Monday, 19 October 2009

Organic Electronics Integration for RFID Sensor Networks

Organic transistors fabricated using various organic semiconductors
Working in the clean room environment
Probe station for measuring transistor characteristics

Introduction and Motivation

RFID, short for radio frequency identification is a big wonder in a little package. No larger than the size of most coins, RFID has seen exponential growth in the recent years due to its flexibility as an automatic identification system. An RFID system consists of a tag or transponder that exchanges information with the tag reader over the wireless medium, allowing rapid and secure data transfer. Endless applications today employ the power of RFID, from being embedded into passports, credit cards, public transportation tickets to the tracking of goods in the supply chain. Despite the demand and widening of RFID application base, the cost of RFID tags has not lowered down as much as many would like. At several cents per tag, RFID is considered to be expensive for large scale deployment, relative to traditional barcode systems; although one could argue that a typical RFID system has better features. RFID tags can be attached with sensors, have larger data capacity and can be scanned at much faster rates. RFID is undoubtedly a great technology, but RFID that costs less is even better!

Thankfully, scientists have begun exploring ways of lowering the cost of RFID tags, with efforts focused on investigating cheap large scale manufacturing technologies such as amorphous silicon technology and organic electronics. Organic electronics is particularly interesting as organic materials have been demonstrated to be compatible with printing technologies, allowing cost effective means of manufacturing electronics – think RFID tags that may potentially be “free” to print out. Generally, present day organic electronics have plenty of room for improvements in terms of material stability and device performance; but there have also been excellent strides in this field, as demonstrated by the recent introduction of active matrix organic light emitting diodes (AMOLED) displays that feature tremendous improvements in colour reproduction and viewing angles compared to conventional LCD displays.

The Research

This research explores the use of organic electronics to develop supporting electronics for a novel temperature sensor designed for use with passive RFID tags. The sensor is a low cost device intended for use with existing passive RFID tags. Tasks in this research include:

1. Designing a simple transistor based circuit to detect temperature profiles from our sensor.
2. Fabrication of the organic circuit using standard laboratory methods such as spin-coating, evaporation and photolithography. We aim to use the best possible organic electronic technologies that are available to us.
3. Examining the performance delivered by the circuit when used with our sensor.
4. Conclude the feasibility of organic electronics covering the challenges and limitations of state of the art organic transistors for sensory applications in RFID technology.

Work in Detail

Due to the relatively new nature of the organic electronics research, various fabrication technologies have been proposed for fabricating organic transistors with equally as many types of organic materials to use. As a starting point, work involved narrowing down suitable transistor technologies that can be used for organic logic circuits. This was done via fabricating several organic transistor types differing in structure (bottom gate, top gate), insulator materials (metal oxides, polymer and silicon oxide) as well as using various organic semiconductors (P3HT, PTAA, PBTTT etc). We then examine each transistor type to its own and decide upon the most suitable transistor technology that fulfils the requirements of our sensor circuitry. Current work involves optimizing of fabrication steps for fabricating interconnect-able organic transistors. Future works encompass the fabrication of various organic transistor devices such as inverters and ring oscillators as part of the final circuit design.

Ming Yu Shi, Syngenta Sensors University Innovation Centre, University of Manchester, UK

Prof Aimin Song, School of Electrical and Electronic Engineering, University of Manchester, UK

Would you like to become a research partner? Are there other aspects of this research that we should be bringing in?