A sensor that can detect the presence of a date rape drug from a cocktail is expected to be on the market in a few years, researchers in Israel say. Fernando Patolsky and Dr. Michael Ioffe of Tel Aviv University\'s Sackler Faculty of Exact Sciences say they developed an easy-to-use sensor that, when dipped into a cocktail, instantly detects the presence of a date rape drug. When ready for commercial purchase in a few years, the sensor will be lightweight and discreet and easily transportable in a pocket or purse, the researchers said. The sensor can detect GHB and ketamine -- the most commonly used date rape drugs. In the United States, 200,000 women were raped in 2007 with the aid of a date rape drug, but because so many cases go unreported, the actual number is believed to be 80 percent to 100 percent higher, Patolsky said.Though date rape drugs are effective because they\'re colorless and tasteless when mixed into a cocktail, they subtly change the optical properties of the drink, Patolsky said. When a ray of light comes into contact with a drugged drink, a \"signal change\" occurs and the sensor sounds the alarm, which could be a beeping noise or a small flashing light in environments that are dark and loud, the researchers said.All elements of the system have been patented with Ramot at Tel Aviv University Ltd., the researchers said.