A continuously driven microfluidic pump device utilizing liquid evaporation effect

Abstract

The present invention discloses a continuously driven microfluidic pump device utilizing the liquid evaporation effect, comprising: a camera, an isolation cover, a microfluidic chip, a heating plate, a bottom layer, a humidifier, and a thermo-hygrometer; the camera is connected to the isolation cover, and the bottom layer is provided with a microfluidic chip; a heating plate is provided below the microfluidic chip; a humidifier is provided on the left side of the microfluidic chip, and a thermo-hygrometer is provided on the right side; the isolation cover and the bottom layer cover the microfluidic chip heating plate, humidifier, and hygrometer to form a closed space; wherein the microfluidic chip comprises an evaporation layer, a microfluidic channel layer, and an adhesive layer; the microfluidic pump device proposed by the present invention utilizes the evaporation effect of the liquid as a driving force to achieve precise, continuous, and efficient driving of liquid flow, and has great application value in the field of microfluidic technology.

Description

Technical Field

[0001] The present invention relates to the field of biochemical analysis instruments and technologies, and in particular to a continuously driven microfluidic pump device utilizing liquid evaporation effect. Background Art

[0002] With the development of micromachining technology, microfluidics technology is widely used in medical applications such as cell sorting, cell analysis, protein crystallization, immunoassay, DNA analysis, etc. Fluid processing and transmission are very important parts of the above applications, so continuous and high-precision pumping of liquids can greatly improve the operating efficiency of the equipment.

[0003] Microplates are common tools used in laboratories for clinical diagnosis and are often used for immunoassay analysis. During immunoassay analysis, the measurement results of analytes in microplates are often related to the rate of material exchange. However, the reaction of substances in microplates mainly achieves material exchange through diffusion, which makes the detection of low-concentration analytes more time-consuming. In addition, long-term measurements can easily cause sample evaporation from the microfluidics, affecting the test results. During cell culture, cell culture fluid needs to be continuously and slowly transported to the culture area. Conventional pumping devices are prone to introducing additional bubbles at the connection between the pipe and the equipment. Bubbles in the culture fluid are toxic to cells, damaging cell membranes and causing cell death. Therefore, researchers urgently need micropumps that can pump liquids at low speeds and accurately without introducing excess bubbles. In existing technologies, microfluidic pumping is often achieved through methods based on pneumatic pressure, electroosmosis, or piezoelectricity. These traditional methods all rely on external forces to push the sample solution to the target area to achieve liquid pumping. Although these active delivery methods can effectively regulate the pumping rate of the liquid, they still have many negative effects. For example, the pumping process can easily introduce unnecessary bubbles, affecting experimental results; there is a minimum sample volume during pumping, which makes it difficult to pump extremely small amounts of liquid. In addition, devices based on centrifugal force, surface acoustic waves, or micromechanical actuation have gradually emerged, but most of these devices are bulky, severely limiting their portability. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a continuously driven microfluidic pump device that utilizes the liquid evaporation effect to solve the problems existing in the background technology. By using evaporation as the driving force, the liquid can produce a continuous flow in the microfluidic channel, thereby realizing continuous and precise driving of the liquid. The device can be widely used in micro-devices such as microreactors, microanalyzers, microfluidic chips, and biochips.

[0005] Technical solution: The present invention discloses a continuously drivable microfluidic pump device utilizing the liquid evaporation effect, characterized in that it comprises: a camera (1), an isolation cover (2), a microfluidic chip (3), a heating plate (4), a bottom layer (5), a humidifier (6), and a thermometer and hygrometer (7);

[0006] The camera (1) is connected to the isolation cover (2); the bottom layer (5) is provided with a microfluidic chip (3); a heating plate (4) is provided below the microfluidic chip (3); a humidifier (6) is provided on the left side of the microfluidic chip (3), and a thermometer and hygrometer (7) is provided on the right side;

[0007] The isolation cover (2) and the bottom layer (5) cover the microfluidic chip (3), the heating plate (4), the humidifier (6), and the hygrometer (7) to form a closed space.

