Sharp-edge–driven spiral acoustic micromixers for functional nanoarray engineering

Abstract

Acoustic microfluidics has a remarkable influence on mixing but still face significant challenges of low throughput. Here, a robust acoustic micromixer with a spiral microchannel and side-wall sharp-edge structures is first proposed for facilitating microscale fluid mixing at wide-range flow rates. A micromixer that integrates acoustics with hydrodynamics enables fast and homogeneous mixing, ranging from 4 μL/min to over 2500 μL/min. the mixing performance shows a transition from acoustics domination at low flow rates to hydrodynamics domination at high flow rates. The increases of transducer amplitude, curvature, and sharp-edge density are positively correlated with mixing performance, while the increase of a tilted angle shows the opposite. The acoustic micromixer is leveraged to synthesize a functional ZnO nanoarray inside glass capillaries as portable microanalytical systems. ZnO nanofiber and nanosheet arrays are developed and their performances are systematically investigated by photodegradation of organic dye and enrichment of a heavy metal ion. Generally, efficiencies in photodegradation and enrichment can be well regulated by residence time, and a ZnO nanofiber shows more outstanding activity and robust stability than a ZnO nanosheet. These findings not only shed new light on the rational design of advanced lab-on-a-chip devices but also provide important guidelines for the controllable synthesis and applications of functional nanomaterials.