A nanomagnetic fluid medium micro pump drive system

Abstract

The invention discloses a nano-magnetic fluid medium micropump drive system, including a pump chamber, a flow guide baffle, a liquid inlet, a liquid outlet, a liquid inlet channel, a liquid outlet channel, a motor, a rotating shaft, a rotating magnet, a magnet tray, a glass substrate and a PDMS chip; the pump chamber, the flow guide baffle, the liquid inlet, the liquid outlet, the liquid inlet channel and the liquid outlet channel are designed in the PDMS chip, and the glass substrate is arranged at the bottom of the PDMS chip; the liquid inlet and the liquid outlet are arranged side by side on one side of the pump chamber, and the liquid inlet is connected to the pump chamber through the liquid inlet channel, and the liquid outlet is connected to the pump chamber through the liquid outlet channel; the liquid inlet channel, the liquid outlet channel and the pump chamber form a fluid channel; the flow guide baffle is in an arc shape; the rotating magnet is fixed in the magnet tray, and the magnet tray is connected with the motor; the motor rotating shaft is coaxial with the rotating magnet and the central axis of the pump chamber. The magnetic field control of the invention is simple, no multi-stage drive is required, and the pumping stability can be effectively guaranteed, the pumping efficiency is improved, the micropump structure is simplified, and the micropump size is reduced.

Description

Technical Field

[0001] The invention relates to a nano-magnetic fluid medium micro pump driving system, belonging to the technical field of fluid transmission and control. Background Art

[0002] As a key actuator of microfluidic systems, micropumps are micro devices that can accurately transport liquids or gases at a microscale. Based on mechanical, electromagnetic, chemical and other driving principles, micropumps can achieve high-precision, low-flow medium transportation and provide fluid power support for microsystems. Due to their miniaturization, integration, high efficiency and precise control, micropumps occupy an important position in modern micro-nano technology and have promoted the development of laboratory chips, biosensors and portable devices.

[0003] A magnetic fluid medium micropump is a micropump that uses magnetic fluid as the pumping fluid and uses the force generated by the magnetic fluid under the action of an external magnetic field to drive the flow of liquid. Unlike magnetic fluid piston pumps and magnetic fluid membrane pumps, the driving process of magnetic fluid medium micropumps does not rely on mechanical moving parts, but directly controls the movement of magnetic fluid through magnetic fields. It has the advantages of simple structure, no vibration, low noise and high precision. However, the existing technology of magnetic fluid medium micropumps faces problems such as large structure size, complex magnetic field control, low pumping efficiency and poor pumping stability.

[0004] The published patent "Valveless Magnetic Fluid Driven Micropump with Curved Baffle", publication number CN110454384A, is driven in the following way: the cylindrical permanent magnet is eccentric to the center line of the micropump cavity, and the magnetic field force generated drives the magnetic fluid microdisk in the cavity to rotate, and continuous pumping is achieved through changes in inlet and outlet pressures. However, the structure and working principle are too complicated, and the pumping stability and efficiency cannot be guaranteed.

[0005] The patent "Magnetic Fluid Micropump" has been published, publication number CN118367749A, and its driving method is: using two magnets to form valve magnetic fluid and piston magnetic fluid in the annular flow channel, thereby enhancing the driving force of the magnetic fluid, but using multiple magnets and the difficulty of controlling the magnetic field is large. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned technical problems and provide a nano-magnetic fluid medium micropump drive system, which adopts an arc-shaped guide baffle to simplify the micropump structure and reduce the size, thereby reducing the processing difficulty; the coordinated design of the four-leaf rotating magnet and the magnet tray does not require multi-stage drive, and the magnetic field control is simple, which can effectively ensure the pumping stability and improve the pumping efficiency.

