A smart device could soon be even smarter with a new infrared light emitting diode (LED) that is “tuneable” to different wavelengths of light – meaning it could enable fridges to pinpoint when food is going off.

The technology has been developed by the University of Melbourne, the Lawrence Berkeley National Laboratory, the University of California, Berkeley, and the Australian Research Council Centre of Excellence for Transformative meta-Optical Systems (TMOS). 

Scientists have come up with a device that could identify a suite of gases, potentially including lethal ones, improving the safety of firefighters, miners and the military. The work appeared in the journal nclick="updateothersitehits('Articlepage','External','OtherSitelink','A bright idea? LEDs can detect when food goes off using wavelengths of light','A bright idea? LEDs can detect when food goes off using wavelengths of light','323656','https://www.nature.com/articles/s41586-021-03701-1', 'article','A bright idea? LEDs can detect when food goes off using wavelengths of light')">Nature.

New wavelengths
Infrared (IR) spectrometers are common laboratory equipment that can identify different materials by analyzing their infrared signatures invisible to the human eye. 

Just like an AM radio can be tuned to different radio waves, IR spectrometers can be tuned to different wavelengths, giving a broad-spectrum analysis of a gas sample. However, these machines are bulky and expensive and not practical to take out of the laboratory and into the field.

New LED technology has the potential to benefit firefighters, miners, the military, plumbers and households. (Credit: Berkeley Engineering)“Our new technology bonds a thin layer of black phosphorus crystals to a flexible, plastic-like substrate, allowing it to be bent in ways that cause the black phosphorus to emit light of different wavelengths, essentially creating a ‘tuneable’ infrared LED that allows for the detection of multiple materials,” Kenneth Crozier, Professor at the University of Melbourne says. 

“This technology could fit inside smartphones and become part of everyday use.”

For example, the bacteria found in meat release various gases as they multiply. These gases are a good indication that the meat is spoiling and is no longer fit for consumption.

“The device placed inside a fridge could send a notification that meat is going off. When pointed at a handbag, it could reveal whether the bag is made of real leather or a cheaper substitute,” notes Professor Crozier, who is also the Deputy Director of TMOS.

Light-emitting devices
Current materials used for IR photodetectors and light emitting devices can be challenging to manufacture, in large part due to the need for multiple layers of ideally linked crystals. 

This new black phosphorus technology requires just one layer allowing the device to be flexible, giving it unique properties when bent.

“The shift in black phosphorus’ emission wavelength with bending is quite dramatic, enabling the LED to be tuned across the mid-infrared,” adds Dr. Ali Javey, from the University of California at Berkeley, whose group led the work.

Notably, the device could make the work of firefighters, miners and the military safer, allowing them to identify potentially lethal gases from safe distances as the ultra-thin, ultra-light devices can be placed on small drones. 

The low-cost technology could also make its way into devices for use by plumbers and building managers.

“Our IR photodetectors could be integrated into a camera so that we could look at our phone screen and ‘see’ gas leaks or emissions and be able to determine what kind of gas it is,” Dr. Crozier concludes.

Last November, FoodIngredientsFirst reported that the freshness of meat could be assessed in real-time with an artificial olfactory system that mimics the mammalian nose. The technology could help reduce food waste by confirming whether meat fits consumption faster and more accurately than the best before date, suggests research from Nanyang Technological University, Singapore (NTU Singapore).