A method for controlling the movement of a microtube by liquid drop and controlling the movement of a liquid drop by light

Abstract

This invention relates to a microtube for controlling droplet motion and a method for optically controlling droplet motion. The microtube comprises a microtube and a polypyrrole membrane distributed in a grid pattern on the outer surface of the microtube. A droplet is injected into the microtube, and the droplet motion is controlled by irradiating the polypyrrole membrane with a light source. The invention features a simple preparation method, eliminating the need for complex fabrication processes. The droplet control principle is straightforward, and the control method offers high reusability. It eliminates the need for complex and large optical devices and enables rapid and precise droplet control even with low light intensity. Furthermore, the droplets are not easily contaminated by the external environment. This invention can control not only different types of droplets but also achieve complex droplet motions, demonstrating significant application potential in the biological field.

Description

Technical Field

[0001] This invention relates to the field of optically controlled droplet technology, and in particular to a microtube for controlling droplet motion and a method for optically controlled droplet motion. Background Technology

[0002] Manipulation of small amounts of liquid has potential applications in many chemical and biological processes, including reaction control, drug delivery, and material analysis. Compared to other microfluidic-based liquid control strategies that require pumps, valves, or electrodes, light-controlled droplet manipulation is gaining increasing attention due to its non-contact nature, instantaneous reactivity, biocompatibility, and excellent spatial and temporal resolution. Several mechanisms for light-driven manipulation of small amounts of liquid have been developed, including photopressure, holographic optical tweezers, photoinduced wettability gradients, photosensitive surfactants, and photoinduced electroosmosis. The most common method for manipulating droplets is to use solid or liquid surfaces modified with azobenzene-containing materials, which can exhibit specific photosensitive surface properties. However, current research still faces some challenges, such as excessively high light source intensity, complex optics, and susceptibility to liquid contamination by coating materials. Besides optical manipulation, significant progress has been made in the theoretical simulation of thermocapillary effects for droplet manipulation. However, reports on practical applications are scarce. Furthermore, these studies primarily utilize thermocouples mounted at both ends to provide temperature gradients on planar substrates, which is unsuitable for diverse applications. Therefore, further research is needed on experimental manipulation of droplets in microtubes based on thermocapillary effects. It is evident that existing optical droplet manipulation technologies require complex optical components and devices, demand excessively high light source intensity, exhibit slow and inaccurate droplet control response, and are susceptible to external contamination. More importantly, current technologies struggle to achieve complex droplet movements and manipulations, and the short droplet transport distances limit their application in biological systems. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a droplet motion manipulation microtube and a method for manipulating droplet motion. Using this actuator, droplet manipulation can be achieved horizontally, through curved channels, and even vertically by simply applying / closing light source stimulation. Compared to previous photoinduced droplet manipulation methods, this invention offers faster and more accurate control over droplet motion rate and is more suitable for complex applications, providing new insights for the application of photoresponsive materials in biomedicine and microreaction control.

[0004] The first objective of this invention is to provide a droplet motion manipulation microtube, the droplet motion manipulation microtube comprising a microtube and a polypyrrole (PPy) membrane distributed in a grid pattern on the outer surface of the microtube.

[0005] Furthermore, the microtube is a capillary.

[0006] Furthermore, the microtube can be linear or non-linear, such as complex shapes like V-shapes or spirals.

[0007] Furthermore, the angle between the microtube and the horizontal plane is 0-90°.

[0008] Furthermore, the method for preparing the droplet motion control microtube involves mixing a film-forming agent and an oxidant with an organic solvent to obtain a mixed solution. This mixed solution is then coated onto the outer surface of the microtube to form a grid-like thin film. Pyrrole gas is then polymerized on the grid-like thin film to form polypyrrole, thus obtaining the droplet motion control microtube. Compared to surface coating methods, the polypyrrole film formed by in-situ reaction is denser and more uniform in thickness, resulting in better photothermal effects and thus improved droplet control performance.

[0009] Furthermore, the film-forming agent is preferably polyvinyl alcohol, the oxidant is preferably an iron salt, and the organic solvent is preferably polyethylene glycol.

[0010] A second objective of this invention is to provide a method for controlling the movement of light-induced droplets, comprising the following steps: injecting droplets into the microtube controlled by the droplet movement, and controlling the movement of the droplets by irradiating a polypyrrole membrane with a light source.

[0011] Furthermore, the droplet is a water droplet, a hydrophobic droplet, a hydrophilic droplet, or a solid-liquid mixture droplet.

