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Major retailers are insisting that suppliers soon start using RFID tags, to replace tags with bar codes. But RFID tags that rely on silicon chips are too expensive to be practical, so going to printable organic materials is crucial. Getting there, however, depends on developing readily printable organics that operate in the needed frequency ranges. In a promising first step, researchers in Belgium have developed a type of organic diode that can rectify ac at 50 megahertz--in the range allowed by international conventions for RFID applications.

An RFID tag is in fact a tiny transponder that reacts to an RF signal from a reader by transmitting data stored in its memory. Typically, such a tag contains logic circuitry, a memory, a transmitter, and a power source. Organic semiconductor circuits are sluggish compared with silicon, because the mobility of charge carriers is low. This isn't a problem for the logic circuitry and memory, because the amount of data to be processed is very small (several hundred bytes of memory suffice for the smaller RFIDs). But it is a problem in the diodes that rectify the high-frequency current obtained from the reader in order to power the RFID's circuitry and transmitter.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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