[0008] The microfluidic chip (3) includes an evaporation layer (31), a microfluidic channel layer (32) and an adhesive layer (33).

[0009] Furthermore, the isolation cover (2) is composed of a top plate (21) and surrounding baffles (22), all of which are made of transparent PMMA material; the flow of liquid in the microfluidic chip (3) can be observed through the top plate (21); four heating plates (221) are attached to the baffle (22), and the four heating plates are connected in parallel to form a whole, which can heat the closed environment in the isolation cover, and the temperature of the closed environment in the isolation cover can be controlled by changing the input power corresponding to the heating plates (221).

[0010] Furthermore, the evaporation layer (31) is made of filter paper and is placed in the outlet area (324), absorbing the liquid from the inlet area (321) and evaporating it to the outside;

[0011] The microfluidic channel layer (32) is made of PDMS and consists of an inlet area (321), a calibration area (322), a detection area (323) and an outlet area (324); wherein the inlet area (321) is circular, runs through the microfluidic channel layer (32) from top to bottom, and allows liquid to enter the microfluidic channel layer (32); the calibration area (322) is located outside the spiral channel, where the fluid velocity is observed; the detection area (323) is rectangular, and is used to place related detection devices; the outlet area (405) is circular, runs through the microfluidic channel layer (32) from top to bottom, and is the placement area of ​​the evaporation layer (31);

[0012] The adhesive layer (33) is made of pressure-sensitive adhesive and is composed of acrylic ester. It is bonded to the microfluidic channel layer (32) and the evaporation layer (31) under pressure to form a whole, thereby preventing the liquid in the microfluidic channel layer (32) from leaking out.

[0013] Furthermore, the heating plate (4) includes a heating wire (401) and a temperature sensor (402); the heating wire 401 and the temperature sensor (402) are spiral-shaped and closely attached to the outlet area (324), and are used to heat the evaporation layer (31) located in the outlet area (324) and stabilize the temperature value.

[0014] Furthermore, the humidifier (6) is an atomizing humidifying device that humidifies the surrounding environment.

[0015] Furthermore, the hygrometer (7) is a thermo-hygrometer that can collect, transmit and display the temperature and humidity values ​​of the surrounding environment.

[0016] The method for using a microfluidic pump device that can be continuously driven by liquid evaporation effect according to the present invention comprises the following steps:

[0017] (1) Calibrate the microfluidic pump device;

[0018] (2) Drop the liquid into the inlet area. Under the action of capillary force, the liquid will enter the calibration area and the detection area in turn, and finally reach the outlet area, evaporating to the outside through the evaporation layer. The evaporation layer is made of fast filter paper, which contains a large number of capillaries. When the liquid on the surface of the filter paper evaporates to the outside, a gas-liquid interface will be formed on the surface of the evaporation layer. The pressure in the capillary tube under the interface decreases, generating water absorption force, pushing the liquid in the tube to the surface of the evaporation layer.

[0019] (3) Changing the temperature of the evaporation layer to adjust the evaporation rate of the liquid on its surface, thereby controlling the pumping rate of the liquid in the microfluidic channel.

[0020] Furthermore, the step (1) is specifically as follows:

[0021] (11) Adding deionized water to the inlet area, so that the deionized water fills the microfluidic channel layer 32 and reaches the outlet area, so that the evaporation layer is completely soaked;

[0022] (12) Add density-matched tracer particles to the inlet area, place the microfluidic chip on the experimental platform, focus the camera on the center of the calibration area, and connect the power supply to power the device;

[0023] (13) Adjust the operating power of the heating plate to ensure that the temperature at the bottom of the evaporation layer is always stable at 22°C-24°C;

[0024] (14) Start the temperature control system consisting of the heating plate and the thermometer and hygrometer, adjust the power of the heating plate around the isolation cover, and ensure that the closed environment temperature is stable at 22°C-24°C;

