Miniature rotors and methods for detecting low surface tension in liquids based on miniature rotor rotation speed

Abstract

This invention discloses a micro-rotor and a method for detecting low surface tension in liquids based on the rotational speed of the micro-rotor, belonging to the technical field of liquid surface tension testing devices. The micro-rotor includes a rotation center with at least two unidirectional spiral arms. Each spiral arm has an arc-shaped hydrophilic groove communicating with the rotation center, and the end of the arc-shaped hydrophilic groove is connected to the outside. The width of the arc-shaped hydrophilic groove gradually decreases from the rotation center to the end of the spiral arm. By adding a low surface tension liquid to the rotation center of the micro-rotor and analyzing the actual motion state of the micro-rotor using Tracker software, the rotational speed test results of the micro-rotor characterize the surface tension of different low surface tension liquids, achieving rapid detection of low surface tension liquids miscible with water substrates. The micro-rotor of this invention has good reusability, and the preparation method is highly applicable, making it widely applicable in fields such as biomedicine, chemical engineering, and environmental monitoring.

Description

Technical Field

[0001] This invention belongs to the technical field of liquid surface tension testing devices. More specifically, this invention relates to a micro rotor and a method for detecting low surface tension of liquids based on the rotational speed of the micro rotor. Background Technology

[0002] With the continuous development of the medical and chemical industries, low surface tension liquids are widely used in chemical reactions, urban sewage treatment, biomedicine, and environmental monitoring. Therefore, rapid detection of low surface tension liquids is of great significance. Traditional methods for detecting liquid surface tension mainly include the pendant drop method, the suspended plate method, and the rotating drop method. Although these methods have high accuracy under laboratory conditions, they generally suffer from problems such as large equipment size, complex operation, long processing time, large sample requirements, and difficulty in achieving real-time or on-site detection. Developing a portable and easy-to-operate micro-rotor is an effective solution to the problem of rapid detection of liquid surface tension.

[0003] Existing methods for detecting low surface tension liquids typically involve expensive instruments that are difficult to integrate and widely adopt, limiting their application in portable detection and microfluidic systems. A comparison is as follows:

[0004] The method and apparatus for measuring liquid surface tension disclosed in patent CN101142472A achieve low-cost and interference-resistant dynamic surface tension measurement by measuring bubble lifetime, but it is relatively sensitive to gas flow stability.

[0005] Patent CN101887002A discloses a liquid surface tension coefficient measuring instrument, which adopts an ultra-thin metal sheet stretching frame and a communicating vessel-type liquid level lifting mechanism, effectively improving the measurement accuracy and stability. However, the structure is relatively complex and the thin metal sheet is easily deformed, which may affect the long-term durability.

[0006] Patent CN109520893A discloses a device for measuring the surface tension coefficient of a liquid. It has a relatively simple structure, low cost and intuitive operation, making it suitable for teaching demonstrations. However, manual operation has large errors, low accuracy and lack of environmental control, making it unsuitable for testing in different scenarios.

[0007] The tension measuring ring and liquid surface tension measuring device disclosed in patent CN116380724A significantly improve the measurement stability and accuracy through the design of rigid rod and V-shaped contact edge, but the structure is complex, the cost is high and the operation is relatively cumbersome.

[0008] To further expand current methods for detecting liquid surface tension, there is an urgent need to develop a micro-rotor driven by liquid surface tension difference, using the rotor's rotational speed to characterize the magnitude of the liquid surface tension. This rotor must meet the following core requirements: the selected materials must meet both hydrophilic and hydrophobic properties; the materials must be further modified using physical methods to avoid chemical hazards; the structural design must be asymmetrical; the diameter of the central droplet must be sufficient for the volume of a single liquid; and it must maintain good durability and repeatability. Summary of the Invention

[0009] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0010] To achieve these and other advantages according to the invention, the present invention provides a miniature rotor comprising:

[0011] A rotating center has at least two rotating arms that are aligned in the same direction. Each rotating arm has an arc-shaped hydrophilic groove that communicates with the rotating center. The end of the arc-shaped hydrophilic groove is connected to the outside.