[0012] Furthermore, when the droplet is hydrophilic, it moves away from the light source; when the droplet is hydrophobic, it moves towards the light source.

[0013] Furthermore, the light source is one of ultraviolet light, visible light, infrared light, and near-infrared light.

[0014] A third objective of this invention is to provide the application of the aforementioned droplet motion manipulation microtubes in the non-destructive transport of droplets.

[0015] A fourth objective of this invention is to provide applications of the aforementioned droplet motion manipulation microtubes in the biological field, such as for drug delivery and single-molecule detection.

[0016] By means of the above-described solution, the present invention has at least the following advantages:

[0017] This invention develops a novel droplet manipulation actuator capable of rapidly and precisely manipulating small amounts of liquid using photothermal capillary mechanisms. This droplet manipulation actuator is simple to fabricate and requires no complex optical equipment for droplet manipulation. It enables long-distance, complex movements of droplets under low light intensity, and the droplets are not easily contaminated by the external environment. The principle of droplet manipulation is simple, and the manipulation device offers high reusability. This invention can not only manipulate different types of droplets but also, by designing the shape of the droplet manipulation actuator and applying / deactivating unilateral near-infrared light stimulation, achieve horizontal, curved, spiral, and even vertical upward transport of droplets, as well as droplet manipulation such as mixing, chemical reactions, and intracellular droplet manipulation. This invention provides a new perspective for designing complex photofluidic devices, biomedicine, and microreactions.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the following describes the preferred embodiments of the present invention in conjunction with detailed drawings. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0020] Figure 1 Characterization of the polypyrrole material on the surface of a droplet manipulation actuator with a polypyrrole lattice structure;

[0021] Figure 2 Fabrication of a droplet manipulation actuator with a polypyrrole lattice structure and a droplet manipulation method;

[0022] Figure 3 Optical photographs and repeatability tests of a droplet driven back and forth using unilateral near-infrared light within a droplet manipulation actuator with a polypyrrole grid structure;

[0023] Figure 4 The performance and influencing factors of a droplet manipulation actuator with a polypyrrole grid structure for droplet manipulation;

[0024] Figure 5 The effects of PPy width, inner diameter, and light intensity on droplet manipulation performance;

[0025] Figure 6 For droplet transport rates under different tube lengths;

[0026] Figure 7 A schematic diagram illustrating the mechanism of optically controlled droplet motion within the actuator;

[0027] Figure 8This is a diagram illustrating the manipulation of droplets by a droplet control actuator based on a polypyrrole lattice structure made of polypropylene.

[0028] Figure 9 This is a diagram illustrating the manipulation of droplets by a droplet control actuator based on a polypyrrole lattice structure made of polyethylene.

[0029] Figure 10 Testing for light-driven droplet manipulation under complex conditions and its application in biological systems. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0031] The materials and methods involved in the following embodiments are as follows:

[0032] 1. Reagents

[0033] Pyrrole monomer, ferric chloride hexahydrate (FeCl3•6H2O), polyvinyl alcohol (PVA, 98% alcoholysis, molecular weight Mn≈44050), and polyethylene glycol (PEG, molecular weight Mn≥10000) were purchased from Aladdin Reagent Co., Ltd.

[0034] 2. Fabrication of a PPy lattice-structured droplet manipulation actuator

[0035] PVA was dissolved in water and stirred. PEG was added dropwise and stirring continued. FeCl3•6H2O was added and stirred until completely dissolved. The solution was then coated onto the outer wall of a plasma-treated capillary using a pointed brush. The coated capillary was placed above a petri dish containing pyrrole, and the petri dish was heated. This allowed the volatilized pyrrole gas to react in situ at the coating site, ultimately forming a dense black polypyrrole film with a grating-like structure on the outer surface of the capillary, thus obtaining a photoresponsive droplet actuator.

[0036] 3. Methods for controlling droplets within a PPy grid-like droplet control actuator

[0037] A certain amount of liquid is injected into the capillary of the droplet actuator using a micro-syringe. A near-infrared laser with a wavelength of 808 nm (maximum power 15 W; spot area 2×2 mm) is then used to irradiate the polypyrrole material on one end of the actuator. The instantaneous Laplace force induces droplet movement. The near-infrared irradiation distance is adjusted within the range of 2-5 cm using a laser collimator (inner diameter 400 μm; connector type SMA-905).

