 SAW devices have been able to detect and distinguish between organophosphates, chlorinated hydrocarbons, ketones, alcohols, aromatic hydrocarbons, saturated hydrocarbons, and water.Such a device made at Sandia National Laboratories runs at a very high frequency (approximately 525 MHz), and the velocity and attenuation of the signal are sensitive to the viscoelasticity and mass of the thin film.The SAW device has four channels, each channel consisting of a transmitter and a receiver, separated by a small distance.