Henning Rost and Wolfgang Mildner

On the Way toPrinted ElectronicsLatest Advances

6/2008Organ deutscher Kunststoff-Fachverbände www.kunststoffe.de 98. Jahrgang

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PolyIC GmbH & Co. KG Tucherstr. 2 D - 90763 FuerthGermanyPhone: +49 911 202 49 0 Fax: +49 911 202 49 8001 Email: info@polyic.comWebsite: www.polyic.com

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RF ID■

© Carl Hanser Verlag, Munich Kunststoffe international 6/2008

HENNING ROSTWOLFGANG MILDNER

Conventional RFID technology (Ra-dio Frequency Identification) basedon silicon electronics became estab-

lished several years ago, as we all know.But its application in the supply chain ofconsumer articles has caused agroundswell of interest in it. Even moreareas of application can be optimized byutilizing RFID technology, such as au-tomation, brand protection and identifi-cation. In everyday life, consumers are al-ready coming in contact with many RFIDapplications – from non-contacting skipasses, to company ID’s with access con-trol, to the timing of sports events.

Printed electronics can expand RFID’sareas of application into price-sensitivemass markets, such as consumer goodspackaging, electronic brand protection,simple identification, electronic ticketingand many others. PolyIC GmbH & Co.KG of Fürth, Germany, has set as its goal

an Electronic Product Code (EPC), anRFID label capable of replacing the opti-cal barcodes on goods in supermarkets.PolyIC has become a member of EPC-global – a global organization dedicatedto standardizing RFID.

It won’t be long until the vision of antransponder label on your yogurt cup hasbeen realized. Of course, the aim here isnot to displace conventional silicon elec-tronics, but instead to move into newmarkets where low prices and high vol-ume are more important than top tech-nological requirements. So printed andconventional electronics will coexist in

the foreseeable future – but in differentmarkets.

Meanwhile, the market for printedelectronics has opened.As announced lastyear [1],PolyIC was able to present its firstproducts at the ”Organic Electronics Con-ference“ (OEC) 2007 in Frankfurt, Ger-many.The company presented the world’sfirst roll-to-roll printed 13.56 MHz RFIDtag. Moreover, they introduced two newproduct lines: one in the area of printedRFID tags, brand-named PolyID, and asecond one in the area of Smart Objects,brand-named PolyLogo.These first print-ed products are aimed at entirely differ-

On the Way to Printed Electronics

Latest Advances. Printed electronic parts are based on semiconducting and elec-

troconductive plastics and can be mass produced quickly on printing machines.

The resulting cost and price structures will create entirely new markets. Cheap

transponder labels, so-called RFID tags, are a leading candidate for applying this

technology.

Besides logic cir-cuits, a PolyLogocontains other elec-tronic componentssuch as displays,sensors and batter-ies (all sources and

photos: PolyIC)

Electrodesconductive Polymers,metals, nano materials

Dielectricsinsulating polymer

Semiconductorconjugated polymer

Substratethin polyester film

G

S D

Fig. 1. Structure ofa Polymer FieldEffect Transistor(PFET)

© KunststoffeTranslated from Kunststoffe 6/2008, pp. 108–113

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ent market segments from conventionalRFID tags. Right now, PolyIC is doingtests with various pilot customers on di-verse potential areas of application. Thefirst products in their PolyID line providepresence detection with up to 4 bits mem-ory and even a display function in thePolyLogo version [2]. The first applica-tions envisioned for PolyIC products liein the areas of brand protection, coupons,marketing and logistics.

All 400 passes to the above-men-tioned OEC conference were equippedwith a PolyID tag as part of PRISMA,i. e., the Printed Smart Labels projectsubsidized by the German Federal Min-istry of Education and Research (Bun-desministerium für Bildung und For-schung), in which PolyIC acts as theconsortium leader. The passes were readand evaluated by a radiowave frequen-cy reader at 13.56 MHz while holdersentered the conference hall. Thisamounted to a field test for printed elec-

tronics by using it to control access aswell as to count attendance.

RFID Tag Structure

Constant advances during product devel-opment can also be observed on the labresults at PolyIC. Whereas, in the begin-ning, simple transistors were developed,soon complex components were realized,such as inverters and rapid ring oscilla-tors [3].

How does such a transistor, i.e. the ba-sic element of the printed electronics de-scribed here, look? A Polymer Field EffectTransistor (PFET) is built up essentiallyfrom four components (Fig. 1) which, ex-cept for the substrate, are printed in theform of electronic ink.

