Al writes "A handheld developed by Philips for law enforcement detects traces of cocaine, heroin, cannabis, and methamphetamine in 90 seconds. The system uses magnetic nanoparticles attached to ligands that bind to traces of these drugs. Once saliva has been placed inside the device, an electromagnet mixes the sample and the nanoparticles. Frustrated total internal reflection (FTIR) — the same phenomenon that underlies fingerprint scanners and multitouch screens — is then used to measure a change to the refractive index. By immobilizing different drug molecules on different parts of a sensor surface, the analyzer is able to identify traces of each different drug. An electronic screen displays instructions and a simple color-coded readout of the results."