Position and Orientation Control of Complex-Shaped Samples in Acoustic Levitation

Controlled levitation has been limited to sub-wavelength samples with few exceptions of spheres and cubes. We demonstrate controlled airborne levitation of 2λ-sized complex-shaped objects (3D letters, X, U, T). The pressure field was tailored to a particular sample shape by arranging multiple small asymmetric acoustic traps. This allows stable locking of the object and control of its orientation and position in mid-air. The pressure field was produced with a 450-element phased array (f = 40kHz) featuring element-wise amplitude and phase control.