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They say the chip can detect drugs from samples of blood, breath, urine or saliva.

The chip uses surface-enhanced Raman spectroscopy (Sers).

“The chips used for Sers are typically fabricated using expensive methods,” said researcher Nan Zhang, “we created our chip by depositing various thin layers of materials on a glass substrate, which is cost-effective and suitable for industrial-scale production.”

The chip has several horizontal layers comprising a sheet of dielectric material (e.g. silicon dioxide, aluminum oxide, etc.) sandwiched between a silver mirror (the base of the chip) and a hybrid nanomaterial made from gold and silver nanoparticles (the chip’s active surface).

Molecules of cocaine or other substances are placed on the chip and molecules fall into the spaces between the nanoparticles on the chip’s surface. 

Then, when the structure is exposed to light for testing, the silver mirror and the dielectric layer act as an “optical cavity,” manipulating light in a way that increases the number of photons at the surface of the chip. 

Ultimately, this intensifies the scattering signature of compounds being sensed, which improves detection.

“The high-performance chip we designed was able to detect cocaine within minutes in our experiments,” says associate professor Qiaoqiang Gan, “it’s also inexpensive: It can be produced using raw materials that cost around 10 cents, and the fabrication techniques we used are also low-cost.”

“In the future, we are hoping to also use this technology to detect other drugs, including marijuana,” adds Gan, “the widening legalisation of marijuana raises a lot of societal issues, including the need for a system to quickly test drivers for drug use.”