Plastic electronic (1)


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Plastic electronic (1)

  2. 2. 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- CHARGE2
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  5. 5. :INTRODUCTION: Plastic electronics or organic electronics is a branch of electronics that deals with device made fromorganic 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 ofliving things. This is as oppose to traditional electronics which relies on inorganic conductors such as siliconor copper Conduction mechanisms involve resonance stabilization and delocalization of pi-electrons along entirepolymers backbones as well as mobility gaps, tunneling and phonon –assisted hopping conductive polymersare lighter, more flexible and less expensive than inorganic conductors. This makes them a desirablealternative in many applications. It also creates the possibility of new applications that would be impossibleusing copper or silicon. New application includes small windows and electronic paper. Conductive polymers are expected toplay an important role in the emerging science of molecular computing. In general, organic conductivepolymers have a higher resistance hence therefore conduct electricity poorly and inefficiently, as compared toinorganic conductors. Researchers currently are exploring way of doping, organic semiconductors likemelanin, with relatively small amount of conductive metals to boost conductivity. However, for manyapplications, inorganic conductors will remain the only viable option. 5
  6. 6. GENERAL OUTLOOK-October 10, 2000We are used to the great impact scientific discoveries have on our ways of thinking. This years NobelPrize in Chemistry is no exception. What we have been taught about plastic is that it is a goodinsulator - otherwise we should not use it as insulation in electric wires. But now the time has comewhen we have to change our views. Plastic can indeed, under certain circumstances, be made tobehave very like a metal - a discovery for which Alan J. Heeger, Alan G. MacDiarmid and HidekiShirakawa are to receive the Nobel Prize in Chemistry 2000. The men principally credited for the discovery and development of highly-conductivepolymers(at least of the rigid backbone “polyacetelene”)class are Alan J. Heeger, Alan G. macDiramidand Hideki Shirakawa, who were jointly awarded the noble prize in chemistry in 2000 fordevelopment 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 tothe 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 istherefore necessary to use a parameter the resistivity which is a material property and is defined as theresistance of a conductor of unit length with unit cross-sectional area. Resistivity has unit of ohmmeters (Ωm) in the S.I. system. To compare the properties of conductors it is more convenient to useconductivity 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 reciprocalohm meters or siemens per meter (S/M).Electrically conductive polymers are mainly derivative of poly acetylene black (the simplest melanin)6
  7. 7. 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 ofconductivity compared with covalently-bonded insulators such as Diamonds where there are none.The effect of chemical bonding upon conductivity can be seen in fig.17
  8. 8. EXAMPLES-POLY ACETELENE- It is produced in two isomeric forms, cis and Trans polyacetelenes. The particular isomerobtained depends upon the temperatures at which the polymerization was performed. Reactions at78۠0C produce mainly the cis-confirmation where as none of the trans-form is also be converted to thethermodynamically more stable trans-form by heating typically at 170۠0C for 20 minutes. The properties of the polymer are also affected by this isomerisation. Films of the cis materialare red in transmitted light and the smooth surface has a coppery appearance where as the transmaterial is blue in transmission and silvery in reflection. More important the conductivity of thepolymer increase with the cis to Tran’s isomerisation from about 10 -9 S/cm to up to 10-4 S/cm. Hencepure 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 tometallic 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 alkalimetals. It is pointed out however that the term doping in thix context refers to the inclusion ofsubstantial quantities of dopant in the polymer. This is to be contrasted with conventialsemiconductors technology where dopant concentrate are measure in ppm.8
  9. 9. There is a rapid rise more slowly with further addition of dopant. The measured conductivityfor PA treated with different dopant are listed in table-1 with the highest value(S) 1000(S/cm) beingobtained 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 theconductivities of the polymers vary considerably. Doped polyacetylene is, e.g., comparable to goodconductors 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 dopedconducting polymers is produced at the anode when the monomer solution is electrolyst in thepresence 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 purepolymer but contain one BF4 ion for every four pyrrole rings.9
