Instantly identifying illicit drugs

A Taiwanese research collaboration has built a tiny biochip that can instantly identify illicit drugs such as cocaine and amphetamines in their natural powdered form.

The method involved simply depositing the powder to be identified into a small, rectangular glass-and-plastic biochip containing some electronic components. The powder settles into channels 20 microns deep. Inside the biochip, a small transmitter beams electromagnetic radiation in the terahertz (THz) range (in between the microwave and infrared), to which biomolecules are very sensitive. By recording how much radiation the powder absorbs over a range of frequencies, the researchers obtain distinctive chemical fingerprints of the molecules that make up the powder.

Using this method, the researchers, led by Chi-Kuang Sun from the National Taiwan University, were able to distinguish powders of cocaine (which absorbs a maximum of radiation at 0.8 THz) and amphetamine (1.03 THz) from powders of potato starch, flour, and lactose. Less than five seconds were required to complete each scan. In addition, the drug's distinctive THz signatures make them possible to detect even when mixed in with another ingredient such as flour.

Present forensics techniques such as gas chromatography, in addition to using bulky equipment, all require tampering with the sample, such as vaporising it or attaching a fluorescent molecule to it. This can add time, expense, and complication to the process of identifying a drug. The new technique bypasses these steps and could be a more efficient alternative.

In recent experiments, the latest, more sensitive, version of the biochip could also identify specific molecules dissolved in water, which tends to absorb terahertz radiation strongly and obscure the signals from other molecules, for potential applications such as DNA identification in saliva.

Researchers also believe the chip may prove useful for molecular biology applications, such as studying the folding patterns of proteins, which could help design new drugs.