WO2021118494A1

WO2021118494A1 - Micropump for microfluidic systems and operation method thereof

Info

Publication number: WO2021118494A1
Application number: PCT/TR2020/050806
Authority: WO
Inventors: Utku HATIPOGLU; Yigit OSKAY; Barbaros CETIN; Ender YILDIRIM; Alper TOPUZ; Atakan ATAY; Eyup KOCAK
Original assignee: Ihsan Dogramaci Bilkent Universitesi; Cankaya Universitesi
Priority date: 2019-12-09
Filing date: 2020-09-04
Publication date: 2021-06-17
Also published as: DE112020006029T5; TR201919668A1

Abstract

The present invention relates to a micropump developed to be used in microfluidic systems and operating on electromagnetic effects. Micropump can be mounted to the liquid inlet port of the microfluidic structure and have a cylindrical form, wherein it is comprised of a liquid reservoir and two circular diaphragms.

Description

MICROPUMP FOR MICROFLUIDIC SYSTEMS AND OPERATION METHOD

THEREOF

Technical Field The present invention relates to a micropump developed to be used in microfluidic systems and operating on electromagnetic effects. Micropump can be mounted to the liquid inlet port of the microfluidic structure and have a cylindrical form, wherein it is comprised of a liquid reservoir and two circular diaphragms. State of the Art

Microfluidic chips are systems that enable control and manipulation of fluids in microliters and smaller volumes inside the microchannels. Lately, since it is implemented in various fields such as chemistry, biology, medicine, and physics, it has appeared as a particular research field. Said systems generally are used in life sciences such as chemistry, biology, and medicine and also called as miniature total analysis systems (μTAS) and Lab-on-a-Chip/LOC. LOG systems are microfluidic platforms that are capable of integrating complex chemical management and analysis systems only on a chip with a scale of only a millimeter or centimeter and also interacting with electronic and optical sensing systems. It is possible by means of these microfluidic chips to observe and comprehensively analyze physical interaction, chemical reaction, and biological events through a millimetric or centimetric chip. Furthermore, microfluidics technology reduces sample and chemical agent consumption and decreases test periods and also decreases expenditures for these processes. By means of the sufficiency of the small-volume samples, the microfluidics technology would constitute a proper alternative for the known laboratory techniques, since it is able to gather up multiple laboratory protocols in a single chip with a size of only a few centimeter square. Microfluidic systems are commonly used in many applications such as blood cell separation, pathogen and toxin detection, biochemical measurements, chemical synthesis, genetic analysis, drug screening, electrochromatography, and organ-on-a-chip. Microfluidic chips are fabricated through micro-manufacturing techniques on silicone, glass, or polymeric

(polydimethylsiloxane/PDMS, polymethyl methacrylate/PMMA, etc.) substrates. A microfluidic chip is comprised of a molded or engraved microchannel pattern. The microchannel network located in the microfluidic chip is connected to the macro environment via the holes opened on the chip.

It is generally needed pumps to ensure the flow and microvalves to regulate the process in the microfluidic systems. Micropumps are active devices to control the flow of a microfluid through channels. There are various micropumps used in the microfluidic systems and developed in line with the system features in the state of the art. Micropumps commonly comprises one valve each at the inlet and the outlet and a diaphragm in the reservoir located between the valves. As the volume of the diaphragm reservoir increases by means of the diaphragm movement, the valve at the inlet opens simultaneously and thus fluid enters the diaphragm reservoir. As the volume of the diaphragm reservoir decreases by means of the diaphragm movement in the other direction, the valve at the outlet opens simultaneously and thus the fluid passes through the outlet valve and transferred towards the microchannel. Valveless micropumps operate on the principle of peristaltically moving generally 3 successive diaphragms placed on the microchannel and thus advancing the fluid in the channel. In valved and valveless micropumps, a second and third diaphragm beside a single diaphragm or valves are needed, and all of these elements should be operated in a synchronized manner. In case unidirectional passive valves or diffusers and nozzles are used at the inlet and the outlet of valved micropumps, the need for the synchronized operation of the valves is eliminated, however in such case, the flow rate and pressure performance of the micropump decrease due to the backflow in the passive valves or diffuser and nozzle.

