Packaging that measures food freshness closer to reality with plastic electronics

A new low-cost plastic sensor circuit has been developed that could be used in food packaging to detect spoilage. This new technology, presented last week at a solid-state circuit conference in San Fransisco, is a plastic analog to digital converter (ADC) circuit that converts analog signals – such as the measuring output of a sensor – into digital information. This technology can be printed on plastic films, making it ideal for use in packaging to monitor food freshness.

In developed countries, an estimated 100 kilos of food per person is thrown away every year, according to a study by the Food and Agriculture Organization of the United Nations in 2011. Part of this is due overly-cautious sell-by dates, causing the disposal of perfectly safe out-of-date food . Packaging that monitors factors such as the acidity of food could eliminate the need for this. ADC circuits allow the conversion of sensor data into information that can be read by a scanner or smart phone, meaning users could, for example, scan their package of chicken breasts to see whether they were safe to eat.

The circuit technology was already available to do this; the problem was cost, says one of the researchers working on the technology, Eugenio Cantatore. “All you need is a sensor and some basic electronics to read out the sensor. Standard silicon chips would be fine for that, except they’re too expensive.” These new plastic circuits would cost less than one euro cent per unit, making them feasible for use in food packaging.

Despite their promising uses, plastic ADC circuits are unlikely to replace silicon in many cases. Plastic electronics are much slower silicon based methods – with signal speeds slower by a factor of one thousand. This is a problem for technologies like smart phones, but not for everything. Plastic ADCs have a wide range of applications beyond monitoring food spoilage, including pharmaceuticals and plastic solar cells.