[0025] (15) Start the humidity control system consisting of a humidifier and a thermometer and hygrometer, adjust the operating power of the humidifier, and ensure that the humidity in the closed environment is stable at 50%-55%;

[0026] (16) Start the camera to capture images of the calibration area, record 10 times with a length of 1 minute at a frame rate of 10 to 20 Hz, and record three times continuously;

[0027] (17) Use MATLAB to record and process the video and calculate the movement speed of particles in the liquid;

[0028] (18) Adjust the power output, increase the temperature of the heating plate by 2°C, and stabilize the temperature value. Repeat steps (14)-(18) until the temperature reaches 50°C;

[0029] (19) The above data were processed and the linear relationship between the temperature of the evaporation layer and the liquid flow rate in the microfluidic channel was plotted as the calibration curve of the device.

[0030] Furthermore, the step (3) of changing the temperature of the evaporation layer includes: controlling the temperature of the heating plate and the temperature of the environment surrounding the microfluidic chip.

[0031] Furthermore, in step (17), the recorded video is processed by a PTV algorithm.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention designs a continuously drivable microfluidic pump device and method using the liquid evaporation effect, using evaporation as a driving force to drive the flow of liquid in the microfluidic chip, achieving precise regulation of the liquid rate without introducing unnecessary bubbles, thereby overcoming the disadvantages of traditional peristaltic pumps.

[0033] (2) The present invention uses a PCB substrate as the positive mold of the microfluidic chip, which is low-cost, simple to manufacture, and reusable. In addition, the evaporation layer in the microfluidic chip is made of filter paper, and the adhesive layer is made of pressure-sensitive adhesive, which can be manufactured by simple cutting.

[0034] (3) The present invention designs a microfluidic channel layer with a spiral pattern, which is composed of an inlet area, an observation area, a detection area, and an evaporation area, and realizes the functions of liquid collection, flow rate observation, target detection, and liquid evaporation. In addition, due to the limited volume of the microfluidic channel layer, the spiral pattern design maximizes the length of the liquid flow channel while avoiding the presence of corners in the channel that hinder liquid flow.

[0035] (4) The present invention proposes a continuously drivable microfluidic pump device that utilizes the liquid evaporation effect. The device has a self-cleaning function. By means of the evaporation of the liquid, impurities in the microfluidic channel are transported to the evaporation layer to complete the cleaning of the chip. In addition, the evaporation layer can be disassembled and replaced at will, which makes the service life of the device good. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 An exploded view of the device of the present invention;

[0037] Figure 2 Schematic diagram of liquid drive of the device of the present invention;

[0038] Figure 3 Dimensional drawings of the key components of the present invention;

[0039] Figure 4 A schematic diagram of the isolation cover of the present invention;

[0040] Figure 5 An exploded view of the microfluidic chip of the present invention;

[0041] Figure 6 A schematic diagram of the evaporation layer of the present invention;

[0042] Figure 7 A structural diagram of the microfluidic channel layer of the present invention;

[0043] Figure 8 A schematic diagram of the adhesive layer of the present invention;

[0044] Figure 9 A schematic diagram of a heating plate of the present invention;

[0045] Figure 10 Flowchart of the method for manufacturing the microfluidic chip of the present invention;

[0046] Figure 11 The temperature control block diagram of the present invention;

[0047] Figure 12 Humidity control block diagram of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0049] like Figure 1 As shown, an embodiment of the present invention provides a continuously drivable microfluidic pump device utilizing the liquid evaporation effect, characterized in that it includes: a camera 1, an isolation cover 2, a microfluidic chip 3, a heating plate 4, a bottom layer 5, a humidifier 6, and a thermo-hygrometer 7;

[0050] The camera 1 is connected to the isolation cover 2, and the bottom layer 5 is provided with a microfluidic chip 3; a heating plate 4 is provided below the microfluidic chip 3; a humidifier 6 is provided on the left side of the microfluidic chip 3, and a thermometer and hygrometer 7 is provided on the right side;

[0051] The isolation cover 2 and the bottom layer 5 cover the microfluidic chip 3, the heating plate 4, the humidifier 6, and the hygrometer 7 to form a closed space to prevent external environmental factors from interfering with the detection of the device.

