Electric field-viscoelastic micro-fluidic focusing nano-particle system with temperature controlled by dry ice

Abstract

The invention discloses an electric field-viscoelastic micro-fluidic focused nanoparticle system with temperature controlled by dry ice. The electric field-viscoelastic micro-fluidic focused nanoparticle system comprises a micro-fluidic chip, a PMMA (polymethyl methacrylate) transparent heat insulation layer, the dry ice, a viscoelastic micro-fluidic chip matched with the dry ice, an electric field and a visual experiment system. According to the method, temperature control, viscoelastic fluid and an external direct-current electric field are combined to control small-size nanoparticles, and the temperature field of the micro-fluidic chip is regulated and controlled through dry ice and PMMA thickness, so that the temperature rise of the channel and the chip caused by the Joule heating effect of the external direct-current electric field in the channel fluid is eliminated; further, stable and continuous focusing of the nanoparticles by a high-voltage electric field-viscoelastic microfluidic method is promoted. Meanwhile, the temperature field is regulated and controlled by the dry ice, so that the temperature-sensitive particles can be protected from being damaged by high temperature during operation. The high-voltage electric field-viscoelastic microfluidics using the dry ice to control the temperature can effectively focus the nano-particles at high flux under high electric field intensity, so that accurate control, focusing and enrichment of the small-size nano-particles are realized.

Description

Technical Field

[0001] This invention relates to temperature control of microfluidic chips and multi-physics field manipulation of nanoparticles, specifically to an electric field-viscoelastic microfluidic focusing nanoparticle system for temperature control using dry ice. Background Art

[0002] Continuous manipulation of nanoparticles has a wide range of applications, including biomedicine, pharmaceuticals, microbiology, hematology, and analytical chemistry. Suitable nanoparticle manipulation techniques can efficiently enrich nanoparticles and biomolecules such as proteins, DNA, and RNA. Traditional particle sorting and enrichment methods include centrifugation, capture, chromatography, and ultrafiltration, as well as combinations thereof. These methods sort particles based on size-density; however, they are cumbersome, have low throughput, are expensive, and require large amounts of fluid, thus limiting their application.

[0003] Microfluidic manipulation of particles has important applications in biomedicine and drug delivery. Developed microfluidic particle manipulation technologies mainly include passive and active microfluidics. Passive microfluidics primarily utilize the structure and fluid properties of the microfluidic channels themselves to manipulate particles, while active microfluidics introduces external physical fields to assist in particle manipulation. Furthermore, inertial migration and viscoelastic focusing based on microfluidics have been widely applied to focusing and separating micron / submicron particles. However, the viscoelastic force acting on nanoparticles decreases sharply, leading to poor focusing or even failure to focus. Efficient and high-throughput manipulation of nanoparticles for focusing is an urgent need and a key technical challenge in this field.

[0004] Manipulating particles within microfluidic channels by applying an external electric field is a technology that has been developed in recent years; however, it still faces many unresolved challenges. Early inertial microfluidics have proven insufficient for manipulating nanoscale particles, while viscoelastic microfluidics, which utilizes viscoelastic non-Newtonian fluids for particle manipulation, suffers from limitations in efficiently focusing particles smaller than 100 nm and insufficient flux. Therefore, combining an external electric field with viscoelastic microfluidics for focusing nanoparticles can integrate the advantages of high energy and fast response of the electric field with the advantages of elastic force manipulation, enabling the focusing of even smaller nanoparticles. However, manipulating small particles requires high voltage, inevitably introducing unnecessary external energy, which is converted into heat through the Joule heating effect, causing a rise in the temperature of the fluid within the microchannel and the microfluidic chip. This has a serious negative impact on nanoparticle focusing and may even damage temperature-sensitive particles. Therefore, developing suitable temperature control techniques and effectively combining them with high-voltage electric fields and viscoelastic microfluidics is crucial for manipulating even smaller nanoparticles and represents an urgent need and technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a dry ice-controlled electric field-viscoelastic microfluidic focusing system for nanoparticles. This invention, through the design of a dry ice-PMMA transparent thermal insulation layer-microfluidic chip structure, combined with high-voltage electric field-viscoelastic microfluidic technology, enables the focusing of nanoparticles as small as 20 nm and above. The temperature control and high-voltage electric field-viscoelastic nanoparticle focusing method designed in this invention can eliminate the harmful temperature rise caused by the Joule heating effect under high voltage, achieving stable focusing experiments on even smaller nanoparticles. This method has the advantages of simple operation, good temperature control, and protection of temperature-sensitive particles.

