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PRINTED ELECTRONICS: INK ON THE BRINK

Printed electronics may be the next big thing in our technological future and promises extremely lowcost, fl exible, and disposable circuitry that you can manufacture with custom ink-jet printers or highspeed presses. Leadingedge companies are using specialized ink technology to transform basic circuit elements—such as thinfi lm transistors, resistors, inductors, and capacitors— into printed batteries, displays, sensors, RFID tags, interactive packaging, solar panels, and even speakers. Although the printed-electronics concept has been around for years, recent advances in conductive-ink chemistry and fl exible substrates promise to deliver a fl ood of new markets and application areas.

Unlike traditional silicon- based circuitry, you manufacture printed electronics using an additive process that deposits multiple layers of conductive, semiconductive, and dielectric materials onto a fl exible medium, such as plastic fi lm, foil, or paper. Most current printing processes— such as ink jet, roll-to-roll offset, fl exography, rotogravure, or screen printing—can place individual layers. With a relatively small investment in capital equipment for manufacturing and the ease of producing millions of copies on demand, printed electronics will target high-volume, simple-function consumer applications that were previously impractical for silicon-based circuitry.

Manufacturers also employ printed electronics in the creation of OLED (organic-light-emittingdiode) displays. These displays rely on organic compounds that a multilayerprinting process deposits in rows and columns onto a fl at carrier. Unlike the traditional liquid-crystal type, OLED displays require no backlight, have a faster response, and consume less power. You can print organic materials onto many substrates, including fl exible or even fabric materials, creating roll-up or wearable displays. A possible drawback of OLED displays is the reduced lifetime of certain colours of organic materials. At this year’s Consumer Electronics Show (www.cesweb.org), Sony (www.sony.com) demonstrated a prototype high-defi nition television with a 27-in. OLED display and a contrast ratio of greater than 1 million-toone.

Electronic paper is another display variation that benefi ts from printed electronics. The migration of coloured microparticles, which an active-matrix backplane of printed transistors and conductors charges, forms images on electronic paper. Also known as an electrophoretic display, electronic paper refl ects light like ordinary paper and is bistable, thus indefi nitely storing text and images without power. Plastic Logic (www.plasticlogic. com) recently opened a factory in Dresden, Germany, to make fl exible displays based on the electrophoretic fi lms from E Ink (www.eink. com). The facility will produce fl exible activematrix- display modules for “take-anywhere, read-anywhere” electronic- reader products (Figure A).

Information

Read the compete version of this article at www.edn.com/article/ CA6466207.html.