We show that in our system, density and speed of sound of the PDMS leads to the diffraction of some fraction of the acoustic wave into the PDMS layer whereby heat is developed. The acoustic pressure wave that propagates when operating our device in the kHz frequency domain maintains most of its mechanical power and enables the coupling of acoustic energy into the surfactant layer between the water droplet and continuous oil phase. This acoustic field mediated surfactant destabilization causes injection of droplets passing a Tjunction with profound precision. Finally, modifications in the design of the injection nozzle could improve the accuracy of the injected volume into each droplet. Our IDT design and operation in the kHz frequency domain could be applied in other droplet manipulation strategies like droplet merging and content release . All in all, our acoustoinjection device is a cost-effective, reliable, and gentle option for microfluidic applications in which future biological content within water-in-oil droplets is not negatively impacted by thermal energy.