Visualization of bubbles generated by microheaters with various current density distributions

This work presents an experimental study to analyze the performance of thermal actuators to generate bubbles. The heaters are designed to have different current density distributions based on numerical analysis. The bubbles generated by heaters are compared to each other by visualization techniques. It is shown that the geometries and driving conditions of the heater strongly affect the bubble behaviors. The geometries like arc or trapezoid-shape induce nonuniform current densities and therefore change the driving conditions for generating bubbles. The experimental result reveals that the proper considerations on heater geometry are required to use the heater as a thermal actuator.