[0038] Example 1: Fabrication of a droplet manipulation actuator with a polypyrrole lattice structure and a droplet manipulation method

[0039] (1) The preparation method is as follows:

[0040] 0.85 g of polyvinyl alcohol (PVA) was dissolved in 10 mL of deionized water and stirred at 100 °C for 30 minutes. Then, 1% (w / w) polyethylene glycol (PEG) was added dropwise and stirring continued for another 30 minutes. Next, 0.3 g of ferric chloride hexahydrate (FeCl3•6H2O) was added to the solution and stirred until completely dissolved. After the solution was allowed to stand at room temperature, it was coated onto the outer wall of a plasma-treated capillary using a brush. The coated capillary was placed above a petri dish containing pyrrole and heated to above 70 °C. The volatilized pyrrole gas reacted in situ at the coated site, ultimately forming a dense black polypyrrole film with a grating-like structure on the outer surface of the capillary, thus obtaining a droplet manipulation actuator with a polypyrrole grating structure.

[0041] Characterization of the polypyrrole material on the surface of the droplet manipulation actuator with a polypyrrole lattice structure is shown in [the figure]. Figure 1 .in, Figure 1 Image a shows a physical diagram of a droplet manipulation actuator with a polypyrrole lattice structure and a polypyrrole film grown in situ on a quartz plate. Figure 1 b is a SEM image of the polypyrrole film. Figure 1 c represents the UV-Vis absorption / reflectance curve of the polypyrrole film. Figure 1 Image d is a SEM image of the dense granular protrusions on the surface of the polypyrrole film. Figure 1 e represents the corresponding EDX image. Figure 1 f is the AFM image representing the size of the particle protrusion. Figure 1 g is an atomic force microscope image used to measure the thickness of a polypyrrole film. The film height curve corresponding to the linear region in 1g is shown below. Figure 1 h, Thermogravimetric analysis curves of polypyrrole materials are shown in [reference needed]. Figure 1 i.

[0042] (2) Control of droplet motion

[0043] A certain amount of methanol liquid was injected into the capillary tube prepared above using a microsyringe. When the polypyrrole material on one end of the droplet actuator was irradiated with an 808 nm near-infrared laser, the droplet was induced to move away from the laser beam due to the instantaneous Laplace force. A schematic diagram of actuator fabrication and droplet motion is shown below. Figure 2 .

[0044] Example 2: Optical photographs and repeatability tests of droplets driven back and forth using unilateral near-infrared light within a droplet manipulation actuator with a polypyrrole grid structure.

[0045] When the actuator is placed horizontally, the droplet (sodium hydroxide solution) remains stationary due to the pinning effect at the contact line. When the polypyrrole material on the left side of the liquid is irradiated with an infrared laser, the polypyrrole heats up instantly due to its strong photothermal effect, and transfers the heat to the left side of the liquid through the capillary wall, causing the droplet to move away from the light source and to the right. After the droplet reaches the right side of the actuator, it remains stationary for a few seconds, and then the light source pushes the droplet to the left in the opposite direction. This achieves the reciprocating motion of the droplet within the actuator. See the results below. Figure 3 Optical images of light-controlled droplets reciprocating within the actuator ( Figure 3 a) and repeated tests were performed on the reciprocating motion ( Figure 3 (b) It was found that after hundreds of cycles, the actuator could still maintain stable and efficient droplet transport, which provides a reliable guarantee for its future practical application. Repeated tests were conducted to induce droplets in the optical actuator to move back and forth.

[0046] Example 3: Performance of a droplet manipulation actuator with a polypyrrole grid structure and influencing factors on droplet manipulation (droplet type, angle, volume, PPy interval).

[0047] Optical images of dimethyl silicone oil in droplet manipulation actuators are shown below. Figure 4 a. Several common laboratory liquids: dimethyl silicone oil, olive oil, liquid paraffin, dichloromethane, ethanol, deionized water, and 9% sodium chloride solution, were injected in equal volumes (8 μL) into identical actuators (1 mm inner diameter), keeping the actuators horizontal and the light source intensity consistent (1.2 W / cm²). 2 After multiple cycles, the average velocity of different liquids in the actuator was obtained. Figure 4 b), by Figure 4 As shown in b, the highest velocity is found in deionized water, whose surface tension changes most significantly with temperature, reaching 6 mm / s. Dimethyl silicone oil, olive oil, liquid paraffin, and dichloromethane move towards the light source, while ethanol, deionized water, and sodium chloride solution move away from the light source.

