The projected surge in atrial fibrillation (AF) cases to 12 million individuals in the United States alone by 2030 necessitates innovative solutions to address diverse user populations. Our project introduces a multi-needle gene therapeutic injection device specifically engineered to target myocardiocytes along the inner wall of the atria, prioritizing enhanced patient comfort, optimized surgical efficiency, and precise drug delivery. We developed fabrication methods for needle cutting, attachment, and drug channel connection via 3D printing and molding, and proposed ideas for needle sheathing, tube material, and device shaping through Solidworks and physical prototyping. We also conducted a single needle injection experiment with agarose gel simulating different heart conditions to inform design parameters such as needle size and spacing. Our future work involves prototyping the distal expansion mechanism, designing a user interface, and exploring methods for improved drug delivery efficacy.