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21 pages, 6151 KiB

Open AccessArticle

Assessment of Blood Biophysical Properties Using Pressure Sensing with Micropump and Microfluidic Comparator

by Yang Jun Kang

Micromachines 2022, 13(3), 438; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13030438 - 13 Mar 2022

Cited by 6 | Viewed by 2180

To identify the biophysical properties of blood samples consistently, macroscopic pumps have been used to maintain constant flow rates in a microfluidic comparator. In this study, the bulk-sized and expensive pump is replaced with a cheap and portable micropump. A specific reference fluid [...] Read more.

To identify the biophysical properties of blood samples consistently, macroscopic pumps have been used to maintain constant flow rates in a microfluidic comparator. In this study, the bulk-sized and expensive pump is replaced with a cheap and portable micropump. A specific reference fluid (i.e., glycerin solution [40%]) with a small volume of red blood cell (RBC) (i.e., 1% volume fraction) as fluid tracers is supplied into the microfluidic comparator. An averaged velocity (<U_r>) obtained with micro-particle image velocimetry is converted into the flow rate of reference fluid (Q_r) (i.e., Q_r = C_Q × A_c × <U_r>, A_c: cross-sectional area, C_Q = 1.156). Two control variables of the micropump (i.e., frequency: 400 Hz and volt: 150 au) are selected to guarantee a consistent flow rate (i.e., COV < 1%). Simultaneously, the blood sample is supplied into the microfluidic channel under specific flow patterns (i.e., constant, sinusoidal, and periodic on-off fashion). By monitoring the interface in the comparator as well as Q_r, three biophysical properties (i.e., viscosity, junction pressure, and pressure-induced work) are obtained using analytical expressions derived with a discrete fluidic circuit model. According to the quantitative comparison results between the present method (i.e., micropump) and the previous method (i.e., syringe pump), the micropump provides consistent results when compared with the syringe pump. Thereafter, representative biophysical properties, including the RBC aggregation, are consistently obtained for specific blood samples prepared with dextran solutions ranging from 0 to 40 mg/mL. In conclusion, the present method could be considered as an effective method for quantifying the physical properties of blood samples, where the reference fluid is supplied with a cheap and portable micropump. Full article

(This article belongs to the Special Issue Microfluidic Rheometry)

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12 pages, 1790 KiB

Open AccessArticle

A Microfluidic Prototype for High-Frequency, Large Strain Oscillatory Flow Rheometry

by Alfredo Lanzaro and Xue-Feng Yuan

Micromachines 2022, 13(2), 256; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13020256 - 03 Feb 2022

Viewed by 1597

Abstract

We introduce a “Rheo-chip” prototypical rheometer which is able to characterise model fluids under oscillatory flow at frequencies f up to 80 Hz and nominal strain up to 350, with sample consumption of less than 1 mL, and with minimum inertial effects. Experiments [...] Read more.

We introduce a “Rheo-chip” prototypical rheometer which is able to characterise model fluids under oscillatory flow at frequencies f up to 80 Hz and nominal strain up to 350, with sample consumption of less than 1 mL, and with minimum inertial effects. Experiments carried out with deionized (DI) water demonstrate that the amplitude of the measured pressure drop

Δ P_{M}

falls below the Newtonian prediction at

f \geq

3 Hz. By introducing a simple model which assumes a linear dependence between the back force and the dead volume within the fluid chambers, the frequency response of both

Δ P_{M}

and of the phase delay could be modeled more efficiently. Such effects need to be taken into account when using this type of technology for characterising the frequency response of non-Newtonian fluids. Full article

(This article belongs to the Special Issue Microfluidic Rheometry)

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Review

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20 pages, 9560 KiB

Open AccessReview

A Review of Microfluidic Devices for Rheological Characterisation

by Francesco Del Giudice

Micromachines 2022, 13(2), 167; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13020167 - 22 Jan 2022

Cited by 16 | Viewed by 4522

Abstract

The rheological characterisation of liquids finds application in several fields ranging from industrial production to the medical practice. Conventional rheometers are the gold standard for the rheological characterisation; however, they are affected by several limitations, including high costs, large volumes required and difficult [...] Read more.

The rheological characterisation of liquids finds application in several fields ranging from industrial production to the medical practice. Conventional rheometers are the gold standard for the rheological characterisation; however, they are affected by several limitations, including high costs, large volumes required and difficult integration to other systems. By contrast, microfluidic devices emerged as inexpensive platforms, requiring a little sample to operate and fashioning a very easy integration into other systems. Such advantages have prompted the development of microfluidic devices to measure rheological properties such as viscosity and longest relaxation time, using a finger-prick of volumes. This review highlights some of the microfluidic platforms introduced so far, describing their advantages and limitations, while also offering some prospective for future works. Full article

(This article belongs to the Special Issue Microfluidic Rheometry)

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