[0012] The width of the arc-shaped hydrophilic groove gradually decreases from the center of rotation to the end of the rotating arm;

[0013] The micro rotor includes a base layer, an intermediate layer attached to the upper surface of the base layer, and a surface layer attached to the upper surface of the intermediate layer; the arc-shaped hydrophilic groove is machined on the surface layer;

[0014] The base layer and surface layer, except for the arc-shaped hydrophilic groove, are superhydrophobic, while the intermediate layer is hydrophilic.

[0015] Preferably, the base layer is made of polytetrafluoroethylene, the intermediate layer is made of polyimide, and the surface layer is made of polytetrafluoroethylene.

[0016] Preferably, the method for preparing the micro rotor includes the following steps:

[0017] Step 1: Apply PTFE hydrophobic tape to the surface of polyimide, then flip it over and apply PTFE tape to the back of the polyimide to form a three-layer structure of base layer, intermediate layer and surface layer.

[0018] Step 2: Design the shape of the miniature rotor using the 2D drawing software AutoCAD;

[0019] Step 3: Use femtosecond laser to modify the surface layer, giving it superhydrophobic properties.

[0020] Step 4: Adjust the laser parameters and ablate the surface of the micro rotor to obtain an arc-shaped hydrophilic groove. The width of the arc-shaped hydrophilic groove gradually decreases from the center of rotation to the end of the rotor arm.

[0021] Step 5: Using laser processing technology, the entire micro rotor is removed from the three-layer structure;

[0022] Step 6: Flip and focus the micro rotor, and use a femtosecond laser to modify it so that the lower surface of the substrate has superhydrophobic properties. The micro rotor fabrication is now complete.

[0023] Preferably, in step three, femtosecond laser technology is used to modify the surface layer. The femtosecond laser performs three unidirectional scans, and the processing parameters are: scan spacing of 50μm~60μm, femtosecond laser power of 50μm~60mW, and scan speed of 0.01m / s~0.02m / s.

[0024] Preferably, in step four, the specific method for obtaining the arc-shaped hydrophilic groove by ablation on the surface includes: performing 30 ablation cycles using a femtosecond laser, with the following processing parameters: scanning interval of 50μm~60μm, femtosecond laser power of 200mW~210mW, and scanning speed of 0.01m / s~0.02m / s.

[0025] Preferably, the specific method of step five includes: using a femtosecond laser to cut off the overall shape of the micro rotor, so that the micro rotor is separated from the three-layer structure. The processing parameters are: 80 to 90 scans, femtosecond laser power of 300mW to 310mW, and scanning speed of 0.01m / s to 0.02m / s.

[0026] Preferably, the specific method of step six includes: flipping and fixing the cut-off micro-rotor, accurately focusing the relative position of the micro-rotor and the laser processing by area focusing, so that the femtosecond laser scanning line can cover the bottom surface of the micro-rotor, and performing three scanning lines. The processing parameters are: scanning interval of 50μm~60μm, laser power of 50mW~60mW, and scanning speed of 0.01m / s~0.02m / s.

[0027] A method for detecting low surface tension in liquids based on the rotational speed of a micro rotor includes the following steps:

[0028] S1. Fix the micro rotor on the water surface. Take liquids of the same concentration and volume but different surface tensions and drop them onto the center of rotation of the micro rotor. The liquids flow outward in the arc-shaped hydrophilic groove and flow out from the end of the arc-shaped hydrophilic groove. The surface tension of the liquid is less than that of water. Due to the Marangoni effect, a rotational torque is generated on the rotor arm of the micro rotor, thereby driving the micro rotor to rotate on the water surface.