[0048] Optical image of a 4 μL deionized water droplet moving within the actuator ( Figure 4 c). We used deionized water as the driving liquid, changing only the volume of the droplets, and after multiple cycles, we obtained the relationship between the droplet velocity and volume. Figure 4 d), by Figure 4As shown in d, when the volume of deionized water droplets increases, the velocity inevitably decreases slowly; the velocity at 20 μL is about 15% lower than that at 4 μL, but it can still reach 5.3 mm / s. Stimulated by infrared light, the droplet manipulation actuator can achieve a "crawling" motion of the droplet from low to high, and the droplet can even overcome its own gravity and move upwards in a vertically placed actuator. Figure 4 e), which is quite rare in previous studies, and also provides greater possibilities for the use of this actuator in complex scenarios. As the actuator placement angle increases from 0° to 90°, the maximum droplet velocity decreases significantly, but at 90° there is still a climbing rate of 0.95 mm / s ( Figure 4 f). Optical photographs of droplet motion at a 1.5 mm PPy spacing ( Figure 4 g).

[0049] The effect of the spacing between PPy segments on motion speed was studied. Each PPy segment was kept 1 mm wide, and different PPy spacings (1-2.5 mm) were set on the outer surfaces of different actuators. Figure 4 h) The velocity of deionized water droplets first increases and then decreases with the increase of the PPy interval distance, reaching its highest value when the interval is 1.5 mm. This provides a basis for setting the actuator parameters in practical applications.

[0050] Example 4 Other influencing factors: PPy width, inner diameter, light intensity, distance

[0051] Optical photographs of the motion of deionized water droplets within an actuator with a width of 0.6 mm PPy are shown below. Figure 5 In the middle ad, the width of each PPy segment was reduced from 1 mm to 0.6 mm. Tests showed that the actuator could still efficiently drive hundreds of droplet reciprocating motions.

[0052] Manipulation of droplets within a 0.6 mm inner diameter actuator ( Figure 5 When a capillary tube with an inner diameter of 0.6 mm is used as the actuator substrate, the effect of capillary effect increases, and liquids such as deionized water move more easily in the actuator. The influence of droplet volume, actuator angle and other conditions on the rate is consistent with the trend of the actuator with an inner diameter of 1 mm.

[0053] The relationship between droplet velocity and light source intensity ( Figure 5 g), light source intensity less than 0.5 W / cm² 2 At this time, the droplet remains stationary or undergoes only very slight motion. As the light source intensity slowly increases, the motion rate increases accordingly, reaching 1.3 W / cm². 2Subsequently, the rate approaches saturation. This may be due to limitations imposed by the size of the capillary. The light source intensity, being the most easily adjustable component, enhances the flexibility of the actuator's operation, providing a convenient and efficient adjustment method for droplet transport under different practical needs.

[0054] By designing the actuator tube length, long-distance droplet transport can be achieved without affecting other droplet properties, such as speed. We designed droplet manipulation actuators with different tube lengths to transport hydrogen peroxide solution (1%), and verified the feasibility of long-distance droplet transport by measuring the droplets. 4 μL of hydrogen peroxide solution (1%) was injected into droplet manipulation actuators with polypyrrole grid structures of lengths of 20 cm, 40 cm, 60 cm, 80 cm, and 100 cm, respectively, while keeping the actuator horizontal and the light source intensity consistent (0.8 W / cm²). 2 The droplet is driven by irradiating the left end of the droplet with 1064nm infrared light until it completely reaches the other end of the actuator, and the time required is recorded. The transport rate is calculated by the transport distance and transport time, and the results are as follows: Figure 6 As shown, the tube length has a negligible effect on the droplet transport rate, and the droplet volume loss after collection and transport is also negligible. Therefore, the droplet manipulation actuator with a polypyrrole grid structure can achieve long-distance droplet transport.

