A hollow fiber actuator and its preparation method and its application in microfluidic manipulation

Abstract

A hollow fiber driver and its preparation method and application in microfluidic manipulation belong to the field of flexible driving materials, and can control the outflow position of the liquid by sensing the temperature of the transported liquid. After twisting, the hollow fiber is fixed in shape after thermal annealing, one end is connected to the fluid inlet, and filled with hot fluid, which can be water or other liquids; when the hot fluid is passed into the hollow fiber driver, axial rotation or extension / contraction occurs, and the normal temperature fluid is immediately restored when the fluid is cooled, and the degree of rotation and extension can be adjusted by controlling the temperature of the hot fluid. It has a high driving stroke (87.5%), a fast response speed (0.88s) and a high temperature sensitivity (rotation of 20° when the temperature changes by 0.5℃); the work capacity and power density of the driver of the present invention are 1.5 times and 90 times that of the air-driven solid fiber, respectively, and the maximum work is as high as 1.73J / g; it is highly stable in experiments in 10,000 cycles. The driver has the advantages of simple structure, small size, and fast response speed.

Description

Technical Field

[0001] The invention belongs to the field of flexible driving materials, and in particular relates to a method for preparing a spiral hollow fiber driver and an application of the driver in microfluidic manipulation for distinguishing liquids at different temperatures. Background Art

[0002] Microfluidic manipulation can accurately deliver trace amounts of liquid and is a widely used technology in modern medical diagnosis, chemical synthesis, biosensing and analysis. One of the key issues is to accurately sense and control the flow rate of the fluid and a series of parameters such as the temperature and concentration of the delivered fluid to meet the reaction requirements of the trace reaction. Traditional microfluidic manipulation devices require multiple devices such as external motors and sensors to meet the needs of liquid delivery and screening, so they are difficult to apply to the narrow space in a closed device; in addition, due to the high flow rate of the delivered liquid, rapid sensing and control are required. Therefore, it is a challenge to obtain real-time data of trace amounts of liquid flowing through microtubes and a compact multifunctional microfluidic system for rapid manipulation of fluids.

[0003] In recent years, stimulus-responsive materials have replaced traditional motors in combination with microchannels to achieve microfluidic control. Typical driving materials used for microfluidics include magnetic or electroactive materials, hydrogels, and liquid crystal polymers, which are controlled by magnetic fields, electric fields, light, temperature, or pH. Magnetic, electrical, and optical stimulation always require additional equipment, while hydrogels are limited by low mechanical strength, weak driving force, and long response time. In addition, these responsive materials always require specific chemical components or complex preparation procedures, which are incompatible with existing microfluidic systems using ordinary tubing. Therefore, it is highly desirable to develop a microfluidic manipulation technology similar to real-time sensing and manipulation of transported fluids by using existing commercial tubing materials.

[0004] Twisted fibers can generate rotational and tensile actuation through volume expansion, showing large actuation stroke and actuation stress. Various reversible / irreversible actuators prepared from them have broad application potential in soft robotics and intelligent control. However, as an important parameter to measure the actuation ability of twisted fibers, the torsion angle α generated by twisting is f =tan -1(πdT)(T: twist density, r: fiber diameter) always shows that the fiber surface is higher than the fiber center. Therefore, the common solid fiber has a small actual twist angle due to the presence of a core with a twist angle close to zero, which limits its driving stroke and unit mass driving force. Secondly, the response time of the thermal response actuator is highly dependent on the heat transfer rate in the polymer fiber. Increasing the heat transfer coefficient of the thermal convection method, increasing the specific surface area of ​​the fiber and reducing the fiber diameter can effectively improve the response time. However, the existing solid fibers have a low driving rate due to the small specific surface area of ​​heat transfer and the small air convection heat transfer coefficient. There are still problems with fluid-driven solid fibers for application scenarios and driving medium recovery. Therefore, the use of a hollow fiber structure can effectively improve the heat transfer from the liquid to the actuator, thereby improving the response rate of the actuator. And better combine microfluidic transmission with drive.