[0029] S2. Use velocity analysis software to analyze the motion state of the micro rotor and obtain the steady-state peak angular velocity ω of the micro rotor. max Simultaneously, using the known surface tension of water and the surface tension of the liquid to be measured, the steady-state peak angular velocity ω of the micro rotor is obtained. max The surface tension difference ∆γ between pure water and the liquid being tested;

[0030] S3. Plot the measurement results and obtain the steady-state peak angular velocity ω of the micro rotor. max Fitting curves to pure water and the surface tension difference ∆γ of liquids; for the unknown liquid at steady-state moment, the steady-state peak angular velocity ω of the micro rotor is used. max The corresponding range of liquid surface tension values ​​can be obtained by fitting the curve of the surface tension difference ∆γ between pure water and the liquid under test. Furthermore, the steady-state peak angular velocity of the unknown low-surface liquid can be substituted into the fitted ω. max The surface tension of a liquid with low surface tension can be obtained by fitting the -∆γ formula.

[0031] Preferably, in step S1, the volume concentration of the liquid is 99%.

[0032] Preferably, in step S2, the speed analysis software is Tracker physics tracking software.

[0033] The present invention offers at least the following advantages: By designing a low-surface-tension liquid droplet to spray tip with a sufficiently large driving torque, and simultaneously optimizing the shape of the micro-rotor, surface resistance is reduced. Inspired by the beak of a waterbird, the present invention designs the micro-rotor with a wedge-shaped groove, enabling spraying from the larger end to the smaller end and improving the rotational efficiency of the micro-rotor.

[0034] The micro rotor of this invention has a contact angle of approximately 156° on its upper and lower surfaces, a rolling angle of less than 2°, and a contact angle of approximately 7° on its arc-shaped hydrophilic groove. It has high reusability, a pollution-free manufacturing process, and is environmentally friendly with a wide range of applications.

[0035] The miniature rotor of this invention is applicable to fields such as chemical engineering, biomedicine, urban wastewater treatment, and environmental monitoring. In biomedicine, many biological samples (such as serum and cell culture media) have low surface tension; in chemical production processes, organic solvents and surfactant solutions often exhibit low surface tension characteristics; in environmental monitoring, the identification and assessment of water pollutants often rely on the determination of their surface physical properties. By using this rotor to obtain fitted curves, it is possible to further achieve rapid and convenient detection of low surface tension liquids. At the same time, this rotor can also macroscopically demonstrate the Marangoni effect in teaching scenarios.

[0036] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the fabrication process of the micro rotor in Example 4;

[0038] Figure 2 The image shows the contact angle measurement results of the arc-shaped hydrophilic groove of the micro rotor prepared in Example 1;

[0039] Figure 3 The image shows the contact angle measurement results of the superhydrophobic lower surface of the micro rotor prepared in Example 1;

[0040] Figure 4 This is a schematic diagram of the structure of the micro rotor prepared in Example 1;

[0041] Figure 5 This is a schematic diagram of the structure of the micro rotor prepared in Example 2;

[0042] Figure 6 A schematic diagram of the structure of the micro rotor prepared in Example 3.

[0043] Figure 7 This is a schematic diagram of the structure of the micro rotor prepared in Example 4;

[0044] Figure 8 This is a schematic diagram of the structure of the micro rotor prepared in Example 5;

[0045] Figure 9 A schematic diagram of the structure of the micro rotor prepared in Example 6;

[0046] Figure 10 This is a schematic diagram of the structure of the micro rotor prepared in Example 7;

[0047] Figure 11 The graphs show the relationship between the number of miniature rotor arms and angular velocity-time for the micro rotors prepared in Examples 1-7.

[0048] Figure 12 The test graphs show the relationship between the size and rotational speed of the miniature rotors prepared in Examples 8-11;

[0049] Figure 13 The graph shows the relationship between the rotation angle θ and time for anhydrous ethanol, ethylene glycol, methanol, isopropanol, n-propanol, and n-butanol under the same test conditions as in Example 12.

