Liquid drop directional movement experiment device and method based on super-hydrophobic motion control

Abstract

The invention provides a liquid drop directional movement experiment device and method based on super-hydrophobic motion control, and belongs to the technical field of liquid drop directional movement experiments. The technical problem to be solved is to provide a liquid drop directional movement experiment device structure based on super-hydrophobic motion control and an experiment method. According to the technical scheme, an X-axis limiting mechanism is installed on a Y-axis limiting mechanism, and the X-axis limiting mechanism and the Y-axis limiting mechanism are arranged in the mode that the included angle between the X-axis limiting mechanism and the Y-axis limiting mechanism is 90 degrees; a servo motor is arranged at one end of a bottom plate of the X-axis limiting mechanism, the output end of the servo motor is connected with a ball screw after being connected with an encoder in series, a limiting boss is movably arranged on the ball screw, a pair of trapezoidal guide rails parallel to the ball screw is further arranged on the two sides of the bottom plate, and sliding blocks are movably arranged on the trapezoidal guide rails. A test sample plate is mounted on the limiting boss, and a super-hydrophobic surface is fixedly mounted on the test sample plate; the device is applied to the liquid drop directional movement experiment.

Description

Technical Field

[0001] The invention provides a droplet directional movement experimental device and method based on super-hydrophobic motion control, belonging to the technical field of droplet directional movement experiments. Background Art

[0002] Compared with the traditional droplet transfer method of microfluidic chip and pipette, the method of realizing droplet transfer by asymmetric periodic motion of super-hydrophobic surface has the advantages of high control accuracy, wide applicable droplet range, free transfer path and prevention of cross-contamination between interfaces, and thus has attracted more and more attention in the fields of biomedicine and chemical analysis; however, the influence of the vibration characteristics of super-hydrophobic surface, including the direction, amplitude, frequency, speed and acceleration curve of vibration on the movement forms such as creeping, rolling, bouncing and their speed of droplets, needs further experimental verification. At present, there is no research method based on the influence of asymmetric periodic motion characteristics on the directional movement behavior of droplets on super-hydrophobic surface, and there is a lack of corresponding experimental equipment; therefore, it is of great scientific significance and application value to design and propose an experimental equipment and method that can exert arbitrary controllable time-speed on super-hydrophobic surface. Summary of the invention

[0003] In order to overcome the deficiencies in the prior art, the present invention aims to solve the technical problem of providing a droplet directional movement experimental device structure and an experimental method based on super-hydrophobic motion control.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a droplet directional movement experimental device based on super-hydrophobic motion control, comprising an X-axis restriction mechanism and a Y-axis restriction mechanism, wherein the X-axis restriction mechanism is installed on the Y-axis restriction mechanism, and the X-axis restriction mechanism and the Y-axis restriction mechanism are arranged horizontally at 90 degrees to each other; The X-axis limiting mechanism comprises a first base plate, a first servo motor is arranged at one end of the first base plate, an output end of the first servo motor is connected to a first ball screw after being connected in series with a first encoder, a first limiting boss is movably arranged on the first ball screw, a pair of first trapezoidal guide rails are also arranged on both sides of the first base plate in parallel with the first ball screw, and a first slider is movably arranged on the first trapezoidal guide rail; A test sample is installed on the first limiting boss, two sides of the test sample are connected and fixed to the first slider, and a super-hydrophobic surface is installed and fixed on the test sample by screws or bolts through the provided fixing holes and spring sleeve holes; The Y-axis limiting mechanism includes a second base plate, a second servo motor is arranged at one end of the second base plate, an output end of the second servo motor is connected to a second ball screw after being connected in series with a second encoder, a second limiting boss is movably arranged on the second ball screw, a pair of second trapezoidal guide rails are also arranged on both sides of the second base plate in parallel with the second ball screw, and a second slider is movably arranged on the second trapezoidal guide rail; The upper side of the second limiting boss is connected and fixed to the center position of the first bottom plate, and the upper side of the second sliding block is connected and fixed to the bottom of the first bottom plate; A plurality of Z-axis limiting mechanisms are also arranged around the bottom of the second bottom plate; A Z-axis compensation mechanism is also provided at the center position of the bottom of the second base plate, and the Z-axis compensation mechanism includes a solenoid valve and a cylinder; The first servo motor, the first encoder, the second servo motor, the second encoder, the Z-axis limiting mechanism, the solenoid valve, and the control end of the cylinder are all connected to the electromagnetic force control device.