[0006] The objective of this invention is achieved through the following technical solution: According to a first aspect of this specification, a dry ice-controlled electric field-viscoelastic microfluidic focusing nanoparticle system is provided, comprising a microfluidic chip, a polymethyl methacrylate transparent heat insulation layer, dry ice, a high voltage power supply, a pumping system, and a microscopic imaging system, for balancing the Joule heating effect generated in the microfluidic chip by the applied high voltage electric field and adjusting the temperature of the microfluidic system. The microfluidic chip integrates a straight microchannel, and the working fluid is a viscoelastic fluid. A pumping system injects non-Newtonian fluid and nanoparticles into the chip channel. Hollow electrodes are installed at the inlet and outlet of the microchannel in the microfluidic chip. A transparent polymethyl methacrylate (PMMA) heat insulation layer is placed on the surface of the microfluidic chip. Dry ice is placed on the PMMA heat insulation layer. The high-voltage power supply provides a DC high-voltage electric field. The DC electric field and fluid pressure are used to drive a non-Newtonian fluid solution with a specific formulation based on the viscoelastic effect, achieving efficient and high-throughput focusing of nanoparticles with diameters as low as 20 nm and above. The lens of the microscopic imaging system is located on the side of the chip without dry ice for microscopic observation.

[0007] Furthermore, in the viscoelastic microfluidic chip, holes are punched at the chip outlet and inlet, and hollow metal needles are inserted as electrodes. A DC voltage is applied to the inlet and outlet electrodes connected to the microfluidic channel, thereby maintaining a DC electric field in the liquid within the channel.

[0008] Furthermore, the viscoelastic fluid operating within the viscoelastic microfluidic chip is a viscoelastic fluid with a concentration of less than 2 wt% polyethylene oxide completely dissolved in 0.01 mM phosphate buffer, with the addition of 0.1% Tween 20.

[0009] Furthermore, the straight microchannel has a rectangular cross-section with a height and width of 10-50 micrometers, and includes an inlet and an outlet. A non-Newtonian fluid is pumped into the chip using an injection pump at a certain inlet flow velocity to generate an inlet-outlet pressure difference, thus creating a velocity surface in the microfluidic channel.

[0010] Furthermore, the polymethyl methacrylate transparent heat insulation layer has a side that is smaller than the microfluidic chip surface and completely covers the microchannels inside the chip. The thickness of the transparent heat insulation layer should be adjusted according to the Joule heating inside the chip and the ambient temperature, so that it can both eliminate the chip temperature rise caused by Joule heating and prevent the fluid in the channels inside the chip from freezing and becoming unable to flow.

[0011] According to another aspect of the specification, a method for focusing nanoparticles in the system is also provided, comprising: Fabricate microfluidic channel structures and microfluidic chips with inlet and outlet hollow electrodes that meet the requirements; A non-Newtonian fluid containing dispersed nanoparticles is pumped into a microfluidic chip to ensure a constant and stable flow. A PMMA transparent heat insulation layer is placed between the chip's inlet and outlet electrodes; Dry ice is placed on top of a transparent PMMA insulation layer; A high-voltage DC electric field and a pressure-driven viscoelastic non-Newtonian fluid are used to focus nanoparticles.

[0012] Furthermore, in the nanoparticle focusing process, the applied high-voltage DC electric field is selected according to the size of the nanoparticles, and a DC electric field of 800 V / cm to 2500 V / cm with the same or opposite flow direction is applied to particles of 20 to 100 nm.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention provides an electric field-viscoelastic microfluidic focusing nanoparticle system with dry ice temperature control, which can efficiently focus particles as small as 20 nm; 2. This invention eliminates the system temperature rise caused by the introduction of external energy through an applied physical field in active microfluidics technology by using dry ice to control the temperature of the microfluidic chip; 3. This invention introduces a PMMA transparent heat insulation layer of a certain thickness, which can adjust the appropriate operating temperature of the microfluidic chip and avoid abnormal temperature rise and fluid freezing caused by dry ice; 4. This invention can effectively protect temperature-sensitive nanoparticles during operation by using a suitable microfluidic chip temperature; 5. This invention has the advantages of high compatibility with active microfluidics technology, low cost, and convenient operation. Attached Figure Description