[0007] To achieve the above object, the present invention provides the following technical solution: a nanomagnetic fluid medium micropump drive system, comprising a pump chamber, a guide baffle, a liquid inlet, a liquid outlet, a liquid inlet channel, a liquid outlet channel, a motor, a rotating shaft, a rotating magnet, a magnet tray, a glass substrate and a PDMS chip; wherein,

[0008] The pump chamber, the guide baffle, the liquid inlet, the liquid outlet, the liquid inlet channel and the liquid outlet channel are designed in the PDMS chip, and the glass substrate is arranged at the bottom of the PDMS chip; the basic structure of the pump chamber is circular, the liquid inlet and the liquid outlet are arranged side by side on one side of the pump chamber, and the liquid inlet is connected to the pump chamber through the liquid inlet channel, and the liquid outlet is connected to the pump chamber through the liquid outlet channel; the liquid inlet channel, the liquid outlet channel and the pump chamber constitute a fluid channel, and a nano-magnetic fluid is arranged in the fluid channel; the guide baffle is in an arc shape, the upper curve thereof is tangent to the liquid outlet channel, the lower curve is tangent to the liquid inlet channel, and the central angle between the two tangents is 0°;

[0009] The rotating magnet is fixed in the magnet tray and arranged below the glass substrate. The magnet tray is connected with the motor. The motor rotating shaft is coaxial with the rotating magnet and the central axis of the pump chamber.

[0010] Furthermore, the radius of the arc baffle at the end of the guide baffle is 1.4mm-1.6mm, the position of the arc baffle is appropriately extended, and its center is located on the upper left or upper right side of the center of the pump chamber. The horizontal distance from the center of the pump chamber is 0.3mm-1.5mm, and the vertical distance is 1.8mm-3mm; when the size and position of the guide baffle have little effect on the flow field, the radius of the arc baffle at the end is reduced, the horizontal and vertical distances between the center of the arc baffle and the center of the pump chamber are shortened, and a larger fluid channel is designed, which can further reduce the pumping resistance of the medium in the pump chamber and improve the pumping efficiency.

[0011] Furthermore, the rotating magnet structure is a four-leaf type, the distance from its center to the center of the blade tip is the same as the radius of the pump chamber, the top of the rotating magnet is 0.8-1.2mm away from the bottom of the glass substrate; the thickness of the rotating magnet is 1.8-2.2mm, and the number of magnets can be increased or decreased according to the maximum magnetization intensity of the nanomagnetic fluid.

[0012] Furthermore, the liquid inlet channel and the liquid outlet channel have the same size, with a width of 1 mm and a length of 5 mm-7 mm, and the upper end of the liquid inlet channel is 2.2 mm-2.5 mm away from the lower end of the liquid outlet channel.

[0013] Furthermore, the depth of the fluid channel composed of the liquid inlet channel, the liquid outlet channel and the pump cavity is 100 μm-150 μm.

[0014] Furthermore, the radius of the pump cavity is 10 mm-12 mm.

[0015] Before the system is operated, nanomagnetic fluid is injected into the pump chamber; the motor drives the rotating magnet to perform uniform circular motion, and the nanomagnetic fluid is pumped from the liquid inlet to the liquid outlet under the action of magnetic attraction; as the medium in the cavity is pumped out, the nanomagnetic fluid will continue to be replenished from the liquid inlet due to the pressure difference between the inside and outside of the pump chamber, and the outlet pressure of the micropump can be adjusted by changing the motor speed or the number of magnets.

[0016] The present invention has the following beneficial effects:

[0017] 1. Since the present invention has no complicated mechanical structure, the size of the micro pump is further reduced, the manufacturing process is simple, the weight is lighter, and the application range is wider, especially it can be applied to the field with high requirements on the volume of the micro pump;

[0018] 2. Using nano-magnetic fluid as the pumping medium avoids the problems of magnetorheological fluid and ordinary magnetic fluid, such as easy coagulation or precipitation, poor fluidity, easy blockage of flow channel, etc., and has better magnetorheological properties, which can provide stable driving force;

[0019] 3. The present invention adopts an arc-shaped guide baffle, which can effectively prevent the backflow of nano-magnetic fluid, improve the pumping stability, and reduce the difficulty of micro-pump processing;

[0020] 4. The present invention adopts a four-leaf rotating magnet, the number of which can be increased or decreased according to the actual working conditions, without the need for multi-stage drive, and the magnetic field control is simple, which can effectively improve the pumping efficiency;

