Researchers from the University at Buffalo in the US have developed a low-cost chemical sensing chip that can detect cocaine in the body within minutes.

The chip could be integrated into a handheld, portable device for detecting drugs taken by drivers. Drugs would be detected in biological samples such as blood, breath, urine or spit. It could provide on the spot results, much like an alcohol breathalyser.

The study, funded by the National Science Foundation, was published on May 7 in the journal Small Methods.

“Currently, there is a great demand for on-site drug testing,” said Qiaoqiang Gan, associate professor of electrical engineering in the University at Buffalo School of Engineering and Applied Sciences.

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

The chip uses nanotechnology to identify a unique pattern of light that is scattered when the chemical or biological molecules from the sample land on its surface. Every chemical has its own unique light-scattering signature, allowing the device to identify which compounds are present.

This method, known as surface-enhanced Raman spectroscopy (SERS), is not new. But crucially, the new chip can be produced at a low cost, with raw materials costing around 10 cents, while maintaining high levels of performance.

“SERS holds a lot of promise for rapid detection of drugs and other chemicals, but the materials required to perform the sensing are usually quite expensive,” said first author of the study Nan Zhang.

“The chips used for SERS are typically fabricated using expensive methods, such as lithography, which creates specific patterns on a metal substrate.

“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 new design uses a layered structure, known as a metasurface, which consists of silicon dioxide or aluminium oxide sandwiched between a silver mirror at the chip’s base and a hybrid nanomaterial from gold and silver nanoparticles at the chip’s surface.

This design was found to be effective for SERS, with the structure intensifying the scattering signature of compounds being sensed, improving detection.

The chip’s design also gives it a long shelf life, with researchers finding that it performed well after a year in storage.

“With our structure, we can realise both high performance and stable performance over time,” said Gan.

The research team plans to install the chip into a portable testing device that extracts drug molecules from biological samples during a purification process and then transfers any chemicals captured in the procedure to the chip for detection and identification.