Tractor beams have hit the big time. A newly constructed device generates a beam of concentrated sound that, for the first time, exerts a continuous, perceptible tug on objects large enough to see.

In laboratories from Brazil to Munich, researchers are learning to grab matter with sound alone, sculpting ultrasonic waves ...

U-tube: the glass tube and piezoelectric speaker that were used to create the new mass sensor. (Courtesy: William Grover) A $12 device that can measure the mass of microgram-sized objects in fluid has ...