[0021] 5. Use a magnet tray to prevent the rotating magnet from being directly adsorbed on the motor's rotating shaft, reduce or isolate the force of the magnet on the rotating shaft, and effectively further improve pumping stability and pumping efficiency;

[0022] 6. By controlling the intensity of the rotating magnetic field through electrical signals, continuous, stepless and intelligent control of the flow rate of the nano-magnetic fluid medium micropump is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the nano-magnetic fluid medium micropump driving system of the present invention;

[0024] Figure 2 It is a schematic diagram of the structure of a nano-magnetic fluid medium micropump;

[0025] Figure 3 It is the front view of the four-leaf rotating magnet;

[0026] Figure 4 This is a comparison chart of the outlet flow rates of micro pumps with different numbers of blades;

[0027] Figure 5 This is a comparison chart of outlet pressure of micro pumps with different numbers of blades;

[0028] Figure 6is the flow velocity distribution diagram at the outlet of the micro pump system;

[0029] Figure 7 is the pressure distribution diagram at the outlet of the micro pump system;

[0030] Figure 8 is the shear rate distribution diagram at the outlet of the micropump system;

[0031] In the figure: 1-pump chamber, 2-guide baffle, 3-liquid inlet, 4-liquid outlet, 5-liquid inlet channel, 6-liquid outlet channel, 7-motor, 8-rotating shaft, 9-rotating magnet, 10-magnet tray, 11-glass substrate, 12-PDMS chip. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are now described with reference to the accompanying drawings. It will be understood by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific technology, connection relationship or condition is indicated in the embodiments, the technology, connection relationship, condition described in the literature in this field or the product specification is used. If the manufacturer of the materials, instruments or equipment used is not indicated, they are all conventional products that can be purchased.

[0033] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "setting" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention are understood according to specific circumstances.

[0034] like Figure 1 , Figure 2 and Figure 3 As shown, a nano-magnetic fluid medium micropump driving system provided by the present invention includes a pump chamber 1, a guide baffle 2, a liquid inlet 3, a liquid outlet 4, a liquid inlet channel 5, a liquid outlet channel 6, a motor 7, a rotating shaft 8, a rotating magnet 9, a magnet tray 10, a glass substrate 11 and a PDMS chip 12;

[0035] The pump chamber 1, the guide baffle 2, the liquid inlet 3, the liquid outlet 4, the liquid inlet channel 5 and the liquid outlet channel 6 are designed in the PDMS chip 12, and the glass substrate 11 is arranged at the bottom of the PDMS chip 12; the basic structure of the pump chamber 1 is circular, the liquid inlet 3 and the liquid outlet 4 are arranged side by side on one side of the pump chamber 1, and the liquid inlet 3 is connected with the pump chamber 1 through the liquid inlet channel 5, and the liquid outlet 4 is connected with the pump chamber 1 through the liquid outlet channel 6; the liquid inlet channel 5, the liquid outlet channel 6 and the pump chamber 1 constitute a fluid channel, and a nano-magnetic fluid is arranged in the fluid channel; the guide baffle 2 is an arc shape, and its upper curve is tangent to the liquid outlet channel 5, and the lower curve is tangent to the liquid inlet channel 6, and the central angle between the two tangents is 0°;

[0036] The rotating magnet 9 is fixed in the magnet tray 10 and arranged under the glass substrate 11. The magnet tray 10 is connected with the motor 7. The magnet tray can reduce the force of the rotating magnet on the motor rotating shaft. The motor rotating shaft 8 is coaxial with the rotating magnet 9 and the central axis of the pump chamber 1. The rated working voltage of the motor 7 is 12V, the diameter of the motor rotating shaft 8 is 2mm-3mm, and the length is 14mm-16mm. The rotating magnet 9 is Nd2Fe 14 B and other metal compounds as the basis of NdFeB permanent magnet material, the performance grade is not less than N35; the length and width of the magnet tray 10 are slightly smaller than the distance between the two ends of the rotating magnet 9 blades, and the thickness of the magnet tray 10 is consistent with the thickness of the rotating magnet 9; a small hole with a depth of about 1.5 mm is drilled in the center of the magnet tray 10, and the diameter of the small hole is consistent with the diameter of the motor rotating shaft 8. The magnet tray 10 is connected to the motor rotating shaft 8 by an adhesive such as epoxy resin glue.