[0052] The microfluidic chip 3 includes an evaporation layer 31 , a microfluidic channel layer 32 and an adhesive layer 33 .

[0053] Isolation cover 2 Figure 4As shown, the device consists of a top plate 21 and surrounding baffles 22, all made of transparent PMMA. The top plate 21 is highly transparent, allowing researchers to observe the flow of liquid within the microfluidic chip 3 through it. Four heating plates 221 are attached to the surrounding baffles 22. These four heating plates are connected in parallel to heat the sealed environment within the isolation enclosure. By varying the input power to the heating plates 221, the temperature of the sealed environment within the isolation enclosure can be controlled.

[0054] The recommended overall dimensions of the microfluidic chip 3 are 64mm x 75mm. Excessive dimensions increase the sensor's size, while undersized dimensions shorten the fluid channel path, hindering flow rate control. The recommended diameter of the inlet region 321 is 2mm, the detection region 323 is 6mm x 4mm, and the outlet region 324 is 16mm. The recommended width of the remaining microchannels is 0.2mm, and the recommended height is 0.07mm. A narrower channel width increases the difficulty of fabricating the channel layer, while a wider channel width can easily cause the microfluidic channel layer 33 to collapse, compromising device performance.

[0055] The exploded diagram of the microfluidic chip 3 is as follows Figure 5 As shown, it is rectangular in top view, with a recommended size of 64mm×76mm, and is composed of an evaporation layer 31, a microfluidic channel layer 32 and an adhesive layer 33. Figure 6 As shown, the recommended diameter is 14 mm, and the material is fast filter paper, which is placed at the outlet area 324 of the microfluidic channel layer 32. The rich hydrophilic groups and a large number of capillaries in the filter paper spontaneously absorb the liquid from the microchannel and evaporate it to the outside, forming a continuous renewal and flow of sweat. Figure 7 As shown, it is composed of an inlet area 321, a calibration area 322, a detection area 323 and an outlet area 324. The material is polydimethylsiloxane (PDMS) with high light transmittance. The inlet area 321 is circular with a recommended diameter of 2 mm. It runs through the microfluidic channel layer 32 from top to bottom. The liquid enters the microfluidic channel layer 32 through the inlet area 321, passes through the calibration area 322 and the detection area 323 in sequence, and finally reaches the outlet area 324, and evaporates to the outside through the evaporation layer 31; the calibration area 322 is located at the outermost side of the spiral channel, and the liquid passes through multiple turns of the spiral channel as The buffer makes the flow rate of the liquid uniform in the calibration area 322 and the detection area 323. Therefore, the calibration area 322 is used to observe the liquid flow rate and generate a calibration equation for the liquid flow rate in the microfluidic channel layer 32 and the temperature at the evaporation layer 31. The detection area 323 is rectangular and is used to place a detection device (such as a colorimetric device, an electrochemical detection electrode, etc.) to measure the concentration of the marker in the liquid and other related information. The outlet area 324 is circular with a recommended diameter of 16 mm, which is slightly larger than the evaporation layer 31. It runs through the microfluidic channel layer 32 from top to bottom and is used to place the evaporation layer 31. The adhesive layer 33 is as shown in FIG. Figure 8As shown, the adhesive layer 33 is rectangular, with recommended dimensions of 64 mm x 76 mm. It is made of pressure-sensitive adhesive and serves to bond the microfluidic channel layer 32 to the evaporation layer 31. The inlet area 321 and outlet area 324 of the microfluidic channel layer 32 are vertically continuous, while the remaining microfluidic channels are not vertically continuous, forming upward grooves. Therefore, the gap between the adhesive layer 33 and the microfluidic channel layer 32 forms a microfluidic channel through which liquid flows. Furthermore, the adhesive layer 33 can be integrally bonded to the microfluidic channel layer 32 and the evaporation layer 31 with just a slight application of pressure, without the need for additional activation conditions such as heat, water, or solvents.

