Focused surface acoustic waves induced microdroplets generation and its application for microgels

We demonstrate a novel microdroplets generation method by using focused surface acoustic waves (FSAW). The method differs from previous work in the mechanism and the geometry structure of the chip, which is depend on FSAW rather than flow shearing. The acoustic radiation force arising from FSAW acts on the oil-water interface, breaking up the water into microdroplets whose size can be controlled by tuning the driving voltage and frequency of FSAW. This approach overcomes the limitation of microchannel structure and capillary number of the traditional microfluidic droplets formation methods, which enables a fully electrical control of microdroplets size, with a good uniformity. Further, the FSAW-induced microdroplets are used as templates to prepare microgels with uniform size, offering a new platform for the design and synthesis of monodispersed functional microspheres.