[0005] The Z-axis limiting mechanism comprises a vertically arranged hydraulic cylinder housing, an oil inlet hole and an oil outlet hole are arranged on the side wall of the hydraulic cylinder housing, a telescopic rod is movably arranged at the output end of the hydraulic cylinder housing, an optical shaft sleeve hole is arranged at the extended end of the telescopic rod, and the optical shaft sleeve hole is hinged to a fixed ear arranged at the bottom of the second bottom plate through a pin shaft; A hydraulic cylinder is arranged inside the hydraulic cylinder housing, and a one-way valve is also arranged inside the hydraulic cylinder; A truncated cone base is provided at the bottom of the hydraulic cylinder housing, and the truncated cone base is placed on a test bench during use.

[0006] The solenoid valve comprises a valve body, the output end of the valve body is connected to the valve core through an adjusting screw, both ends of the valve core are provided with an electromagnet coil, and a valve cover is provided at the extended end of the valve core; A guide component and a guide spring are also provided on the outer side of the adjusting screw; The cylinder comprises a cylinder barrel, a piston rod is arranged inside the cylinder barrel, a driving end of the piston rod is movably connected to an end cover through a piston, and a sealing ring and a buffer mechanism are also arranged on the inner side of the end cover; The extended end of the piston rod contacts the center position of the bottom of the second bottom plate, and an adjustment spring is also arranged between the cylinder and the second bottom plate; The two ends of the piston rod are respectively connected to the electromagnet coil.

[0007] When the solenoid valve is in use, the gas pressure on the valve core, the thrust of the valve core compression spring, the thrust of the return spring and the inherent friction force are adjusted in real time under the action of the electromagnet coil, the guide component and the adjusting screw.

[0008] When the cylinder is in use, the buffer mechanism, piston and piston rod arranged inside are controlled by the electromagnetic valve, so that the piston rod can output an outward thrust smoothly and obtain a nonlinear periodic speed.

[0009] The first servo motor, the first encoder, the second servo motor, and the second encoder jointly complete the collection and feedback of the displacement data of the water droplets on the super-hydrophobic surface; The motion data collected by the sensors arranged on the first ball screw and the second ball screw are adaptively adjusted according to the needs of the motion thread by the algorithm program built into the electromagnetic force control device.

[0010] The sensor specifically includes a force sensor signal acquisition module, a force sensor signal amplification module, and a communication module; The algorithm program built into the electromagnetic force control device is specifically a PID closed-loop regulation control algorithm and a PWM pulse width modulation algorithm.

[0011] The super-hydrophobic surface is specifically a symmetrical micro-pillar array structure, or a homogeneous and isotropic random micro-nano structure; During the experiment, the super-hydrophobic surface was modified so that the droplets were in a Cassie state on the super-hydrophobic surface.

[0012] Specifically, four Z-axis limiting mechanisms are provided.

[0013] An experimental method for directional movement of droplets based on super-hydrophobic motion control includes the following experimental steps: Step 1: Set the experimental device to the initial position: Move the test sample to the middle of the first bottom plate, move the first bottom plate to the middle of the second bottom plate, and adjust the telescopic height of each hydraulic cylinder housing so that the test sample remains horizontal; The super-hydrophobic surface is fixed to the test specimen by bolts and leveled; Step 2: Preload the superhydrophobic surface: The electromagnetic force control device controls the first servo motor and the second servo motor to start, and after removing the influence of the self-gravity of the test sample and the super-hydrophobic surface, the calculation correction value is brought in to complete the unidirectional movement of the test sample under the action of the servo motor and the X-axis and Y-axis limiting mechanisms, and the collection and feedback of the displacement data are completed, and the recording and debugging are performed; The electromagnetic force control device controls the action of the solenoid valve cylinder, and uses the cylinder to adjust the air source pressure to push the test sample to adjust the acceleration, complete the unidirectional movement of the test sample under the action of the cylinder and the electromagnetic valve, complete the collection and feedback of the displacement data, and perform recording and debugging; Step 3: Use a high-speed camera to capture the time-displacement image of the droplet on the super-hydrophobic surface and observe the dynamic characteristics of the droplet and the velocity of the center of mass; Step 4: Establish the relationship between the super-hydrophobic surface vibration characteristics and the droplet dynamic characteristics and center of mass velocity, and obtain the relationship between the asymmetric vibration of the super-hydrophobic surface and the directional movement performance of the droplet.

