Reflective acoustic metamaterial for dynamic axial sub-wavelength field control in acoustic levitation

Acoustic levitation is a non-contact manipulation techniques used in a wide range of fields from biology, physics to medical research. The manipulation of levitated objects can be achieved by controlling the phase of each transducer in a phased array or by using reflective metamaterial. Reflective metamaterial is the acoustic analogy of spatial light modulators, and horizontal movement of the levitated object may be achieved by physical translation of the metamaterial itself. However, axial movement relative to the reflective metamaterial has not been enabled. Here, we propose a reflective metamaterial for dynamic sub-wavelength field control to realize the axial movement of the levitated object, using the property that levitation points are created at distances multiple of half of a wavelength relative to the reflector in a sound field with sufficient sound pressure. It was shown that by mounting the triangular prisms with multiple of half of a wavelength on a reflector and moving them horizontally, the object would rise/fall by the height of the prism. The simple design of reflectors using the properties of acoustic levitation, paves the way to expand the capability of reflective acoustic metamaterial. [Funded by Strategic Research Platform towards Digital Nature Powered by Pixie Dust Technologies, Inc.]