[0005] In addition, although reversible actuation is highly anticipated due to its high cycle life, disposable actuators are also an indispensable component in the field of smart material manufacturing such as heart stents. Combining disposable and reversible actuation completely with a soft material through different manufacturing methods can provide new trends in the field of smart materials and devices and provide inspiration in a wide range of fields such as biomedicine, sensors and detectors, wearable devices and soft robots. Summary of the invention

[0006] The main purpose of the present invention is to solve the problem of real-time temperature sensing and transmission of microfluids in a small space, as well as the problems of slow response speed, small driving stroke, poor working capacity, low power density and high price of conventional drivers. The present invention uses a spiral hollow fiber driver to provide a compact microfluidic manipulation system that can sense liquid temperature and sort the liquid, and controls the outflow position by sensing the temperature of the transported liquid.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] A hollow fiber driver, wherein a hollow fiber of a general polymer material is selected as a raw material for preparing the driver. Such materials have the advantages of low price, easy acquisition, stable properties, etc., and can well guarantee the mechanical properties of the driver. The hollow fiber (1) material is suitable for various existing polymer materials, including but not limited to any polymer material such as polyethylene (PE), polypropylene (PP), polyamide 6 (PA6), polyamide 66 (PA66), polylactic acid (PLA), polycaprolactone (PCL), polyacrylonitrile (PAN), polycarbonate (PC), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), thermoplastic elastomer (TPU), polyurethane (PU), liquid crystal polymer (LCP), hydrogel, etc.

[0009] The hollow fiber actuator of the present invention includes two types: a hollow fiber torsion actuator and a hollow fiber telescopic actuator, both of which are prepared from twisted fibers formed by twisting polymer hollow fibers. The torsion actuator with a twisted structure is wound around a solid column to form a spiral structure to obtain a hollow fiber telescopic actuator.

[0010] Furthermore, the preparation method of the hollow fiber as a torsion actuator comprises the following steps:

[0011] Step 1: Before twisting, insert a metal wire with a diameter slightly smaller than the inner diameter of the hollow fiber into the fiber as an internal support to prevent the core hollow structure from collapsing during the twisting process.

[0012] Step 2: The top of the hollow fiber is connected to a stepper motor, and a weight is placed on the bottom to keep the fiber in tension. During the twisting process, the bottom of the fiber is restrained to prevent the twist from releasing. The supporting wire is not fixed during the twisting process to ensure that it can be easily removed after sample preparation.

[0013] Step 3: Fix the two ends of the fiber in step 2 and heat and anneal for a period of time to set the shape.

[0014] Step 4: Cool the fiber in step 3 to room temperature and remove the internal metal wire to obtain a torsional hollow fiber actuator. The specific process parameters depend on the type and characteristics of the polymer fiber.

[0015] Furthermore, the hollow polymer fiber forms a twisted structure inside after being twisted and fixed, and when a hot fluid is passed through the polymer hollow fiber with a twisted structure, the fiber rotates. The hollow fiber driver generates rotation through hot fluid, indicating the possibility of sensing temperature and performing torsional manipulation of microfluids.

[0016] Furthermore, the steps of making the hollow fiber as a reversible telescopic actuator include:

[0017] Step 1: Before twisting, a metal wire with a diameter slightly smaller than the inner diameter of the hollow fiber is inserted into the fiber as an internal support.

[0018] Step 2: The top of the hollow fiber is connected to a stepper motor, and a weight is placed on the bottom to keep the fiber in tension. During the twisting process, the bottom of the fiber is restrained to prevent the twist from releasing. The wire used for fixing is not fixed during the twisting process to ensure that it can be easily removed after sample preparation.

[0019] Step 3: The fiber obtained in step 2 is spirally wound on a central axis, and is divided into homochiral spirals (the winding direction is the same as the twisting direction) and heterochiral spirals (the winding direction is different from the twisting direction) according to the similarities and differences between the winding direction and the twisting direction. In order to ensure a large driving stroke, in order to obtain a large driving stroke, homochiral fiber actuators require a large fiber spacing during spiral winding to allow the spiral to shrink, while heterochiral fiber actuators require the fibers to fit tightly to allow the coil to stretch.

[0020] Step 4: Fix the fiber shape in step 3 and heat anneal for a period of time to fix the shape.

[0021] Step 5: Cool the fiber in step 4 to room temperature and remove the internal metal wire to obtain a telescopic hollow fiber actuator. The specific process parameters depend on the type and characteristics of the polymer fiber.

