An integration approach to microfluidic flow sensing and actuation using electrolytic bubbles

In this paper we demonstrate an integration approach for making high-density microfluidic systems. A complex microfluidic system including both sensors and actuators was constructed on silicon chip. Electrically addressable bubble-based valves were used to regulate the fluid flow. A number of electrolytic bubble sensors were placed in parallel channels (sensing limb) connected with the main flow channel for measurements of open channel pressure in real-time. All the fluidic components were made using a single microfabrication process. The pressure dependence of the bubble-based sensor was systematically investigated by applying an inlet pressure ranging from 101 kPa to 133 kPa, while keeping the outlet pressure at atmosphere. The results show that open flow pressure can be accurately measured using the bubble-based sensor located in an adjacent sensing limb. The bubble-shrinking rate can also serve as a measurable parameter for the pressure in main fluidic channel. The experimental data validated with 3D numerical simulation results. The electrolytic bubble-based approach provides an ability to integrate a large number of microfluidic components on a monolithic lab-chip.