Acoustofluidic bubble-driven micromixers for the rational engineering of multifunctional ZnO nanoarray

Abstract

Acoustofluidics that combines acoustics with microfluidics represents an emerging and promising technology for the efficient mixing of fluids and synthesis of functional nanomaterials. However, it remains a great challenge to the controllable synthesis of three-dimensional functional nanostructures in a confined space. Herein, we introduce a robust acoustofluidic bubble-driven micromixer for the controllable synthesis of functional nanoarray inside the glass capillary toward efficient photodegradation and metal ion enrichment. The acoustofluidic micromixer functions with microbubbles-induced acoustic streaming from arrow-patterned microchannels. The morphology, density, and size of ZnO nanorods and nanosheets array can be precisely adjusted by reactant type, seeding phase, and reaction time. ZnO nanorod array exhibits approximately 90% degradation efficiency of R6G even after ten cycles, which are significantly better than ZnO nanosheet array and blank control groups. Enrichment tests of heavy metal ions show that ZnO nanoarray performs better enrichment performance of Cu2+ than that of Ag+. In addition, both photodegradation and enrichment capabilities can be well regulated by tuning the flow rates (i.e., the residence time). These findings provide important guidelines for the rational design of functional nanomaterials and shed new light on the fabrication of advanced lab-on-a-chip devices.