The days of giving blood, urine, or hair samples for drug analysis could be coming to a close. A bit of spit could be all that’s needed to determine if someone has been taking illegal substances, thanks to a microfluidic device that makes use of silver nanoparticles and surface-enhanced Raman spectroscopy, or SERS. A collaboration between Carl D. Meinhart’s and Martin Moskovits’ research groups at the University of California, Santa Barbara’s Institute for Collaborative Biotechnologies led to the development of the device, which can detect nanomolar levels of methamphetamine in saliva in a matter of minutes (ACS Nano 2013, DOI: 10.1021/nn402563f). Such a drug detection scheme could save time and money, the study points out. The system was designed to allow saliva to diffuse into a side stream of the microfluidic device containing silver nanoparticles. Small molecules in the saliva, such as methamphetamine, move more rapidly than larger substances, such as enzymes, and adsorb to the nanoparticles more quickly. Then salt ions are introduced, prompting the silver particles to aggregate into species that generate a strong SERS signal. The system could easily be adjusted to detect other small-molecule drugs or toxins, the researchers say.