Scaling analysis of thermal bubble-driven micro-pumps from micro-scale to meso-scale

Thermal bubble-driven micro-pumps are an upcoming micro-actuator technology that can be directly integrated into micro/mesofluidic channels, have no moving parts, and leverage existing mass production fabrication approaches. As such, these micro-pumps hold great promise for micro/mesofluidic systems such as lab-on-a-chip technologies. To date, thermal bubble-driven micro-pumps have been realized discretely at the micro-scale (10's of mu m) and meso-scale (100's of mu m) which result in flow rates on the order of pL/pulse to nL/pulse respectively. However, no current work has studied how pump performance scales as a function of pump area. In this study, a systematic scaling analysis from micro to meso-scale (10-1000 mu m) of thermal bubble-driven micro-pumps is performed to develop reduced parameter one-dimensional (1D) models with pump area dependency. We present, for the first time, an empirical relationship between bubble strength and resistor area across 4 orders of magnitude that generalizes the prevailing reduced parameter 1D model. Namely, qo(A) = (1.253 x 10-12)A [kg & sdot; m/s] which was found to fit the data with an R2 value of 0.96. Previously, experimental data were required to estimate the bubble strength of a particular micro/mesofluidic channel with a thermal bubble-driven micro-pump of a given area. In this work, the developed empirical relationship estimates bubble strength as a function of resistor area thus eliminating the need for experimental data to perform a first-order analysis of thermal bubble-driven micro-pumps. We envision such reduced parameter 1D models as an important first-order design tool for micro/mesofluidic designers to predict the size of the pump area needed for a desired flow rate.