[0037] Further optimization scheme, the radius of the arc baffle at the end of the guide baffle 2 is 1.4mm-1.6mm, the position of the arc baffle is appropriately extended, and its center is located on the upper left or upper right side of the center of the pump chamber 1, and the horizontal distance from the center of the pump chamber 1 is 0.3mm-1.5mm, and the vertical distance is 1.8mm-3mm; the inlet channel 5 and the outlet channel 6 are of the same size, with a width of 1mm and a length of 5mm-7mm, and the upper end of the inlet channel 5 is 2.2mm-2.5mm away from the lower end of the outlet channel 6; the depth of the fluid channel composed of the inlet channel 5, the outlet channel 6 and the pump chamber 1 is 100μm-150μm, and the cross-sections of the inlet channel 5 and the outlet channel 6 are both rectangular.

[0038] A further optimization scheme is that the structure of the rotating magnet 9 is a four-leaf type, and the distance from its center to the center of the top of the blade is the same as the radius of the pump chamber 1, and the radius of the pump chamber 1 is 10mm-12mm; the top of the rotating magnet 9 is 0.8-1.2mm away from the bottom of the glass substrate 11; the thickness of the rotating magnet 9 is 1.8-2.2mm, and the number of magnets can be increased or decreased according to the maximum magnetization intensity of the nanomagnetic fluid.

[0039] Before the system is operated, nanomagnetic fluid is injected into the pump chamber 1; the motor 7 drives the rotating magnet 9 to perform uniform circular motion, and the nanomagnetic fluid is pumped from the liquid inlet 3 to the liquid outlet 4 under the action of magnetic attraction; as the medium in the cavity is pumped out, the nanomagnetic fluid will continue to be replenished from the liquid inlet 3 due to the pressure difference between the inside and outside of the pump chamber 1, and the outlet pressure of the micropump can be adjusted by changing the motor speed or the number of magnets. Example 1

[0040] like Figure 2 As shown, in this embodiment, the position of the guide baffle 2 should be appropriately extended, and the center of the end arc baffle is located at the upper right of the center of the pump chamber 1, with a horizontal distance of 0.5mm and a vertical distance of 2mm, so as to make full use of the pump chamber space, minimize the horizontal and vertical distances between the guide baffle 2 and the center of the pump chamber 1, and avoid the influence of the excessive extension of the guide baffle 2 on the pumping efficiency. According to the finite element simulation and experimental results, when the horizontal distance of the center of the end arc baffle of the guide baffle 2 is in the range of 0.3mm-1.5mm and the vertical distance is in the range of 1.8mm-3mm, the horizontal distance increases or decreases in proportion to the vertical distance, and the baffle position has little effect on the flow field. Therefore, within the above distance range, designing a larger fluid channel can effectively reduce the pumping resistance of the medium in the pump chamber 1 and improve the pumping efficiency.

[0041] The width, length and depth of the inlet channel 5 and the outlet channel 6 are all kept consistent, so that the medium can maintain a smoother flow, which helps to achieve uniform pressure distribution in the pump chamber 1 and improve the stability and accuracy of pumping. The consistent channel size can also simplify the design and manufacturing process of the micropump, which helps to improve the reliability of the system. The rotating magnet 9 has a four-leaf structure, and the distance from the center to the center of the blade tip is the same as the radius of the pump chamber 1. The top of the magnet is 1 mm away from the bottom of the glass substrate 11. The rotating magnet 9 is coaxial with the motor rotating shaft 8 and the central axis of the pump chamber 1 to ensure that the magnetic field can fully and evenly cover the fluid channel and improve the stability of pumping.

