Devices And Analyses For Manipulating The Nanoscale Materials In Liquid

The acoustic manipulation has the merits such as no selectivity to manipulated objects, less heat damage to biological samples(for some principles), simple and compact structure, and light weight.A method of concentrating nanoscale samples in a film of aqueous suspension on a stationary substrate(not in vibration) was shown, which employs the acoustic streaming generated by an ultrasonically vibrating needle parallel to and above the stationary substrate. The acoustic streaming eddy on the substrate surface brings nano particles to the center of the eddy. The principles of the above phenomena are analyzed and verified by the finite element method.A strategy was demonstrated to ultrasonically rotate a single nanowire in a water film on a substrate surface. Controlled mobile acoustic streaming field generated by the ultrasound around a vibrating micro manipulating probe(MMP) is used to rotate the nanowire at any position on the substrate surface. The method has potential applications in the assembling of micro/nano structures, orientation of biological samples, and measurement of dynamics properties of micro/nano entities.To optimize the transducer for rotary driving of single nanowires, vibration characteristics of the ultrasonic transducer are analyzed by the 3D finite element method, and some useful guidelines for designing the transducer are achieved. It is found that the working point still exists when the commonly used metal materials in ultrasonic transducers are used as the vibration transmission strip, and when the vibration transmission strip's size changes. It is also found that the direction of the elliptical motion of the MMP's tip may be reversed by changing the size of the vibration transmission strip properly. In addition, to ensure the performance consistency of the device, the micro manipulating probe's length Lm or driving frequency should be designed to avoid the resonance of the micro manipulating probe.