In this work, the performance of a piezoelectrically-actuated ultrasonic droplet generator is analyzed by modeling the harmonic response of a two-dimensional representation of the device cross-section. Observed vibrational and acoustic resonances provide insight into optimal design conditions to achieve efficient, robust droplet ejection. Numerical simulations highlight the importance of the coupled electrical and mechanical behavior of the resonator assembly and show that elastic modes can effectively amplify or dampen acoustic modes within the fluid chamber. Experimentally-validated modeling results guide development of an optimization strategy to further improve device performance. In addition, the standing acoustic field that is the focus of the harmonic response model is incorporated into a custom simulation of the acoustophoretic migration of microparticles. Particles achieve terminal distributions at pressure nodes in the quiescent fluid, exhibiting remarkable agreement with experimental observations. The migratory speed of microparticles in a simple rectangular fluid chamber geometry has been shown to be inversely proportional to the square of the particle radius. Here, this relationship is confirmed for particle migration in more complex acoustic microfluidic geometries