  10. 10. HOW CAN PLASTIC BECOME CONDUCTIVE? Plastics are polymers, molecules that form long chains, repeating themselves like pearls in anecklace. In becoming electrically conductive, a polymer has to imitate a metal, that is, its electronsneed to be free to move and not bound to the atoms. The first condition for this is that the polymerconsists 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 electricallyconductive, the plastic has to be disturbed - either by removing electrons from (oxidation), or insertingthem into (reduction), the material. The process is known as doping.10
  11. 11. The game in the illustration to the right offers a simple model of a doped polymer. The piecescannot move unless there is at least one empty "hole". In the polymer each piece is an electron thatjumps to a hole vacated by another one. This creates a movement along the molecule - an electriccurrent. 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 beoxidised with iodine vapour, increasing its electrical conductivity a billion times. This sensationalfinding 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 andmicro miniaturized to the point that thousands or even millions of circuits are contained in a one inchsquare chip which is burned on to ultra thin inorganic materials life refined silicon using very hightemperature.11
  12. 12. Plastic electronics, on the other hand, follow a different manufacturing process. The processstarts with the manufacturing of large sheets of PET plastics. The flexible but tough material used inthe production of plastic bottles. Circuits are then printed on these sheets using ink-jet printers or usingtechniques much like those used to print magazines and news papers- resulting in a process that ischeap, easy to do and faster to produce. The plastic circuit will be used as the active matrix back panes for large but flexible electronicdisplays. In an active matrix display, every dot on displays managed by a switching element such asthin 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 arigid 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 ona substrate to for the active matrix back pane, which is then combined with different front platetechnologies (LCD screens) to form display. For many electronic readers the best front plane technology e-paper which looks like paper andonly uses unit’s power when the image shifts or changes. E-paper however loses its thinness and flexibility when combine with a glass based siliconback pane. The flexible back pane technology of plastic electronic allows the reader device to becomeflexible, light thin and robust enough for a wide range of uses no paper has gone before and to includelarge data storage capacities.12
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  14. 14. INORGANIC Vs ORGANIC- Organic electronic or plastic electronic is the branch of electronic that deals with conductivepolymers 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 photolithography14
  15. 15. Conjugated Polymers: Electronic Conductors The most important aspect of conjugated polymers from an electrochemical perspective is theirability to act as electronic conductors. Not surprisingly -electron polymers have been the focus ofextensive research, ranging from applications of ``conventional polymers (e.g., polythiophene,polyaniline, polypyrrole) in charge storage devices such as batteries and super capacitors, to newpolymers with specialized conductivity properties such as low band gap and intrinsically conductingpolymers. Indeed, many successful commercial applications of these polymers have been available formore 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 ofconducting polymers in the year 2000 will surpass one billion US dollars. Clearly these materials haveconsiderable commercial potential both from the continued development of well establishedtechnologies 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 polymercapable of conducting electricity polyacetylene was reportedly prepared by accident. The subsequentdiscovery by Heeger and MacDiarmid that the polymer would undergo an increase in conductivity of12 orders of magnitude by oxidative doping quickly reverberated around the polymer andelectrochemistry 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 electricalproperties of a metal. The essential structural characteristic of all conjugated polymers is their quasi-infinitesystem extending over a large number of recurring monomer units. This feature results in materialswith directional conductivity, strongest along the axis of the chain. The simplest possible form is ofcourse the archetype polyacetylene (CH) x shown in Figure While polyacetylene itself is too unstableto be of any practical value, its structure constitutes the core of all conjugated polymers. Owing to itsstructural and electronic simplicity, polyacetylene is well suited to ab initio and semi-empiricalcalculations and has therefore played a critical role in the elucidation of the theoretical aspects ofconducting polymers.15
  16. 16. 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 believedthat they possess a spatially delocalized band-like electronic structure. These bands stem from thesplitting of interacting molecular orbital of the constituent monomer units in a manner reminiscent ofthe band structure of solid-state semiconductors.16