[0014] The beneficial effects of the present invention compared with the prior art are as follows: the experimental device provided by the present invention can apply asymmetric periodic vibrations to the super-hydrophobic surface by setting a limiting mechanism in the corresponding direction, so as to realize the creeping and rolling of the droplets on the surface, and then realize the precise control of the directional movement of the droplets. In conjunction with a high-speed camera, the dynamic situation of the droplets can be observed in real time, and the dynamic process can be recorded in real time. The whole device has a simple and compact structure and can be conveniently placed on a microscope stage or in a test environment with limited space, so as to realize the experiment and research on the directional movement of droplets on the super-hydrophobic surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is a structural schematic diagram of the experimental device of the present invention; Figure 2 for Figure 1 Side view of Figure 3 It is a structural schematic diagram of the X-axis limiting mechanism of the present invention; Figure 4 It is a structural schematic diagram of the Y-axis limiting mechanism of the present invention; Figure 5 It is a structural schematic diagram of the Z-axis limiting mechanism of the present invention; Figure 6 It is a structural schematic diagram of the solenoid valve of the present invention; Figure 7 It is a structural schematic diagram of the cylinder of the present invention; In the figure: 1 is an X-axis limiting mechanism, 2 is a Y-axis limiting mechanism, 3 is a Z-axis limiting mechanism, 4 is a solenoid valve, 5 is a cylinder, and 6 is a super-hydrophobic surface; 100 is a first base plate, 101 is a first servo motor, 102 is a first encoder, 103 is a first trapezoidal guide rail, 104 is a first ball screw, 105 is a first slider, 106 is a first limit boss, 107 is a test sample, 108 is a fixing hole, and 109 is a spring sleeve hole; 200 is a second base plate, 201 is a second servo motor, 202 is a second encoder, 203 is a second trapezoidal guide rail, 204 is a second ball screw, 205 is a second slider, 206 is a second limiting boss, and 207 is a fixing ear; 300 is a hydraulic cylinder housing, 301 is a smooth shaft sleeve hole, 302 is a telescopic rod, 303 is an oil inlet hole, 304 is a hydraulic cylinder, 305 is an oil outlet hole, 306 is a one-way valve, and 307 is a round table base; 401 is a valve cover, 402 is an electromagnet coil, 403 is a valve core, 404 is a guide spring, 405 is a guide component, 406 is an adjusting screw, and 407 is a valve body; 501 is an end cover, 502 is a sealing ring, 503 is a buffer mechanism, 504 is a piston, 505 is a piston rod, 506 is a cylinder, and 507 is an adjusting spring. DETAILED DESCRIPTION

[0016] like Figures 1 to 7 As shown, the present invention provides an experimental device and method for realizing directional movement of micro-nano droplets based on asymmetric periodic motion of super-hydrophobic surface. The provided experimental device can apply asymmetric periodic vibration with arbitrarily controllable frequency, vibration mode, time-velocity curve and vibration direction to the super-hydrophobic surface, so as to study the above-mentioned vibration characteristics and the geometric and chemical properties of the microstructure of the super-hydrophobic surface, as well as the influence of parameters such as droplet size, density and surface tension on the directional movement performance of droplets.

[0017] The experimental device provided by the present invention can apply asymmetric periodic vibration to a super-hydrophobic surface to realize creeping and rolling of droplets on the surface, thereby realizing precise control of directional movement of droplets. By providing three vibration adjustment mechanisms in mutually perpendicular directions, it is ensured that the super-hydrophobic surface can be simultaneously subjected to vibrations in three directions, thereby ensuring that the movement trajectory of droplets forms an arbitrary curve in three-dimensional space: when vibration in the X direction is applied through an X-axis limiting movement mechanism, the droplets creep or roll along the X direction on the super-hydrophobic surface; when vibrations in two directions are simultaneously applied in the X direction through the X-axis limiting movement mechanism and in the Y direction through the Y-axis limiting movement mechanism, the droplets synthesize an arbitrary curve in the XY plane; when vibrations in three directions of X, Y and Z are simultaneously applied through the X-axis limiting movement mechanism, the Y-axis limiting movement mechanism and the Z-axis limiting movement mechanism, the droplets move along an arbitrary controllable spatial curve in three-dimensional space.

[0018] The present invention utilizes the relevant classification of the kinematic pairs to extract the main motion category, limit and reduce the influence of other motions, and can independently apply precise vibrations in the X, Y and Z directions.

[0019] The time-displacement curves of the loads in the X-direction, Y-direction and Z-direction provided by the present invention within one cycle can be arbitrarily adjusted, such as linear function, cubic function, sine function, tangent function and other odd function curves, the amplitude can be arbitrarily adjusted between 1μm~10mm, and the frequency can be arbitrarily adjusted within the range of 100Hz~1000Hz.

[0020] The glass slide of the present invention has good interchangeability, avoids the problem of disassembly and assembly of the experimental table when measuring different super-hydrophobic surfaces, and improves the efficiency of the test.

[0021] The present invention can be equipped with a high-speed camera to observe the dynamic situation of the droplets in real time and record the dynamic process in real time.

[0022] The processing parts of the present invention are all made of stainless steel and are chrome-plated on the surface, which ensures that the whole device has good installation and measurement accuracy.