[0022] Furthermore, the aforementioned hollow fiber driver is driven repeatedly under different load stresses by continuously switching high and low temperature fluids.

[0023] Further, according to the torsion angle formula α f =tan -1 (πdT)(T: twist density, r: fiber diameter), by increasing the twist density and reducing the proportion of fiber sheath in the fiber, the fiber can obtain a larger effective torsion angle, thereby improving the working capacity of the hollow fiber drive.

[0024] Furthermore, the heat transfer between the flowing liquid and the hollow fiber is modeled by thermomechanical method, and the relationship between the rotating and stretching hollow fiber actuator and the driving temperature and various parameters of the preparation process is quantified, so as to guide the design and driving mechanism research of the hollow fiber actuator for precise microfluidic manipulation. It is determined that the temperature change of the hollow fiber actuator is a transient heat conduction problem caused by the forced convection of the flowing liquid (inside) and the natural convection of the ambient (outside) air. A two-step model of radial heat conduction and axial heat conduction of any cross section of the hollow fiber actuator is established, and the functional relationship between the radial and axial temperature of the hollow fiber actuator and time is obtained.

[0025] The thermomechanical modeling of the present invention comprises the following steps:

[0026] Step 1: Transient heat transfer analysis of the forced convection of the flowing liquid (inside) and the natural convection of the ambient (outside) air that causes the temperature change of the hollow fiber driver.

[0027] First, the governing equation for radial transient heat conduction in an arbitrary cross section of a hollow fiber is:

[0028]

[0029] θ(r, t) is the temperature, R iand R o is the inner and outer diameter of the hollow fiber, and the thermal diffusion coefficient α is defined as

[0030]

[0031] Where k is the thermal conductivity, ρ is the mass density, c p is the specific heat capacity.

[0032] Secondly, the convection boundary conditions on the inner and outer surfaces of the hollow fiber are given by

[0033]

[0034]

[0035] where h w and h a are the heat transfer coefficients of the fluid and air respectively. w and θ a They correspond to the temperatures of the hot fluid and air respectively, where the heat transfer coefficient of the fluid depends on multiple factors such as the internal geometry of the hollow fiber, surface roughness, physical properties of the fluid, and flow state (laminar or turbulent).

[0036] Further, when the axial heat conductivity is much lower than the fluid flow rate as shown in the present invention, the heat fluid and radial conduction are the main factors of axial heat transfer. The temperature of the fluid is substituted into the above radial heat conduction equation as a function of the flow position and time to obtain the temperature distribution of the hollow fiber in the axial direction. The fluid temperature θ w depends on the initial temperature, flow rate, heat losses due to transfer to the hollow fiber driver and ultimately to the ambient air. When the flow rate is high and the heat losses are relatively low, θ w (x,t) is expressed as:

[0037] θ w (x,t)=θ w0 H(vt-x) (5)

[0038] θ w0 is the initial temperature of the hot fluid, v is the liquid flow rate, and H(·) is the Heaviside step function.

[0039] Step 2: Modeling of hollow fiber rotation drive caused by radial heat conduction and axial heat conduction of arbitrary cross-section of hollow fiber drive:

[0040] When heated, the polymer chain expands radially and contracts axially, resulting in changes in the length, diameter and twist of the hollow fiber. The relationship between the resulting twist change and temperature and twist density can be obtained according to the formula

[0041]

[0042] It is known that, where λ and Δλ are the length and length change of the helical oriented polymer chain, respectively, and the temperature parameter is introduced for further correction, the formula can be rewritten as

[0043]

[0044] where α λ and α d are the axial thermal expansion coefficient and radial thermal expansion coefficient of the hollow fiber, α f is the aforementioned torsion angle. Δθ=θ w (x, t) is the temperature change obtained from the previous transient heat transfer analysis.

[0045] Step 3: Modeling of hollow fiber telescopic drive:

[0046] Furthermore, based on the tensile actuation mechanism of twisted, helical polymer fibers around a mandrel, the relationship between the length change generated by the actuation and the temperature and twist density in the tensile actuation model of the hollow polymer fiber actuator can be obtained by rewriting the rotational actuation model:

[0047]

[0048] Where L and ΔL represent the helix length and the change in helix length, respectively; l is the length of the twisted hollow fiber; and N is the number of coil turns.

