Syringe pumps offer low-cost solutions to drive and control flow through microfluidic chips, especially in biomedical applications. Mechanical oscillations resulting from their stepper motors, however, can limit their performance.

Haque et al. report findings of how mechanical oscillations play a role in performance loss in two-phase separation devices. Using a novel low-cost coded compressive rotating mirror camera, the group investigated the effect of fluctuations in a hydrodynamic microfluidic separation device based on a cell-free layer design. Their work looks to improve the ability of such microfluidic devices to withstand pulsating or fluctuating flow conditions without the use of ancillary equipment.

“We demonstrated fairly accessible low cost syringe pumps can be used for hydrodynamic separation systems,” said co-author Maïwenn Kersaudy-Kerhoas. “We hope that the article will help researchers when choosing an appropriate flow pumping system, and that it will help designers avoid undesirable loss in performance when using these types of pumps.”

While the effects of such oscillations have been documented in microdroplet production, the group’s work marks an early investigation into how pressure fluctuations affect applications, such as separating plasma from blood in microfluidic systems.

They found the the fluctuations of the width of the cell-free zone created in the microfluidic plasma-separating structures followed the frequency and amplitude of the pump-induced pressure fluctuations and diminished the particle separation performance.

The relative pressure fluctuations plateau at flow rates faster than 5 milliliters per hour.

Kersaudy-Kerhoas hopes to apply their approach to better understand pressure fluctuations in commercial pumps.

Source: “Effects of syringe pump fluctuations on cell-free layer in hydrodynamic separation microfluidic devices,” by Md Ehtashamul Haque, Amirali Matin, Xu Wang, and Maïwenn Kersaudy-Kerhoas, Physics of Fluids (2021). The article can be accessed at