Electrodes made from a conductivematerial (source and drain) lie atop a flex-ible substrate carrier which is covered bysemi-conducting polymer and by a layerof insulating polymer. Completing thestructure is a so-called gate electrodewhich is also printed on in the form of aconductive material. It is essential that theentire structure be produced by modern

printing processes to a total thickness ofjust a few micrometers.

Polyethylenterephthalate (PET) is thesubstrate material of choice for printedRFID tags. In addition to its electricalproperties, it also has the mechanicalproperties profile required by high-speedroll-to-roll processes. Intrinsically con-ductive polymers, such as polyanilin [4]or the PEDOT/PSS system [5] are suit-able materials for electrodes. Conductivenanoparticles or metals are also de-scribed in the literature [6]. The most im-portant layer, electrically speaking, i. e.the semiconductor, often consists of con-jugated polymers. These plastics are char-acterized by strongly alternating se-quences of single and double bonds, so

that they possess semiconductive prop-erties [1].

A well-designed circuit layout – a printimage, so to speak – thus makes it possi-ble to combine many hundreds of tran-sistors in such a way that an RFID chipcomes out at the end of the printingprocess.

In order to understand the difficultpath from a simple transistor to a chipand to the finished transponder, let ustake another look at the individual ele-ments of an RFID tag (Fig. 2). The print-ed transponders illustrated need no en-ergy supply. They get their energy fromthe radio frequency field of the transmit-ter/reader (HF at 13.56 MHz). Fig. 2shows how an LC oscillator, usually con-sisting of an antenna and a capacitor, isarranged in the tag to absorb energy. TheAC current induced there has to be recti-fied by a capacitor-diode combination.The resulting DC voltage energizes thechip which is made up of several hundredprinted transistors. Depending on thememory, the transponder system absorbsenergy at defined time intervals from theelectromagnetic field emitted by the

Transmitter/Reader

Standardelectronics

RFID TagInductive coupling

DistancePrinted

electronics

Energy

Information

Antenna

Resonancecapacitor Rectifier

Transponder chipTransponder chip

· clock· clock· modulator· modulator· multiplexer· multiplexer· memory· memory

Fig. 2. Basic components of a transponder label (RFID tag)

© Kunststoffe

PolyIC GmbH & Co. KG was founded inNovember 2003 as a joint venture betweenLeonhard Kurz GmbH & Co. KG (51%, coat-ings and hot embossing technology) andSiemens AG (49%, electronics) to developand manufacture printed polymer electron-ics. PolyIC is located in Fürth, Germany, onthe grounds of the Leonhard Kurz Stiftung &Co. KG. The company is a leader in the de-velopment of polymer electronic compo-nents and supplies products and compo-nents with printed electronics. PolyIC willsupply low-cost electronics products formass markets based on organic and/orprintable semiconductors.

Company Profile!

Cathodeconductive pasteor metal

Electrodesconductive material

Insulatorinsulating polymer

Semiconductorconjugated polymer

Diode Capacitor

UoutUinGND

OUT

IN DC

Fig. 3. Structure of a printed polymer rectifier

© Kunststoffe

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transmitter at 13.56 MHz, whereby theinformation stored on the chip is ulti-mately transmitted.

However, to manufacture printedRFID tags, not only the transistors, butother electrical components as well, suchas capacitors and diodes, have to be pro-duced by printing technology in highquality. The diodes used to be regarded asan especially critical component until afew years ago. It was assumed that the ma-terials properties of the then available or-ganic semiconductors (e. g., in the formof conjugated polymers) made them un-suitable for rectifying high-frequencyalternating fields. PolyIC was able todemonstrate, however, that regioregular

poly(3-hexylthiophene) [cf. 1] functionssurprisingly well as diode material for rec-tifying alternating current at a frequencyof 13.56 MHz [7].

In Fig. 3 one can see by analogy withthe polymer field effect transistor [cf. 3]that integrated polymer rectifiers – con-sisting of diodes and capacitors – also havea relatively simple layer structure. This isanother reason why such components canbe manufactured by additive printing onflexible polymer films. Fig. 4 shows boththe input voltage at 13.56 MHz (bluecurve) and the DC voltage generated inthe printed component which is requiredfor chip operation (red line).

