited silicon must be crystallized using laser pulses at high temperatures.

• OTFTs

Active layers can be thermally evaporated and deposited on any organic substrate a flexible

piece of plastic at much lower temperatures.

ADVANTAGE OF ORGANIC TRANSISTORS

– Compatibility with plastic substances

– Lower temperature is used while manufacturing (60-120°C)

– Lower cost and deposition processes such as spin-coating, printing and evaporation

DISADVANTAGE OF ORGANIC TRANSISTORS

– Lower mobility and switching speeds compared to Si wafers

– Usually does not operate under invasion mode.

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CHALLENGES INVOLVED

– Workarounds for complications with photo resists.

– To find organic semiconductors with high enough mobility and switching times.

FEATURES OF OTFTs-

Mobility greater than 0.1 cm2/Vs

On/off ratio greater than 106

ORGANIC NANO RADIO FREQUENCY IDENTIFICATION

DEVICES

• Quicker Checkout

• Inventory Control

• Reduced Waste

• Efficient flow of goods from

PRODUCTION SPECIFICATIONS OF MANUFACTURING A

NANO-RFID

• > 96 bits

• Four main communication Bands: 135 KHz, 13.56 MHz, 900 MHz, 2.4 GHz

• Vacuum Sublimation

SMART TEXTILES

•Integrates electronic devices into textiles, like clothing

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•Made possible because of low fabrication temperatures

•Has many potential uses, including: Monitoring heart-rate and other vital sign controlling embedded

devices (mp3 players), keep the time…

LAB ON CHIP

•A device that incorporates multiple laboratory functions in a single chip

•Organic is replacing some Si fabrication methods:

1. Lower cost

2. Easier to manufacture

3. More flexible Portable, Compact Screens

•Screens that can roll up into small devices

BRILLIANT APPLICATIONS-

Metal wires that conduct electricity can be made to light up when a strong enough current is

passing - as we are reminded of every time we switch on a light bulb. Polymers can also be made to

light up, but by another principle, namely electroluminescence, which is used in photodiodes. These

photodiodes are, in principal, more energy saving and generate less heat than light bulbs.

In electroluminescence, light is emitted from a thin layer of the polymer when excited by an electrical

field. In photodiodes inorganic semiconductors such as gallium phosphide are traditionally used, but

now one can also use semiconductive polymers.

Electroluminescence from semiconductive polymers has been known for about ten years. Today there

is extensive commercial interest in photodiodes and in light-emitting diodes (LEDs). A LED can

consist of a conductive polymer as an electrode on one side, then a semiconductive polymer in the

middle and, at the other end, a thin metal foil as electrode. When a voltage is applied between the

electrodes, the semiconductive polymer will start emitting light.

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High resolution

There are many applications of this brilliant plastic. In a few years, for example, flat television

screens based on LED film will become reality, as will luminous traffic signs and information signs.

Since it is relatively simple to produce large, thin layers of plastic, one can also imagine light-emitting

wallpaper in our homes, and other spectacular things.

Some applications of conductive polymers that have come onto the market, or are undergoing trials,

are:

Polythiophene derivates, those are of great commercial use in antistatic treatment of

photographic film. They can also be used in devices in supermarkets for marking products. The

checkouts will then automatically register what the customer has in the trolley.

Doped polyaniline in antistatic material, e.g. in plastic carpets for offices and operating

theatres, where it is important to avoid static electricity. It is also used on computer screens,

protecting the user from electromagnetic radiation, and as a corrosion inhibitor.

Materials such as polyphenylenevinylene may soon be used in mobile phone displays.

Polydialkylfluorenes are used in the development of new colour screens for video and TV.

