Syringe-pump-induced fluctuation in all-aqueous microfluidic system implications for flow rate accuracy

Area of Science:

• Fluid dynamics
• Microfluidics
• Analytical chemistry

Background:

• Syringe pumps are widely used in microfluidics for precise fluid delivery.
• Fluctuations in flow can significantly impact experimental outcomes, such as droplet size and formation.
• Understanding the sources of these fluctuations is crucial for improving microfluidic device performance.

Purpose of the Study:

• To develop a method for visualizing and quantifying microfluidic flow fluctuations induced by syringe pumps.
• To identify the stepper motor as a primary source of these flow fluctuations.
• To provide a predictive model for understanding syringe pump-induced fluctuations.

Main Methods:

• Utilized a liquid-liquid system with ultralow interfacial tension to amplify flow variations.
• Compared the frequency of observed interfacial ripples with the pulsation frequency of the syringe pump's stepper motor.
• Quantified fluctuations under varying conditions: flow rates, syringe diameters, and pump settings.

Main Results:

• Demonstrated that stepper motor pulsations directly correlate with observed ripples at the liquid interface.
• Quantified the impact of flow rate, syringe diameter, and pump settings on fluctuation amplitude and frequency.
• Established a method to predict the frequency of fluctuations based on syringe pump parameters.

Conclusions:

• Syringe pumps, specifically their stepper motors, are a significant source of fluctuations in microfluidic flows.
• These fluctuations can contribute to polydispersity in generated droplets.
• The findings offer a means to predict and potentially mitigate syringe pump-induced flow variations in microfluidic systems.