[0042] like Figure 4 , Figure 5 As shown in the figure, at the same speed, the outlet flow rate and pressure of the micro pump under the four-leaf magnet are higher than those of the three-leaf magnet and the five-leaf magnet. When the basic structure of the rotating magnet 9 is four-leaf, the system pumping efficiency can be effectively improved. Too few blades will cause the pumping flow rate and outlet pressure to drop, and easily cause uneven flow field and fluid pulsation; too many blades will cause additional friction and disturbance to the medium flow, increase the resistance in the pump cavity, and reduce the pumping efficiency.

[0043] In order to better use this embodiment, a magnet tray 10 is provided between the rotating magnet 9 and the motor 7, and is connected with the motor rotating shaft 8 by drilling, bonding, etc. Without the magnet tray, the magnet will be directly adsorbed on the motor rotating shaft, and form a local magnetic field in the pump cavity, which will change the magnetic force line path and density distribution, affect the motion trajectory and speed distribution of the pumped fluid, and reduce the system pumping efficiency; the magnet tray can reduce or isolate the force of the magnet on the rotating shaft.

[0044] In this embodiment, the nano-magnetic fluid medium micropump is made of PDMS material, and is made by using traditional soft lithography technology through four steps: mask production, micropump mold production, PDMS chip production, and micropump packaging and fixing. The micropump mold is made of transparent materials such as quartz glass sheets as the substrate, and uses materials with high resolution, high precision and high chemical stability such as SU-8 negative photoresist, and is made through processes such as substrate treatment, spin coating, soft baking, exposure, development, and hardening. The PDMS chip 12 is made of PDMS prepolymer and PDMS cross-linking agent in a ratio of about 10:1, and is made through steps such as mixing PDMS, reverse molding hardening, and demolding and punching.

[0045] Nano magnetic fluid is water-based or oil-based nano magnetic fluid, with an average particle size of less than 20nm, a particle concentration of 1wt%-10wt%, and magnetic particles of NiFe2O4, Ni 0.5 Zn 0.5 For soft magnetic materials such as Fe2O4, viscosity reducers can be added to oil-based nano magnetic fluids to reduce viscosity.

[0046] like Figure 6 , Figure 7 As shown in the figure, the velocity distribution at the outlet of the micropump shows a trend that the velocity increases as it approaches the center, and the pressure distribution is opposite to the velocity distribution, with higher pressure at the left and right ends close to the center line, and lower pressure as it moves toward the center. This distribution trend can effectively guide the fluid to accelerate toward the center, reduce the lateral diffusion of the fluid at the outlet, and help reduce the turbulence intensity and flow loss in the subsequent flow, thereby improving the efficiency and flow quality of the overall system.

[0047] like Figure 8 As shown in the figure, the shear rate distribution at the outlet of the micropump is high near the two ends of the center line and gentle in the middle, which is caused by the combined effect of the boundary layer effect and the magnetic field driving force. The nanomagnetic fluid is affected by friction on the wall, resulting in a decrease in flow velocity. The existence of the velocity gradient makes the shear rate near the wall area higher. The drive of the magnet is mainly concentrated on the two sides, which further increases the shear rate at both ends of the center line. A higher shear rate can effectively overcome the viscous resistance of the fluid, reduce the viscous loss near the wall, and help form a fast flow path. The gentle shear rate in the middle area also ensures the uniformity of the entire flow process.

[0048] Table 1 is a comparison of the performance parameters of the present invention and the prior art

[0049]

[0050] Prior art 1-4 are all magnetic fluid medium micro pumps. Prior art 1, prior art 3 and prior art 4 are rectangular parallelepiped pump chamber structures, matched with four coils or circular magnets, and prior art 2 is a double circular pump chamber structure, matched with double circular magnets. As can be seen from Table 1, the outlet flow rate of this embodiment can reach up to 226μL / min, and the outlet pressure can reach 1776Pa. Under the same technical conditions, compared with prior art 1-4, the micro pump of the present invention has been optimized in size and structure. The use of four-leaf magnets has significantly improved the system pumping flow rate and pressure.