[0023] The device of the present invention has a simple and compact structure and can be conveniently placed on a microscope stage or in a test environment with limited space.

[0024] In order to achieve the above technical effects, the structure of the droplet directional movement experimental device provided by the present invention is specifically as follows: The experimental device includes an X-axis limiting mechanism 1 and a Y-axis limiting mechanism 2, wherein the X-axis limiting mechanism 1 is installed on the Y-axis limiting mechanism 2, and the X-axis limiting mechanism 1 and the Y-axis limiting mechanism 2 are arranged horizontally at 90 degrees to each other; The X-axis limiting mechanism 1 comprises a first base plate 100, a first servo motor 101 is arranged at one end of the first base plate 100, an output end of the first servo motor 101 is connected in series with a first encoder 102 and then connected to a first ball screw 104, a first limiting boss 106 is movably arranged on the first ball screw 104, a pair of first trapezoidal guide rails 103 are also arranged on both sides of the first base plate 100 in parallel with the first ball screw 104, and a first slider 105 is movably arranged on the first trapezoidal guide rails 103; A test sample 107 is installed on the first limiting boss 106, and both sides of the test sample 107 are connected and fixed to the first slider 105. The super-hydrophobic surface 6 is fixed to the test sample 107 by screws or bolts through the fixed holes 108 and the spring sleeve holes 109; The Y-axis limiting mechanism 2 includes a second base plate 200, a second servo motor 201 is arranged at one end of the second base plate 200, an output end of the second servo motor 201 is connected in series with a second encoder 202 and then connected to a second ball screw 204, a second limiting boss 206 is movably arranged on the second ball screw 204, a pair of second trapezoidal guide rails 203 are also arranged on both sides of the second base plate 200 in parallel with the second ball screw 204, and a second slider 205 is movably arranged on the second trapezoidal guide rails 203; The upper side of the second limiting boss 206 is connected and fixed to the center position of the first bottom plate 100, and the upper side of the second sliding block 205 is connected and fixed to the bottom of the first bottom plate 100; Four Z-axis limiting mechanisms 3 are also provided at the bottom of the second bottom plate 200; A Z-axis compensation mechanism is also provided at the center of the bottom of the second base plate 200, and the Z-axis compensation mechanism includes a solenoid valve 4 and a cylinder 5; The control ends of the first servo motor 101 , the first encoder 102 , the second servo motor 201 , the second encoder 202 , the Z-axis limiting mechanism 3 , the solenoid valve 4 , and the cylinder 5 are all connected to the electromagnetic force control device.

[0025] The Z-axis limiting mechanism 3 includes a vertically arranged hydraulic cylinder housing 300, an oil inlet hole 303 and an oil outlet hole 305 are arranged on the side wall of the hydraulic cylinder housing 300, a telescopic rod 302 is movably arranged at the output end of the hydraulic cylinder housing 300, an optical shaft sleeve hole 301 is arranged at the extended end of the telescopic rod 302, and the optical shaft sleeve hole 301 is hinged to the fixing ear 207 arranged at the bottom of the second bottom plate 200 through a pin shaft; The hydraulic cylinder housing 300 is provided with a hydraulic cylinder 304 inside, and a one-way valve 306 is also provided inside the hydraulic cylinder 304; A truncated cone base 307 is disposed at the bottom of the hydraulic cylinder housing 300 . The truncated cone base 307 is placed on a test bench during use.

[0026] The solenoid valve 4 comprises a valve body 407, the output end of the valve body 407 is connected to the valve core 403 via an adjusting screw 406, both ends of the valve core 403 are provided with an electromagnet coil 402, and a valve cover 401 is provided at the extended end of the valve core 403; A guide component 405 and a guide spring 404 are also provided on the outer side of the adjusting screw 406; The cylinder 5 includes a cylinder barrel 506, a piston rod 505 is disposed inside the cylinder barrel 506, a driving end of the piston rod 505 is movably connected to an end cover 501 through a piston 504, and a sealing ring 502 and a buffer mechanism 503 are further disposed on the inner side of the end cover 501; The extended end of the piston rod 505 contacts the center position of the bottom of the second bottom plate 200, and an adjustment spring 507 is also provided between the cylinder 506 and the second bottom plate 200; Both ends of the piston rod 505 are connected to the electromagnet coil 402 respectively.