[0049] Based on the above theoretical simulation, the driving process length and rotation angle of the hollow fiber actuator can quantitatively adjust the rotation degree of the hollow fiber to meet the needs of microfluidic manipulation.

[0050] Furthermore, by regulating the thermal annealing temperature of the above-mentioned reversible actuator to a temperature below the softening point and adjusting the upper limit of the driving temperature to above the annealing temperature, the hollow fiber can be used as an irreversible actuator when the driving temperature is higher than the annealing temperature, and can be used as a partially reversible actuator when the driving temperature is lower than the annealing temperature.

[0051] The beneficial effects of the present invention are:

[0052] 1. The present invention proposes an actuator made of heat-driven twisted hollow fibers, which assembles functions such as fluid transport, rapid sensing and precise control in a single hollow fiber, and realizes rapid manipulation of compact microfluids that is difficult to achieve using ordinary optical or electronic sensors in combination with motors, thereby promoting its use in micro-control systems.

[0053] 2. The driver provided by the present invention is a new type of soft driver with simple structure, light weight, low preparation cost, and raw materials that can be obtained through commercial procurement. At the same time, its properties are highly stable, and there is no performance degradation in 10,000 driving cycles.

[0054] 3. The helical hollow fiber proposed in the present invention can realize different motion modes, such as rotation and translation, and has the fastest response speed (0.88s) and the highest drive stroke (87.5%) of tubular telescopic actuators to date. In the thermal response actuator using a single polymer fiber, it also shows a maximum work of 1.73J / g and a thermally driven rotation of up to 40° / ℃.

[0055] 4. The actuator driving motion proposed by the present invention responds linearly to the change of fluid temperature, wherein the hollow fiber torsional actuator can distinguish the fluid temperature difference range as low as 0.5°C.

[0056] 5. The present invention provides a larger average deflection angle than solid fibers with the same diameter by inserting twist into polymer fibers. The resulting polymer hollow fibers have a working capacity 1.5 times that of solid fiber muscles with the same diameter, and a power density 90 times that of solid fiber muscles. The internal fluid drive greatly improves the heat transfer efficiency from the heating source to the tube drive, and the drive speed is 20 times faster than air drive.

[0057] 6. The driver proposed in the present invention can switch between reversible driving mode and irreversible driving mode by adjusting the annealing temperature and the driving temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0059] Figure 1 The schematic diagrams of the hollow fiber actuator of the present invention for microfluid manipulation are shown in FIG. 1 , wherein (1) is a schematic diagram of microfluid rotation manipulation of a torsional actuator, and (2) is a schematic diagram of microfluid telescopic manipulation of a helical telescopic actuator.

[0060] Figure 2 The present invention shows a method for preparing the driver (1) and a physical diagram (2).

[0061] Figure 3 The driving performance of the hollow fiber actuator under different conditions, where (1) is the rotational driving of the hollow fiber actuator at different temperatures in Example 1. (2) is the 10,000 repeated experiments and response speed of the homochiral hollow fiber actuator in Example 2. (3) is the telescopic driving stroke of the actuator under different twisting densities of homochirality and heterochirality in Example 2. (4) is the reversible / irreversible driving of the actuator by changing the thermal annealing temperature in Example 4.

[0062] Figure 4The working capacity of the hollow fiber driver. (1) is the comparison of the driving response rate of the hollow fiber and the solid fiber in Example 2. (2) is the comparison of the driving response rate of the thermal fluid of the fibers with different inner and outer diameters in Example 3. (3) is the comparison of the working performance of the fibers with different inner and outer diameters in Example 3. (4) is the working performance in Example 5.

[0063] Figure 5 The device is a temperature screening device for rotating microfluids and the relationship between fluid temperature and rotation angle. Liquids with a temperature difference of 0.5°C can be screened.

[0064] Figure 6 The relationship between the contraction position and the temperature of the fluid to be screened can be used to screen liquids with a large temperature difference. (2) The relationship between the contraction position and the temperature of the screened fluid. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below in conjunction with specific embodiments, but the present invention is not limited to the embodiments.