[0014] Figure 1 A schematic diagram showing the relative positions of dry ice, a PMMA transparent thermal insulation layer, and a microfluidic chip with hollow metal electrodes in an electric field-viscoelastic microfluidic focusing nanoparticle system for dry ice temperature control, provided as an embodiment of the present invention. Figure 2A schematic diagram of a microfluidic method for efficiently and efficiently focusing nanoparticles using a combination of DC electric field and pressure to drive non-Newtonian fluid, according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a channel structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a microfluidic chip channel structure (half of a symmetrical structure) provided in an embodiment of the present invention.

[0015] The numbers on the map are: 1. DC power supply; 2. Conduit; 3. Dry ice; 4. Hollow metal electrode; 5. Fluid channel; 6. PMMA transparent thermal insulation layer; 7. Microfluidic chip; 8. Non-Newtonian fluid; 9. Fluid pressure source; 10. Grounding; 51. Channel inlet; 52. Rectangular channel section; 53. Outlet expansion section; 54. Channel outlet; 55. Hollow metal electrode inlet; 56. Hollow metal electrode hole. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate understanding of the present invention and are not intended to limit it in any way. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0017] like Figure 1 As shown, this embodiment provides a dry ice-controlled electric field-viscoelastic microfluidic focusing nanoparticle system, including a microfluidic chip, a transparent heat insulation layer of polymethyl methacrylate (PMMA), a dry ice high-voltage power supply, a pumping system, and a microscopic imaging system, used to balance the Joule heating effect generated by the applied high-voltage electric field in the microfluidic chip and regulate the temperature of the microfluidic system; The microfluidic chip integrates a straight microchannel, and the working fluid is a viscoelastic fluid. A non-Newtonian fluid and nanoparticles are injected into the chip channel through a pumping system. Hollow electrodes are installed at the inlet and outlet of the microchannel in the microfluidic chip. A transparent polymethyl methacrylate (PMMA) heat insulation layer is disposed on the surface of the microfluidic chip. Dry ice is placed on the PMMA heat insulation layer. The high-voltage power supply is used to provide a DC high-voltage electric field. The DC electric field and fluid pressure are used to drive a non-Newtonian fluid solution with a specific formulation based on the viscoelastic effect, so as to achieve efficient and high-throughput focusing of nanoparticles with diameters as low as 20 nm and above. The lens of the microscopic imaging system is located on the side of the chip without dry ice for microscopic observation.

[0018] The dry ice-controlled temperature electric field-viscoelastic microfluidic focusing nanoparticle system includes a specific configuration and size design of dry ice and PMMA transparent heat insulation layer, adapted to the high voltage electric field-viscoelastic microfluidic focusing nanoparticle method, to achieve effective cooling of the fluid in the microfluidic chip and its microchannel, and to eliminate the negative impact of the Joule heating effect caused by the external electric field on the focusing of nanoparticles. The dry ice physically cools the microfluidic chip. A transparent heat insulation layer separates the dry ice and the microfluidic chip. The dry ice and the transparent heat insulation layer are placed on one side of the chip, while the other side of the chip is used for visualization. The dry ice can be of any shape and size, but it must be compatible with the size of the microfluidic chip. The transparent material of the dry ice allows light to pass through.

[0019] The transparent heat insulation layer can be made of PMMA or other materials. It has moderate thermal resistance and good transparency. The side that contacts the surface of the microfluidic chip is smaller than the microfluidic chip and completely covers the microchannels inside the chip. The thickness of the transparent heat insulation layer should be adjusted according to the Joule heating inside the chip and the ambient temperature so that it can eliminate the chip temperature rise caused by Joule heating without causing the fluid in the channels inside the chip to freeze and become unable to flow.

[0020] The viscoelastic microfluidic method includes a microfluidic chip with inlet and outlet hollow electrodes and a specific microchannel structure, as well as the manipulation of nanoparticles using viscoelastic fluid.

[0021] The Joule heating effect of the applied high-voltage electric field in the channel caused the chip temperature to rise, and the combined effect of this temperature and the working fluid pressure caused particle focusing instability.

[0022] The method can control nanoparticles with sizes as low as 20 nm and above, but has no restrictions on the material and shape of the nanoparticles.