[0027] The super-hydrophobic surface provided by the present invention is specifically fixed on a test sample (slide table) by screws or bolts, and a horizontal linear displacement X-axis limiting mechanism is installed on a Y-axis limiting mechanism to achieve sliding cooperation with the Y-axis limiting mechanism; the moving direction of the slider of the horizontal linear displacement X-axis limiting mechanism is the X-axis direction, the direction perpendicular to the X-axis in the plane where the upper surface of the Y-axis limiting mechanism is located is the Y-axis direction, and the direction perpendicular to the plane where the X-axis limiting mechanism and the Y-axis limiting mechanism intersect is the Z-axis direction, that is, the vertical direction; the horizontal linear displacement X-axis limiting mechanism is used to drive the test sample to move along the X-axis straight line on the Y-axis limiting mechanism; The Z-axis limiting mechanism is installed on the bottom of the base plate of the Y-axis limiting mechanism through the optical shaft sleeve hole and the pin shaft, and the X-axis limiting mechanism and the Y-axis limiting mechanism form a sliding connection in the X and Y directions through the trapezoidal guide rails. The servo motor drives the ball screw to make periodic spiral rotation, thereby driving the slider to make radial variable speed displacement. Under the auxiliary restriction of the limit boss, the top super-hydrophobic surface can be driven by the slide table to perform a small amplitude, limited incremental displacement, and realize the passive limit of the plane movement of the test sample.

[0028] The 1024-line encoder and servo motor set in the device are combined to complete the collection and feedback of displacement data, which is convenient for test personnel to record and debug. The sensor is installed on the ball screw through the connecting guide rod and rotates with it, so as to adjust the effective motion thread here according to actual needs, providing a signal source for PID closed-loop regulation and control. The adaptive force control system using electromagnetic force control device can effectively realize the joint control of control module, drive module, controlled object and detection module. The force control process of electromagnetic force control device adopts pulse width modulation PWM technology to realize the joint use of PID algorithm and PWM technology. After preliminary testing, the adaptive force control strategy based on PID algorithm has fast response speed and high stability. The PID algorithm is based on the original classical theoretical algorithm, combined with the electromagnetic force control device to feedback the force of the top super-hydrophobic surface to the control system, so as to build and calculate different mathematical models of plate physical vibration, write corresponding algorithms, and complete the precise control of mechanical structure.

[0029] The Z-axis limiting mechanism adopts the form of a hydraulic telescopic sleeve rod. Through the vibration in the Z-axis direction, the hydraulic cylinder is used for self-limiting adjustment. It can effectively complete the up and down movement while the load-bearing degree is sufficient, and finally realize the auxiliary work of the sealing hydraulic cylinder. The top super-hydrophobic surface is fixed to the slide table with screws or bolts through the test sample fixing holes. In this process, the auxiliary adjustment spring adjusts and limits the movement in each direction through the four spring sleeve holes on the slide table, and at the same time completes the force compensation and reduces the inertial impact.

[0030] The piston rod is fixed on the electromagnet coil. The geometric center of the bottom plate of the Y-axis limiting mechanism is the position where the solenoid valve controls the cylinder to act on the test sample, and the four surrounding fixed loads are spring fixed positions to prevent the test sample from tilting. This is the position where the force in the Z-axis direction is applied. All connection forms are hinged forms to ensure the independent action of forces in each direction. For the X-axis and Y-axis movement modes, the servo motor drive mode is used to generate displacement increments. Based on the above-mentioned 1024-line encoder and algorithm adjustment, etc., the collected information is used, and the slide is driven by the ball screw to perform variable speed movement with it, thereby achieving a target specific movement mode.

[0031] Under the basic structure of the solenoid valve, such as the valve cover, valve core, and valve body, the gas pressure on the valve core, the thrust of the valve core compression spring, the thrust of the return spring, and the inherent friction force are adjusted in real time through the action of the electromagnet coil, the guide component, and the adjusting screw. The target acceleration change curve of the test sample is obtained by autonomously adjusting the gas source pressure of the two-position three-way solenoid valve.

[0032] The end cover, sealing ring and cylinder barrel together constitute the basic structure of the cylinder. The cylinder realizes stable outward thrust output under the control of the solenoid valve by utilizing the buffer mechanism, piston and piston rod, ensuring that the piston rod obtains a nonlinear periodic speed.

[0033] The experimental device provided by the present invention utilizes four hydraulic rod support mechanisms, namely, an X-axis limiting mechanism, a Y-axis limiting mechanism and a Z-axis limiting mechanism, to form an association. The X-axis limiting mechanism and the Y-axis limiting mechanism are responsible for high-precision positioning and stabilization of the water droplets on the plate on the horizontal plane (i.e., the X-axis and Y-axis directions), allowing it to perform a variable acceleration motion. The Z-axis limiting mechanism serves as a passive regulating power source in the vertical direction, and enables the water droplets on the plate to perform an asymmetric periodic motion in the Z direction through the telescopic length of the telescopic rod.