[0050] Figure 14This is a graph showing the relationship between the rotation angle θ and time for acetone, ethyl acetate, acetonitrile, and acetic acid under the same test conditions as in Example 12.

[0051] Figure 15 The graph shows the relationship between the angular velocity ω and time for anhydrous ethanol, ethylene glycol, methanol, isopropanol, n-propanol, and n-butanol under the same test conditions as in Example 12.

[0052] Figure 16 The graph shows the relationship between the angular velocity ω of acetone, ethyl acetate, acetonitrile, and acetic acid and time under the same test conditions as in Example 12.

[0053] Figure 17 The figure shows the fitting curve of steady-state peak angular velocity ω and liquid surface tension difference ∆γ under the same test conditions as in Example 12.

[0054] Figures 4-10 The corresponding labels for each structure of the micro-rotor are: 1-rotation center, 2-rotor arm, 3-arc hydrophilic groove, 4-jet end, 101-through hole. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0056] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0057] like Figures 4-10 As shown, the structure of the micro rotor in each embodiment includes:

[0058] A rotating center 1 is provided with at least two rotating arms 2 in the same direction. The rotating center has a through hole 101 for rotating and fixing a micro rotor. The rotating arms 2 are provided with an arc-shaped hydrophilic groove 3 that communicates with the rotating center 1. The end of the arc-shaped hydrophilic groove 3 (i.e., the spray end 4) is connected to the outside.

[0059] The width of the arc-shaped hydrophilic groove 3 gradually decreases from the rotation center 1 to the end of the rotating arm 2.

[0060] The micro rotor includes a base layer, an intermediate layer attached to the upper surface of the base layer, and a surface layer attached to the upper surface of the intermediate layer; the arc-shaped hydrophilic groove is machined on the surface layer;

[0061] The base layer and surface layer, except for the arc-shaped hydrophilic groove, are superhydrophobic, while the intermediate layer is hydrophilic.

[0062] Figures 4-10 The following are schematic diagrams of the micro rotors with different numbers of spiral arms prepared in Examples 1-7, respectively.

[0063] A capillary tube is passed through the through-hole 101 of a micro-rotor, which is then rotated and fixed on the water surface. The capillary tube is fixed to the container wall at the bottom of the water surface. Different liquids are dripped onto the rotation center 1. The liquid flows from the rotation center 1 to the arc-shaped hydrophilic groove 3, and finally flows out from the spray end 4 of the arc-shaped hydrophilic groove 3, thereby driving the micro-rotor to rotate around the capillary tube. The surface tension difference is calculated from the known surface tension of water and the surface tensions of different liquids. The steady-state peak angular velocity of the micro-rotor under different liquid driving conditions is measured using Tracker physics tracking software. Points are plotted and fitted to obtain a curve showing the steady-state peak angular velocity and the surface tension difference. When measuring a liquid with unknown surface tension, simply drip the liquid with the desired surface tension onto the rotation center 1 of the micro-rotor, obtain the steady-state peak angular velocity of the micro-rotor under this liquid driving condition, and then obtain the surface tension range of the liquid based on the fitted curve of the steady-state peak angular velocity and the surface tension difference. Alternatively, the steady-state peak angular velocity of the unknown low-surface-tension liquid can be substituted into the fitted ω. max The tension of an unknown low-surface liquid can be obtained by fitting the -∆γ formula.

[0064] Example 1

[0065] A method for preparing a miniature rotor includes the following steps:

[0066] Step 1: Lay the hydrophilic material polyimide (PI) and the hydrophobic material polytetrafluoroethylene (PTFE) together to achieve a hydrophilic middle layer and hydrophobic upper and lower surfaces. Specifically, this includes:

[0067] Step 1: Clean and dry the polyimide (PI) material and fix it on a transparent glass plate. Then, evenly apply polytetrafluoroethylene (PTFE) hydrophobic tape to the surface of the polyimide (PI) material, ensuring that no air layer is formed during the application. Then, flip the plate over and apply the tape again, ensuring that it overlaps with the first application of the PTFE hydrophobic tape. The selected polyimide (PI) material is 200 μm thick, and the PTFE hydrophobic tape is 50 μm thick. This results in a three-layer structure consisting of a base layer, an intermediate layer, and a surface layer.

