Scientists have developed a low-cost chemical sensing chip that could test people for cocaine as quickly as a breathalyser identifies alcohol.
Such a technology has long been on the wish list of police officers and others looking to monitor drug use and curb dangerous driving, said researchers from the University at Buffalo in the US.
The chip could be integrated into a hand-held, portable device for detecting drugs in biological samples such as blood, breath, urine or spit.
"Currently, there is a great demand for on-site drug testing," said Qiaoqiang Gan, an associate professor in the University at Buffalo.
"The high-performance chip we designed was able to detect cocaine within minutes in our experiments. It is also inexpensive: It can be produced using raw materials that cost around 10 cents, and the fabrication techniques we used are also low-cost," said Gan.
"In the future, we are hoping to also use this technology to detect other drugs, including marijuana," he said.
The new chip, described in the journal Small Methods, is an engineered nanostructure that traps light at the edges of gold and silver nanoparticles.
When biological or chemical molecules land on the chip's surface, some of the captured light interacts with the molecules and is "scattered" into light of new energies.
This effect occurs in recognisable patterns that act as fingerprints, revealing information about what compounds are present.
Because all chemicals - cocaine, opioids, and active ingredients in marijuana - have their unique light-scattering signatures, researchers can use the technology to quickly identify a wide range of chemicals.
This sensing method is called surface-enhanced Raman spectroscopy (SERS), and it is not new.
However, the chip is noteworthy for its high performance and low cost.
The new chip - a structure known as a metasurface - resembles a layer cake, with several horizontal layers of material sitting atop one another.
The technology consists of a sheet of dielectric material (eg 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).