Analyses of acoustic streaming field in the probe-liquid-substrate system for nanotrapping

Abstract

The probe-liquid-substrate system, in which a micro-manipulation probe (MMP) is inserted into a liquid film of nanosuspension on a substrate, is very useful in nanomanipulations. With the MMP’s vibration, a three-dimensional (3D) acoustic streaming field around the MMP is generated, which has been used to trap, transfer and rotate nanoentities in the liquid film. However, research on the details of the 3D acoustic streaming field in the probe-liquid-substrate system has been scarce. In this work, the 3D acoustic streaming field in a probe-liquid-substrate system for the contact-type trapping of individual nanowires is numerically investigated by the finite element method. The computational results show that the MMP root’s elliptical vibration can generate an acoustic streaming field capable of trapping a single nanowire in the contact mode. This conclusion can well explain the experimental phenomena that the MMP can trap a single nanowire at some frequencies and cannot at others. The computational results clarify the effect of the distance between the MMP and substrate, the MMP’s radius and length, and the water film’s thickness on the acoustic streaming field.