Imagine an electronic display that is as thin as a piece of paper and can be rolled up or even folded up and put into a pocket. Long a dream of doctors, pilots, soldiers on the battlefield and many others, the technology to build such a device is becoming a reality.
Although today's integrated circuits and electronic devices are small enough to produce Dick Tracy-like devices that navigate, communicate, and do everything but drive your car for you, new printed integrated circuit technologies promise even smaller and flatter devices in the future. Flat integrated circuits printed on flexible substrates will soon make it possible to create a wide variety of applications in addition to flexible displays, such as or truly wearable computers that blend in with clothing or pouches. Other applications include RFID tags that conform to product shape, large area electronics used in large sensors and medical applications. Printed integrated circuits can even be transparent, opening up many other possibilities as well, particularly in the health industry.
Many electronic components, such as resistors and capacitors, are fabricated by industrial printers today that are based on traditional printing processes, but the techniques currently in use are difficult to extend directly to complex integrated circuits. The biggest challenges still facing printed integrated circuit technology are the lack of suitable inks and printers that can achieve the resolution and quality required by integrated circuits. Higher printing speeds are also needed to enable mass-produced industrial applications.
Recent developments in both unipolar and ambipolar polymeric semiconductors show promise for overcoming these difficulties. Although their unipolar cousins currently have the lead in technology, ambipolar polymer semiconductors can achieve both n-type (electron) and p-type (hole) transporting operations in a single layer. Both types of polymeric semiconductors can now be used to create a stable and noise-resistant "CMOS-like" logic that is suitable for building complete circuits on flexible substrates.
Another technology being examined uses single-walled carbon nanotubes (SWCNT) material processes to print circuits directly onto flexible plastic substrates. SWNCT materials are used for n- and p-channels, metallic contacts and interconnects that are then combined with polymeric gate dielectrics to build the thin-film transistors that make up the printed integrated circuit. In addition to providing the printed integrated circuit, the printed SWNCT technology is also expected to compete with other SWCNT efforts that simply emphasize nanometer-scale devices for further miniaturization.
Once the technology for producing printed integrated circuits is well-developed, additional engineering work will still be needed to further reduce the scale of the printed integrated circuits and to develop the printing equipment suitable for large-scale manufacturing applications. However, the recent breakthroughs in technology hold out the promise that truly flat, flexible and even invisible devices and computers may become a reality before the decade is over.
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