Smartphone Tech Could Find Material Defects

FRIDAY, APRIL 28, 2023

Recent research from the University of New South Wales has reportedly demonstrated that organic light-emitting diodes (OLEDs) can be harnessed to map magnetic fields.

“Our findings show that OLEDs, a commercially available technology, can be used not only for displays and lighting, but also for quantum sensing and magnetic field imaging by integrating a small piece of microwave electronics,” said author Dr. Rugang Geng

“If this technology is properly developed, people could simply use their smartphones to map the magnetic fields around them, for example to spot defects in diamonds or jewelry. This also has applications in industry, such as finding defects in construction materials or as a biomedical sensor.”

The research, led by Geng and Professor Dane McCamey from the UNSW School of Physics, was published in the journal Nature Communications.

About the Technology

OLEDs are a semiconductor material commonly found in screens for flat-screen televisions, smartphones and other digital displays.

“The basic working principle of an OLED device is that when a voltage is applied, electrons and holes are injected into different layers of the device,” said Geng. “When the electrons and holes meet in the central layer, they form ‘excitons,’ which emit visible light when they decay, and that’s what makes OLEDs useful as displays and lighting sources.”  

According to UNSW’s release, this light emission process exploits the charge characteristics of electrons, which have a negative charge, and holes, which have a positive charge.

They both also have another intrinsic property called spin, which either points up or down and is very sensitive to external magnetic fields. It can also switch directions, or “flip-flop,” under magnetic conditions.

“By measuring the signal change, both in electric current and emission light, induced by such a flip-flop, we are able to detect the strength of any magnetic field the device is exposed to,” said Geng. 

The research team reportedly integrated an OLED with a microwave resonator, generating a tiny oscillating magnetic field across the OLED device. This reportedly allowed individual pixels of the OLED screen to act as a small magnetic field sensor.

“We weren’t surprised at the result—we have been pursuing this for a few years,” said McCamey. “But we were surprised at the resolution of the images we could make—we can see details on sub-micron length scales, similar to the size of a bacteria or neuron.”

The university reports that this research represents the next step in the development of magnetic field imaging equipment. Existing quantum sensing and magnetic field imaging equipment tends to be large and expensive, requiring either additional power from a high-powered laser, or extremely low temperatures.

However, the latest technique can conversely function at a microchip scale and doesn’t require input from a laser, showing great potential for applications in scientific research, industry and medicine. 

“Next, we hope to improve the overall performance of the device including optimizing the device architecture and exploring other techniques that can significantly increase the field sensitivity,” said Geng.  

“We are also exploring collaborations with OLED technology companies as their experience at moving devices from the lab to commercial products will help accelerate translation of this technology.”  


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