Damping hydrodynamic fluctuations in microfluidic systems

Kalantarifard, Ali; Haghighi, Elnaz Alizadeh; Elbüken, Çağlar

doi:10.1016/j.ces.2017.12.045

Cited by 30 publications

(15 citation statements)

References 30 publications

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“…According to previous studies [22,23,26,29], air compliance was widely used to stabilize fluidic instability resulting from syringe pumps. In this study, a reference fluid was injected at a constant flow rate with a syringe pump.…”

Section: Variations Of Time Constant With Respect To Air Cavity In Reference Fluid Syringementioning

confidence: 99%

“…However, during the process of supplying a blood sample into a microfluidic device, the syringe pump causes fluidic instability at low flow rates [22]. To stabilize unstable flows resulting from the syringe pump, several techniques including air cavity in a driving syringe [23] or microfluidic channel [24,25], portable air cavity unit [22,26], and flexible compliance unit [27][28][29][30][31][32], were demonstrated in microfluidic systems. These methods act on the compliance element in the fluidic circuit model.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

Kang

2020

Micromachines

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Air compliance has been used effectively to stabilize fluidic instability resulting from a syringe pump. It has also been employed to measure blood viscosity under constant shearing flows. However, due to a longer time delay, it is difficult to quantify the aggregation of red blood cells (RBCs) or blood viscoelasticity. To quantify the mechanical properties of blood samples (blood viscosity, RBC aggregation, and viscoelasticity) effectively, it is necessary to quantify contributions of air compliance to dynamic blood flows in microfluidic channels. In this study, the effect of air compliance on measurement of blood mechanical properties was experimentally quantified with respect to the air cavity in two driving syringes. Under periodic on–off blood flows, three mechanical properties of blood samples were sequentially obtained by quantifying microscopic image intensity (<I>) and interface (α) in a co-flowing channel. Based on a differential equation derived with a fluid circuit model, the time constant was obtained by analyzing the temporal variations of β = 1/(1–α). According to experimental results, the time constant significantly decreased by securing the air cavity in a reference fluid syringe (~0.1 mL). However, the time constant increased substantially by securing the air cavity in a blood sample syringe (~0.1 mL). Given that the air cavity in the blood sample syringe significantly contributed to delaying transient behaviors of blood flows, it hindered the quantification of RBC aggregation and blood viscoelasticity. In addition, it was impossible to obtain the viscosity and time constant when the blood flow rate was not available. Thus, to measure the three aforementioned mechanical properties of blood samples effectively, the air cavity in the blood sample syringe must be minimized (Vair, R = 0). Concerning the air cavity in the reference fluid syringe, it must be sufficiently secured about Vair, R = 0.1 mL for regulating fluidic instability because it does not affect dynamic blood flows.

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Section: Variations Of Time Constant With Respect To Air Cavity In Reference Fluid Syringementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

Kang

2020

Micromachines

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“…We use a model based on the microfluidic circuit analogy to determine the correct ink dispensing profiles required for multimaterial printing. The MCA model has already been thoroughly discussed and used in several other applications, thus its derivations are outside of the scope of this manuscript . Briefly, several components of a DIW printing system have direct analogs with electronic circuit systems ( Table 1 ).…”

