Paper-based "Zero-Cost" Printed Electroionic Gas Sensors

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The UK throws away 4.2 million tonnes of food each year (worth 12.5 billion GBP) which is otherwise safe to consume. Currently, there is no method to effectively determine whether or not packaged food items, especially fresh foods, are safe to consume other than the estimated "use-by" date on the packaging. Most foods, however, are good for consumption for an extended period past their use-by date. Given the fact that the UK sources 50% of its food from abroad, reducing food waste and managing resources more efficiently are important steps in reducing reliance to increasing imports. Furthermore, despite the use of conservative use-by dates, there are still 1 million cases of food poisoning (20,000 hospitalizations, 500 deaths, 1.5 billion GBP) every year in the UK alone due to spoiled foods. Low-cost technologies for monitoring spoilage can play an important role in reducing the amount of waste and preventing foodborne illnesses at the same time. In this 12-month project, an entirely new class of ultra-low-cost printed electrical gas sensors based on cellulose paper will be developed. This new versatile sensor technology, which exploits the intrinsic properties of paper, works at room temperature, is low power (in the order of micro watts), disposable, lightweight and compatible with current high-volume printing technologies. Our laboratory prototypes fabricated for producing the preliminary data for this grant application costed 0.005 GBP per sensor but the cost can be potentially driven down below ~0.0001 GBP through high-volume manufacturing, rendering the technology proposed, near "zero-cost". At this price point, these sensors can be placed in every food package, allowing monitoring of spoilage of foods. This would in turn prevent untimely disposal of food products while informing the consumer of spoiled items.In contrast to existing methods of detecting gases electrically using electronic materials (such as metal-oxide semiconductors - i.e. MOS - or organic semiconductors), this new technology exploits the effect of gases on the concentration of ions in the surface bound layer of water (adsorbed from the moisture in air) present on cellulose fibres, hence the term electroionic gas sensing. Unlike other technologies for sensing of gases, the technology proposed is particularly suitable for operation in environments with high relative humidity, which are known to reduce the sensing performance or lifetime of existing technologies (e.g., MOS). Our initial results show that this new sensor technology is capable of sensing NH3 (an important by-product of decomposition of protein rich foods such as meat) at concentrations below 4 ppm (the limit of detection to be determined in this project) - well within the relevant range for monitoring spoilage. Our pilot results for monitoring spoilage of raw meats also suggest that this technology is feasible.The final deliverable of this project is an elegant yet simple, fully characterized disposable Paper-based Printed Electroionic Gas Sensor (PES) capable of detecting food spoilage, focusing primarily on raw meats. In the future, our vision is to extent this technology to interface with RFID tags for wireless spoilage monitoring in homes, shops and food processing facilities.