Micropumps are not only fabricated by means of micro-manufacturing methods and be an integral part of the chip but also may be off-the-chip and connected to the chip by means of a tubing. If these micropumps are an integral part of the chip, they limit the design and manufacturing of the microfluidic chip. In case it is off-the-microfluidic chip, it is connected to the inlet hole of the microfluidic chip through a tubing. In such a case, the fluid in the tubing remains as a dead volume. Therefore, plug-and-play micropumps that can be directly mounted at the inlet holes of the microfluidic chip and thus minimizing the dead volume are needed. Diaphragms in micropumps are generally moved piezoelectrically, pneumatically, electrostatically or electromagnetically. In the state of the art, micropumps operated on different principles are presented in the following table. Table 1. Works on micropumps operating on different principles in the state of the art.

Patent application US20030235504A1 in the state of the art relates to a magnetohydrodynamic pump, wherein it includes a microfluidic channel, an electrode/magnet system functionally connected to the microfluidic channel, and a system for promoting the flow of the fluid in one direction in the microfluidic channel. Patent application CN102395790B relates to a micropump that is used for transferring microfluids through magnetic forces and comprises a first chamber and a second chamber and a flexible diaphragm. Another patent application US4344743A in the state of the art relates to a micropump having a self-priming and gas pumping piezoelectric motor and being suitable for implantation into the human body. Another patent application US6827559B2 relates to a piezoelectric micropump comprising diaphragm and valves. Further patent application US20060233648A1 in the state of the art relates to a method for fluid transfer and a micropump based upon the method.

The present invention relates to a plug-and-play electromagnetic micropump that can be directly connected to any microfluidic chip, wherein disadvantages in the state of the art are eliminated.

BRIEF DESCRIPTION and OBJECTS OF THE INVENTION

The present invention discloses an electromagnetically operated micropump that can be directly connected to the inlet of any microfluidic chip.

Another object of the invention is to ensure that the design of the microfluidic chip is not limited. The inventive micropump is not manufactured as an integrated component of the chip and thus, it does not limit the fabrication and the design of the microfluidic chip.

Another object of the invention is to simplify the use of off-chip-micropumps. The inventive off-chip-micropump eliminates the necessity of the tubing connection since it can be directly connected to the inlet of any microfluidic chip. This reduces the dead volume of liquid that cannot be pumped and facilitate the use thereof.

By means of the invention, it is possible to pump the liquid by means of moving a single diaphragm without the need for synchronized operation of additional diaphragms or valves. This facilitates the operation of said micropump.

DESCRIPTION OF FIGURES

FIGURE1: Schematic view of the micropump

FIGURE2: Schematic view of the diaphragms, when the upper diaphragm moves upwards

FIGURE3: Schematic view of the diaphragms, when the upper diaphragm moves downwards FIGURE4: Simulation result indicating the flow vectors occurred when the upper diaphragm moves upwards

FIGURES: Simulation result indicating the flow vectors occurred when the upper diaphragm moves downwards

FIGURE6: Simulation result indicating the change of the frequency-dependent flow rate in a preferred embodiment of the invention

FIGURE7: Simulation result indicating the change of the flow rate with respect to the back-pressure in a preferred embodiment of the invention

DESCRIPTION OF ELEMENTS/PARTS/COMPONENTS OF THE INVENTION

Parts and components in the figures are enumerated to understand the inventive micropump fully and correspondence of every number is given below:

1 . Liquid reservoir

2. Upper diaphragm

3. Lower diaphragm

4. Electromagnet

5. Cover

6. Liquid charging hole

7. Outlet hole

8. Upper chamber

9. Lower chamber

10 . A hole at the center of the upper diaphragm

11 . Permanent magnet

12 . Holes positioned at the same distance from the center of the lower diaphragm 13. Working liquid

