Holographic Acoustic Tweezers

Holographic optical tweezers use focused light to manipulate multiple objects independently without contact. They are used in tasks such as measuring the spring constant of DNA, the pulling force of the kinesin protein, or to trap matter in exotic states. Differently, acoustic tweezers use sound radiation forces to trap particles at a larger scale (i.e., from micrometers to centimeters). However, previous implementations did not provide individual control. We present the realization of holographic acoustic tweezers. Using an array of sound emitters, we engineer the generated sound field to manipulate multiple particles individually. This enables applications in contactless assembly both at the micrometer and centimeter scale as well as the creation of displays in which the pixels are levitating particles.