[0066] The preparation method of the present invention is combined with Figure 2 The instructions are as follows:

[0067] Example 1.

[0068] Combination Figure 1-3 , 5 illustrate this embodiment. Figure 1 (1) shows a microfluidic liquid temperature screening device with a hollow fiber driver as the main body: a rotary microfluidic manipulation that drives the fiber to rotate by temperature to sort the liquid.

[0069] Specifically, the steps of making the polyethylene hollow fiber driver include:

[0070] Step 1: Before twisting, insert a metal wire with a diameter slightly smaller than the inner diameter of the hollow fiber into the fiber as internal support.

[0071] Step 2: The top of the hollow fiber is connected to a 42-stage servo motor, and the bottom is loaded with a weight of 0.53 MPa. During the twisting process, the bottom of the fiber is restrained to prevent the twist from being released. The metal wire used for fixing is not fixed during the twisting process to ensure that it can be easily removed after sample preparation.

[0072] Step 3: Fix the two ends of the fiber in step 2 and heat to the softening point temperature for a period of time to set the shape.

[0073] Step 4: Cool the fiber in step 3 to room temperature and remove the internal metal wire to obtain a hollow fiber torsion actuator. The specific process parameters depend on the type and characteristics of the polymer fiber.

[0074] The advantage of this embodiment is that the rotationally driven temperature screening has a temperature sensitivity of up to 40° / °C and can accurately distinguish liquids with a temperature difference of 0.5°C, with a response speed of up to 1 s.

[0075] Example 2.

[0076] This embodiment is a microfluidic liquid temperature screening device with a hollow fiber telescopic actuator as the main body: the fiber is driven by temperature to produce telescopic motion and then the telescopic microfluidic control of liquid is sorted. Figure 1-4 6 describes this embodiment. This embodiment further adjusts the twisting operation of the hollow fiber in embodiment 1. Specifically, the fiber obtained in step 2 is spirally wound on a central axis to obtain a hollow fiber. Figure 2 The helical hollow fiber shown below is divided into homochiral helix (the winding direction is the same as the twisting direction) and heterochiral helix (the winding direction is different from the twisting direction) according to the similarities and differences between the winding direction and the twisting direction. The other structures and materials are the same as those in Example 1. After annealing treatment, the following is obtained: Figure 1 The main structure of the microfluidic liquid temperature screening device shown in (2) is the hollow polymer fiber telescopic actuator.

[0077] The advantage of this embodiment is that the fiber is driven to shrink by temperature, thereby filtering liquids with large temperature differences; ( Figure 3 (3)) Different degrees of telescopic drive are achieved by changing the twist density and drive temperature.

[0078] Example 3.

[0079] Combination Figure 4 This embodiment is described. In this embodiment, this embodiment is a further adjustment of the hollow fiber aperture ratio selected in Example 2. Specifically, three polyethylene hollow fibers with different inner and outer diameter ratios and fiber sheath thicknesses are selected, and twisting and high-temperature annealing are performed in the same manner as in Example 2. The torsion angles formed by the three fibers after twisting are the same, and the fiber parameters are:

[0080] PE1, inner diameter 0.28 mm, outer diameter 0.64 mm, fiber sheath thickness to outer diameter ratio of 0.5;

[0081] PE2, inner diameter 0.58 mm, outer diameter 0.99 mm, fiber sheath thickness to outer diameter ratio 0.41;

[0082] PE3, inner diameter 0.38mm, outer diameter 1.09mm, and the ratio of fiber sheath thickness to outer diameter is 0.65.

[0083] The advantage of this embodiment is that reducing the thickness of the hollow fiber shell and the fiber diameter ratio can achieve a hollow fiber driver with faster response speed and better working capacity.

[0084] Example 4.

[0085] Combination Figure 2 This embodiment is described. In this embodiment, the raw material selection of the hollow twisted fiber actuator is further adjusted. Specifically, the polypropylene hollow fiber is twisted and coiled in the same manner as in Example 2, and annealed at 150° C. for 2 hours to prepare the hollow polypropylene fiber actuator. The actuator is driven by hot ethylene glycol liquid.

[0086] The advantage of this embodiment is that the polypropylene material has a higher maximum driving temperature than the material of the previous embodiment, and can sense and sort other high-boiling-point liquids except water.

