Characterization of syringe-pump-driven versus pressure-driven microfluidic flows

We compare the dynamic characteristics of syringe-pump-driven and pressure-driven microfluidic flows based on the experimental measurements of the step response of the inlet pressure pi. For syringe-pump-driven flows, periodic fluctuations of pi are observed experimentally, which are induced by the flow-rate fluctuations coming from the mechanical oscillations of the pump motor. For pressure-driven flows, it takes much less time for pi to become steady and no periodic fluctuations are observed. To reduce the deviation between the predicted and the measured pi, a closed-loop control system with feedback of pi is established for pressure-driven flows. Using a PI controller, the deviation can be eliminated, and meanwhile, high stability and accuracy of flow-rate supply can be achieved for pressure-driven flows.