Scientists have developed a novel sensor that can be used in smartphone-sized devices to detect dangerous chemicals based on a unique fingerprint of absorbed and emitted light.<br />”<br />”<br />”Devices called spectrometers are light-splitting instruments that have long been both bulky and expensive, preventing their use outside the lab.<br />”<br />”<br />”However, researchers at the University of Wisconsin-Madison in the US have now developed a spectrometer so small and simple that it could integrate with the camera of a typical cellphone without sacrificing accuracy.&nbsp;<br />”<br />”<br />”Zhu Wang, who was among the team of engineers that created the device, said that this is a compact, single-shot spectrometer that offers high resolution with low fabrication costs.&nbsp;<br />”<br />”<br />”The device also has an advanced capability called hyperspectral imaging, which collects information about each individual pixel in an image to identify materials or detect specific objects amidst a complicated background.<br />”<br />”<br />”Hyperspectral sensing, for example, could be used to detect seams of valuable minerals within rock faces or to identify specific plants in a highly vegetated area, according to the research published in the journal Nature Communications.<br />”<br />”<br />”Spectrometers usually rely on prisms or gratings to split light emitted from an object into discrete bands — each corresponding to a different wavelength, researchers said.&nbsp;<br />”<br />”<br />”To resolve the difference among a mixture of different colours, spectrometers usually must be relatively large with a long path length for light beams to travel and separate.&nbsp;<br />”<br />”<br />”The team created tiny spectrometers, measuring just 200 micrometres on each side, that is roughly one-20th the area of a ballpoint pen tip, and delicate enough to lie directly on a sensor from a typical digital camera.&nbsp;<br />”<br />”<br />”The small size was possible because the researchers based their device on specially designed materials that forced incoming light to bounce back and forth several times before reaching the sensor.&nbsp;<br />”<br />”<br />”Those internal reflections elongated the path along which light travelled without adding bulk, boosting the devices' resolution.<br />”<br />”<span style="color: #222222;">The device performed hyperspectral imaging, resolving two distinct images from a snapshot of an overlaid projection that combined the pair into something indistinguishable to the naked eye.</span><br />