Movie S4.

Tunability of acoustic wells. Here, 10-μm-diameter polystyrene beads are pushed to form the rectangle-shaped pressure nodes along the horizontal direction with input signals (power along the horizontal direction = 10 mW, frequency along the horizontal direction = 13.35 MHz, power along the vertical direction = 30 mW, and frequency along the vertical direction = 13.45 MHz). By gradually increasing the power along the horizontal direction from 10 to 30 mW and decreasing the power along the vertical direction from 30 to 10 mW (frequency along the horizontal direction = 13.35 MHz, frequency along the vertical direction = 13.45 MHz), beads are first compressed to a square-like pressure node, and then trapped in the rectangle-shaped pressure nodes along the vertical direction. The movie is in real time.