[0056] The microfluidic channel layer can be prepared by a variety of methods, such as 3D printing, photolithography, etc., and different methods can be selected according to different materials. The preferred material of this patent is PDMS. In addition, the evaporation layer 31 and the adhesive layer 33 can be prepared by simple cutting. The process flow chart of the microfluidic chip manufacturing method is as follows: Figure 10 shown.

[0057] The specific preparation process of the microfluidic chip is as follows:

[0058] (S1) Making a positive mold for a microfluidic chip. The shape of the positive mold is opposite to the shape of the microfluidic channel. It can be made by precision CNC, photolithography, 3D printing, laser engraving, etc. In this patent, a PCB board is used as the bottom positive mold. The PCB board is surrounded by a baffle. After being thoroughly cleaned with deionized water, PDMS is prepared for pouring.

[0059] (S2) Liquid PDMS and pre-curing agent were thoroughly mixed in a ratio of 10:1, poured onto the positive mold of the microfluidic chip, and after vacuum degassing, placed in an oven and cured at 70°C for 2 hours.

[0060] (S3) Carefully peel off the cured PDMS from the male mold to complete the demolding.

[0061] (S4) Punching holes at the liquid inlet and outlet positions of the microfluidic channel layer using a puncher, and the microfluidic channel layer is prepared.

[0062] (S5) Cutting the filter paper and the pressure-sensitive adhesive to obtain an evaporation layer and an adhesive layer.

[0063] (S6) The evaporation layer, the microfluidic channel layer and the bonding layer are arranged in a Figure 5 A 0.5 kg weight is used to press on top of the layers for 2 hours to make the layers tightly bonded, and the microfluidic chip is completed.

[0064] Heating plate 4 Figure 9As shown, it consists of a heating filament 401 and a temperature sensor 402, using PI as the substrate and prepared using inkjet printing technology. The heating filament 401 and temperature sensor 402 are spiral-shaped and closely attached to the outlet area 324. They are slightly larger than the outlet area 324, with a recommended line width of 200μm. The heating filament has a starting radius of 6mm, an ending radius of 12mm, and a number of turns of 2. The temperature sensor has a starting radius of 6mm, an ending radius of 10mm, and a number of turns of 1.5. The heating filament 401 and temperature sensor 402 form a constant temperature control system. The temperature sensor 402 is used to detect the temperature at the outlet area 324. When the temperature is lower than the set value, the heating filament 401 heats up. When the temperature reaches the set value, the heating filament 401 stops heating, stabilizing the temperature at a certain value.

[0065] The bottom plate 5 is made of PMMA material and is the substrate for carrying the isolation cover 2 , the microfluidic chip 3 , the humidifier 6 and the thermo-hygrometer 7 .

[0066] The humidifier 6 humidifies the enclosed space, adjusts the air humidity and stabilizes it at a certain value.

[0067] Thermohygrometer 7 measures the temperature and humidity of the enclosed space formed by the base plate 7 and the isolation cover 2. It is used in conjunction with the heating plate 221 on the isolation cover 2 to adjust the temperature in the isolation cover to a stable value; it is used in conjunction with the humidifier 6 to adjust the humidity in the isolation cover to a stable value.

