Magnetic levitation (maglev) is best known for use in high speed trains. George Whitesides and his team from Harvard University have discovered a new use for the technique. They use it to analyze the fat and salt content of a variety of foods.
The scientists built a special device to analyze food and water samples. The sensor consists of two magnets on top of each other with like poles facing each other. A container filled with a paramagnetic fluid (that is, a fluid that is attracted to external magnets, but is not inherently magnetic) is placed between the poles with a droplet of the substance to be tested suspended within it. The density of the substance, which directly relates to its fat and/or salt content, determines where the droplet will float once the maglev device is switched on.The device has successfully been used to compare the fat content of different types of milk or vegetable oils, cheeses or peanut butter samples, and to estimate the salinity of different water samples.