Thursday 24 April, 2014

Ultra-sensitive sensor to help detect cancer signs, hidden explosives

Published On: Tue, Mar 22nd, 2011 | Photonics | By BioNews

Princeton engineers have developed an ultra- sensitive sensor that could help detect a wide range of substances, from tell-tale signs of cancer to hidden explosives.

The sensor, which is the most sensitive of its kind to date, relies on a completely new architecture and fabrication technique developed by the researchers.

The device boosts faint signals generated by the scattering of laser light from a material placed on it, allowing the identification of various substances based on the color of light they reflect. The sample could be as small as a single molecule.

The technology is a major advance in a decades-long search to identify materials using Raman scattering, a phenomena discovered in the 1920s by Indian physicist C Raman, where light reflecting off an object carries a signature of its molecular composition and structure.

Researchers have been trying for decades to tease out these light frequencies, but it was hard to see them even with the most sophisticated laboratory equipment.

“Raman scattering has enormous potential in biological and chemical sensing, and could have many applications in industry, medicine, the military and other fields,” said Stephen Y. Chou, the professor of electrical engineering who led the research team.

“But current Raman sensors are so weak that their use has been very limited outside of research. We”ve developed a way to significantly enhance the signal over the entire sensor and that could change the landscape of how Raman scattering can be used,” he added.

Chou and his colleagues developed a completely new surface enhanced Raman scattering (SERS) architecture — a chip studded with uniform rows of tiny pillars made of metals and insulators.

The chip uses arrays of metal pillars, which have small cavities at their bases and tops and a bunch of plasmonic nanodots on their sides.
The cavities serve as antennae, trapping light from the laser so it passes by the nanodots multiple times, generating the Raman signal more than once.

The team has named their new sensor as ‘disk-coupled dots-on-pillar antenna-array’ or D2PA, which is a billion times more sensitive than was previously possible.

“This is a very powerful method to identify molecules. The combination of a sensor that enhances signals far beyond what was previously possible, that”s uniform in its sensitivity and that”s easy to mass produce could change the landscape of sensor technology and what”s possible with sensing,” said Chou.

The discovery has been detailed in the February issue of journal Optics Express.

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