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

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.

The outcomes of this project will have a direct impact on the economy, society, academic community (through dissemination by conference presentations and peer-reviewed publications) and researchers involved in the project by providing a training opportunity.

Every year, in the UK alone, 4.2m tonnes of food is thrown away which is otherwise safe to consume. A smart indicator, such as the sensor proposed in this project, would prevent untimely disposal of foods which would in turn reduce waste produced by the consumers and industry. Food waste costs over 12.5bn GBP to the UK economy and even a modest 10% recovery would spare enough funds to create new programmes to tackle this important national and international problem. Reduced waste would also increase availability of food to the public at a lower price since the retailers and producers can make further savings through the reduction of waste. Monitoring and detecting spoilage will also have a significant impact on public health through the prevention of foodborne illnesses. In the UK, every year there are 1 million cases of food poisoning, of which 20,000 are serious cases, requiring hospitalization; the high rate of hospitalizations, unfortunately, results in 500 deaths per year and 1.5bn GBP in medical expenses. Spoilage monitoring using sensors has the potential to reduce the number of hospitalizations due to foodborne diseases, tremendously. If the consumer can be warned through the use of sensors that a food item is no longer edible (thus spoiled), food poisoning can be largely avoided. The sensor technology proposed will fill a large technological gap in smart packaging, therefore, it has a strong potential for commercialization, creation of new jobs and opportunities.

Academic researchers working in the areas of gas sensors and microsystems technologies, food science, packaging technologies and analytical chemistry will benefit from the outcomes of the programme proposed. This new gas sensing technology also has the potential for use in other areas of research such as medical diagnostics, environmental monitoring etc. Scientists working in these fields may produce new adaptations of this technology to solve various problems involving sensing of volatile compounds. In order to ensure that the academic community has access to the knowledge and methods generated within this project, the result of this work will be published in peer-reviewed journals and presented at scientific meetings.

The programme proposed is also highly interdisciplinary and presents a unique training opportunity for the researchers involved in the project. The participants will work closely and acquire new skills in the fields of analytical chemistry, sensor engineering, food science in addition to developing new skills in project management.