[0055] Example 5 Mechanism Explanation

[0056] A schematic diagram of the mechanism of optically controlled droplet motion within the actuator is shown below. Figure 7 The actuator is placed horizontally, and the black rectangle on the left represents the PPy membrane. The liquid inside the actuator is initially at rest, containing two identical menisci (solid lines). Generally, each meniscus has a corresponding radius of curvature depending on the solid-liquid contact angle. The curvature of the menisci generates a pressure difference between the gas and liquid phases at both ends of the actuator, namely the Laplace pressure (capillary pressure), which can be expressed by the following formula:

[0057]

[0058] in, It is Laplace pressure. It is the interfacial pressure on the gas side. It is the interfacial pressure on the liquid side. θ is the contact angle between the solid and liquid phases. Let d be the surface tension of the liquid, d be the inner diameter of the capillary, and G be a constant related to the geometry of the internal channels of the actuator. This formula applies not only to static droplets but also approximately to moving droplets. Although a Laplace pressure difference is generated at both ends of the gas-liquid interface, the pressure remains balanced due to the relatively uniform surface of the actuator, thus keeping the droplet stationary. By changing the surface tension at one end of the droplet, a pressure difference can be generated, which can drive the movement of the liquid. Among the methods to reduce the surface tension of the liquid, increasing the temperature is a simple and easily controllable option, and therefore can be achieved through photothermal heating.

[0059]

[0060] The formula above illustrates the relationship between surface tension and temperature, where a and b are two positive constants. Figure 7 As shown, if it is a hydrophilic droplet, the liquid surfaces at both ends are concave, and heating one end of the droplet will cause it to move away from the heat source. Conversely, if it is a hydrophobic droplet, the liquid surfaces are convex, and heating one end will cause the droplet to move towards the heat source. Because this mechanism is widely applicable, any capillary material that can cause the liquid surfaces on both sides of the droplet to bend can be processed into an actuator to manipulate the droplet. In addition to the glass microtubes used in the above experiments, quartz microtubes, polypropylene microtubes, polyethylene microtubes, polyvinyl chloride microtubes, polyethylene terephthalate microtubes, polyamide microtubes, polymethyl methacrylate microtubes, polyvinylidene fluoride microtubes, glass fiber toughened plastic microtubes, and perfluoroethylene propylene copolymer microtubes have also been tested, and their use as droplet actuators has been confirmed to be feasible.

[0061] Example 6: Universality of Capillary Materials

[0062] (1) Preparation and manipulation of a droplet manipulator based on a polypyrrole grid structure made of polypropylene. A polypyrrole thin film coating with a grid structure was formed on the surface of polypropylene microtubes through in-situ reaction, thereby obtaining a droplet manipulator based on polypropylene. 4 μL of 1% Löwley's basic methylene blue solution was injected into the droplet actuator. The droplet was transported to the right end by irradiating the polypyrrole thin film coating at the left end of the droplet with a visible mercury lamp. Figure 8 As shown.

[0063] (2) Preparation and manipulation of a droplet manipulator based on a polypyrrole grid structure made of polyethylene. A polypyrrole thin film coating with a grid structure was formed on the surface of polyethylene microtubes through in-situ reaction, thereby obtaining a droplet manipulator based on polypropylene. 4 μL of ammonia solution (1%) was injected into the droplet actuator. The droplet was transported to the right end by irradiating the polypyrrole thin film coating at the left end of the droplet with ultraviolet light at a wavelength of 365 nm. Figure 9 As shown.

[0064] Example 7: Light-driven droplet manipulation under complex conditions

[0065] (1) Motion of droplets in microtubes with complex shapes

[0066] Optical photographs of the motion (β=15°) of deionized water droplets stained with Lüssler's basic methylene blue solution in a spiral droplet manipulation actuator are shown below. Figure 10 a. The motion of the droplet in the V-shaped droplet manipulator is shown in [the diagram]. Figure 10 b. In previous reports, optically controlled droplet motion typically involves climbing upwards on a horizontal plane or a slight slope. Propelling liquid in bends is generally more difficult than in straight pipes due to secondary flow caused by flow resistance. Our actuator can be molded into complex microchannels, such as helical tubes and V-tubes, through simple heat treatment, within which the droplet can still maintain a high motion rate. Figure 10 g).

[0067] (2) Motion of droplets in solid-liquid mixtures

[0068] Polystyrene microspheres (approximately 5 μm in diameter) were dispersed in deionized water, and light induced them to move smoothly and rapidly within microtubules. Figure 10 c). This demonstrates that the droplet manipulation actuator of the present invention can manipulate not only pure liquids but also solid-liquid mixtures. More importantly, by measuring the volume and mass of the polystyrene dispersion droplets before and after transport, it was found that the changes in volume and mass before and after droplet transport are negligible under current measurement precision instruments, both being 8 μL and 6.4 mg. Simultaneously, the polystyrene microspheres move in the actuator in a laminar rather than turbulent manner during the process. This movement mode allows the uniformly dispersed solid-liquid mixture to remain intact, completing the non-destructive transport operation. This implies that the droplet manipulation actuator has great application potential in fields such as microreactions.

