Schematic of micro-object manipulation using an untethered microrobot: (a) Initial state; (b) When an acoustic wave generated by a piezo-actuator excites a bubble attached on the bottom of a microrobot, the acoustically excited bubble generates a radiation force. Because of the radiation force, an neighboring object is pulled and captured to the bubble; (c) The captured object can be carried with the microrobot propelled by electromagnetic actuation to a desired place. Note that the piezo-actuator is still turned on to hold the captured object during the carrying operation; (d) When the microrobot reaches the desired place, the carried object is released from the bubble by turning the piezo-actuator off. This work has been selected for inculsion in IOP Select.