“Our approach could allow unprecedented miniaturisation of spectroscopic devices, to an extent that could see them incorporated directly into smartphones, bringing powerful analytical technologies from the lab to the palm of our hands.”Tawfique Hasan
Tiny spectrometer that can respond to a range of colors across the visible spectrum. Source: Ella Maru Studio.Researchers from the University of Cambridge, with colleagues from the UK, China and Finland, have developed an ultra-miniaturised device made from a single nanowire that can directly image single cells without requiring a microscope. This simplest possible spectrometer platform, nearly a thousand times smaller than any previous spectrometer, could be used to check the freshness of foods, the quality of medicines, identifying counterfeit banknotes, as well as a range of other applications dependent on its small size and weight.
Optical spectrometers are fundamental in a range of industrial applications and areas of scientific research as they analyse the properties of light to inform on material properties and processes. While most spectrometers involve the separation of light into different spectral components, this limits their size, making them bulky and complex, and not easy to reduce to manageable dimensions. However, as reported in the journal Science [Yang et al. Science (2019) DOI: 10.1126/science.aax8814], this study produced an ultracompact microspectrometer based on a single nanowire that can be incorporated into a smartphone camera.
The researchers used a nanowire whole material composition that varies along its length, allowing it to respond to a range of colors of light across the visible spectrum, with a series of light-responsive sections then being created on the nanowire, with individual responses from each section being directly fed into a computer algorithm to reconstruct the incident light spectrum. This system meant they could omit dispersive elements to allow a more straightforward set-up than that from standard spectrometers.
As team leader Tawfique Hasan said, “Our approach could allow unprecedented miniaturisation of spectroscopic devices, to an extent that could see them incorporated directly into smartphones, bringing powerful analytical technologies from the lab to the palm of our hands”. The new device can also directly image single cells without requiring a microscope, and could provide detailed information of the chemical fingerprint of pixels as each pixel stored would contain data points from right across the visible spectrum.
In accessing an engineered nanostructure responsive to a broad visible spectrum, the team were able to focus on issues of device architecture, reliability and hardware/software integration. They now hope to identify suitable material systems to enable seamless integration to extend the operation wavelength region in both the ultraviolet and infrared direction, with a range of potential uses in consumer, research and industrial applications, such as lab-on-a-chip systems, biological implants and smart wearable devices, as well as aiding astronomy and environmental studies.