[0023] The viscoelastic microfluidic technology uses a non-Newtonian fluid with certain viscoelastic properties as the working fluid, capable of supporting high-voltage DC systems above 1000 V and visualization microscopic imaging systems. The non-Newtonian fluid is a viscoelastic fluid with a specific polymer concentration. The nanoparticles to be focused are dispersed in the non-Newtonian fluid, with a low concentration of electrolyte salt solution and an appropriate amount of surfactant added. The working fluid used in the viscoelastic microfluidic technology is a non-Newtonian fluid with certain viscoelastic properties, such as a PEO solution. A pressure difference between the inlet and outlet is generated by pumping the non-Newtonian fluid into the chip using a specific inlet flow velocity, creating a specific flow field in the microfluidic channel.

[0024] The microfluidic chip with inlet and outlet hollow electrodes and a specific microfluidic channel structure includes a microfluidic channel with a specific shape, a chip of any material, and hollow metal electrodes connected to the inlet and outlet of the microfluidic channel within the chip.

[0025] Specifically, Figure 1 The diagram illustrates the relative positions of dry ice, a transparent PMMA insulating layer, and a microfluidic chip with hollow metal electrodes in a dry ice-controlled temperature-field-viscoelastic microfluidic nanoparticle focusing system. In this embodiment, a rectangular PMMA (10 mm × 18 mm × 20 mm) is placed on the surface of a straight-channel microfluidic chip, and a cylindrical dry ice is placed on top of the PMMA. A high-voltage DC electric field and pressure-driven viscoelastic non-Newtonian fluid are applied together to focus the nanoparticles at a certain flow rate. The microfluidic chip has a rectangular cross-section channel with a cross-sectional height and width of 50 μm and a length of 2 cm. The working fluid is a viscoelastic fluid with a concentration of 1.2 wt% polyethylene oxide (PEO, 600 kDa) completely dissolved in 0.01 mM phosphate buffer. 0.1% Tween 20 is added to the solution to reduce particle adhesion and aggregation. In this embodiment, 20 nm polystyrene (PS) particles are used. By combining a -800 V / cm DC electric field ("-" indicates that the DC electric field direction is opposite to the flow direction) and pressure drive, 100 nm particles can be focused in the channel. By controlling the chip temperature with dry ice and a PMMA transparent thermal insulation layer, and by combining a -2000 V / cm DC electric field and pressure drive (average flow velocity of 6 mm / s in a rectangular straight channel), 20 nm particles can be focused in the channel.

[0026] Figure 2 This diagram illustrates a microfluidic method for efficiently and efficiently focusing nanoparticles using a non-Newtonian fluid driven by a combined DC electric field and pressure. In this embodiment, a DC electric field and pressure are jointly applied in a straight-channel microfluidic chip to drive the non-Newtonian fluid to focus nanoparticles. Microchannels are fabricated on a silicon wafer using soft photolithography to form a mold according to design drawings. PDMS is then cast onto the mold and cured at 70°C. Holes are drilled at the chip's inlet and outlet, and hollow metal needles are inserted as electrodes. A rectangular substrate of PDMS is treated with plasma and subsequently heated to form the microfluidic chip. A long PTFE tube is connected to the end of each hollow metal electrode, and a high-precision injection pump is used for fluid drive. The outlet is connected to a waste liquid cylinder. The electric field is provided by a signal generator connected to a high-voltage amplifier, and the positive and negative terminals of the voltage output wires are connected to the metal electrodes at the chip's inlet and outlet using alligator clips.

[0027] Figure 3 The diagram shows a straight channel structure with a cross-sectional height and width of 50 micrometers and a length of 2 centimeters. The microchannel is designed as a rectangular channel, including an inlet, an outlet, and expansion regions at both ends for observation. This microchannel is integrated into a microfluidic chip made of polydimethylsiloxane (PDMS) using standard soft lithography.

[0028] Figure 4 The diagram shows a microfluidic chip structure with a straight microchannel having a cross-sectional height and width of 50 micrometers and a length of 2 centimeters. Since the microfluidic chip has a symmetrical structure, half of the symmetrical structure is shown for ease of demonstration and observation. The microchannel is designed as a straight rectangular channel, including an inlet, an outlet, and expansion regions at both ends for observation. This microchannel is integrated into a microfluidic chip made of polydimethylsiloxane (PDMS) using standard soft lithography.

