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A microfluidic device based on an evaporation-driven micropump.

Nie C, Frijns AJ, Mandamparambil R, den Toonder JM - Biomed Microdevices (2015)

Bottom Line: Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10(-3) to 1.2 × 10(-1) μL/min are achieved.The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor.The theoretical and experimental results are in good agreement.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.

ABSTRACT
In this paper we introduce a microfluidic device ultimately to be applied as a wearable sweat sensor. We show proof-of-principle of the microfluidic functions of the device, namely fluid collection and continuous fluid flow pumping. A filter-paper based layer, that eventually will form the interface between the device and the skin, is used to collect the fluid (e.g., sweat) and enter this into the microfluidic device. A controllable evaporation driven pump is used to drive a continuous fluid flow through a microfluidic channel and over a sensing area. The key element of the pump is a micro-porous membrane mounted at the channel outlet, such that a pore array with a regular hexagonal arrangement is realized through which the fluid evaporates, which drives the flow within the channel. The system is completely fabricated on flexible polyethylene terephthalate (PET) foils, which can be the backbone material for flexible electronics applications, such that it is compatible with volume production approaches like Roll-to-Roll technology. The evaporation rate can be controlled by varying the outlet geometry and the temperature. The generated flows are analyzed experimentally using Particle Tracking Velocimetry (PTV). Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10(-3) to 1.2 × 10(-1) μL/min are achieved. When the surface temperature is increased by 9.4°C, the flow rate is increased by 130 %. The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor. The theoretical and experimental results are in good agreement.

No MeSH data available.


The liquid-air interface profile in a pore during evaporation pumping experiments, measured by interferometry. (a) liquid surface height profile across the center line of a pore; (b) Pores under the microscope; (c) one pore as characterized by an interferometry measurement; the profile in (a) is measured along the line shown in (c)
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Fig5: The liquid-air interface profile in a pore during evaporation pumping experiments, measured by interferometry. (a) liquid surface height profile across the center line of a pore; (b) Pores under the microscope; (c) one pore as characterized by an interferometry measurement; the profile in (a) is measured along the line shown in (c)

Mentions: The circular pores in the porous structure have diameters in the range 50 μm to 250 μm. A typical result in Fig. 5 shows that the profile of the liquid–gas interface during the evaporation process is relatively flat, and the maximum height difference the measured liquid profile within the pore is around 3.5 μm which is much smaller than its diameter (D = 250 μm). From simple trigonometric functions the value of θ ' can be estimated as θ = 0.056 rad. The resulting value of F(θ) = 0.642 then follows from Eq. 3, which is close to (0.78 % larger than) the value for θ = 0 : F(0) = 2/π = 0.637. However, this value is not perfectly distributed evenly in one pore due to small imperfections caused by the manufacture process which is seen in Fig. 5a and c. For simplicity, the contact angle is approximated by θ = 0 in our estimations of the evaporation rate using the model presented in section 3.1.Fig. 5


A microfluidic device based on an evaporation-driven micropump.

Nie C, Frijns AJ, Mandamparambil R, den Toonder JM - Biomed Microdevices (2015)

The liquid-air interface profile in a pore during evaporation pumping experiments, measured by interferometry. (a) liquid surface height profile across the center line of a pore; (b) Pores under the microscope; (c) one pore as characterized by an interferometry measurement; the profile in (a) is measured along the line shown in (c)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4372687&req=5

Fig5: The liquid-air interface profile in a pore during evaporation pumping experiments, measured by interferometry. (a) liquid surface height profile across the center line of a pore; (b) Pores under the microscope; (c) one pore as characterized by an interferometry measurement; the profile in (a) is measured along the line shown in (c)
Mentions: The circular pores in the porous structure have diameters in the range 50 μm to 250 μm. A typical result in Fig. 5 shows that the profile of the liquid–gas interface during the evaporation process is relatively flat, and the maximum height difference the measured liquid profile within the pore is around 3.5 μm which is much smaller than its diameter (D = 250 μm). From simple trigonometric functions the value of θ ' can be estimated as θ = 0.056 rad. The resulting value of F(θ) = 0.642 then follows from Eq. 3, which is close to (0.78 % larger than) the value for θ = 0 : F(0) = 2/π = 0.637. However, this value is not perfectly distributed evenly in one pore due to small imperfections caused by the manufacture process which is seen in Fig. 5a and c. For simplicity, the contact angle is approximated by θ = 0 in our estimations of the evaporation rate using the model presented in section 3.1.Fig. 5

Bottom Line: Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10(-3) to 1.2 × 10(-1) μL/min are achieved.The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor.The theoretical and experimental results are in good agreement.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.

ABSTRACT
In this paper we introduce a microfluidic device ultimately to be applied as a wearable sweat sensor. We show proof-of-principle of the microfluidic functions of the device, namely fluid collection and continuous fluid flow pumping. A filter-paper based layer, that eventually will form the interface between the device and the skin, is used to collect the fluid (e.g., sweat) and enter this into the microfluidic device. A controllable evaporation driven pump is used to drive a continuous fluid flow through a microfluidic channel and over a sensing area. The key element of the pump is a micro-porous membrane mounted at the channel outlet, such that a pore array with a regular hexagonal arrangement is realized through which the fluid evaporates, which drives the flow within the channel. The system is completely fabricated on flexible polyethylene terephthalate (PET) foils, which can be the backbone material for flexible electronics applications, such that it is compatible with volume production approaches like Roll-to-Roll technology. The evaporation rate can be controlled by varying the outlet geometry and the temperature. The generated flows are analyzed experimentally using Particle Tracking Velocimetry (PTV). Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10(-3) to 1.2 × 10(-1) μL/min are achieved. When the surface temperature is increased by 9.4°C, the flow rate is increased by 130 %. The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor. The theoretical and experimental results are in good agreement.

No MeSH data available.