In Focus: Increasing RFIDMemory Complexity

For printed RFID systems, too, the aim is,of course, to transmit as much informa-tion as possible, even though a few databits are quite sufficient for the simplestapplications. It should be noted that theinformation is 2BIT. In an 8-bit system,that means that 28, i. e., 256 different sig-nals can be transmitted in the form of se-rial numbers.

In 2006, PolyIC introduced an 8-bitpolymer transponder produced undercleanroom conditions that can be read at13.56 MHz [8]. Apart from the antennaand electrodes, all other components aremade from plastics. Within approx. one-tenth of a second, the entire informationcan be read at a maximum reading dis-tance of 7.5 cm via inductive coupling.This RFID tag in fact has 16 bits, namely8 protocol und 8 data bits from 00000000to 10111011. In the lower part of Fig. 5,the eight data bits can be seen and, in theupper part, the information registered bythe reader.

Meanwhile, the company has intro-duced a laboratory sample of a 32 bitRFID tag and, in 2007, the world’s firstinductively coupled 64 bit polymertransponder [9]. This demonstrated theprinciple feasibility of highly complexRFID tags based on commercially avail-able plastics.

Parameters for Evaluating aPrinted RFID System

The current greatest challenge consists intransferring the results obtained in clean-room technology to a high volume, high-speed roll-to-roll printing process. Firstof all, the key parameters have to be iden-tified that apply to a printing process suit-able for printed electronics. Nowadaysthis is often oversimplified in the litera-ture and pinned onto a few individual pa-rameters, such as the charge carrier mo-bility of the organic semiconductor or theshape of transistor characteristics. How-ever, it could be demonstrated that print-ed electronics represents a highly com-plex system of many individual parame-ters that all have to be identified, thenmeasured and handled. It should be clearthat a change in a single parameter, suchas raising layer thickness, often has astrong effect on the entire system.

When evaluating the entire system,special attention should be paid to the fol-lowing four points:

Materials/Chemistry:■ high charge carrier mobility of the

semiconductor,■ suitable electrode work function,■ regioregularity of the semiconductor

[cf. 1],■ suitable solvents,■ chemical resistance of materials uti-

lized,■ environmental compatibility of the

manufacturing process.Circuitry design:■ new circuit concepts,

UoutRLUin C

DUout

Uin

Time

15

V

5

0

-5

-10

-15200150 ns100500

Volta

ge

Generation of DC Voltage

Fig. 4. Rectification of a 13.56 MHz signal by printed electronics

© Kunststoffe

16 bit: 8 protocol & 8 data bits

Time

1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 00 0 0 0 0 0 0 0

-0.2

0

0.2

V

0

Read

er s

igna

l

50 100 150 ms 200

Readout of Information

Fig. 5. Transmissionof 8 data bits byprinted electronics

© Kunststoffe

PolyIC GmbH & Co. KGTucherstr. 2D-90763 FürthGermanyTel. +49/09 11/2 02 49-0Fax +49/09 11/2 02 49-8001www. polyic.com

Useri

5 © Carl Hanser Verlag, Munich Kunststoffe international 6/2008

■ layout design,■ circuit simulation, since concepts fa-

miliar to silicon electronics cannotsimply be taken over.

Device physics:■ adaptation of transistor channel

lengths and widths to currently avail-able printing techniques,

■ investigation of interfaces,■ parasitic capacitances to be avoided,■ service life of the overall component.Geometry:■ layer thickness,■ lateral dimensions.PolyIC has meanwhile identified the keyparameters for its first product genera-tion. This has led to a combined and con-tinuous roll-to-roll printing process withspeeds of approx. 20 m/min. Moreover,they are concentrating their efforts on aninline quality assurance with optical andelectrical measures for analysis, since thetags are manufactured in large lots and,of course, have to be monitored as to theirfunctionality.

New Product Lines

One of printed electronics’ great advan-tages is its capability for integration ingoods and packaging. For example, thethin and flexible product can be attachedto flexible packaging materials by lami-nating, labeling or direct application.Thisapplies at first to labels with printed elec-tronics (e.g. RFID tags or displayelements). Later on, it will be possible tointegrate the printed electronics directlyin the packaging and thus created “intel-ligent products”, i.e. products capable ofcommunicating directly with their corre-sponding readers. This will make it pos-sible to realize visions of the “internet ofobjects”, for example, in the form of in-telligent refrigerators and washing ma-chines, intelligent shopping carts insupermarkets or even for improving

automation in many manufacturingprocesses.