  17. 17. 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 themotion of charged defects within the conjugated framework. The charge carriers, either positive p-typeor negative n-type, are the products of oxidizing or reducing the polymer respectively. The followingoverview describes these processes in the context of p-type carriers although the concepts are equallyapplicable 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 comprisesboth the hole site and the structural distortion which accompanies it. This condition is depicted inFigure 1.4A. The cation and radical form a bound species, since any increase in the distance betweenthem would necessitate the creation of additional higher energy quinoid units. Theoretical treatmentshave demonstrated that two nearby polarons combine to form the lower energy bipolaron shown inFigure 1.4 B. One bipolaron is more stable than two polarons despite the coulombic repulsion of the17
  18. 18. two ions. Since the defect is simply a boundary between two moieties of equal energy -- the infiniteconjugation chain on either side -- it can migrate in either direction without affecting the energy of thebackbone, provided that there is no significant energy barrier to the process. It is this charge carriermobility that leads to the high conductivity of these polymers. The conductivity of a conducting polymer is related to the number of charge carriers n andtheir mobility : σ α µn Because the band gap of conjugated polymers is usually fairly large, n is very small underambient conditions. Consequently, conjugated polymers are insulators in their neutral state and nointrinsically conducting organic polymer is known at this time. A polymer can be made conductive byoxidation (p-doping) and/or, less frequently, reduction (n-doping) of the polymer either by chemical orelectrochemical means, generating the mobile charge carriers described earlier. The cyclicvoltammetry of electronically conducting polymers is characterized by broad non-Nernstian waves. Atypical example is shown in Figure for an N-substituted pyrrole based conducting polymer. Figure 1.5: Cyclic voltammogram of a substituted polypyrrole.18
  19. 19. SPECIFYING PLASTICS FOR ELECTRONICS DESIGN Although not always an easy task, selecting the right plastics can help ensure the safety andreliability of todays electronics. Most electronic equipment uses some type of thermoplastic. It is important to understand thecharacteristics of plastics used in electronics equipment to determine which plastic is appropriate for agiven application. These characteristics often affect the safety and reliability of the final product. Thisarticle examines many factors surrounding plastics selection that engineers should consider during aproducts design stages. Underwriters Laboratories (UL) has one of the most comprehensive materials databasesavailable, and UL 94 ratings are widely accepted flammability performance standards for plasticmaterials. The UL 94 standard explains various flammability categories and describes the test methodsused for each rating. CLASSIFICATION Each material tested can receive several ratings based on color and thickness. The amount andtype of color additive can vary the flammability rating of a plastic. The UL plastic componentdirectory normally specifies four colors: black, white, red, and natural. When specifying a material foran application, the UL rating should be applicable for the thickness used in the wall section of theplastic part. It is very important to remember that the thickness must always be reported with the ULrating to provide meaningful information about the materials characteristics. Ratings are categorizedas follows:Ratings are differentiated primarily by the testing method. The classification depends on the followingfactors: • Sample orientation (horizontal or vertical). • Burn rate. • Time to extinguish. • Resistance to dripping.19
  20. 20. • Drip flammability. These parameters affect the end results, and hence the classification. With this in mind, eachmaterial tested could receive several ratings, depending on its color and thickness. Some ratings applyto specific product types. VTM, for example, refers to very thin material. HBF, HF-1, and HF-2 referto foamed materials. These ratings, therefore, should not be compared to those in other categories. Inother words, a vertically rated plastic material is better than a plastic that simply meets the HBrequirements. In addition, a material accepted for a 5V rating must first comply with the vertical testrequirements for V-0, V-1, or V-2. Depending on the end-product application, a designer could specifyone or more ratings for a product. OPERATING TEMPERATURE Some engineers make the erroneous assumption that there is a direct correlation between amaterials UL rating and its operating temperature. UL ratings relate only to a materials behavior whenintroduced to a flame source. How a material reacts when the flames come in direct contact with itdetermines its UL rating. For example, for a rating of 94V-0, a material must be self-extinguishing andmust not drip or run while burning. 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 materialmust not have dripped from the burning sample. If the material continues to burn or if it drips andruns, it cannot be rated 94V-0. For this rating, operating temperature never comes into play. Component Flammability Requirements Enclosure 94V-1 or better Printed circuit board 94V-1 or better Integrated circuit, 94HB or better transistor, optocoupler package, capacitor, and20