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OTHERS APPLICATIONS

The Powerstrip that could save your lifeWednesday, December 19th, 2007

Every now and then an invention comes along that looks or sounds silly. The Smoke Shutoff power strip, from Exact Products, is the exact opposite. Ingenuity at its best, this product is one of those things you wish you thought of. It’s a power strip which shuts off electricity to attached devices when smoke is detected. On top of that, an alarm sounds until the smoke hazard is gone. And on top of that, the strip won’t restore power until you hit a reset button! That’s 3 levels of safety craziness!!! This product could be used anywhere, but I really see it working well in businesses that use a lot of machines. The Smoke Shutoff has completed testing and now just needs a distributor, so someone contact Exact Products and get going!

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Batteries of the Future!!!

Monday, March 26th, 2007

They say that plastic is good for us. Three scientists in Japan decided that it was great for us. They created an organic polymer film that can be used as a rechargeable battery. They claim it could retain a charge over longer periods of time and have a life lasting over 1,000 recharging. The craziest thing is that it can recharge fully in only one minute. This would definitely be useful in any of the emergency fields in all sorts of electronics and emergency response gear, but it seems like they could easily get lost. My slogan pitch- ‘This radio is charged by the minute-man.’ Careful, it might develop a complex.

Wireless Digital Pen and MouseSunday, March 4th, 2007

EPOS had the right idea with the new digital pen they came out with. Users can capture and display handwritten notes on a computer, use it as a mouse, and or draw those fun Waldo pictures we all love, all without the need for paper or tablets. The best part is that the pen is wireless, so you don’t have to worry about it getting in the way, but you do have to worry about losing it in between the seat of your car. For all those agencies stuck in the Stone Age, this would be great for digitizing your reports, and for everyone else in the technological ‘know’, this would be useful in a plethora of situations.

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Digital Cameras with printersMonday, February 5th, 2007

A new company called Zink, with Polaroids help, is working on a digital Polaroid camera. The sweet camera will have a built in printer. Zink is developing the miniaturized printers that will be small enough to fit into the cameras. Instead of using ink the company is testing paper that is capable of turning any color and the printer would just tell every ‘pixel’ what color to turn. Sounds cool and creepy at the same time. Either way this would be awesome out in the field for photo support for accidents, parking disputes, or anything else. Now you won’t be able to blame the camera on deleting your photos. -

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Self-Energizing Medical GadgetsThursday, December 21st, 2006

Energy is something that all medical gadgets and products need to run. Pacemakers and the like all use some type of power to function. A consortium in the UK consisting of Zarlink Semiconductor, InVivo Technology, Finsbury Orthopedics and others are being commissioned by the UK Department of Trade and Industry to create a power source for any and all medgadgets by using our own kinetic energy. This prototype that is pictured works by the motion of a moving coil through a static magnetic field to induce a voltage across the coil, which creates the energy. This could definitely help in not just the medical fields, but in any emergency related fields.

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Release the Wild Charger in you!!Thursday, December 14th, 2006

We are still a few years off from complete wireless charging of every device in the world, but for now Wild charger has the idea. The Wild charger charges your electronic devices through the metal contacts on your devices. The only cord in the whole ordeal is the AC Cord for the charger. This thing could definitely tidy up the work area of cords as well as charge all 5 billion of your devices. They hope to release it early next year with a price tag between $40 and $100. I’m guessing it will go for the latter amount. This kind of technology would be great for charging cell phones, radios, AED’s, etc…

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Mini Display for Designer Glasses

Wednesday, December 13th, 2006

Lumus-Optical out of Isreal decided that the horrible LCD Goggles that are out on the market aren’t fashionable enough. They say they have a working prototype of LCD Glasses. The glasses come with two micro displays that are capable of displaying a projected image of 60 inches from 10 feet. The best part is that they use Light-guide Optical Element that displays this image on your regular lenses so you can still see through the glasses. This would make watching a movie way easier while driving. The image quality boasts a 640×480 resolution and will even come with a tiny projector on the arm. This would be awesome for Police Officers out in the field. They would be able to watch movies during down timer see the returns of pictures of bad guys from dispatch. There could be a multitude of ways to use this in the Emergency field.

