Image: Mary O’Reilly (MIT)

MIT Researchers Shrink Spectrometer to Nano-size to Fit Into Smartphone

Smartphones have become the in-thing in modern Internet age that MIT students have created a spectrometer that can fit into the device to diagnose skin diseases among others.

Based on properties of light, spectrometers are useful in chemical and biological research but huge in size and non-portable. The researchers of Massachusetts Institute of Technology were able to shrink it to a size that can fit into the smartphone making use of the camera in it.

MIT research is unique as other spectrometer approaches have complicated systems to create the required optical structures. They consisted of prisms that separate light into its constituent wavelengths, while current models use optical equipment such as diffraction gratings.

MIT scientists ahve used in their quantum dots, filters generated by printing liquid droplets. This approach is unique and advantageous in terms of flexibility, simplicity, and cost reduction.

“Such devices could be used to diagnose diseases, especially skin conditions, or to detect environmental pollutants and food conditions,” explained Jie Bao, lead author and former post-doctoral fellow at the MIT.Comparison of spectrometer mechanisms.

Quantum dots are made by lead or cadmium in combination with sulfur, selenium by controlling the ratio of their temperature and reaction time at required temperature. Discovered in 1980, scientists are now able to produce them in massive quantity with difference called ‘band gap’ that determines the wavelength of light to be absorbed.

Now to fit them into a smartphone, researchers used quantum filters printed into a thin film that is fixed to a photodetector or charge-coupled devices (CCDs) on a smartphone.

Based on the percentage of photons absorbed by each filter, the information is put together to calculate intensity and wavelength of the light, which means higher number of quantum dots indicate higher resolution.

For their spectrometer, researchers have used 200 types of quantum dots in a range of 300 nonometres. Fitted in a smartphone, these quantum dots help diagnose skin condition or analyze urine samples, besides tracking pulse and oxygen levels in the body, said researchers.

Operation of quantum dot spectrometers.

Operation of quantum dot spectrometers.

“Using quantum dots for spectrometers is such a straightforward application compared to everything else that we’ve tried to do, and I think that’s very appealing,” says Moungi Bawendi, the Lester Wolfe Professor of Chemistry at MIT and the paper’s senior author.

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