  21. 21. other small parts Cord anchorage bushing 94HB or better Operating temperature is determined by establishing the point at which temperature causes anend product to cease to perform as it was intended. This premise applies to minimum as well asmaximum temperatures. Most nylon materials, for example, have a maximum operating temperatureof 250°F (120°C). However, the actual operating temperatures of finished goods vary depending onthe mass (volume of material), temperature variations over time, and mold factor. A 94V-0 rating for amaterial 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 forplastics in electronics. Requirements normally cover plastics that support live parts, such as atransformers bobbin; enclosure of live parts, such as a monitor cover; and decorative parts, such as alamp cover. EN 60950, for example, has guidelines specifying minimum requirements for plasticparts. Most electrical and electronic equipment has some type of enclosure. Enclosures are normallyevaluated 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 andelectrical enclosures meet certain parameters in order to be considered effective. A summary of theserequirements is presented here, but it is essential that designers refer to the standard for completedetails.21
  22. 22. The top and side openings of the enclosure must satisfy one of the following conditions: do notexceed 5 mm in any dimension; do not exceed 1 mm in width regardless of length; are constructedwith louvers shaped so that they deflect external, vertically falling objects outward; are located so thatobjects, 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, fireenclosures are considered to comply without test if, in the smallest thickness used, the material is offlammability class 5V. The bottom of a fire enclosure—or individual barriers—must provide protection underneath allinternal parts, including partially enclosed components or assemblies that could emit, under faultconditions, 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 screenmust have a flammability rating of 5V. However, if a hole is cut to accommodate a fuse holder, aswitch, or similar components, then there is no need for these components to meet 5V flammabilityrequirements, provided that such components have appropriate approvals. DESIGN TIPSResources. One source of valuable information is the UL Recognized Component Directory, also knownas the UL Yellow Book. This directory provides names of companies authorized by UL to provideplastic 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 Abbreviations22
  23. 23. 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) isapplied.CTI: Comparative Tracking Index.CTI is expressed as the voltage that causes tracking after 50 drops of 0.1% ammonium chloridesolution have fallen on the material. The results of testing the nominal 3-mm thickness are consideredrepresentative of the materials performance in any thickness.D-495: Arc Resistance.Measured in accordance with ASTM D-495, arc resistance is expressed as the number of seconds thata material resists the formation of a surface conducting path when subjected to an intermittentlyoccurring arc of high-voltage, low-current characteristics. The results of testing the nominal 3-mmthickness are considered representative of the materials performance in any thickness.HAI: High Amp Arc Ignition. Ignition performance is expressed as the number of arc rupture exposures (standardized as toelectrode type and shape, and electric circuit) necessary to ignite a material when applied at a standardrate 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 thesurface of the material under standardized test conditions. A note is made if the material ignites. The23
  24. 24. results of testing the nominal 3-mm thickness are considered representative of the materialsperformance in any thickness.HWI: Hot Wire Ignition. Ignition performance is also expressed as the mean number of seconds needed to either ignitestandard specimens or to burn through specimens without ignition. Specimens are wrapped withresistance 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 becausea 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.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 UL746B. The temperature index indicates the temperature (°C) above which the material is likely todegrade prematurely. The printed value refers to the extrapolation to approximately 100,000 hourswith the retention of at least 50% of its original value after the aging test. Depending on the propertyrequirements 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).24
