Exploit photonics for home disease detection

In the not-too-distant future, people may have a simple device to monitor and report health indicators, even identify traces of undesirable biomarkers in blood or saliva, and to serve as an early warning system for diseases. This is one of the promises of personalized medicine.

Such a technological revolution could be a little closer thanks to a powerful tool developed by researchers at EPFL's BioNanoPhotonic Systems (BIOS) laboratory. It consists of a miniaturized ultra-thin optical chip coupled to a standard CMOS camera and powered by image analysis, which counts the biomolecules individually in a sample and determines their location. Their research was published in Photonic Nature.

A very powerful sensor

This technology is based on metasurfaces, a recent development in the field of photonics. Metasurfaces are sheets of artificial materials covered with millions of nano-sized elements arranged in a particular way. At a certain frequency, these elements are able to compress light in extremely small volumes, creating ultra-sensitive optical hot spots.

When the light illuminates the metasurface and hits a molecule at one of these hot spots, the molecule is immediately detected. In fact, the molecule abandons itself by changing the wavelength of the light that strikes it.

Scan molecules and take their picture

By shining colored lights of different colors on the metasurface and taking a picture each time with a CMOS camera, researchers are able to count the number of molecules in a sample and learn exactly what is happening on the sensor chip. "We then use intelligent data science tools to analyze the millions of CMOS pixels obtained through this process and identify trends," says Filiz Yesilkoy, the first author of the article. "We demonstrated that we could detect and image not only individual biomolecules in hot spots, but even a single graphene sheet of an atom of thickness."

Going a little further in their work, the researchers developed a second version of their system, with metasurfaces programmed to resonate at different wavelengths in different regions. "This technique is simpler, but it is also less accurate in locating molecules," says Eduardo R. Arvelo, one of the article's co-authors.

Hatice Altug, who heads the BIOS Lab and leads the project at the School of Engineering, sees tremendous potential in the field of optics. "Light has many attributes – such as intensity, phase, and polarization – and is able to traverse space. This means that optical sensors could play a major role in solving future challenges, especially in personalized medicine.