[0068] The present invention also provides a method for using a continuously drivable microfluidic pump device utilizing a liquid evaporation effect, comprising the following steps:

[0069] (1) Calibrate the microfluidic pump device as follows:

[0070] (11) Adding deionized water to the inlet area, so that the deionized water fills the microfluidic channel layer 32 and reaches the outlet area, so that the evaporation layer is completely soaked;

[0071] (12) Add density-matched tracer particles to the inlet area, place the microfluidic chip on the experimental platform, focus the camera on the center of the calibration area, and connect the power supply to power the device;

[0072] (13) Adjust the operating power of the heating plate to ensure that the temperature at the bottom of the evaporation layer is always stable at 22°C-24°C;

[0073] (14) Start the temperature control system consisting of the heating plate and the thermometer and hygrometer, adjust the power of the heating plate around the isolation cover, and ensure that the closed environment temperature is stable at 22°C-24°C;

[0074] (15) Start the humidity control system consisting of a humidifier and a thermometer and hygrometer, adjust the operating power of the humidifier, and ensure that the humidity in the closed environment is stable at 50%-55%;

[0075] (16) Start the camera to capture images of the calibration area, record 10 times with a length of 1 minute at a frame rate of 10 to 20 Hz, and record three times continuously;

[0076] (17) Use MATLAB to record and process the video and calculate the moving speed of particles in the liquid; the processing of the recorded video is implemented by the PTV algorithm. Specifically, it includes four steps: preprocessing, particle identification, particle matching, and velocity vector calculation. Preprocessing: Due to circuit noise, optical system errors, etc., image distortion or blurring may occur. Preprocessing can remove noise and background images, perform sub-pixel interpolation on the image, and improve accuracy. Particle identification: The size and brightness of the particles scattered into the flow field are different. When the number of particles is too large, it is very easy to have continuous overlapping particle images. It is necessary to identify the particles in the image. Related methods include single threshold method, digital mask method, and dynamic threshold method. Particle matching: After identifying the particles in the images of two adjacent frames, particle matching is required. Only after particle matching can the movement status of the same particle in the two frames be determined. The recommended method is the nearest neighbor method. Velocity vector calculation: After matching the particles in the images of two adjacent frames, the movement direction and distance of the particles in the flow field can be obtained. The time interval between the two adjacent frames is fixed, and the movement speed of the particles in the flow field can be calculated.

[0077] Particle tracer velocimetry (PTV) scatters tracer particles into the flow field, uses an imaging system to capture two or more exposures of the particle images, and uses image processing technology to analyze the particle images to obtain the flow conditions of the flow field. It has the advantages of high precision and non-interference measurement.

[0078] (18) Adjust the power output, increase the temperature of the heating plate by 2°C, and stabilize the temperature value. Repeat steps (14)-(18) until the temperature reaches 50°C;

[0079] (19) The above data were processed and the linear relationship between the temperature of the evaporation layer and the liquid flow rate in the microfluidic channel was plotted as the calibration curve of the device.

[0080] (2) Drop the liquid into the inlet area. Under the action of capillary force, the liquid will enter the calibration area and the detection area in turn, and finally reach the outlet area, evaporating to the outside through the evaporation layer. The evaporation layer is made of fast filter paper, which contains a large number of capillaries. When the liquid on the surface of the filter paper evaporates to the outside, a gas-liquid interface will be formed on the surface of the evaporation layer. The pressure in the capillary tube under the interface decreases, generating water absorption force, pushing the liquid in the tube to the surface of the evaporation layer.

[0081] (3) Changing the temperature of the evaporation layer to adjust the evaporation rate of the liquid on its surface, thereby controlling the pumping rate of the liquid in the microfluidic channel. Changing the temperature of the evaporation layer includes: temperature control of the heating plate and temperature control of the environment around the microfluidic chip. The temperature control block diagram of the heating plate 4 is shown in FIG. Figure 11 As shown, a temperature sensor 402 is used to detect the temperature at the bottom of the evaporation layer 31, and the deviation between the set value and the measured value is input into the PID regulator. After proportional, integral, and differential operations, the relevant parameters are input into the control module to control the heating to determine whether the heating wire 401 is running or not. The temperature is detected again by the temperature sensor 402, and the deviation value is sent to the PID regulator for temperature control. This cycle is repeated until the temperature reaches the target value. The parameter setting in the PID regulator is obtained by simulation through MATLAB. First, a step voltage signal is applied to the input end of the heating wire, and the temperature sensor reading is measured at the same time. The reading is the step response of the temperature control system. The transfer function of the control system is obtained based on the response curve. Then, MATLAB is used to build and simulate the control system. The simulation model is used. Figure 11 As shown in the system block diagram, the PID control link is replaced by the relevant PID toolbox, and the parameter tuning in the PID control is automatically adjusted by the toolbox, thereby obtaining the correlation coefficients in the proportional, integral, and differential links of the PID regulator in the control system.