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Gamma Radiation WatchSaturday, December 9th, 2006

No, this doesn’t shoot lasers at bad guys. The Gamma Watch from Environmental Instruments Canada Inc. actually detects radiation. It displays dose rate as well as cumulative dose. You do need to make sure you set the radiation level that you want the alarm to go off before you deteriorate. This thing is so popular (in the UK I’m guessing) that it is actually sold out and a newer model is being made. It will go for $250 and will be especially helpful when you’re diving up to 50 meters. By

Acoustic Sensitive to the touchThursday, November 30th, 2006

Researchers in Europe have come up with Tai-Chi or the Tangible Acoustic Interfaces for Computer-Human Interaction that is a series of acoustic sensors that turn any surface into a touch-sensitive computer interface. The system uses sonar tracking that senses surface vibrations and can track up to two things at once. This could be very useful in the work place like hospitals who are concerned about hygiene, because the clean up is non-existent. This could also clear the bulk of wires and hardware used in the Police and Fire fields when typing up reports or using your Mobile Date Computer to respond to calls. There is no release date for any products yet, but I’m sure once its perfected there will be a product. Soon, we could all have the holographic touch screens just like in the futuristic movies.

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Gamma-Scout- Life Saving ToolThursday, November 30th, 2006

Eurami got it right when they created the Gamma-Scout Radiation detector. The control panel lets you display alpha, beta, gamma, and x-rays in pulse or rate mode on the LCD. You can punch in time, date, and logging intervals; and check the battery level. The set-and-forget device sounds an alert when radiation exceeds a specified limit, and bundled software lets you shoot data to your PC for analysis via USB 2.0. The unit is packaged in high impact Novodur molding so you can bang it all over the place without ruining it and the V-Max battery, also included, is good for a decade of always-on monitoring. That’s a damn good long time for measuring radiation during the nuclear holocaust years to come. All this at only 6oz., I would have to say for any Police/Fire/Medical agency needing a gieger counter to go out and spend the $399, which isn’t a bad price for the use and longevity.

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Snapalarm: Like legosWednesday, November 29th, 2006

Everyone has had to replace their smoke detector batteries a billion times in their homes. You have to get a chair and try and pry the whole thing off the ceiling to shut it up. Now with the Snapalarm smoke detector it makes it much easier to simplify these menial tasks. The Snapalarm is a clam shell design that will snap onto any wire, chain, or wire/chain size cord. The best part is that it won’t lock close unless it has a working battery. It sells for $50, which is not too bad for the stylish bulb that may just save your life some day.

COPS all the timeWednesday, November 22nd, 2006

It was only a matter of time, but British Police in London will now be wearing helmets that have a camera the size of a AA battery on them that will be recording in the direction that the officers are looking. They record to a utility belt (Batman?), and are said to be high digital quality. The main reasons for these cameras are for aggressive deterance of anti-social behavior. Mind you, London is already the camera capital of the world, with the most cameras recording everything ever. These will also be great for court and evidence, unless more of the LAPD style of arrests keep happening.

Radiation detecting watchWednesday, November 15th, 2006

I know what you’re all thinking. When the hell would I ever need this thing? Well, you never know when the 3rd World War will start, unless you work for the CIA, or maybe you live near a nuclear reactor, or work for Hazmat, well that’s where you’ll need this thing, so there!!!! Sorry. Along with

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the regular watch functions this thing just comes with a radiation meter. It will set you back $250 so start saving. Now it would be cool if it made that white noise sound you hear in the movies when they are detecting radiation.

