Variation in polydispersity in pump- and pressure-driven micro-droplet generators

Abstract

The polydispersity of droplets produced in a typical T-junction microfluidic channel under both syringe-pump-driven and pressure-driven flow configurations is measured quantitatively. Both flow systems exhibit high-frequency flow fluctuations that result in an intrinsic polydispersity due to the mechanism of droplet generation. In addition to this intrinsic polydispersity, the syringe-pump-driven device also exhibits low-frequency fluctuations due to mechanical oscillations of the pump, which overwhelm the high-frequency flow fluctuations and produce a signficantly heightened level of polydispersity. The quantitative difference in polydispersity between the two configurations and time-resolved measurements of individual droplet sizes are presented in order to enable the design of better flow control systems for droplet production.

Image-based closed-loop feedback for highly mono-dispersed microdroplet production

“…Figure 3 shows that the distribution of microdroplet sizes created using the stepper motor driven syringe pump is relatively broad with periodic oscillations. This behaviour can be understood in terms of the discrete movements of the stepper motor which drives the syringe 24 , 25 . Significantly narrower distributions can be achieved using pulseless syringe pumps which do not show the same oscillations, however when compared to pressure driven pumps which apply a constant pressure, the distribution is still very broad.…”

Vaporizing Liquid Microthrusters with integrated heaters and temperature measurement

“…Although it is a reliable way of controlling the thrusters, it is only applicable for experimental testing since in does not represent the system as in the real application which will consist of a pressurized tank that provides the propellants to the thruster. Also, the syringe pump causes low frequency pressure fluctuations in the flow[21,22,23]. These fluctuations might affect the stability of the two-phase flow inside the chamber (i.e.…”

Damping hydrodynamic fluctuations in microfluidic systems

“…More importantly, we demonstrate a fundamental difference between displacement-driven and pressure-driven systems in terms of their flow stability performance. We prove that pressure pumps inherently make use of the compliance effect, which decreases the pressure fluctuation caused by the pressure regulator, thus achieving higher flow stability in most cases compared to displacement pump-driven systems (Glawdel and Ren, 2012;Korczyk et al, 2011;Zeng et al, 2015b). Since displacement pump systems lack such a damping mechanism, so far they have remained inferior.…”

“…Several studies have compared the droplet monodispersity of displacement pump-driven and pressure pump-driven microfluidic chips. It has repeatedly been shown that pressure pumps perform better than syringe pumps, achieving higher droplet monodispersity (Korczyk et al, 2011;Zeng et al, 2015b). The best coefficient of variation (CV) of droplet size that has been achieved using T-junction devices is in the range of 1%-3% (Hwang et al, 2014;Li et al, 2015;Link et al, 2004;Pang et al, 2014;Xu et al, 2006a).…”