  25. 25. MATERIALS Selecting the appropriate plastic material for a particular design is often the most difficult taska 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 designers 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 datasheets. Values from data sheets often represent laboratory tests that may not duplicate real-lifemolding conditions. For example, it is a mistake to choose the most economical material for a part bycomparing the cost per pound of various plastics. Some plastics weigh twice as much per cubic inch asothers, and so it would then require twice as much material to fill a given cavity-and cost twice asmuch to ship. The choice of any material should be based on the best combination of required properties. Anideal material will have a value for each required property just sufficient to perform properly andsafely in a given application. A molded plastic part is significantly affected by processing factors suchas 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 byprocessing conditions. There is no simple procedure for selecting the best plastic for a new application. Understandingthe behavior of a plastic under real-life conditions is critical to determining how the material willperform after it is molded. Successfully designing plastic parts that demonstrate optimal cost andperformance characteristics requires learning as much as possible about many different plastics, andunderstanding the peculiarities of their processing. COMPOUND SELECTION25
  26. 26. One of the first design considerations to establish is whether thermosetting materials orthermoplastics are appropriate. Thermosetting materials are initially soft but change irreversibly hardupon 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 theirdifferences. 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 internalfactors such as production, engineering, purchasing, and marketing considerations. Molders can oftendetect and correct visible problems or readily measured factors such as color, surface condition, anddimensions. However, without extensive testing and quality control, less-apparent property changesmay 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. Moldingprocesses can alter the published data-sheet properties, reducing strength as well as creating areas ofstress concentrations. HOW POLYMER CONDUCTIVITY WAS REAVEALED? The leading actor in this story is the hydrocarbon polyacetylene, a flat molecule with an angleof 120° between the bonds and hence existing in two different forms, the isomers cis-polyacetyleneand trans-polyacetylene. At the beginning of the 1970s, the Japanese chemist Shirakawa found that itwas possible to synthetisize polyacetylene in a new way, in which he could control the proportions ofcis- and trans-isomers in the black polyacetylene film that appeared on the inside of the reactionvessel. Once - by mistake - a thousand-fold too much catalyst was added. To Shirakawas surprise, thistime a beautiful silvery film appeared.Shirakawa was stimulated by this discovery. The silvery film was trans-polyacetylene, and thecorresponding reaction at another temperature gave a copper-coloured film instead. The latter filmappeared to consist of almost pure cis-polyacetylene. This way of varying temperature andconcentration of catalyst was to become decisive for the development ahead.In another part of the world, chemist MacDiarmid and physicist Heeger were experimenting with a26
  27. 27. metallic-looking film of the inorganic polymer sulphur nitride, (SN)x. MacDiarmid referred to this at aseminar in Tokyo. Here the story could have come to a sudden end, had not Shirakawa andMacDiarmid happened to meet, accidentally, during a coffee-break.When MacDiarmid heard about Shirakawas discovery of an organic polymer that also gleamed likesilver, he invited Shirakawa to the University of Pennsylvania in Philadelphia. They set aboutmodifying polyacetylene by oxidation with iodine vapour. Shirakawa knew that the optical propertieschanged in the oxidation process and MacDiarmid suggested that they ask Heeger to have a look at thefilms. One of Heegers 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 inthe article "Synthesis of electrically conducting organic polymers: Halogen derivatives ofpolyacetylene (CH)n" in The Journal of Chemical Society, Chemical Communications. The discoverywas considered a major breakthrough. Since then the field has grown immensely, and also given riseto many new and exciting applications. We shall return to some of them. DOPING- FOR BETTER MOLECULE PERFORMANCEA metal wire conducts electric current because the electrons in the metal are free to move.27
  28. 28. The higher no. of free electrons in metals such as copper and iron leafs to higher levels ofconductivity compared with covalently-bonded insulators such as Diamonds where there are none.When describing polymer molecules we distinguish between (sigma) bonds and (pi) bonds. Thebonds are fixed and immobile. They form the covalent bonds between the carbon atoms. Theelectrons in a conjugated double bond system are also relatively localised, though not as stronglybound as the electrons. Before a current can flow along the molecule one or more electrons have tobe removed or inserted. If an electrical field is then applied, the electrons constituting the bonds canmove rapidly along the molecule chain. The conductivity of the plastic material, which consists ofmany polymer chains, will be limited by the fact that the electrons have to "jump" from one moleculeto 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 ofpolyacetylene the reactions are written like this:Oxidation with halogen (p-doping): [CH]n + 3x/2 I2 --> [CH]nx+ + x I3-Reduction with alkali metal (n-doping): [CH]n + x Na --> [CH]nx- + x Na+The doped polymer is a salt. However, it is not the iodide or sodium ions that move to create thecurrent, but the electrons from the conjugated double bonds. Furthermore, if a strong enough electricalfield is applied, the iodide and sodium ions can move either towards or away from the polymer. Thismeans that the direction of the doping reaction can be controlled and the conductive polymer caneasily be switched on or off. POLARONS- DOPED CARBON CHAINS In the first of the above reactions, oxidation, the iodine molecule attracts an electron from thepolyacetylene chain and becomes I3- . The polyacetylene molecule, now positively charged, is termed aradical cation, or polaron (fig. b below).28
