Understanding frequency response of thermal micropumps using electrical network analogy

In this article the frequency response of a thermal micropump is investigated using electrical network analogy modeling technique. This technique is based on dividing the micropump into subsystems and representing each subsystem using the equivalent network analogy. Obtained mathematical models of subsystems are then represented using transfer functions and block diagrams. As an example, thermopneumatic micropump is considered. Model simulation suggests an increase in the net flow rates of the micropump as the operating frequencies increased, until a first cut-off frequency is reached. A second cut-off frequency is observed with further increase in operating frequencies. Model simulations are consistent with qualitative experimental trends reported in the literature. The model is used to obtain a relationship between cut-off frequencies and design properties of the micropump. Model simulations show that lower cut-off frequency is related to mechanical properties of the thermopneumatic micropump, including stiffness and damping. Upper cut-off frequency is related to thermal properties of the thermopneumatic micropump, including thermal conductivity, heat capacity, and working fluid density.