[0087] Example 5.

[0088] Combination Figure 3 This embodiment is described. In this embodiment, the thermal annealing temperature of embodiment 4 is further adjusted. Specifically, the thermal annealing temperature is selected to be a certain temperature between room temperature and softening point temperature for thermal fixation of the hollow fiber to obtain an irreversible and partially reversible hollow fiber actuator. The actuator is partially reversibly driven when it is driven below the thermal annealing temperature, and is irreversibly driven when it is driven at a temperature above the thermal annealing temperature.

[0089] The advantage of this embodiment is that the driving mode of the hollow fiber driver can be regulated by adjusting the annealing temperature and the driving temperature.

[0090] Example 6.

[0091] Combination Figure 4 To illustrate this embodiment, in this embodiment, the raw material selection and production of the previously shown hollow twisted fiber actuator are further adjusted. Specifically, the nylon 6 hollow fiber is twisted into a self-helical shape under a bottom end load of 23.4 MPa stress in the same manner as in Example 2, and annealed at 180°C for 2 hours to prepare a hollow self-helical nylon 6 actuator.

[0092] The advantage of this embodiment is that the nylon 6 material has a higher temperature driving range than the material of the previous embodiment, and the self-helical fiber is stronger than the spiral fiber formed by winding around the central axis, which increases the maximum work of the driver to 1.72 J / g as a whole. Figure 4 (2) as shown.

[0093] This hollow polymer fiber actuator is an innovative preparation method for flexible intelligent materials. It can provide rotation, extension and contraction movements and can be applied to different fields, such as fluid screening, robotics, etc. When applied to fluid screening, fluids of different temperatures can move the other end of the hollow fiber actuator fixed at one end to different positions, thereby transporting fluids of different temperatures to different areas. Combined with the liquid separation tank, accurate screening of liquid temperature can be achieved. The preparation process of this new thermal response rotation and extension artificial muscle is simple, the material is cheap and easy to obtain, and the repeatability is good ( Figure 3 (2)), the preparation of the rotary telescopic hollow fiber actuator can be achieved by only accurately twisting, forming a spiral, and heating and annealing.

[0094] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modification, equivalent change and modification made within the spirit and principle of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a hollow fiber driver, characterized in that: The hollow fiber actuator is prepared from a twisted fiber formed by twisting a polymer hollow fiber (3), and includes two types: a hollow fiber torsion actuator (1) and a hollow fiber telescopic actuator (2). The hollow fiber torsion actuator (1) having a twisted structure is wound around a solid column to form a spiral structure to further obtain a hollow fiber telescopic actuator (2); the hollow fiber actuator is shaped by thermal annealing, does not spontaneously untwist in a static state, and its hollow structure does not collapse; the hollow fiber actuator realizes axial rotation or telescopic movement by filling a hot fluid into the hollow cavity, and the driving mode can be adjusted to reversible or irreversible drive by changing the relationship between the thermal annealing temperature and the temperature of the driving hot fluid; The rotation and extension motion of the hollow fiber driver can be obtained by performing thermomechanical modeling on the heat transfer between the flowing liquid and the hollow fiber to obtain the relationship between the driving stroke and the twisting density and the driving temperature. The steps of the thermomechanical modeling include: Step 1: Through the transient heat conduction analysis of the forced convection of the internal flowing liquid and the natural convection of the external ambient air, the axial and radial temperature of the hollow fiber driver as a function of time is obtained: θ w (x,t)=θ w0 H(vt-x), where θ w0 is the initial temperature of the hot fluid, v is the liquid flow rate, and H(·) is the Heaviside step function; Step 2: Solve the twist equation based on the thermal drive of the twisted fiber The temperature parameter is introduced to correct the temperature correlation of the rotary drive, and the relationship between the rotary drive angle, twisting density and temperature change is obtained as follows: where α λ and α d Corresponding to the axial thermal expansion coefficient and radial thermal expansion coefficient of the hollow fiber, α f =tan -1 (πdT) is the twist angle, T and ΔT correspond to the twist density and twist change respectively, d is the fiber diameter, Δθ=θ w (x, t) is the temperature change obtained from transient heat transfer analysis; Step 3: According to the thermally driven expansion and contraction motion formula of spiral fibers The heat-driven untwisting equation and heat conduction equation are introduced to correct it, and the relationship between the fiber stretch length and the twist density and temperature change is obtained as follows: Where L and ΔL correspond to the helix length and the change of helix length respectively; l is the length of the twisted hollow fiber; N is the number of coil turns; Transient heat conduction analysis is constructed through a two-step model: first, radial heat conduction simulation is performed on any cross section of the hollow fiber driver; then, based on the assumption that the heat conduction rate along the hollow fiber axis is much lower than the water flow rate and the radial heat conduction rate, an axial heat conduction model is constructed. Specifically, the radial transient heat conduction of any cross section of the hollow fiber can be calculated by the control equation We get, where θ w (x, t) is the temperature, R i and R o is the inner and outer diameter of the hollow fiber, and the thermal diffusion coefficient α is defined as α=k / (ρ·c p ), where k is thermal conductivity, ρ is mass density, c p is the specific heat capacity. Since the axial heat conductivity is much lower than the specific heat fluid flow rate, the axial heat transfer is regarded as the contribution of the heat fluid and radial conduction. w =θ w (x, t), and the hot fluid position is substituted into the above control equation as x to obtain the axial temperature distribution of the hollow fiber.

