Li, DongqingLi, Mengqi2017-02-082017-02-082016-05http://dx.doi.org/10.1007/s10404-016-1741-2http://hdl.handle.net/10012/11291The final publication is available at Springer via http://dx.doi.org/10.1007/s10404-016-1741-2.In this study, the Janus droplet is an oil droplet covered with aluminum oxide nanoparticles on one side of the droplet surface under applied DC electrical field. The vortices around Janus droplets fixed on a horizontal surface were studied in this paper. A numerical model was set up to simulate the vortices around the Janus droplet in electric field. The simulation results illustrate that the electric field determines the strength of the vortices around a fixed Janus droplet, and the surface coverage of the positively charged nanoparticles on a Janus droplet affects the size and location of the vortices. The numerically predicted results were further validated experimentally by visualizing the vortices around Janus droplets in an externally applied DC electric field. Furthermore, as the Janus droplets are generated in electric field, the surface coverage by the nanoparticles depends on the strength of the electric field; therefore, the effect of the electric field on the nanoparticle covered surface area of a Janus droplet and the vortices was analyzed.enJanus dropletCharged nanoparticlesElectroosmotic flowVorticesArticle