Levitation of Iridium and Liquid Mercury by Ultrasound

Single-axis acoustic levitation of the heaviest solid (iridium, ρ=22.6 g cm^-3) and liquid (mercury, ρ=13.6 g cm^-3 on the Earth is achieved by greatly enhancing both the levitation force and stability through optimizing the geometric parameters of the levitator. The acoustically levitated Pb-Sn eutectic alloy melt (ρ=8.5 g cm^-3) is highly undercooled by up to 38 K, which results in a microstructural transition of ``lamellae---broken lamellae---dendrites.'' The drastic enhancement of levitation capability indicates a broader application range of single-axis acoustic levitation.