[0034] The experimental device integrates high-precision sensors (force sensor signal acquisition module, force sensor signal amplification module, external communication module, etc.) and embedded intelligent algorithms (PID closed-loop regulation control algorithm, pulse width modulation PWM technology) to monitor the movement state of water droplets on the top super-hydrophobic surface in real time, ensure that the board moves precisely in three-dimensional space according to the predetermined path, realize the coordination of physics and algorithms, achieve closed-loop feedback under the action of the target, and use the adaptive force control strategy design method to complete auxiliary control.

[0035] The X-axis limiting mechanism, Y-axis limiting mechanism, and Z-axis limiting mechanism provided by the present invention adopt a modular design, which is easy to disassemble and reduces the maintenance cost to a certain extent. In addition, this project adopts energy-saving and efficient hydraulic pumps and valve groups to reduce energy consumption and noise processing. A through hole is processed on the set slide, and a circle of step surface is processed on the inner wall of the through hole. The installation, fixing and disassembly of the top super-hydrophobic surface can be achieved with screws or bolts, simplifying the operation process. The X-axis limiting mechanism, Y-axis limiting mechanism, Z-axis limiting mechanism, trapezoidal guide rail, ball screw, slider, limit boss, slide, test sample fixing hole, spring sleeve hole, etc. used in the present invention are all made of stainless steel materials and chrome-plated on the surface.

[0036] The present invention selects a suitable stiffness correction coefficient in the Z-axis direction to support the auxiliary adjustment spring of the test specimen of the suspension system, and realizes the four-corner positioning of the test specimen through the spring sleeve holes, which not only avoids the instability of directly acting on the top super-hydrophobic surface, but also realizes the elastic regulation of the load force applied to the cylinder telescopic rod, effectively realizing continuous motion measurement and small deformation monitoring.

[0037] An experimental method based on the above experimental device to realize the directional movement of micro-nano droplets by using asymmetric periodic motion of super-hydrophobic surface is provided, which specifically includes the following experimental steps: Step 1: Fix the experimental device: Fix the z-axis limit mechanism of the experimental device on the shock-absorbing test bench by bolts, and connect the round table base at the bottom to the test bench by strong magnetic attraction, so as to complete the fixation of the entire experimental device; Step 2: Prepare super-hydrophobic surface: The super-hydrophobic surface can be a symmetrical micro-pillar array structure, a homogeneous isotropic random micro-nano structure or other asymmetric micro-nano structure. After surface modification, the droplets are in a Cassie state on the super-hydrophobic surface. Step 3: Set the initial position of the test device: move the slide to the middle of the X-axis limit mechanism, move the X-axis limit mechanism to the middle of the Y-axis limit mechanism, and adjust the Z-axis limit mechanism to keep the slide level; Step 4: Install the super-hydrophobic surface to be tested and level it; fix the super-hydrophobic surface to be tested on the slide and fix it with the bolts in the fixing holes of the test sample.

[0038] Step 5: Determine the preload force: The main power part of this equipment in the Z-axis direction is composed of a cylinder and a solenoid valve. The speed is affected by two factors: gas pressure and load. The acceleration is adjusted by adjusting the gas source pressure. The passive constraint part uses a Z-limiting mechanism to complete the auxiliary restriction of the unidirectional precise movement of the test sample under the action of the cylinder and the solenoid valve, so as to complete the test of the target droplet by making the piston rod act on the auxiliary control device, avoiding the interference vibration and tilt caused by the uneven force distribution and the elastic deformation of the adjustment spring due to direct action on the test sample.

[0039] The main power part in the X and Y axis directions of this equipment is generated by the servo motor drive, which is affected by the algorithm control and the process of the ball screw guide. Compared with the Z axis direction, after removing the influence of the self-gravity of the slide and the super-hydrophobic surface itself, the calculation correction value is brought in again to complete the unidirectional precise movement and auxiliary restriction of the test sample under the action of the driving mechanism and the X and Y axis restriction mechanism.

[0040] The middle force-applying part is the solenoid valve controlling the cylinder's action position on the steel test specimen. The four surrounding fixed loads are spring-fixed positions to prevent the test specimen from tilting. Under the action of the electromagnetic force composed of the gas pressure on the valve core, the thrust of the valve core compression spring, the thrust of the return spring and the friction force, the cylinder pushes the test specimen to complete the variable acceleration adjustment.

[0041] For the X and Y axis limiting mechanism, the servo motor + encoder mode is adopted to realize the linkage with the cylinder + solenoid valve. The cylinder and solenoid valve control are the main body, and the plane movement is passively limited. At the same time, the collection and feedback of the displacement data are completed, which is convenient for the test personnel to record and debug. The effective motion thread here can be adjusted according to actual needs.

