No abstract

Controlled levitation has been limited to subwavelength 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.

We present a simulation model that can be used to study the movement of an object in an acoustic levitator. The model uses the boundary element method (BEM) to compute the levitator's acoustic field, and the finite element method (FEM) to compute the movement of the levitating object.The model was built to act as a virtual tool for testing how objects move in acoustic pressure fields generated by phased array transducers (PATs). This was demonstrated by comparing object dynamics for different PAT optimization methods. We studied the stability of the levitation in fields created by two optimization methods. The fields were optimized to levitate an ellipsoid in the middle of our PAT geometry. By slightly displacing the levitating object from the intended levitation spot, we were able to show that the levitation became unstable and that the object would drop out from the trap.The results demonstrate that the model can be used to rapidly validate optimizers instead of having to run long experiments.