Nanostructured surfaces enable lab-on-a-chip lung cancer diagnosis.
A miniaturized plasmonic spectrometer that creates a rainbow pattern that shifts in the presence of a chemical or biological sample has been developed. Crucially, these spectral shifts can be observed in a standard optical microscope.
For a beam of light to be able to interact with its surroundings, the smallest length scale is roughly equivalent to half of its wavelength. It is this principle that sets the fundamental restriction on the maximum resolution imaging optics, such as microscopes or spectrometers, can achieve. But this limit can be surpassed using plasmonics.
Plasmonic devices use nanoscale patterns to induce strong coupling between light and electrons at the surface of a metal and create so-called plasmons. Plasmons can be confined on subwavelength spatial scales and significantly enhance the strength of light-matter interactions. The former enables superresolution imaging, while the latter can be harnessed in sensitive sensors.
Qiaoqiang Gan from KAUST, together with co-workers from The State University of New York and Northeastern University in the United States, fabricated nanostrips of gold on a silica wafer.
The width and separation of the strips slowly increased across the device. This meant that light of different colors plasmonically coupled to distinct spatial regions on the chip. For example, the location of the red light was separated by approximately 50 micrometers from where blue light was trapped. “Importantly, a spatial displacement of the resonant pattern of just 35 nm was resolved by a 4× microscope system,” explains Gan. “That is equivalent to a distance of about 2.50 micrometers with 650-nanometer wavelength light.”
Read more at KAUST Discovery.