Section: Definition Of Circuit Model Variables and Fluidic Analogsmentioning

confidence: 99%

3D Printing of Compositional Gradients Using the Microfluidic Circuit Analogy

Nguyen

Yee

Dudukovic

et al. 2019

Adv Materials Technologies

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multimaterial DIW printer uses two separate ink dispensers joined at a single nozzle junction to simultaneously 3D print two viscoelastic inks through a single nozzle. Some models have been established to help control the printing of viscoelastic inks, but they have not been applicable for use in structures with complex compositional gradients. [18,22,23] As illustrated in Figure 1A, the toolpath of the printer is directly coupled with a desired composition (Φ) in order to determine the dispensing rate of each material. A distinction between the programmed dispensing rate of an ink (Q i ) and the measured flow rate out of the nozzle (Q Ni ) must be made when considering how to obtain an accurate compositional profile. Ideally, the increases and decreases in the measured ink flow rate synchronously follow the programmed dispensing rate. In reality, a number of factors introduce significant differences between the ideal ink dispensing rates and the realized outputs. Achieving accurate compositional 3D printing involving gradient transitions requires that we account for more complex behaviors, such as hydraulic compliance and non-Newtonian ink response, that result in significant differences between the programmed Q i and the realized Q Ni ( Figure 1B). For binary compositional changes within the same component, a combination of ink retraction and over extrusion can be used to account for these nonidealities. [22] For gradient compositional changes, the microfluidic circuit analogy (MCA) can be used to model and inform the ink dispensing profile that is required to achieve accurate compositional control ( Figure 1C).Here, we first describe the MCA model that is used to prescribe the ink-dispensing profile for improved compositional deposition accuracy in 3D-printed geometries with compositional gradients. We outline a calibration procedure to extract the MCA model parameters, which are then used in the MCA model to quantitatively guide the ink-dispensing profile for the desired compositional gradients to be printed. We finally validate the model in a DIW system using viscoelastic polydimethylsiloxane (PDMS) inks with time-dependent compositional changes. The ability to print multiple materials with accurate compositional profiles in a programmable manner enables the fabrication of new functional materials that were previously inaccessible.We use a model based on the microfluidic circuit analogy to determine the correct ink dispensing profiles required for 3D printing of structures with compositional gradients requires accurate dispensing control to achieve desired profiles. Here, empirical data are used with a model based on the microfluidic circuit analogy (MCA) to project dispense rate profiles that yield improved compositional accuracy in the printed part. Since minor variation in the experimental setup for each printing session can result in significant changes, a calibration procedure is developed to measure the system response. This calibration enables the extraction of the empirical MCA model parameters speci...

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“…flow inside microchannels) which is not suitable for further characterisation and processing of the produced NPs on chip. While channel microfluidics is perfect for continuous‐flow synthesis [8], it lacks the ability to hold liquid samples stationary on device due to diffusion and secondary unpredicted flows such as hydrostatic [9], capillary [10], and compliance‐induced [11] flows. Although these secondary flows could be eliminated by introducing on‐chip valves [12, 13], this solution is complicated in terms of device fabrication and the control setup required.…”

Section: Introductionmentioning

confidence: 99%

Miniaturised preparation of polymeric nanoparticles using droplet manipulation on open surfaces

Abualsayed

Abouelmagd

Abdelgawad

2019

Micro & Nano Letters

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A digital microfluidics platform for the preparation of poly(lactic-co-glycolic) acid (PLGA) nanoparticles (NPs) was developed. Droplets of PLGA in dimethylformamide were merged with droplets of deionised water by electrical actuation on a digital microfluidics device to form PLGA NPs through nanoprecipitation. The developed platform is automated and allows for the preparation of polymeric NPs with small size and high uniformity. Using the platform, the authors were able to prepare monodisperse PLGA NPs as small as 115 nm with a polydispersity index (PDI) of 0.14 which can be challenging with conventional preparation techniques on the macroscale. Size of the prepared NPs can be tuned through proper choice of the volume ratio between the two merged droplets which controls the induced internal convection flow after merging. Concentration of PLGA in the dimethylformamide droplet also had an effect on the size and polydispersity of the formed NPs. These results prove the potential use of digital microfluidics for testing combinatorial synthesis of different polymeric NPs for various applications. This approach allows robust and automated screening of NP preparations using only few microlitres of the reagents used, thus conserving precious and costly NP components and loaded therapeutic agents.

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Damping hydrodynamic fluctuations in microfluidic systems

Cited by 30 publications

References 30 publications

Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

3D Printing of Compositional Gradients Using the Microfluidic Circuit Analogy

Miniaturised preparation of polymeric nanoparticles using droplet manipulation on open surfaces

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