  29. 29. The lonely electron of the double bond, from which an electron was removed, can move easily. As aconsequence, the double bond successively moves along the molecule. The positive charge, on theother hand, is fixed by electrostatic attraction to the iodide ion, which does not move so readily. If thepolyacetylene chain is heavily oxidised, polarons condense pair-wise into so-called solitons. Thesesolitons are then responsible, in complicated ways, for the transport of charges along the polymerchains, 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 electricallyconductive.29
  30. 30. 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 ofelectrophosphorescence. Several types of organic material that will glow red, green and blue areplaced between two layers of conductive material and covered with glass or another translucentprotective material. When electric current is applied, the conductive layers act as anode (positivelycharged) and cathode (negatively charged), enabling the flow of energy from the negative layer to the30
  31. 31. positive layer and stimulating the organic material to emit a bright light. The two most common typesof 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 vapordepositionPoly-OLED or Polymer OLED:Layers are prepared by spin coating a surface with large molecular structure organic polymersFor the deposition of organic thin film, our group investiagates evaporation techniques such as VapourThermal Evaporation (VTE) and Organic Vapur Phase Deposition (OVPD). In combination with ourexperimental 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.31
  32. 32. OLED vs. LCDA non-organic LCD display does not emit light; a backlight sits behind the LCD panel and to createthe image you see on screen, individual liquid crystals allow light to pass or block it. OLED computerdisplays do not require a backlight since the organic material self-generates light, so they require verylittle external power. 1. Active OLED 2. Passive OLED FIGURE OF PASSIVE OLED32
  33. 33. 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) andoptical (e.g. light emitting diodes) devices.In the field of organic transistors (OTFT – Organic Thin-Film Transistors), especially crystallinematerials 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 importantadvantages of organic over inorganic transistors (e.g. based on silicon or germanium) are the ability oflow-cost production and the prospect of using flexible substrates. This facilitates the development ofelastic displays.In contrast to the crystalline materials employed for OTFTs, amorphous organic films are used fororganic light emitting diodes (OLEDs). Already today, OLEDs can be found in many products such ascell 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 todisplays 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.33
  34. 34. ORGANIC THIN FILM TRANSISTORS (OTFTs)Organic transistors are transistors that use organic molecules rather than silicon for their activematerial.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 flexiblepiece 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 evaporationDISADVANTAGE OF ORGANIC TRANSISTORS– Lower mobility and switching speeds compared to Si wafers– Usually does not operate under invasion mode.34
  35. 35. 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 SublimationSMART TEXTILES•Integrates electronic devices into textiles, like clothing•Made possible because of low fabrication temperatures•Has many potential uses, including: Monitoring heart-rate and other vital sign controlling embeddeddevices (mp3 players), keep the time…35
  36. 36. 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 ispassing - as we are reminded of every time we switch on a light bulb. Polymers can also be made tolight up, but by another principle, namely electroluminescence, which is used in photodiodes. Thesephotodiodes 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 electricalfield. In photodiodes inorganic semiconductors such as gallium phosphide are traditionally used, butnow one can also use semiconductive polymers.Electroluminescence from semiconductive polymers has been known for about ten years. Today thereis extensive commercial interest in photodiodes and in light-emitting diodes (LEDs). A LED canconsist of a conductive polymer as an electrode on one side, then a semiconductive polymer in themiddle and, at the other end, a thin metal foil as electrode. When a voltage is applied between theelectrodes, the semiconductive polymer will start emitting light.36
  37. 37. High resolutionThere are many applications of this brilliant plastic. In a few years, for example, flat televisionscreens 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-emittingwallpaper 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.37
