In this study we are presenting a proof-of-concept microfluidic device that simultaneously applies the conditions required for microelectroporation and micro-sonoporation in a flow-through fashion that allows for high throughput, high efficiency transfection of mammalian cells. During the design stage, we developed a low-cost, high-resolution polymer microfabrication technique termed laser stenciling. While few other electro-sonoporation protocols have been reported, to the best of our knowledge, we are the first to incorporate microelectroporation, which has been well established in literature to be advantageous to conventional electroporation, with flow-through micro-sonoporation. When comparing transfection efficiency for our electro-sonoporation method to that of sonoporation or microelectroporation alone, we observed single batch improvements up to 20 percent and 17 percent, respectively. The average improvement in efficiency was approximately 15 percent greater than achieved with sonoporation and 10 percent greater than that of electroporation. Importantly, there was little difference in short term cell viability between the three methods (maintained at > 90 percent). The average transfection efficiency for electro-sonoporation was 81.25 percent and cell viability was 91.56 percent. Overall, we have presented a device and electro-sonoporation method that meets or outperforms the transfection efficiency and cell viability standards for HeLa cells set by other reported electroporation and sonoporation methods.