[0069] Example 8: Embedded Application in Biological Organisms

[0070] To demonstrate the potential applications of near-infrared light-driven droplet motion in the biomedical field, we placed a 1 mm thick piece of chicken skin between the light source and the actuator. The light source had a power of 1 W / cm². 2 At the same time, it is still possible to precisely control the droplets in the tube on both horizontal and small slopes. Figure 10 d). This demonstrates the excellent penetrability of 808 nm near-infrared light to epidermal tissue. For most biological tissues, the harm caused by near-infrared light is less than that caused by ultraviolet light. This makes our droplet manipulation method more advantageous compared to some ultraviolet-driven methods.

[0071] To investigate the effects of polypyrrole materials on organisms, we conducted cytotoxicity tests on polypyrrole. Figure 10 First, three sets of droplet manipulation actuators, each with an outer diameter of 1.2 mm and a length of 5 cm, were immersed in 5 mL of deionized water and allowed to stand for 24, 48, and 72 hours, respectively. After removing the actuators, the remaining liquid was sonicated, and the concentration of polypyrrole in the remaining liquid was calibrated using a UV spectrophotometer. Figure 10 As shown in Figure e, after immersion in deionized water for 48 hours, the concentration of polypyrrole material dispersed in the actuator increased only slightly, reaching 0.6 μg / mL after 72 hours. We then selected several polypyrrole concentrations (0–0.5 μg / mL and 1–20 μg / mL) for 72-hour cell culture and performed cytotoxicity tests. Figure 10 As shown in f, when the polypyrrole concentration is below 2 μg / mL, the cell survival rate is above 90%. However, when the polypyrrole concentration is higher at 20 μg / mL, the cell survival rate is approximately 73%. The above experiments demonstrate that this droplet actuator has the potential for application in liquid manipulation systems embedded in living organisms.

[0072] Example 9 Manipulation of Other Droplets

[0073] Using the actuator prepared in Example 1, 8 μL of different liquids were injected into capillaries with an inner diameter of 1 mm, while keeping the actuator horizontal and the light source intensity consistent (808 nm near-infrared light, 1.2 W / cm²). 2 The average velocity of different liquids in the actuator was measured in multiple cycles, and the results are shown in the table below.

[0074]

[0075] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A microtube for controlling droplet motion, characterized in that: The droplet motion control microtube is used for the optically controlled motion of droplets. It includes a microtube and a polypyrrole film distributed in a grid pattern on the outer surface of the microtube. The microtube is a glass microtube, quartz microtube, polypropylene microtube, polyethylene microtube, polyvinyl chloride microtube, polyethylene terephthalate microtube, polyamide microtube, polymethyl methacrylate microtube, polyvinylidene fluoride microtube, glass fiber toughened plastic microtube, or perfluoroethylene propylene copolymer microtube; the microtube is a capillary.

2. The droplet actuation microtube according to claim 1, wherein: The microtubes can be linear or non-linear.

3. The droplet actuation microtube according to claim 1, wherein: The angle between the microtube and the horizontal plane is 0-90°.

4. The droplet actuation microtube of claim 1, wherein: The method for preparing the droplet motion control microtube is as follows: a film-forming agent and an oxidant are mixed with an organic solvent to obtain a mixed solution; the mixed solution is coated on the outer surface of the microtube to form a grid-like thin film; and then pyrrole gas is polymerized on the grid-like thin film to form a polypyrrole film, thereby obtaining the droplet motion control microtube.

5. A method for optically controlled droplet motion, characterized in that, The method includes the following steps: injecting droplets into the microtube for droplet motion control as described in any one of claims 1-4, and controlling the droplet motion by irradiating the polypyrrole membrane with a light source.

6. The method according to claim 5, characterized in that: The droplet is a hydrophobic droplet, a hydrophilic droplet, or a solid-liquid mixture droplet.

7. The method of claim 6, wherein: The droplets are water.

8. The method of claim 6, wherein: When the droplet is hydrophilic, it moves away from the light source; when the droplet is hydrophobic, it moves towards the light source.

9. The method of claim 5, wherein: The light source is one of ultraviolet light, visible light, or infrared light.

10. The method of claim 9, wherein: The light source is near-infrared light.

11. The application of the droplet motion manipulation microtube according to any one of claims 1-4 in the non-destructive transport of droplets.

12. The application of the droplet motion manipulation microtube according to any one of claims 1-4 in the biological field.

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