14 . Microfluidic chip Detailed Description of the Invention

The present invention relates to an electromagnetic micro pump to be used in microfluidic systems that can be directly connected to any microfluidic chip. Micropump is of a form that can be mounted to the inlet port of the microfluidic chip (14) and has a cylindrical structure. The inventive micropump comprises a liquid reservoir (1), two circular diaphragms (2, 3) positioned on top of each other in the micropump such that they divide the liquid reservoir into two portions, a cover (5) positioned at the upper portion of the liquid reservoir (1 ) and comprising an electromagnet (4) at its center, a liquid charging hole (6) positioned on the cover and transferring fluid to the micropump and an outlet hole (7) positioned at the bottom of the liquid reservoir (1) and transferring fluid to the microfluidic chip (14). The diaphragms positioned on top of each other (2, 3) are posed in the micropump such that they divide the liquid reservoir (1) into two portions, namely the upper chamber (8) and the lower chamber (9). There is a hole (10) at the center of the upper diaphragm (2). The permanent magnet (11) is positioned around the hole (10) at the center of the upper diaphragm (2). Lower diaphragm (3) comprises multiple holes (12) that are radially at the same distance from the center and of at different angular positions. Figure 1 shows the schematic view of the micropump.

The operation principle of the inventive micropump is based on the electromagnetic activation and basically, the upper diaphragm (2) is oscillated electromagnetically in the direction of the micropump axis (axis z shown in Figure 1) and the working liquid (13), which was loaded to the liquid reservoir (1) from the liquid charging hole (6) on the cover (5) of the micropump prior to the operation, is transferred to the microfluidic chip (14) to which the micropump is connected.

The working liquid (13) in the cylindrical liquid reservoir (1) is transferred into the microfluidic chip (14) by moving the upper diaphragm (2) comprising a hole (10) and permanent magnet (11) thereon by means of the electromagnet (4). The magnetic field generated by applying an input voltage in the sine waveform to the electromagnet (4), makes the upper diaphragm (2) comprising a permanent magnet (11 ) oscillate in the vertical axis (axis z shown in Figure 1) depending on the magnitude of the voltage and the frequency of the sine wave. Because of the resulting oscillatory motion, while the upper diaphragm (2) moves upwards in the vertical axis, the working liquid (13) in the upper chamber (8) passes through the hole (10) at the center of the upper diaphragm (2) and flow towards the lower chamber (9). Figure 2 shows the schematic view of the upper diaphragm (2) and lower diaphragm (3) during the upward motion of the upper diaphragm (2). During the downward motion of the upper diaphragm (2), the upper diaphragm (2) closes holes (12) on the lower diaphragm (3) and pumps the working liquid (13) in the lower chamber (9) towards the microfluidic chip (14). Figure 3 shows the schematic view of the upper diaphragm (2) and lower diaphragm (3) during the downward motion of the upper diaphragm (2). Consequently, the average flow rate in each period of the voltage in the form of the sine wave applied to the electromagnet (4), is towards the microfluidic chip (14). This transfers the working liquid (13) to the microfluidic chip (14).

Figure 4 shows the simulation result indicating the flow vectors resulting from the upward motion of the upper diaphragm (2) in a preferred embodiment of the invention, in which the diameter and the thickness of the diaphragms are 16 mm and 0.5 mm, respectively, diameter of the holes is of 2 mm. Figure 5 shows the simulation result indicating the flow vectors resulting from the downward movement of the upper diaphragm (2) in the same preferred embodiment of the invention,. In the simulations, whose results are shown in Figures 4 and 5, one half of the upper diaphragm (2) and the lower diaphragm (3) symmetric about their central axes are modeled.

