Millions of tons of food are thrown away each year because the 'best before' date has passed. But this date is always a cautious estimate, which means a lot of still-edible food is thrown away. Wouldn't it be handy if the packaging could 'test' whether the contents are still safe to eat? Researchers at Eindhoven University of Technology, Universitá di Catania, CEA-Liten and STMicroelectronics have invented a circuit that makes this possible: a plastic analog-digital converter. This development brings plastic sensor circuits costing less than one euro cent within reach. Beyond food, these ultra-low-cost plastic circuits have numerous potential uses, including, pharmaceuticals. The invention was presented last week at the ISSCC in San Francisco, the world's most important conference on solid-state circuits.
Consumers and businesses in developed countries throw away around 100 kilograms of food per person (*), mainly because the 'best before' date on the packaging has passed. That waste is bad for consumers' budgets and for the environment. Much of this wastage results from the difficulty in estimating how long food will stay usable. To minimize the risk of selling spoiled food to consumers, producers show a relatively short shelf life on their packaging.
Less than one cent
To fight food waste, producers could include an electronic sensor circuit in their packaging to monitor the acidity level of the food, for example. The sensor circuit could be read with a scanner or with your mobile phone to show the freshness of your steak, or whether your frozen food was defrosted. Researcher Eugenio Cantatore of Eindhoven University of Technology (TU/e): "In principle that's all already possible, using standard silicon ICs. The only problem is they're too expensive. They easily cost ten cents. And that cost is too much for a one euro bag of crisps. We're now developing electronic devices that are made from plastic rather than silicon. The advantage is you can easily include these plastic sensors in plastic packaging." The plastic semiconductor can even be printed on all kinds of flexible surfaces, which makes it cheaper to use. And it makes sensor circuits costing less than one eurocent achievable.
The very first printed ADC
The researchers have succeeded in making two different plastic ADCs (analog-to-digital converters). Each converts analog signals, such as the output value measured by a sensor, into digital form. One of these new devices is the very first printed ADC ever made. "This paves the way toward large area sensors on plastic films in a cost-effective way through printing manufacturing approaches", says Isabelle Chartier, Printed Electronics Business developer at CEA-Liten. The ISSCC rated the papers on these inventions as highlights of the conference.
The new plastic ADCs bring applications in the food and pharmaceuticals industries within reach. A sensor circuit consists of four components: the sensor, an amplifier, an ADC to digitize the signal and a radio transmitter that sends the signal to a base station. The plastic ADC has been the missing link; the other three components already exist. "Now that we have all of the pieces, we need the integration," says Cantatore. He expects that it will still take at least five years before we can expect to see the new devices on supermarket shelves. Other potential applications are in pharmaceuticals, man-machine interfaces and in ambient intelligence systems in buildings or in transport.
Making this development was no easy task. The electrical characteristics of 'ordinary transistors' are highly predictable, while those of plastic transistors vary greatly. "All plastic transistors behave differently in the low-cost production processes at low temperatures," explains Cantatore. "That makes it much more difficult to use them in devices. You need complex mathematical models to be able to predict their behavior accurately."
The printed ADC circuit offers a resolution of four bits, and has a speed of two hertz. The circuits printed by CEA-Liten include more than 100 n- and p-type transistors and a resistance level on transparent plastic substrates. The carrier mobility of the printed transistors are above the amorphous silicon widely used in the display industry.
(*) 'Global Food Losses and Food Waste', a study by the Food and Agriculture Organization of the United Nations (FAO), 2011
About Eindhoven University of Technology
Eindhoven University of Technology (TU/e) is a research-driven, design-oriented university of technology with a strong international focus. The university was founded in 1956, and has around 7,200 students and 3000 staff. TU/e has defined strategic areas focusing on the societal challenges in Energy, Health and Smart Mobility. The Brainport Eindhoven region is one of world's smartest; it won the international title Intelligent Community of the Year 2011. Further information on www.tue.nl
CEA-Liten (Laboratory of Innovation for New Energy Technology and Nanomaterials) is an internationally recognized technological research organization part of the CEA's Technological Research Division. Liten aims at developing and transferring technologies to industrial partners. Liten has a staff of 1000 people, an annual budget of 170M€ and an active portfolio of 840 patents. LITEN Printed Electronics activity focuses on large area printing processes development, covering a large range of materials and devices for System On Foil applications: passive devices (R,L,C), sensors (organic photodiodes, pressure, temperature...),organic transistors and logic circuits. CEA PICTIC is the French Printing technology platform dedicated to the ramp-up of printing processes, prototyping and small series production of printed electronics systems for applications in the field of sensors on foils, smart packaging, user interface to accelerate industrial transfer and minimize associated risks. CEA : Commissariat à l'énergie atomique et aux énergies alternatives.
About Universitá di Catania
The University of Catania (UNICT) is a partner of the EU project COSMIC through its "Dipartimento di Ingegneria Elettrica Elettronica e Informatica" (DIEEI). This department has 8 research groups whose activity covers several fields within the area of the information technology, i.e. electrical, electronics, systems, and computer engineering. The research groups are also involving in national and international collaborations with industries and public institutions. Presently, the research staff of the DIEEI includes 55 teaching members.
Within the DIEEI, the Microelectronic Group has a long-standing experience in the field of analog integrated circuits. The group is supported by STMicroelectronics of Catania, Italy, and can take advantage of design and measurement labs, which are well equipped with modern CAD tools and high-performance test instrumentations.
ST is a global leader in the semiconductor market serving customers across the spectrum of sense and power technologies and multimedia convergence applications. From energy management and savings to trust and data security, from healthcare and wellness to smart consumer devices, in the home, car and office, at work and at play, ST is found everywhere microelectronics make a positive and innovative contribution to people's life. By getting more from technology to get more from life, ST stands for life.augmented. In 2012, the Company's net revenues were $8.49 billion. Further information on ST can be found at www.st.com.
Note for editors (not for publication)
You can read a longer story about this invention on the website of TU/e magazine Cursor: http://www.
Attached is a photo which can be used provided that reference is made to the source: Eindhoven University of Technology/Bart van Overbeeke.
Photo caption: The plastic analog-to-digital converter (ADC). The ADC shown is still relatively large, in its final form it will be smaller.
For more information, please contact:
Eindhoven University of Technology:
dr.ir. Eugenio Cantatore
tel. 31-40-247-3388 (office)
You can also contact Science Information Officer ir. Ivo Jongsma
tel. 31-40-247-2110 (office)
Commissariat à l'Energie Atomique:
Vincent Coronini, Press Officer
Printed Electronics laboratory
Romain Coppard, Head of Printed Electronics laboratory
Universitá di Catania:
Michael Markowitz, Director Technical Media Relations