[0068] Step 2: Design the shape of the miniature rotor using the 2D drawing software AutoCAD. The designed miniature rotor has a diameter of 8mm and two rotor arms (e.g., ...). Figure 4 (as shown)

[0069] Step 3: Adjust the laser parameters and perform scanning and modification on the bonded surface to give the surface superhydrophobic properties. The specific parameters are: femtosecond laser power 60mW, scanning speed 0.01m / s, scanning interval 50μm, and scanning times 3.

[0070] Step 4: Two arc-shaped hydrophilic grooves are obtained on the surface by laser ablation. The width of the arc-shaped hydrophilic grooves gradually decreases from the rotation center to the end of the spiral arm, with a maximum width of 0.78 mm and a minimum width of 0.19 mm. The specific parameters are: femtosecond laser power 200 mW, scanning speed 0.01 m / s, scanning interval 50 μm, and 30 scans.

[0071] Step 5: Adjust the laser power parameters to completely remove and separate the micro rotor. The specific parameters are: femtosecond laser power of 300mW, scanning speed of 0.01m / s, and 90 scans.

[0072] Step 6: Flip the removed micro-rotor, adjust the laser parameters, and modify the lower surface of the micro-rotor to make the lower surface superhydrophobic. The specific parameters are: laser power of 60mW, scanning speed of 0.01m / s, scanning spacing of 50μm, and scanning times of 3 times. The micro-rotor is now fabricated.

[0073] The method for detecting low surface tension in liquids using the micro rotor prepared in this embodiment includes:

[0074] S1. Take a capillary tube with a diameter of 300μm and pass it through the through hole of the rotation center of the micro rotor with a diameter of 500μm. Then fix the micro rotor on the water surface by rotation, so that the micro rotor can rotate around the capillary tube.

[0075] S2. Take 2 μL of anhydrous ethanol liquid and drop it onto the center of rotation of the micro rotor. The anhydrous ethanol liquid flows outward in the arc-shaped hydrophilic groove and flows out from the end of the arc-shaped hydrophilic groove. The surface tension of the liquid is less than that of water. Due to the Marangoni effect, a rotational torque is generated on the rotor arm of the micro rotor, thereby driving the micro rotor to rotate on the water surface.

[0076] S3. Using Tracker physics tracking software, analyze the motion state of the micro rotor and obtain its steady-state peak angular velocity ω. max The surface tension difference ∆γ between ethanol and the water substrate was calculated, and the measurement results were plotted at second-by-second intervals to obtain the steady-state peak angular velocity ω of the micro rotor. max Fitting curve of the surface tension difference ∆γ between ethanol and water substrate.

[0077] Example 2

[0078] The difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 3 (e.g., Figure 5 (As shown), the remaining steps are the same as in Example 1.

[0079] Example 3

[0080] The difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 4 (e.g., Figure 6 (As shown), the remaining steps are the same as in Example 1.

[0081] Example 4

[0082] like Figure 1 As shown, the difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 5 (e.g., Figure 7 (As shown), the remaining steps are the same as in Example 1.

[0083] Example 5

[0084] The difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 6 (e.g., ...). Figure 8 (As shown), the remaining steps are the same as in Example 1.

[0085] Example 6

[0086] The difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 7 (e.g., Figure 9 (As shown), the remaining steps are the same as in Example 1.

[0087] Example 7

[0088] The difference between this embodiment and Embodiment 1 is that the number of spiral arms of the micro rotor is set to 8 (e.g., ...). Figure 10 (As shown), the remaining steps are the same as in Example 1.