[0042] For the Z-axis limiting mechanism, a hydraulic telescopic sleeve is adopted. Through vibration in the Z-axis direction, the hydraulic cylinder is used for autonomous limit adjustment. It can effectively complete the up and down movement while having sufficient load-bearing capacity, and finally realize the auxiliary work of the sealing hydraulic cylinder.

[0043] Finally, with the cooperation of the cylinder, solenoid valve and XYZ limiting mechanism, independent control of the test sample in one direction is achieved. By adding high-precision sensors (force sensor signal acquisition module, force sensor signal amplification module, external communication module, etc.) and embedded intelligent algorithms (PID closed-loop regulation and control algorithm, pulse width modulation PWM technology), complete closed-loop feedback regulation is achieved, and finally the target displacement in the three directions of XYZ - the regulation and control of motion is achieved.

[0044] Similarly, for simultaneous vibration in two directions like X and Y, linkage control can be used in the above steps to complete it. Similarly, for the simultaneous application of loads in X, Y and Z directions, the joint control method can also be used to achieve synchronous or asynchronous control, and ultimately the expected effect can be achieved.

[0045] Step 6: Use a high-speed camera to capture the time-displacement image of the droplet and observe the dynamic characteristics of the droplet (creeping, rolling, jumping, breaking, etc.) and the velocity of the center of mass; Step 7: Establish the relationship between the super-hydrophobic surface vibration characteristics (amplitude, frequency, time-displacement curve form) and the droplet dynamic characteristics (creeping, rolling, jumping, breaking, etc.) and center of mass velocity, reveal the mechanism of the asymmetric vibration of the super-hydrophobic surface on the directional movement of droplets, and achieve precise, efficient, non-destructive and pollution-free control of the directional movement of droplets on the super-hydrophobic surface.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A droplet directional movement experimental device based on super-hydrophobic motion control, comprising an X-axis limiting mechanism (1) and a Y-axis limiting mechanism (2), characterized in that: The X-axis limiting mechanism (1) is mounted on the Y-axis limiting mechanism (2), and the X-axis limiting mechanism (1) and the Y-axis limiting mechanism (2) are arranged horizontally at 90 degrees to each other; The X-axis limiting mechanism (1) comprises a first base plate (100), a first servo motor (101) is arranged at one end of the first base plate (100), an output end of the first servo motor (101) is connected in series with a first encoder (102) and then connected to a first ball screw (104), a first limiting boss (106) is movably arranged on the first ball screw (104), a pair of first trapezoidal guide rails (103) are also arranged on both sides of the first base plate (100) in parallel with the first ball screw (104), and a first slider (105) is movably arranged on the first trapezoidal guide rail (103); A test sample (107) is mounted on the first limiting boss (106), two sides of the test sample (107) are connected and fixed to the first slider (105), and a super-hydrophobic surface (6) is mounted and fixed on the test sample (107) by means of screws or bolts through the provided fixing holes (108) and spring sleeve holes (109); The Y-axis limiting mechanism (2) comprises a second base plate (200), a second servo motor (201) is arranged at one end of the second base plate (200), an output end of the second servo motor (201) is connected in series with a second encoder (202) and then connected to a second ball screw (204), a second limiting boss (206) is movably arranged on the second ball screw (204), a pair of second trapezoidal guide rails (203) are also arranged on both sides of the second base plate (200) in parallel with the second ball screw (204), and a second slider (205) is movably arranged on the second trapezoidal guide rail (203); The upper side of the second limiting boss (206) is connected and fixed to the center position of the first bottom plate (100), and the upper side of the second sliding block (205) is connected and fixed to the bottom of the first bottom plate (100); A plurality of Z-axis limiting mechanisms (3) are also arranged around the bottom of the second bottom plate (200); A Z-axis compensation mechanism is also provided at the center position of the bottom of the second base plate (200), wherein the Z-axis compensation mechanism comprises a solenoid valve (4) and a cylinder (5); The control ends of the first servo motor (101), the first encoder (102), the second servo motor (201), the second encoder (202), the Z-axis limiting mechanism (3), the electromagnetic valve (4), and the cylinder (5) are all connected to the electromagnetic force control device.

2. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 1, characterized in that: The Z-axis limiting mechanism (3) comprises a vertically arranged hydraulic cylinder housing (300), the side wall of the hydraulic cylinder housing (300) being provided with an oil inlet hole (303) and an oil outlet hole (305), a telescopic rod (302) being movably provided at the output end of the hydraulic cylinder housing (300), an optical shaft sleeve hole (301) being provided at the extended end of the telescopic rod (302), and the optical shaft sleeve hole (301) being hingedly connected to a fixing ear (207) provided at the bottom of the second bottom plate (200) via a pin; A hydraulic cylinder (304) is disposed inside the hydraulic cylinder housing (300), and a one-way valve (306) is also disposed inside the hydraulic cylinder (304); A truncated cone base (307) is provided at the bottom of the hydraulic cylinder housing (300); when in use, the truncated cone base (307) is placed on a test bench.

3. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 1, characterized in that: The solenoid valve (4) comprises a valve body (407), the output end of the valve body (407) being connected to the valve core (403) via an adjusting screw (406), an electromagnet coil (402) being provided at both ends of the valve core (403), and a valve cover (401) being provided at the extended end of the valve core (403); A guide component (405) and a guide spring (404) are also provided on the outer side of the adjusting screw (406); The cylinder (5) comprises a cylinder barrel (506), a piston rod (505) is arranged inside the cylinder barrel (506), a driving end of the piston rod (505) is movably connected to an end cover (501) via a piston (504), and a sealing ring (502) and a buffer mechanism (503) are also arranged on the inner side of the end cover (501); The extended end of the piston rod (505) contacts the center position of the bottom of the second bottom plate (200), and an adjustment spring (507) is also provided between the cylinder (506) and the second bottom plate (200); Both ends of the piston rod (505) are respectively connected to the electromagnet coil (402).

4. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 3 is characterized in that: When the solenoid valve (4) is in use, the gas pressure, the thrust of the valve core compression spring, the thrust of the return spring, and the inherent friction force of the valve core (403) are adjusted in real time under the action of the electromagnet coil (402), the guide component (405), and the adjustment screw (406).

5. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 4, characterized in that: When the cylinder (5) is in use, the buffer mechanism (503), the piston (504), and the piston rod (505) arranged inside the cylinder (5) are controlled by the solenoid valve (4) so ​​that the piston rod (505) can output an outward thrust smoothly and obtain a nonlinear periodic speed.

6. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 1, characterized in that: The first servo motor (101), the first encoder (102), the second servo motor (201), and the second encoder (202) jointly complete the collection and feedback of water droplet displacement data on the super-hydrophobic surface (6); The motion data collected by sensors arranged on the first ball screw (104) and the second ball screw (204) are adaptively adjusted according to the needs of the motion thread by an algorithm program built into the electromagnetic force control device.

7. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 6, characterized in that: The sensor specifically includes a force sensor signal acquisition module, a force sensor signal amplification module, and a communication module; The algorithm program built into the electromagnetic force control device is specifically a PID closed-loop regulation control algorithm and a PWM pulse width modulation algorithm.

8. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 1, characterized in that: The super-hydrophobic surface (6) is specifically a symmetrical micro-pillar array structure, or a homogeneous and isotropic random micro-nano structure; During the experiment, the super-hydrophobic surface (6) was surface-modified so that the droplets on the super-hydrophobic surface (6) were in a Cassie state.

9. The droplet directional movement experimental device based on super-hydrophobic motion control according to claim 1, characterized in that: Specifically, four Z-axis limiting mechanisms (3) are provided.

10. An experimental method for directional movement of droplets based on super-hydrophobic motion control, characterized in that: The experimental steps include the following: Step 1: Set the experimental device to the initial position: Moving the test sample (107) to the middle of the first bottom plate (100), moving the first bottom plate (100) to the middle of the second bottom plate (200), and adjusting the telescopic height of each hydraulic cylinder housing (300) so that the test sample (107) remains horizontal; The super-hydrophobic surface (6) is fixed to the test sample (107) by bolts and leveled; Step 2: Preload the superhydrophobic surface (6): The electromagnetic force control device controls the first servo motor (101) and the second servo motor (201) to start, and after removing the influence of the self-gravity of the test sample (107) and the super-hydrophobic surface (6), a calculation correction value is introduced to complete the unidirectional movement of the test sample (107) under the action of the servo motor and the X-axis and Y-axis limiting mechanisms, complete the collection and feedback of the displacement data, and perform recording and debugging; The electromagnetic force control device controls the action of the electromagnetic valve (4) and the cylinder (5), and the cylinder (5) adjusts the gas source pressure to push the test sample (107) to adjust the acceleration, so as to complete the unidirectional movement of the test sample (107) under the action of the cylinder and the electromagnetic valve, complete the collection and feedback of the displacement data, and perform recording and debugging; Step 3: Use a high-speed camera to capture a time-displacement image of the droplet on the super-hydrophobic surface (6) to observe the dynamic characteristics of the droplet and the velocity of the center of mass; Step 4: Establish the relationship between the vibration characteristics of the super-hydrophobic surface (6) and the dynamic characteristics of the droplet and the center of mass velocity, and obtain the relationship between the asymmetric vibration of the super-hydrophobic surface (6) and the directional movement performance of the droplet.

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