[0051] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A nano-magnetic fluid medium micropump drive system, characterized in that: It comprises a pump chamber (1), a flow guide baffle (2), a liquid inlet (3), a liquid outlet (4), a liquid inlet channel (5), a liquid outlet channel (6), a motor (7), a rotating shaft (8), a rotating magnet (9), a magnet tray (10), a glass substrate (11), and a PDMS chip (12); wherein: The pump chamber (1), the flow guide baffle (2), the liquid inlet (3), the liquid outlet (4), the liquid inlet channel (5) and the liquid outlet channel (6) are designed in a PDMS chip (12), and the glass substrate (11) is arranged at the bottom of the PDMS chip (12); the basic structure of the pump chamber (1) is circular, the liquid inlet (3) and the liquid outlet (4) are arranged side by side on one side of the pump chamber (1), and the liquid inlet (3) is connected to the pump chamber (1) through the liquid inlet channel (5), and the liquid outlet (4) is connected to the pump chamber (1) through the liquid outlet channel (6); the liquid inlet channel (5), the liquid outlet channel (6) and the pump chamber (1) form a fluid channel, and a nano-magnetic fluid is arranged in the fluid channel; the flow guide baffle (2) is in an arc shape, the upper curve thereof is tangent to the liquid outlet channel (5), and the lower curve thereof is tangent to the liquid inlet channel (6), and the central angle between the two tangents is 0°; The rotating magnet (9) is fixed in a magnet tray (10) and arranged below the glass substrate (11); the magnet tray (10) is cooperatively connected to the motor (7); the motor rotating shaft (8) is coaxial with the rotating magnet (9) and the central axis of the pump chamber (1).

2. A nano-magnetic fluid medium micropump driving system according to claim 1, characterized in that: The radius of the arc baffle at the end of the guide baffle (2) is 1.4 mm-1.6 mm, the arc baffle is appropriately extended, the center of the arc baffle is located on the upper left or upper right side of the center of the pump chamber (1), the horizontal distance from the center of the pump chamber (1) is 0.3 mm-1.5 mm, and the vertical distance is 1.8 mm-3 mm.

3. A nano-magnetic fluid medium micropump driving system according to claim 1, characterized in that: The rotating magnet (9) has a four-leaf structure, the distance between its center and the center of the blade tip is the same as the radius of the pump chamber (1), and the top of the rotating magnet (9) is 0.8-1.2 mm away from the bottom of the glass substrate (11); the thickness of the rotating magnet (9) is 1.8-2.2 mm, and the number of magnets can be increased or decreased according to the maximum magnetization intensity of the nanomagnetic fluid.

4. A nano-magnetic fluid medium micropump driving system according to claim 1, characterized in that: The liquid inlet channel (5) and the liquid outlet channel (6) have the same size, with a width of 1 mm and a length of 5 mm to 7 mm. The upper end of the liquid inlet channel (5) is 2.2 mm to 2.5 mm away from the lower end of the liquid outlet channel (6).

5. A nano-magnetic fluid medium micropump driving system according to claim 1 or 4, characterized in that: The depth of the fluid channel formed by the liquid inlet channel (5), the liquid outlet channel (6) and the pump chamber (1) is 100 μm-150 μm.

6. A nano-magnetic fluid medium micropump driving system according to claim 1, 2 or 3, characterized in that: The radius of the pump chamber (1) is 10 mm to 12 mm.

7. A nano-magnetic fluid medium micropump driving system according to any one of claims 1 to 6, characterized in that: Before the system is operated, nano-magnetic fluid is first injected into the pump chamber (1); the motor (7) drives the rotating magnet (9) to perform uniform circular motion, and the nano-magnetic fluid is pumped from the liquid inlet (3) to the liquid outlet (4) under the action of magnetic attraction; as the medium in the chamber is pumped out, the nano-magnetic fluid will continue to be replenished from the liquid inlet (3) due to the pressure difference between the inside and outside of the pump chamber (1), and the outlet pressure of the micro pump can be adjusted by changing the motor speed or the number of magnets.

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