[0089] Example 8

[0090] The difference between this embodiment and embodiment 4 is that the diameter of the micro rotor is set to 4mm, while the rest of the steps are the same as in embodiment 4.

[0091] Example 9

[0092] The difference between this embodiment and embodiment 4 is that the diameter of the micro rotor is set to 12mm, while the rest of the steps are the same as in embodiment 4.

[0093] Example 10

[0094] The difference between this embodiment and embodiment 4 is that the diameter of the micro rotor is set to 16mm, while the rest of the steps are the same as in embodiment 4.

[0095] Example 11

[0096] The difference between this embodiment and embodiment 4 is that the diameter of the micro rotor is set to 20mm, while the rest of the steps are the same as in embodiment 4.

[0097] Example 12

[0098] A method for detecting low surface tension in liquids based on the micro rotor rotation speed in Example 4 includes the following steps:

[0099] S1. Take a capillary tube with a diameter of 300μm, pass it through the rotation center of the micro rotor with a diameter of 500μm, and fix it on the water surface by rotation.

[0100] S2. Take 2 μL of ethylene glycol, methanol, n-propanol, isopropanol, n-butanol, acetone, ethyl acetate, acetonitrile, and acetic acid of the same concentration (all with a volume concentration of 99%) and test them. Drop ethylene glycol, methanol, n-propanol, isopropanol, n-butanol, acetone, ethyl acetate, acetonitrile, and acetic acid onto the rotation center of the micro rotor. Each liquid flows outward in the arc-shaped hydrophilic groove and flows out from the end of the arc-shaped hydrophilic groove, thereby driving the micro rotor to rotate on the water surface.

[0101] S3. Using Tracker physics tracking software, the motion state of the micro rotor under different sample liquids was analyzed; the steady-state peak angular velocity ω was measured. max Plot the points corresponding to the surface tension difference ∆γ between pure water and liquid at the pure concentration, and draw a linear fitting curve ω. max -∆γ, to obtain the relationship curves between different liquid tension differences and the steady-state peak angular velocity of the micro rotor.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 4 is that the laser ablation path in step four has been modified. Specifically, the arc-shaped hydrophilic groove in Example 4 has been changed from a large-end to a small-end structure design to an arc-shaped hydrophilic groove of equal width.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 4 is that only steps one to five are performed to obtain a micro rotor whose lower surface has not been hydrophobically treated.

[0106] Performance tests were performed on all micro rotor samples, including: using a contact angle meter, adding 5 μL of pure water to measure the wettability (contact angle, roll-off angle) of the sample surface and the arc-shaped hydrophilic groove; and titrating the same volume and concentration of anhydrous ethanol to test the highest angular velocity at steady state.

[0107] Table 1 Performance data of the micro rotors prepared in Examples 1-12 and Comparative Examples 1-2

[0108]

[0109] The difference between Examples 1-7 lies in the testing of the steady-state peak angular velocity of the micro-rotor with 2-8 rotor arms under the same volume of anhydrous ethanol. The data shows that as the number of rotor arms increases, the steady-state peak angular velocity ω... max The resistance will decrease accordingly, mainly because: with the increase in the number of spiral arms, the surface resistance also increases. Although the arc-shaped hydrophilic channel increases and the rotation speed increases accordingly, when titrating a single liquid, the resistance caused by the increased contact area between the micro-rotor and the water surface plays a dominant role. The contact angle measurement results of the arc-shaped hydrophilic channel and the hydrophobic lower surface of the micro-rotor prepared in Example 1 are as follows: Figure 2 and Figure 3 As shown, the contact angle of the arc-shaped hydrophilic groove of the micro rotor is 7.96°, and the contact angle of the hydrophobic lower surface of the micro rotor is 156.1°.