  38. 38. OTHERS APPLICATIONS The Powerstrip that could save your life Wednesday, December 19th, 2007Every now and then an invention comes along that looks or sounds silly. The Smoke Shutoff powerstrip, from Exact Products, is the exact opposite. Ingenuity at its best, this product is one of thosethings you wish you thought of. It’s a power strip which shuts off electricity to attached devices whensmoke 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!!! Thisproduct could be used anywhere, but I really see it working well in businesses that use a lot ofmachines. The Smoke Shutoff has completed testing and now just needs a distributor, so someonecontact Exact Products and get going!38
  39. 39. Batteries of the Future!!! Monday, March 26th, 2007They say that plastic is good for us. Three scientists in Japan decided that it was great for us. Theycreated an organic polymer film that can be used as a rechargeable battery. They claim it could retaina charge over longer periods of time and have a life lasting over 1,000 recharging. The craziest thingis that it can recharge fully in only one minute. This would definitely be useful in any of theemergency fields in all sorts of electronics and emergency response gear, but it seems like they couldeasily get lost. My slogan pitch- ‘This radio is charged by the minute-man.’ Careful, it might developa complex. Wireless Digital Pen and Mouse Sunday, March 4th, 2007EPOS had the right idea with the new digital pen they came out with. Users can capture and displayhandwritten 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 toworry about it getting in the way, but you do have to worry about losing it in between the seat of yourcar. For all those agencies stuck in the Stone Age, this would be great for digitizing your reports, andfor everyone else in the technological ‘know’, this would be useful in a plethora of situations.39
  40. 40. Digital Cameras with printers Monday, February 5th, 2007A new company called Zink, with Polaroids help, is working on a digital Polaroid camera. The sweetcamera will have a built in printer. Zink is developing the miniaturized printers that will be smallenough to fit into the cameras. Instead of using ink the company is testing paper that is capable ofturning any color and the printer would just tell every ‘pixel’ what color to turn. Sounds cool andcreepy at the same time. Either way this would be awesome out in the field for photo support foraccidents, parking disputes, or anything else. Now you won’t be able to blame the camera on deletingyour photos. -40
  41. 41. Self-Energizing Medical Gadgets Thursday, December 21st, 2006Energy is something that all medical gadgets and products need to run. Pacemakers and the like alluse 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 Departmentof Trade and Industry to create a power source for any and all medgadgets by using our own kineticenergy. This prototype that is pictured works by the motion of a moving coil through a static magneticfield to induce a voltage across the coil, which creates the energy. This could definitely help in notjust the medical fields, but in any emergency related fields.41
  42. 42. Release the Wild Charger in you!! Thursday, December 14th, 2006We are still a few years off from complete wireless charging of every device in the world, but for nowWild charger has the idea. The Wild charger charges your electronic devices through the metalcontacts on your devices. The only cord in the whole ordeal is the AC Cord for the charger. Thisthing 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 gofor the latter amount. This kind of technology would be great for charging cell phones, radios, AED’s,etc…42
  43. 43. Mini Display for Designer Glasses Wednesday, December 13th, 2006Lumus-Optical out of Isreal decided that the horrible LCD Goggles that are out on the market aren’tfashionable enough. They say they have a working prototype of LCD Glasses. The glasses come withtwo micro displays that are capable of displaying a projected image of 60 inches from 10 feet. Thebest part is that they use Light-guide Optical Element that displays this image on your regular lensesso 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 moviesduring down timer see the returns of pictures of bad guys from dispatch. There could be a multitudeof ways to use this in the Emergency field.43
  44. 44. Gamma Radiation Watch Saturday, December 9th, 2006No, this doesn’t shoot lasers at bad guys. The Gamma Watch from Environmental InstrumentsCanada Inc. actually detects radiation. It displays dose rate as well as cumulative dose. You do needto make sure you set the radiation level that you want the alarm to go off before you deteriorate. Thisthing is so popular (in the UK I’m guessing) that it is actually sold out and a newer model is beingmade. It will go for $250 and will be especially helpful when you’re diving up to 50 meters. By Acoustic Sensitive to the touch Thursday, 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-sensitivecomputer interface. The system uses sonar tracking that senses surface vibrations and can track up totwo things at once. This could be very useful in the work place like hospitals who are concerned abouthygiene, because the clean up is non-existent. This could also clear the bulk of wires and hardwareused in the Police and Fire fields when typing up reports or using your Mobile Date Computer torespond to calls. There is no release date for any products yet, but I’m sure once its perfected therewill be a product. Soon, we could all have the holographic touch screens just like in the futuristicmovies.44
