A team of researchers from the BioNanoPhotonic Systems (BIOS) Laboratory at the École Polytechnique Fédérale de Lausanne (EPFL; Lausanne, Switzerland) has developed an ultrathin and miniaturized optical chip that, when coupled with a standard CMOS camera and powered by image analysis, is able to count biomolecules one by one in a sample and determine their location. The development could someday lead to a home-use device that identifies trace amounts of undesirable biomarkers in blood or saliva, and serves as an early-warning system for disease detection.
The technology is based on metasurfaces, which are sheets of artificial materials covered in millions of nano-sized elements arranged in a special way. At a certain frequency, these elements are able to squeeze light into extremely small volumes, creating ultrasensitive optical hotspots. When light shines on the metasurface and hits a molecule at one of these hotspots, the molecule is detected immediately. In fact, the molecule gives itself away by changing the wavelength of the light that hits it.
By using different colored lights on the metasurface and taking a picture each time with a CMOS camera, the 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 smart data science tools to analyze the millions of CMOS pixels obtained through this process and identify trends," says Filiz Yesilkoy, the first author of a paper that describes the work. "We've demonstrated that we can detect and image not just individual biomolecules at the hotspots, but even a single graphene sheet that's only one atom thick."
With a photonic chip and an ordinary CMOS camera, EPFL researchers have managed to count biomolecules one by one in a small sample and determine their position. (Image credit: EPFL)
Taking their work one step further, the researchers developed a second version of their system, where the metasurfaces are programmed to resonate at different wavelengths in different regions. "This technique is simpler, yet it is also less precise in locating the molecules," says Eduardo R. Arvelo, one of the paper's co-authors.
Hatice Altug, who runs the BIOS lab and is leading the project, sees immense potential in the field of optics. "Light possesses many attributes—such as intensity, phase, and polarization—and is capable of traversing space. This means that optical sensors could play a major role in addressing future challenges, particularly in personalized medicine."
Full details of the work appear in the journal Nature Photonics.