[0110] The difference between Examples 8-11 is that, with the same number of rotor arms and the same volume of anhydrous ethanol, the steady-state peak angular velocity ω increases with the increase of the micro rotor size. max Consequently, the steady-state peak angular velocity of the micro rotor decreases. Comparative Example 1, where no laser modification was applied to the lower surface of the micro rotor, shows a decrease in steady-state peak angular velocity under the same conditions, primarily due to the greater resistance between the liquid surfaces. The test results are as follows... Figures 11-16 As shown, under the same conditions, the micro rotor with 5 spiral arms has a relatively stable motion state compared to the micro rotor with fewer spiral arms. However, for the volume of a single drop of liquid being titrated, under the same conditions, as the number of spiral arms of the micro rotor increases, the surface resistance of the liquid plays a dominant role. The micro rotor with 5 spiral arms has less negative impact from the steady-state peak angular velocity and the resistance between the liquid surfaces during titration compared to other types of micro rotors, making it the optimal micro rotor for detecting low surface tension in liquids.

[0111] Table 2. Data on the tension difference of liquids with different low surface tensions and the peak angular velocity at steady state.

[0112]

[0113] Experiments verified that, through various embodiments and comparative examples, by utilizing the optimal micro-rotor, different low surface tension liquids were tested under the same conditions and concentration (99%). The peak angular velocity of the micro-rotor at steady state and the corresponding liquid surface tension values ​​are shown in Table 2. The steady-state peak angular velocity ω was established. max A scatter plot of ∆γ versus the surface tension difference of the liquid was generated, and a fitting analysis was performed on the scatter plot to obtain a linear relationship between the two. For example... Figure 17As shown, the steady-state peak angular velocity ω obtained by fitting the data of ethylene glycol, methanol, n-propanol, isopropanol, n-butanol, acetone, ethyl acetate, acetonitrile, and acetic acid obtained by the micro-rotor measurement is... max The fitting formula for ∆γ, which is the difference in surface tension of the liquid, is:

[0114] ω max =0.04322×∆γ 1.75685 -0.12582

[0115] The above experimental results demonstrate that this invention can utilize this rotor in fields such as chemical engineering, biomedicine, and environmental monitoring to conduct real-time detection of unknown low surface tension liquids. Specifically, using the micro rotor of this invention, sampling and titration tests are performed on unknown low surface tension liquids, and the steady-state peak angular velocity is measured within a predetermined ω... max By marking points on the -∆γ curve, the approximate value of the liquid surface tension can be determined, or the steady-state peak angular velocity of the unknown low-surface liquid can be substituted into the fitted ω. max The -∆γ fitting formula can be used to obtain the tension of an unknown low surface tension liquid, enabling rapid real-time detection of low surface tension liquids.

[0116] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0117] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A miniature rotor, characterized in that, include: A rotating center has at least two rotating arms that are aligned in the same direction. Each rotating arm has an arc-shaped hydrophilic groove that communicates with the rotating center. The end of the arc-shaped hydrophilic groove is connected to the outside. The width of the arc-shaped hydrophilic groove gradually decreases from the center of rotation to the end of the rotating arm; The micro rotor includes a base layer, an intermediate layer attached to the upper surface of the base layer, and a surface layer attached to the upper surface of the intermediate layer; the arc-shaped hydrophilic groove is machined on the surface layer; The base layer and surface layer, except for the arc-shaped hydrophilic groove, are superhydrophobic, while the intermediate layer is hydrophilic.

2. The micro rotor as described in claim 1, characterized in that, The base layer is made of polytetrafluoroethylene, the intermediate layer is made of polyimide, and the surface layer is made of polytetrafluoroethylene.