  45. 45. Gamma-Scout- Life Saving Tool Thursday, November 30th, 2006Eurami got it right when they created the Gamma-Scout Radiation detector. The control panel lets youdisplay 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 alertwhen radiation exceeds a specified limit, and bundled software lets you shoot data to your PC foranalysis via USB 2.0. The unit is packaged in high impact Novodur molding so you can bang it allover 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 holocaustyears to come. All this at only 6oz., I would have to say for any Police/Fire/Medical agency needing agieger counter to go out and spend the $399, which isn’t a bad price for the use and longevity.45
  46. 46. Snapalarm: Like legos Wednesday, November 29th, 2006Everyone has had to replace their smoke detector batteries a billion times in their homes. You have toget a chair and try and pry the whole thing off the ceiling to shut it up. Now with the Snapalarmsmoke detector it makes it much easier to simplify these menial tasks. The Snapalarm is a clam shelldesign that will snap onto any wire, chain, or wire/chain size cord. The best part is that it won’t lockclose unless it has a working battery. It sells for $50, which is not too bad for the stylish bulb that mayjust save your life some day. COPS all the time Wednesday, November 22nd, 2006It was only a matter of time, but British Police in London will now be wearing helmets thathave a camera the size of a AA battery on them that will be recording in the direction that the officersare looking. They record to a utility belt (Batman?), and are said to be high digital quality. The mainreasons for these cameras are for aggressive deterance of anti-social behavior. Mind you, London isalready the camera capital of the world, with the most cameras recording everything ever. These willalso be great for court and evidence, unless more of the LAPD style of arrests keep happening. Radiation detecting watch Wednesday, November 15th, 2006I know what you’re all thinking. When the hell would I ever need this thing? Well, you never knowwhen the 3rd World War will start, unless you work for the CIA, or maybe you live near a nuclearreactor, or work for Hazmat, well that’s where you’ll need this thing, so there!!!! Sorry. Along with46
  47. 47. the regular watch functions this thing just comes with a radiation meter. It will set you back $250 sostart saving. Now it would be cool if it made that white noise sound you hear in the movies when theyare detecting radiation. Viewsonic Ruggedized Handheld Wednesday, November 15th, 2006Viewsonic the makers of all things monitor goodness have decided to come out with not one, butseven, ah ah ah, Ruggedized handhelds. You know? Count from Sesame…ah forgets it. Here are thedeets and there are a lot of them. The units run on older Windows Mobile 2003 so they can run allprograms created when the PDA boom took off and are powered by Intel XScale processors. Thedevices meet IP54 design standards for sealing against dust, moisture and extreme environmentalconditions. The features include 3.5-inch 240 x 320 (QVGA) LCD display, 416MHZ-520MHZ IntelXscale processor, Jog dial, SD card slot and swappable Lithium Ion batteries which allow batterychanges without shutdown or loss of data. They also come with 802.11b/g wireless, Bluetooth, barcode scanner, 1.3 megapixel camera (With most models), fingerprint sensor (with most models) andGPS (Global Positioning System) support with one model. This thing is loaded and it only weighs 12oz so it fits in the Christmas stocking very nice like.47
  48. 48. Fujufilm Face Recognizer Thursday, November 9th, 2006FujiFillm just released a new camera that has a facial recognizer in it. It will actually find up to 10faces in the picture focus on them as a whole and take the best picture possible. It includes 3x Opticalzoom, 6.3 megapixel, intelligent flash, and an image generator that will take pictures adjusted foruploading to places like My Space that have a lower image size. It also has a 2.5 inch scratch resistantLCD screen. It comes in a plethora of colors to boot. There is no pricing yet, but it will be availablein January in case you didn’t buy enough during Christmas.48
  49. 49. CONCLUSIONPlastics play an important role in the design of electronic products. It is crucial that engineersunderstand the characteristics of plastics in order to select the appropriate plastic for a givenapplication. Many factors affect this decision, including the required properties and the moldingprocess. Ultimately, selecting the right plastics can help ensure the safety and reliability of the finalproduct. 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 usingcopper or silicon.49
  52. 52. Thank you for your attention…•,,sid9_gci512140,00.html•••Materials Matter 2007, Volume 2, 3: Special Issue on Organic Electronicshttp://seminor.4u.blogspost.comhttp://www.acreo.schttp://www.discoverengineering.orghttp://www.plasticelectronics.orghttp://www.imce.behttp://www.escher.clis.ugent.be52