The radio frequency identification (RFID) market is huge, already over £2 billion. Within this market passive RFID is expected to be the prime candidate for printing but so far the main thrust has been the printing of the antennae. Often silver inks are used but the price fluctuations of silver (currently very high) cause many companies to look for alternatives such as copper, aluminium and organic conductive polymers. The expensive part of an RFID tag is the chip and there are not many companies who have tried printing the chips. Kovio Inc. was the first using nanosilicon on a variety of substrates.
The real advantage of printed RFID is the potential to produce tags and labels cheaply, perhaps even being able to print them directly as is done with barcodes today. Applications like library tags, that currently use high cost silicon memory chips, tend to use HF rather than UHF and I believe this is where the potential for printed RFID is to be found.
Kovio Inc. were recently granted a third patent in a series which all relate to methods for making devices such as RFID tags at lower cost. The key phrase from their abstract is:
The present invention advantageously provides semiconducting thin film structures having qualities suitable for use in electronics applications, such as display devices or RFID tags, while enabling high-throughput printing processes that form such thin films in seconds or minutes, rather than hours or days as with conventional photolithographic processes.
Their recent series of patents are summarized in the table below:
The most recent patent can be viewed here and has 67 method claims, the earlier patents relate to the materials and the thin film structure. The 7553545 patent is also interesting in that it details the linewidths and gaps that can be printed.