- Researchers develop the smallest spectrometer that is one thousand times thinner than a human hair.
- It could enable assessing the quality of drugs, freshness of foods, and much more, from a smartphone camera.
In 1666, Isaac Newton’s experiment of bending white light through a prism sowed the seeds for a new phenomenon: spectroscopy. It involves studying the interaction between matter and electromagnetic radiation.
Optical spectrometers have now become essential instruments: they are used in various fields of scientific research, from analyzing properties of protein molecules to observing processes within galactic nebulae, millions of light-years away.
However, even today, most of the spectrometers rely on basic principles that Newton demonstrated in the 17 century — separating light into different spectral components. This is why it is extremely difficult to reduce the size and complexity of spectrometer. If you look around you won’t find a spectrometer smaller than a coin.
Recently, researchers at the University of Cambridge developed a new device that is 1,000 times smaller than existing spectrometers. It is the smallest spectrometer ever built using a single nanowire.
The Miniaturized Spectrometer
The material composition of nanowire varies along its length, which makes it responsive to different light colors across the visible spectrum. Researchers built a series of light-responsive segments on the nanowire.
This nanowire doesn’t include any dispersive components, such as a prism, and is far simpler than traditional spectrometers. The data obtained from individual segments of the nanowire can be directly fed into a computer program, which transforms the data into the incident light spectrum.
Reference: ScienceMag | DOI:10.1126/science.aax8814 | University of Cambridge
The program reconstructs incident-light signals by probing the photocurrent and cross-referencing with a precalibrated response function for each of a series of points along the nanowire. With a sufficient number of points, both monochromatic and broadband spectra can be precisely reconstructed.
How much detail it can provide?
The information of a photograph is stored in pixels. This is usually limited to only three elements – Red, Green, and Blue. These three light are added together in various ways to reproduce a broad array of colors.
In the new device, on the other hand, each pixel consists of data points from across the visible spectrum. Thus, it can provide in-depth information far beyond the color humans eyes can perceive. For example, it can give insights into chemical processes taking place in the frame of the image.
Applications
The device can be used to assess the quality of drugs, freshness of foods, and identify counterfeit products. It can directly capture single cells without needing a microscope.
Since the spectroscopic device is so tiny, it could be incorporated directly into smartphones. The technology could literally put powerful analytical processes from the lab to the palm of our hands.
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Moreover, the growth of nanowires with different composition engineering could lead to a whole new generation of miniature spectrometers working across any wavelength range from the infrared to ultraviolet. It could be used in various industrial, research, and consumer applications, including smart wearable devices, biological implants, and lab-on-a-chip systems.
