Microfluidic oscillator for gas flow control and measurement

Microfluidic oscillators were obtained from wall attachment microfluidic amplifiers using a feedback loop from the outputs to the control inputs. These devices can be used as flow meters when the oscillation frequency is proportional to the volumetric flow rate in subsonic and moderately compressible conditions. They can also be used as actuators, for applications involving flow control and/or mixing. The devices, presenting critical dimensions of the order of 280 μm, were fabricated using SU-8 based epoxy photoresist and conventional photolithography. The article shows the results obtained in the experimental device tests with gases (nitrogen, argon, and carbon dioxide). The typical variation of the frequency with volumetric flow presents a range close to thousands of hertz. The oscillation frequencies were obtained using hot wire filament anemometers (in this case with a diameter of 12 μm). The experimental results indicate that the operation of the microfluidic oscillator was a direct function of the length of the feedback loops and of the velocity inside of the interaction region.