2. The method for preparing a hollow fiber actuator according to claim 1, characterized in that: The preparation steps of the hollow fiber torsion actuator (1) include: Step 1: inserting a metal wire (4) having a diameter slightly smaller than the inner diameter of the hollow fiber as a support into the interior of the polymer hollow fiber (3) to form a composite fiber (5) of the metal wire and the polymer; Step 2: Connect one end of the composite fiber (5) obtained in step 1 to a stepper motor, fix the other end vertically, and load a certain weight to ensure that the fiber is in a tensioned state, and twist it to form a composite fiber with twisted fiber wall; Step 3: Fixing the composite fiber in step 2 and performing thermal annealing treatment, specifically, heating the polymer fiber to any temperature within the temperature range of room temperature and softening point and maintaining it for a period of time; Step 4: Cooling, extracting the metal wire (4) from the polymer fiber (3) to obtain the hollow fiber torsional actuator (1).

3. The method for preparing the hollow fiber actuator according to claim 1, characterized in that: The preparation steps of the hollow fiber telescopic actuator (2) include: Step 1: inserting a metal wire (4) having a diameter slightly smaller than the inner diameter of the hollow fiber into the polymer hollow fiber (3) to form a composite fiber (5) of the metal wire and the polymer; Step 2: Fix one end of the composite fiber (5) obtained in step 1, and connect the other end to a stepping motor for twisting; Step 3: Wind the twisted composite fiber in step 2 around a central rod to form a spiral structure and fix it; Step 4: Fixing the composite fiber in step 3 and performing a thermal annealing treatment, specifically, heating the polymer fiber to any temperature within the temperature range of room temperature and softening point and maintaining it for a period of time; Step 5: Cooling, pulling out the metal wire (4) from the polymer fiber (3) to obtain the hollow fiber telescopic actuator (2).

4. The method for preparing the hollow fiber actuator according to claim 3, characterized in that: The telescopic direction of the telescopic drive can be changed by changing the similarities and differences between the spiral winding direction and the twisting direction in step 3. The drive with the same winding direction as the twisting direction undergoes contraction movement when heated, and the drive with the opposite winding direction to the twisting direction undergoes extension movement when heated.

5. The method for preparing a hollow fiber actuator according to claim 1, characterized in that: The response speed, work capacity and driving stroke of the hollow fiber driver can be adjusted by changing the twisting density and driving temperature, and can shrink or stretch and rotate longitudinally according to different spiral directions.

6. A hollow fiber driver, characterized in that: The hollow fiber (3) is prepared by the method of any one of claims 1 to 5, and is applicable to various existing polymer materials, including any polymer material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyamide 6 (PA6), polyamide 66 (PA66), polylactic acid (PLA), polycaprolactone (PCL), polyacrylonitrile (PAN), polycarbonate (PC), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), thermoplastic elastomer (TPU), polyurethane (PU), liquid crystal polymer (LCP) or hydrogel.

7. Use of the hollow fiber actuator according to claim 6 in microfluidic manipulation.

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