South African scientists are responsible for new technology that will soon allow food and medicines to be constantly monitored to ensure proper temperature control.

A printed temperature sensor developed by PST Sensors, a nanotechnology company started by two physicists in Cape Town is at the heart of a thin-film sensor label announced by Norwegian company Thin Film Electronics.

The labels will soon be mass produced, printed on to plastic film and stuck onto containers – from bottle to boxes – to take temperature readings, and perhaps spare the unnecessary dumping of perishable foods and medicines.

David Britton and Margit Härting started the Nanosciences Innovation Centre at the University of Cape Town 10 years ago. Before long, they were talking boldly of a not-too-distant future where self-powered, printed temperature sensors would be pasted onto bottles, vials and containers to keep tabs on perishable goods.

They spoke of the unwarranted waste of foods and medicines, how these precious cargoes were often stored or transported under poorly controlled conditions, and then had to be dumped wholesale when prescribed to do so by best-before dates for want of better measures.

In October, Thin Film Electronics announced its first successful demonstration of a “fully functional, stand-alone smart sensor label”. Resembling a conventional printed circuit board, the temperature-tracking label is designed with the monitoring of perishable goods in mind.

Stuck on to a box with, say, dairy products or medicines inside, the sensor system – about the size and shape of a credit card – takes a reading of the temperature of that box, giving retailers a more educated sense of shelf life and product safety.

Every component – from PST’s sensor, battery and memory to transistor logic – is printed. The working electronics is found in the electronic inks, harnessing materials that can conduct a variety of signals.

At the heart of the Smart Sensor Label is the sensor from PST Sensors, the nanotechnology company that Härting and Britton have spun out from UCT, which is headquartered in Cape Town.

The PST sensors are printed with environment-friendly and non-toxic water- or natural oil-based inks containing silicon nanoparticles that form the necessary electronic material. The nanoparticles are super-fine grains – each particle less than a hundred nanometres – of silicon.

“This shows what is possible with printed electronics technology,” says Britton. “It’s a major step and very important from a commercial point of view.”

Pictured are Dr David Britton and Dr Margit Härting of PST Sensors, here with sensor technologist Stanley Walton, at the printer with which they print their temperature sensors.