Acoustofluidic Tweezers for the 3D Manipulation of Microparticles.

Non-contact manipulation is of great importance in the actuation of micro-robotics. It is challenging to contactless manipulate micro-scale objects over large spatial distance in fluid. Here, we describe a novel approach for the dynamic position control of microparticles in three-dimensional (3D) space, based on high-speed acoustic streaming generated by a micro-fabricated gigahertz transducer. The hydrodynamic force generated by the streaming flow field has a vertical component against gravity and a lateral component towards the center, thus the microparticle is able to be stably trapped at a position far from the transducer surface, and to be manipulated over centimeter distance in 3D. Only the hydrodynamic force is utilized in the system for particle manipulation, making it a versatile tool regardless the material properties of the trapped particle. The system shows high reliability and manipulation velocity, revealing its potentials for the applications in robotics and automation at small scales.