The products in the above mentionedPolyID line enable electronic identifica-tion of tagged products via radio frequen-cy signals. These PolyID tags are availablein inlay form or as stickers on a roll in sizesand layouts specified by the customer. Po-tential first applications (Fig. 6) dependon memory depth, e.g. non-contactingidentification, attendance checking andbrand protection.

Nowadays, glossy brochures with col-orful pictures are no longer enough toarouse the attention of potential cus-tomers. But when light effects and otheractive functions arouse curiosity or evenplay instinct, the customer is practicallyconvinced. That is why, in addition to log-ic circuits, PolyLogo products containelectronic components such as displays,sensors and batteries (Title photo).A firstPolyLogo product has been created witha simple or, if desired, segmented displaythat can be activated by a radio frequen-cy signal at 13.56 MHz (HF range). Suchdisplays carry a pre-defined symbol andcan also be integrated in the label (Fig. 7).

In an inactive state, the symbol is in-visible. It only appears when the label iswithin the range of a matching radio fre-quency transmitter. Then it is technical-ly possible to have information visible inthe display disappear after a short time,or to have the information be irreversibly“branded in” and always be visible. Withthe aid of this optical indicator, it couldalso be possible, for example, to seewhether a tag has already been read. Suchproducts will fulfill the customer’s strongwish to link identification to a visible, op-tical change.

Conclusions

The realization of a first printed RFID tagshows that the platform technology of

printed electronics enables active andintelligent products at a price that cannotbe beaten. Johannes Gutenberg, morethan 500 years ago after his pioneeringinvention of the printing press, wouldnever have dared to dream that a newprint-revolution is about to conquer theworld and enhance the life of the con-sumer. ■

REFERENCES1 Rost, H.: Off the Reel. Kunststoffe international 5

(2007), pp. 60–63, PE1038812 Press release, PolyIC GmbH & Co. KG, Fürth, Sep-

tember 2007 (Information number: PolyIC 200709-001de)

3 Rost, H.: From Polymer Transistor to Printed Elec-tronic. Kunststoffe international 10 (2005),PE103333

4 Rost, H., et al.: All-polymer Organic Fieldeffect-Transistors. Proceedings of the Materials Week2001, published on CD, ISBN 3-88355-302-6(2002)

5 Rost, H., et al.: Air-stable all-polymer field-effecttransistors with organic electrodes. Synth. Met.145 (1) (2004) pp. 83–85

6 Fix, W., et al.: Fast polymer integrated circuits.Appl. Phys. Lett. 81 (9) (2002) pp. 1735–1737

7 Zipperer, D., et al.: Polymer-based Rectifiers andIntegrated Circuits for Printable RFID Tags. Paper,MRS Spring Meeting (2005), San Francisco, CA,USA

8 Clemens, W.: Printed RFID for high-volume appli-cations. Paper, RFID Smart Labels 2006, Boston,MA, USA

9 Ullmann, A., et al.: Polymer Multi-Bit RFIDTransponder. Paper, International Conference forOrganic Electronics 2007, Eindhoven, Netherlands

THE AUTHORSDR. HENNING ROST, born 1966, is Project Manag-

er for Material Matters at PolyIC GmbH & Co. KG,Fürth, Germany; henning.rost@polyic.com

WOLFGANG MILDNER, born 1959, is CEO at Poly-IC GmbH & Co. KG, Fürth, Germany.

Fig. 6. Authenticity verification of medicines by RFID labels integrated inthe packaging

Fig. 7. Smart label with RF-activated display

RF ID■

Smart Objects

PolyLogo® Smart Objects include, in addition to printed electronics,

small displays to indicate symbols and information. PolyLogo® Smart

Objects are used in brand protection, authenticity control, packaging

and labeling, and many other fields.

You can find more information at: www.polyic.com/polylogo

PolyID® printed RFID tags employ radio technology to exchange

information with a reader, e.g. a product code. PolyID® printed RFID

tags are used, for example, in presence control, anti-theft protection,

sorting applications, logistics and many other fields.

You can find more information at: www.polyic.com/polyid

printed RFID tags

Would you like to learn more about PolyID® and PolyLogo®? We regularly present the latest trends and

developments in printed electronics and at PolyIC on our website: www.polyic.com

PolyIC GmbH & Co. KG | Tucherstrasse 2 | D-90763 Fürth | Germany

Printed Electronics everywhereThe revolution in printed electronics!