The flow rate provided by the micropump varies depending on the frequency and voltage amplitude of the sine wave applied. Figure 6 shows the simulation result indicating the frequency-dependent flow rate, for a preferred embodiment of the invention, in which the diameter and the thickness of the diaphragms are of 16 mm and 0.5 mm, respectively, and the diameter of the holes is of 2 mm, it also shows in case the backpressure at the outlet hole of the micropump is zero. Accordingly, there is a frequency range, in which the flow rate is positive and a frequency value, in which the flow rate is highest. For the same preferred embodiment of the invention, the simulation result indicating the flow rate value varying with respect to the backpressure at the outlet hole, in case the micropump is operated at the frequency value, in which the flow rate is highest, is shown in Figure 7. According to the simulation results shown in Figure 7, the flow rate is affected by the backpressure, and the flow rate decreases as the backpressure increases. In this case, in the preferred embodiment of the invention, the micropump should be operated in cases in which the frequency is 110 Hz and the backpressure values are lower than 60 Pa. The frequency in which the flow rate is highest and the range of backpressure at which the micropump can be operated can be controlled by altering the stiffness of the upper diaphragm (2) and the lower diaphragm (3) such that their diameters are between 5 mm and 30 mm and their thicknesses are between 0.1 and 1 mm and the diameter of the hole (10) at the center of the upper diaphragm (2) and the diameter of the holes (12) positioned at the same distance as the center of the lower diaphragm (3) are changed such that it is of 0.5 mm to 5 mm, thereby controlling.

The inventive micropump may be fabricated monolithically by using an elastomeric material, preferably polydimethylsiloxane (PDMS). In an embodiment of the invention, it is possible that only diaphragms are manufactured from an elastomeric material, preferably from polydimethylsiloxane (PDMS), and said diaphragms are mounted to a liquid reservoir (1) manufactured from any material that does not interact chemically with the working liquid.

The inventive micropump is connected directly to the microfluidic chip (14) without any need for tubing connection. Thus, dead working liquid volume to remain in the tubing is avoided.

The operation principle of the inventive micropump is as follows; i. Transferring the working liquid (13) into the liquid reservoir (1) through the liquid charging hole (6) on the cover (5), ii. Generating an alternating magnetic force by applying an input voltage in the form of a sine wave to an electromagnet (4) on the upper portion of the micropump, iii. Oscillating the upper diaphragm (2) comprising a permanent magnet (11) in the vertical axis depending on the voltage amplitude and the frequency of the sine wave by means of the alternating magnetic force generated, iv. Moving the upper diaphragm (2) upwards in the vertical axis due to the oscillatory motion generated and flow of the working liquid (13) in the upper chamber (8) towards the lower chamber (9) as a result of this motion, v. Moving the upper diaphragm (2) downwards again due to the oscillatory motion generated and closing the holes (12) on the lower diaphragm (3) by the upper diaphragm (2), vi. Transferring the working liquid (13) in the lower chamber (9) towards the microfluidic chip (14) through the outlet hole (7) by way of the joint downward movement of the upper diaphragm (2) and lower diaphragm (3).

REFERENCES: 1. Hatch, A. et al. 2001. “A Ferrofluidic Magnetic Micropump”, Journal of Microelectromechanical Systems, 10(2):2015-221

2. Zhang, T., Wang, M.Q. 2005. “Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices”, Journal of Power Sources, 140(1): 72-80.

3. Yamahata, C., Lotto, C., Al-Assaf, E., Gijs, M.A.M. 2005. “A PMMA valveless micropump using electromagnetic actuation”, Microfluidics and Nanofluidics, 1(3): 197-207

4. Liu, G., Shen, C., Yang, Z., Cai, X., Zhang, H., 2010. “A disposable piezoelectric micropump with high performance for closed-loop insulin therapy system”, Sensors and Actuators A: Physical, 163(1 ):291 -296.

5. Ni, J., Wang, B., Chang, S., Lin, Q. 2014. “An integrated planar magnetic micropump”, Microelectronic Engineering, 117(1):35-40.

