Submarine propulsion scheme by a cavitation microstreaming flow: (a) Initial state, (b) A submarine moves to the left when the bubble on the rear side of the submarine is excited by a piezo-actuator attached to the bottom of a water chamber around the bubble resonant frequency. 

Schematics of 3D manipulation of a droplet in parallel plates consisting of the patterned arrays of EWOD electrodes: (a) 3D envisioned image; (b) 2D droplet motion images. 

Schematic diagram of a proposed electromagnetically driven on-chip micromanipulator: When a bubble on the tip of the micromanipulator is acoustically excited at its natural frequency by a piezoactuator attached beneath the chip, it oscillates and simultaneously generates a radiation force, called a Bjerknes force, which results in pulling a neighboring object onto its surface, as shown in Fig. 1(b). The captured object can be transported to any location with the micromanipulator actuated by an external magnetic controller consisting of precisely controllable 2D traverse and twin permanent magnets (Fig. 1(c)). When the object carried with the micromanipulator reaches a target location, it can be released from the bubble simply by turning the piezoactuator off and transporting the micromanipulator to the original position, as shown in Fig. 1(d). 

Conceptual schematic of the microfluidic-based magnetic-field-driven manipulation of the liquid metal: (a) coating with Fe particles, (b) HCl treatment and suction of the liquid metal, (c) HCl-treated liquid metal injection into the PDMS-based microfluidic channel filled with HCl or NaOH, and (d) on-demand magnetic manipulation of the HCl-treated liquid metal.