Fluidic low pass filter for hydrodynamic flow stabilization in microfluidic environments

Abstract

Fluctuations in flow rate invariably occur in microfluidic devices. This fluidic instability results in a deteriorating performance and the suspension of their unique functions occasionally. In this study, a fluidic-LPF (low pass filter), which is composed of an ACU (air compliance unit) and a FCSP (fluidic channel with high fluidic resistance for sufficient preload), has been proposed for providing the stabilization of hydrodynamic flow in microfluidic devices. To investigate the characteristics of various fluidic networks including our fluidic-LPF, we used a parametric identification method to estimate the time constants via a transient response that was based on a discrete parameter model. In addition, we propose the use of a pulsation index (PI) to quantify the fluctuations in flow rate. We verified the formula for PI derived herein by varying individually both the periods and the air compliance volumes in the ACU, both theoretically and experimentally. We found that the PI depended strongly on either the time constants or the periods of the flow rates at the inlet. Additionally, the normalized differences between the experimental results and the theoretical estimations were less than 6%, which shows that the proposed formula for PI can provide an accurate quantification of the fluctuations in flow, and estimate the parametric effects. Finally, we have successfully demonstrated that our fluidic-LPF can regulate fluctuations in the flow at extremely low flow rates (~ 10 μL h(-1)) and can also control severe fluidic fluctuations (PI = 0.67) with excessively long periods (100 s) via a microfluidic viscometer. We therefore believe that the stabilization of hydrodynamic flow using a fluidic-LPF could be used easily and extensively with a range of microfluidic platforms that require constant flow rates.

Fluid-Dynamic Optimal Design of Helical Vascular Graft for Stenotic Disturbed Flow

“…A 15 W centrifugal pump circulated the working fluid through the circuit at a constant flow rate. A 0.5 L air container was installed as a fluidic low-pass filter using a three-way connector to stabilize possible fluctuations in flow rate [27], [28]. To measure the flow rate, a variable area-type flow meter (Visi-Float, Dwyer Instruments, Inc., Michigan, USA) was installed after proper re-calibration with the working fluid.…”

Simultaneous measurement of erythrocyte deformability and blood viscoelasticity using micropillars and co-flowing streams under pulsatile blood flows

“…Using Eq. (3), pulsation index (PI), 26 which is defined as the ratio of the difference between the maximum flow rate (Q max ), and the minimum flow rate (Q min ) to the average flow rate (Q ave ), is analytically derived as…”

A simple microfluidic dispenser for single-microparticle and cell samples

“…To further dampen oscillations, compliance reservoirs 31 ~2 mm diameter hydrophobic reservoirs were added downstream of the particle isolation section to absorb pressure waves from falling droplets (Figure 6a) and designed to dampen the high amplitude oscillations. These minimize the spike in local pressure with slow discharge while the next droplet forms, preventing large pressure waves from moving upstream and affecting microparticle isolation.…”