[0082] The temperature control of the environment around the microfluidic chip 3 is similar to the temperature control of the heating plate 4. The corresponding block diagram is as follows: Figure 11 As shown, the thermometer and hygrometer 7 measures the ambient temperature, and the deviation between the set value and the measured value is input into the PID regulator. After PID adjustment, the control parameters are input into the control module, which controls the operation of the heating plate on the isolation cover 2. The temperature is measured again using the thermometer and hygrometer 7, and the deviation is input into the relevant control module. This cycle continues until the target temperature is reached. The parameter tuning method is the same as that described in the previous section.

[0083] Humidity control is achieved by using a humidifier 6 and a thermo-hygrometer 7 in conjunction with each other. The control block diagram is shown in FIG. Figure 12 As shown, the PID method is used to control the ambient humidity, the thermometer and hygrometer 7 is used to observe the ambient humidity, and the hygrometer 6 humidifies the environment. The specific control process is similar to the above-mentioned temperature control method.

[0084] First, a control system consisting of a thermo-hygrometer 7 and a heating plate on the isolation cover 2 is used to maintain a constant temperature of the environment surrounding the microfluidic chip 3. Then, a control system consisting of a thermo-hygrometer 7 and a humidifier 6 is used to maintain a constant humidity of the environment in which the microfluidic chip 3 is located. Finally, the evaporation layer 31 is gradient-heated by the heating plate 4 to control the liquid pumping rate in the microfluidic chip 3.

Claims

1. A continuously drivable microfluidic pump device utilizing liquid evaporation effect, characterized in that: include: Camera (1), isolation cover (2), microfluidic chip (3), heating plate (4), bottom layer (5), humidifier (6), thermometer and hygrometer (7); The camera (1) is connected to the isolation cover (2); the bottom layer (5) is provided with a microfluidic chip (3); a heating plate (4) is provided below the microfluidic chip (3); a humidifier (6) is provided on the left side of the microfluidic chip (3), and a thermometer and hygrometer (7) is provided on the right side; The isolation cover (2) and the bottom layer (5) cover the microfluidic chip (3), the heating plate (4), the humidifier (6), and the hygrometer (7) to form a closed space; The microfluidic chip (3) includes an evaporation layer (31), a microfluidic channel layer (32) and an adhesive layer (33); the evaporation layer (31) is made of filter paper and is placed in the outlet area (324), absorbing the liquid from the inlet area (321) and evaporating it to the outside; The microfluidic channel layer (32) is made of PDMS and consists of an inlet area (321), a calibration area (322), a detection area (323) and an outlet area (324); wherein the inlet area (321) is circular, runs through the microfluidic channel layer (32) from top to bottom, and allows liquid to enter the microfluidic channel layer (32); the calibration area (322) is located outside the spiral channel, where the fluid velocity is observed; the detection area (323) is rectangular, and is used to place related detection devices; the outlet area (324) is circular, runs through the microfluidic channel layer (32) from top to bottom, and is the placement area of ​​the evaporation layer (31); The adhesive layer (33) is made of a pressure-sensitive adhesive composed of acrylic ester, and is bonded to the microfluidic channel layer (32) and the evaporation layer (31) under pressure to form a whole, thereby preventing the liquid in the microfluidic channel layer (32) from leaking out.

