Nanowires replace Newton's famous glass prism

Scientists have designed an ultra-miniaturized device that can directly imitate individual cells without the need for a microscope or allow chemical fingerprint analysis from a smartphone.

This device, made from a single nanowire 1000 times finer than a human hair, is the smallest spectrometer ever designed. It could be used in potential applications such as the assessment of the freshness of foods, the quality of drugs or even the identification of counterfeit objects, all from a smartphone camera. The details are reported in the newspaper Science.

In the seventeenth century, Isaac Newton, by his observations on the splitting of light by a prism, laid the foundation for a new scientific field studying the interactions between light and matter: spectroscopy. Optical spectrometers are nowadays essential tools in the industry and in almost all areas of scientific research. By analyzing the characteristics of light, spectrometers can tell us about the processes within galactic nebulae, millions of light years away, up to the characteristics of protein molecules.

However, even now, the majority of spectrometers are based on principles similar to what Newton demonstrated with his prism: the spatial separation of light into different spectral components. Such a base basically limits the size of the spectrometers with regard to: they are usually bulky and complex, and difficult to reduce to sizes much smaller than a coin. Four hundred years after Newton, researchers at the University of Cambridge have taken up this challenge by producing a system a thousand times smaller than those previously described.

The Cambridge team, in collaboration with colleagues from the United Kingdom, China and Finland, used a nanowire whose material composition varies lengthwise, allowing it to react to the different colors of the light in the visible spectrum. Using techniques similar to those used in the manufacture of computer chips, they then created a series of light-sensitive sections on this nanowire.

"We have designed a nanowire that allows us to get rid of the prism-like dispersive elements, producing a much simpler and ultra-miniaturized system than conventional spectrometers allow," said the former. Zongyin Yang author of the Cambridge Graphene Center. "The individual responses we get from nanowire sections can then be directly introduced into a computer algorithm to reconstruct the spectrum of incident light."

"When you take a picture, information stored in pixels is usually limited to three components: red, green, and blue," said co-lead author Tom Albrow-Owen. "With our device, each pixel contains data points from the entire visible spectrum, which allows us to obtain detailed information far beyond the colors that our eyes can perceive.This can tell us, for example, about chemical processes occurring in the frame of the image. "

"Our approach could allow for an unprecedented miniaturization of spectroscopic devices, to such an extent that they could be integrated directly into smartphones, bringing powerful analytics from the lab to the palm of the hand," he said. said Dr. Tawfique Hasan, who led the study.

One of the most promising potential uses of nanowire could be in biology. Since the device is so small, it can directly image individual cells without the need for a microscope. And unlike other bio-imaging techniques, the information obtained by the nanowire spectrometer contains a detailed analysis of the chemical fingerprint of each pixel.

The researchers hope that the platform they created could lead to a whole new generation of ultracompact spectrometers ranging from ultraviolet to infrared. These technologies could be used in a wide range of consumer, research and industrial applications, including in lab-on-a-chip systems, biological implants and smart wearable devices.

The Cambridge team has filed a patent on this technology and hopes to see concrete applications in the next five years.