Viewsonic Ruggedized HandheldWednesday, November 15th, 2006

Viewsonic the makers of all things monitor goodness have decided to come out with not one, but seven, ah ah ah, Ruggedized handhelds. You know? Count from Sesame…ah forgets it. Here are the deets and there are a lot of them. The units run on older Windows Mobile 2003 so they can run all programs created when the PDA boom took off and are powered by Intel XScale processors. The devices meet IP54 design standards for sealing against dust, moisture and extreme environmental conditions. The features include 3.5-inch 240 x 320 (QVGA) LCD display, 416MHZ-520MHZ Intel Xscale processor, Jog dial, SD card slot and swappable Lithium Ion batteries which allow battery changes without shutdown or loss of data. They also come with 802.11b/g wireless, Bluetooth, bar code scanner, 1.3 megapixel camera (With most models), fingerprint sensor (with most models) and GPS (Global Positioning System) support with one model. This thing is loaded and it only weighs 12 oz so it fits in the Christmas stocking very nice like.

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Fujufilm Face RecognizerThursday, November 9th, 2006

FujiFillm just released a new camera that has a facial recognizer in it. It will actually find up to 10 faces in the picture focus on them as a whole and take the best picture possible. It includes 3x Optical zoom, 6.3 megapixel, intelligent flash, and an image generator that will take pictures adjusted for uploading to places like My Space that have a lower image size. It also has a 2.5 inch scratch resistant LCD screen. It comes in a plethora of colors to boot. There is no pricing yet, but it will be available in January in case you didn’t buy enough during Christmas.

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CONCLUSION

Plastics play an important role in the design of electronic products. It is crucial that engineers

understand the characteristics of plastics in order to select the appropriate plastic for a given

application. Many factors affect this decision, including the required properties and the molding

process. Ultimately, selecting the right plastics can help ensure the safety and reliability of the final

product. Plastic are very promising materials to be used in electronic materials.

Organic electronics are lighter, more flexible, and less expensive than their inorganic counterparts.

They are also biodegradable (being made from carbon, e.g.. melanin).

This opens the door to many exciting and advanced new applications that would be impossible using

copper or silicon.

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1. INTRODUCTION2. GENERAL OUTLOOK 3. ELECTRICAL CONDUCTION4. CHEMICAL BONDING AND CONDUCTIVITY5. EXAMPLES

POLYACETYLENE WHAT HAPPENED IN THE PA FILM POLYPYRROLE

6. HOW CAN PLASTIC BECOME CONDUCTIVE MANUFACTURING OF PLASTIC ELECTRONICSINORGANIC Vs ORGANICBENEFITS AND OBSTACLESCONJUGATED POLYMERS: ELECTRONIC CONDUCTORSPECIFYING PLASTIC FOR ELECTRONIC DESIGN

CLASSIFICATIONOPERATING TEMPERATURE SAFETY STANDARDDESIGN TIPS

KEY TERMS AND ABBREVATIONSMATERIALS COMPOUND SELECTIONSHOW POLYMER CONDUCTIVITY WAS REAVEALEDDOPING- FOR BETTER MOLECULE PERFORMANCEPOLARONS

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APPLICATIONOLEDsOTFTsSMART TEXTILEPOWER STRIPSPLASTICS BATTERIESWIRELESS DIGITAL PENS AND MOUSE DIGITAL CAMERA WITH PRINTERSSELF-ENERGIZING MEDICAL GADGETSWILD CHARGER GAMMA RADIATION WATCHACOUSTIC SENSITIVE LIFE SAVING TOOL SNAP ALARM RADIATION DETECTING WATCH

CONCLUSIONREFERENCES

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Thank you for your attention … •

http://whatis.techtarget.com/definition/0,,sid9_gci512140,00.html

•

http://www.chem.uky.edu/research/anthony/tft.html

•

http://en.wikipedia.org/wiki/OLED

•Materials Matter 2007, Volume 2, 3: Special Issue on Organic Electronics

http://seminor.4u.blogspost.com

http://www.acreo.sc

http://www.discoverengineering.org

http://www.plasticelectronics.org

http://www.imce.be

http://www.escher.clis.ugent.be

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