6. Singh, S., Kumar, N., George, D., Sen, A.K. 2015. “Analytical modeling, simulations and experimental studies of a PZT actuated planar valveless PDMS micropump”, Sensors and Actuators A: Physical, 225:81-94

7. Gerasimenko, T.N. et al. 2017. “Modelling and characterization of a pneumatically actuated peristaltic micropump”, Applied Mathematical Modelling, 52:590-602

8. Guevara-Pantoja, P.E. et al. 2018. “Pressure-actuated monolithic acrylic microfluidic valves and pumps”, Lab on a Chip, 18:662-669.

Claims

1. Micropump operating on electromagnetic actuation to be used in microfluidic systems, characterized by comprising; a liquid reservoir (1 ), diaphragms, namely an upper diaphragm (2) comprising a hole at its center and positioned at the upper portion of the liquid reservoir (1) and a lower diaphragm (3) comprising multiple holes being radially at the same distance about the center and at different angular positions, located on top of each other in the micropump such that they divide the liquid reservoir (1) into two halves. a cover (5) positioned at the upper portion of the liquid reservoir and comprising an electromagnet (4) at its center, a liquid charging hole (6) being on the cover (5) and transferring fluid to the micropump and an outlet hole (7) positioned at the bottom of the liquid reservoir, through which the liquid is transferred to the microfluidic chip (14).

2. A micropump according to Claim 1 , characterized in that the upper diaphragm (2) and the lower diaphragm (3) are positioned in the micropump such that they divide the liquid reservoir (1) into two portions, namely the upper chamber (8) and the lower chamber (9).

3. A micropump according to Claim 1, characterized in that the permanent magnet (11 ) is positioned around the hole (10) at the center of the upper diaphragm (2).

4. A micropump according to Claim 1 , characterized in that the upper diaphragm (2) and the lower diaphragm (3) are manufactured from an elastomeric material.

5. A micropump according to Claim 4, characterized in that the upper diaphragm (2) and the lower diaphragm (3) are manufactured from polydimethylsiloxane (PDMS).

6. A micropump according to Claim 1 , characterized in that the upper diaphragm (2) and the lower diaphragm (3) are of a circular form.

7. A micropump according to Claim 1, characterized in that the micropump and the liquid reservoir (1 ) are of a cylindrical form.

8. A micropump according to Claim 1, characterized by being manufactured monolithically from an elastomeric material.

9. A micropump according to Claim 8, characterized by being manufactured monolithically from polydimethylsiloxane (PDMS).

10. A micropump according to Claim 1, characterized by being of the thermoplastic liquid reservoir form, to which the diaphragms manufactured from an elastomeric material are mounted.

11. A micropump according to Claim 1, characterized in that diameters and thicknesses of the upper diaphragm (2) and the lower diaphragm (3) are in the range of 5-30 mm and 0.1-1 mm, respectively.

12. A micropump according to Claim 1, characterized in that the diameter of the hole (10) at the center of the upper diaphragm (2) and the holes (12) positioned at the same distance about the center of the lower diaphragm (3) is in the range of 0.5-5 mm.

13. The operation method of a micropump according to any one of the preceding Claims, characterized by comprising the process steps;

I. Adding the working liquid (13) into the liquid reservoir (1),

II. Generating an alternating magnetic force by applying an input voltage in the form of a sine wave to an electromagnet (4) positioned on the upper portion of the micropump,

III. Oscillating the upper diaphragm (2) comprising a permanent magnet (11 ) in the vertical axis depending on the voltage magnitude and the frequency of the sine wave by means of the alternating magnetic force generated,

IV. Moving the upper diaphragm (2) upwards in the vertical axis due to the resulting oscillatory motion and flow of the working liquid (13) in the upper chamber (8) towards the lower chamber (9) through the hole (10) at the center of the upper diaphragm (2), v. Moving the upper diaphragm (2) downwards again due to the oscillatory motion generated and closing the holes (12) on the lower diaphragm (3) by the upper diaphragm (2), vi. Transferring the working liquid (13) towards the microfluidic chip (14) through the lower chamber (9).