Analyzing food and beverages with magnetic levitation

George Whitesides and colleagues note that measurements of a substance's density are important in the food industry, health care, and other settings because they provide key information about a substance's chemical composition. Density measurements, for instance, can determine the sugar content of soft drinks, the amount of alcohol in wine, or whether irrigation water contains too much salt to use on a farmer's field. Existing devices for making those measurements are far from ideal, and a need exists for simpler, less expensive, easy-to-use technology.

The scientists describe development of a special sensor that uses maglev to meet those needs, suspending solid or liquid samples with the aid of magnets to measure their density. About the size of an ice cube, the sensor consists of a fluid-filled container with magnets at each end. Samples of different materials can be placed inside, and the distance they migrate through the fluid provides a measure of their density. The scientists showed that the device could quickly estimate the salt content of different water samples and the relative fat content in different kinds of milk, cheese, and peanut butter. "Potential applications of maglev may include evaluating the suitability of water for drinking or irrigation, assessing the content of fat in foods and beverages, or monitoring processing of grains (e.g., removing husk or drying)," the article notes.