2. The continuously drivable microfluidic pump device utilizing liquid evaporation effect according to claim 1, characterized in that: The isolation cover (2) is composed of a top plate (21) and surrounding baffles (22), all of which are made of transparent PMMA material; the flow of liquid in the microfluidic chip (3) can be observed through the top plate (21); four heating plates (221) are attached to the baffle (22), and the four heating plates are connected in parallel to form a whole, which can heat the closed environment in the isolation cover. By changing the input power corresponding to the heating plate (221), the temperature of the closed environment in the isolation cover can be controlled.

3. The continuously drivable microfluidic pump device utilizing liquid evaporation effect according to claim 1, characterized in that: The heating plate (4) comprises a heating wire (401) and a temperature sensor (402); the heating wire 401 and the temperature sensor (402) are spiral-shaped and closely attached to the outlet area (324), and are used to heat the evaporation layer (31) in the outlet area (324) and stabilize the temperature value.

4. The continuously drivable microfluidic pump device utilizing liquid evaporation effect according to claim 1, characterized in that: The humidifier (6) is an atomizing humidifying device that humidifies the surrounding environment.

5. The continuously drivable microfluidic pump device utilizing liquid evaporation effect according to claim 1, characterized in that: The hygrometer (7) is a thermo-hygrometer that can collect, transmit and display the temperature and humidity values ​​of the surrounding environment.

6. A method for using the microfluidic pump device that can be continuously driven by liquid evaporation effect according to claim 1, characterized in that: The following steps are involved: (1) Calibrate the microfluidic pump device; (2) Drop the liquid into the inlet area. Under the action of capillary force, the liquid will enter the calibration area and the detection area in turn, and finally reach the outlet area, evaporating to the outside through the evaporation layer. The evaporation layer is made of fast filter paper, which contains a large number of capillaries. When the liquid on the surface of the filter paper evaporates to the outside, a gas-liquid interface will be formed on the surface of the evaporation layer. The pressure in the capillary tube under the interface decreases, generating water absorption force, pushing the liquid in the tube to the surface of the evaporation layer. (3) Changing the temperature of the evaporation layer can adjust the evaporation rate of the liquid on its surface, thereby controlling the pumping rate of the liquid in the microfluidic channel.

7. The method for using a microfluidic pump device according to claim 6, characterized in that: The step (1) is specifically as follows: (11) Adding deionized water to the inlet area, so that the deionized water fills the microfluidic channel layer 32 and reaches the outlet area, so that the evaporation layer is completely soaked; (12) Add density-matched tracer particles to the inlet area, place the microfluidic chip on the experimental platform, focus the camera on the center of the calibration area, and connect the power supply to power the device; (13) Adjust the operating power of the heating plate to ensure that the temperature at the bottom of the evaporation layer is always stable at 22℃-24℃; (14) Start the temperature control system consisting of the heating plate and the thermometer and hygrometer, adjust the power of the heating plate around the isolation cover, and ensure that the closed environment temperature is stable at 22℃-24℃; (15) Start the humidity control system consisting of the humidifier and the thermometer and hygrometer, adjust the operating power of the humidifier, and ensure that the humidity in the closed environment is stable at 50%-55%; (16) Start the camera and capture the image of the calibration area. Record 10 times with a length of 1 minute at a frame rate of 10 to 20 Hz for three consecutive times. (17) Use MATLAB to record and process videos and calculate the movement speed of particles in liquids; (18) Adjust the power output, increase the temperature of the heating plate by 2°C, and stabilize the temperature. Repeat steps (14) to (18) until the temperature reaches 50°C. (19) The above data were processed and the linear relationship between the temperature of the evaporation layer and the liquid flow rate in the microfluidic channel was plotted as the calibration curve of the device.

8. The method for using a microfluidic pump device according to claim 7, characterized in that: The step (3) of changing the temperature of the evaporation layer includes: controlling the temperature of the heating plate and the temperature of the environment surrounding the microfluidic chip.

9. The method for using a microfluidic pump device according to claim 7, characterized in that: In the step (17), the recorded video is processed by the PTV algorithm.

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