[0029] The method for efficiently and efficiently focusing nanoparticles using a combination of DC electric field and pressure to drive non-Newtonian fluid includes the following steps: Fabricate microfluidic channel structures and microfluidic chips with inlet and outlet hollow electrodes that meet the requirements; A non-Newtonian fluid containing dispersed nanoparticles is pumped into a microfluidic chip and flows stably at a certain speed. A PMMA transparent heat insulation layer is placed between the chip's inlet and outlet electrodes; Dry ice is placed on top of a transparent PMMA insulation layer; A high-voltage DC electric field is applied to control the focusing of nanoparticles.

[0030] The basic principles, main features and beneficial effects of the present invention have been described in detail above. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions and equivalent substitutions made without departing from the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dry ice-controlled temperature electric field-viscoelastic microfluidic focusing nanoparticle system, characterized in that, It includes a microfluidic chip, a polymethyl methacrylate transparent heat insulation layer, dry ice, a high-voltage power supply, a pumping system, and a microscopic imaging system, which are used to balance the Joule heating effect generated by the applied high-voltage electric field in the microfluidic chip and regulate the temperature of the microfluidic system. The microfluidic chip integrates a straight microchannel, and the working fluid is a viscoelastic fluid. A pumping system injects non-Newtonian fluid and nanoparticles into the chip channel. Hollow electrodes are installed at the inlet and outlet of the microchannel in the microfluidic chip. A transparent polymethyl methacrylate (PMMA) heat insulation layer is placed on the surface of the microfluidic chip. Dry ice is placed on the PMMA heat insulation layer. The high-voltage power supply provides a DC high-voltage electric field. The DC electric field and fluid pressure are used to drive a non-Newtonian fluid solution with a specific formulation based on the viscoelastic effect, achieving efficient and high-throughput focusing of nanoparticles with diameters as low as 20 nm and above. The lens of the microscopic imaging system is located on the side of the chip without dry ice for microscopic observation.

2. The system according to claim 1, characterized in that, In the viscoelastic microfluidic chip, holes are punched at the chip outlet and inlet, and hollow metal needles are inserted as electrodes. A DC voltage is applied to the inlet and outlet electrodes connected to the microfluidic channel, thereby maintaining a DC electric field in the liquid within the channel.

3. The system according to claim 1, characterized in that, The viscoelastic fluid operating within the viscoelastic microfluidic chip is a viscoelastic fluid with a concentration of less than 2 wt% polyethylene oxide completely dissolved in 0.01 mM phosphate buffer, with the addition of 0.1% Tween 20.

4. The system according to claim 1, characterized in that, The straight microchannel has a rectangular cross-section with a height and width of 10-50 micrometers. It includes an inlet and an outlet. A non-Newtonian fluid is pumped into the chip using a pre-set inlet flow rate via an injection pump to generate an inlet-outlet pressure difference, thus creating a velocity surface in the microfluidic channel.

5. The system according to claim 1, characterized in that, The polymethyl methacrylate transparent heat insulation layer has a side that is smaller than the microfluidic chip and completely covers the microchannels inside the chip. The thickness of the transparent heat insulation layer is adjusted according to the Joule heating inside the chip and the ambient temperature, so that it can eliminate the chip temperature rise caused by Joule heating, and prevent the fluid in the channels inside the chip from freezing and becoming unable to flow.

6. A method for focusing nanoparticles based on the system according to any one of claims 1-5, characterized in that, include: Fabricate microfluidic channel structures and microfluidic chips with inlet and outlet hollow electrodes that meet the requirements; A non-Newtonian fluid containing dispersed nanoparticles is pumped into a microfluidic chip to ensure a constant and stable flow. A PMMA transparent heat insulation layer is placed between the chip's inlet and outlet electrodes; Dry ice is placed on top of a transparent PMMA insulation layer; A high-voltage DC electric field and a pressure-driven viscoelastic non-Newtonian fluid are used to focus nanoparticles.

7. The method according to claim 6, characterized in that, The high-voltage DC electric field applied in the nanoparticle focusing process is selected according to the size of the nanoparticles. A DC electric field of 800 V / cm to 2000 V / cm with the same or opposite flow direction is applied to particles of 20 to 100 nm.

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