Microfluidics-assisted synthesis of hydrogel microparticles with acoustic-magnetic control

•A magnetic microparticle preparation method combining acoustic-magnetic control.•A microfluidics chip integrating generation and solidification of microparticles.•Two mechanisms of tuning droplet size by focused surface acoustic wave were studied. Using one microfluidic device integrating acoustic and magnetic control, we propose a novel preparation method of magnetic fluorescent polyacrylamide hydrogel microspheres and calcium alginate hydrogel microparticles in this paper. The effect of the two interdigital transducers in different position on the droplets generation is studied. By tuning the input parameters of the two focused interdigital transducers (FIDTs), the excited focused surface acoustic wave (FSAW) can induce the generation of magnetic droplets with different sizes flexibly. Then the prepared magnetic droplets are cross-linked after crossing the continuous phase into the laminar flow induced by magnetic force. This method can avoid the direct reaction between the dispersed phase and the continuous phase in the channel, and enable the synthesis of magnetic fluorescent polyacrylamide hydrogel microspheres and calcium alginate hydrogel microparticles more easy and simple.