3. The miniature rotor as described in any one of claims 1-2, characterized in that, The method for preparing the micro rotor includes the following steps: Step 1: Apply PTFE hydrophobic tape to the surface of polyimide, then flip it over and apply PTFE tape to the back of the polyimide to form a three-layer structure of base layer, intermediate layer and surface layer. Step 2: Design the shape of the miniature rotor using the 2D drawing software AutoCAD; Step 3: Use femtosecond laser to modify the surface layer, giving it superhydrophobic properties. Step 4: Adjust the laser parameters and ablate the surface of the micro rotor to obtain an arc-shaped hydrophilic groove. The width of the arc-shaped hydrophilic groove gradually decreases from the center of rotation to the end of the rotor arm. Step 5: Using laser processing technology, the entire micro rotor is removed from the three-layer structure; Step 6: Flip and focus the micro rotor, and use a femtosecond laser to modify it so that the lower surface of the substrate has superhydrophobic properties. The micro rotor fabrication is now complete.

4. The miniature rotor as described in claim 3, characterized in that, In step three, femtosecond laser technology is used to modify the surface layer. The femtosecond laser performs three unidirectional scans with the following processing parameters: scan spacing of 50μm~60μm, femtosecond laser power of 50μm~60mW, and scan speed of 0.01m / s~0.02m / s.

5. The micro rotor as described in claim 3, characterized in that, In step four, the specific method for obtaining the arc-shaped hydrophilic groove by ablation on the surface includes: performing 30 ablation cycles using a femtosecond laser, with the following processing parameters: scanning interval of 50μm~60μm, femtosecond laser power of 200mW~210mW, and scanning speed of 0.01m / s~0.02m / s.

6. The miniature rotor as described in claim 3, characterized in that, The specific method of step five includes: using a femtosecond laser to cut off the overall shape of the micro rotor, so that the micro rotor is separated from the three-layer structure. The processing parameters are: 80 to 90 scans, femtosecond laser power of 300mW to 310mW, and scanning speed of 0.01m / s to 0.02m / s.

7. The miniature rotor as described in claim 3, characterized in that, The specific method of step six includes: flipping and fixing the cut micro-rotor, accurately focusing the relative position of the micro-rotor and the laser processing by area focusing, so that the femtosecond laser scanning line can cover the bottom surface of the micro-rotor, and performing three scanning lines. The processing parameters are: scanning interval of 50μm~60μm, laser power of 50mW~60mW, and scanning speed of 0.01m / s~0.02m / s.

8. A method for detecting low surface tension of liquids based on the rotational speed of a micro-rotor, wherein the micro-rotor is the micro-rotor according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Fix the micro rotor on the water surface. Take liquids of the same concentration and volume but different surface tensions and drop them onto the center of rotation of the micro rotor. The liquids flow outward in the arc-shaped hydrophilic groove and flow out from the end of the arc-shaped hydrophilic groove. The surface tension of the liquid is less than that of water. Due to the Marangoni effect, a rotational torque is generated on the rotor arm of the micro rotor, thereby driving the micro rotor to rotate on the water surface. S2. Use velocity analysis software to analyze the motion state of the micro rotor and obtain the steady-state peak angular velocity ω of the micro rotor. max Simultaneously, using the known surface tension of water and the surface tension of the liquid to be measured, the steady-state peak angular velocity ω of the micro rotor is obtained. max The surface tension difference ∆γ between pure water and the liquid being tested; S3. Plot the measurement results and obtain the steady-state peak angular velocity ω of the micro rotor. max Fitting curves to pure water and the surface tension difference ∆γ of liquids; for the unknown liquid at steady-state moment, the steady-state peak angular velocity ω of the micro rotor is used. max The corresponding range of liquid surface tension values ​​can be obtained by fitting the curve of the surface tension difference ∆γ between pure water and the liquid under test. Furthermore, the steady-state peak angular velocity of the unknown low-surface liquid can be substituted into the fitted ω. max The surface tension of a liquid with low surface tension can be obtained by fitting the -∆γ formula.

9. The method for detecting low surface tension of liquids based on micro rotor rotation speed as described in claim 8, characterized in that, In S1, the volume concentration of the liquid is 99%.

10. The method for detecting low surface tension of liquids based on micro rotor rotation speed as described in claim 8, characterized in that, In S2, the speed analysis software is Tracker physics tracking software.

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