Liquid drop bounce motion feature detection platform and control method thereof

Abstract

The invention discloses a liquid drop bounce motion feature detection platform and a control method thereof, and belongs to the technical field of test instruments. According to the invention, on the basis of the arrangement of the detection platform, the movement of the dropper, the dropping of the liquid drop, the angle adjustment of the angle platform and the collection and processing of image data can be controlled, so that the centralized collection of liquid drop related data is realized; based on the principle that a viscous liquid drop spherically bounces when impacting the super-hydrophobic surface, namely, when the diameter d of a needle tube, the liquid-gas surface tension coefficient gamma and the liquid density rho of the liquid drop to be measured are known, the kinematic viscosity of the liquid drop can be measured by measuring the length L of the liquid drop at the initial moment; calculating the height h1 from the bottom of the liquid drop to the surface of the substrate and the maximum height h2 from the bottom of the liquid drop to the surface of the substrate during the first bounce; and compared with a falling body type viscometer, the non-contact type viscometer can effectively improve the measurement speed and the measurement accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of testing instruments, and in particular relates to a droplet bouncing motion characteristic detection platform and a control method of the detection platform. Background Art

[0002] Viscosity is one of the important physical properties and technical indicators of liquids. The accurate measurement of viscosity is of great significance in many industrial sectors and scientific research fields, especially in the petrochemical, pharmaceutical, metallurgical, food and other industries. For example, in petrochemicals, accurate measurement of oil viscosity can improve the quality and output of its products; in medicine, normal blood circulation in the human body requires blood viscosity to be maintained at an appropriate level. Abnormal blood viscosity can cause microcirculation and tissue metabolism disorders, so accurate measurement of blood viscosity will help timely diagnosis of the disease and effective prevention of the disease; in basic research, the measurement of viscosity also occupies a very important position. For example, studying the viscosity of dilute colloidal solutions can help understand the size and shape of particles, the interaction between particles and the medium, etc. Therefore, viscosity measurement technology has always received much attention, and there are many research results on liquid viscosity measurement methods and devices.

[0003] The phenomenon of droplets colliding with super-hydrophobic surfaces is common in nature and has important applications in many biological, environmental and engineering fields. For example, raindrops hit leaves swaying in the wind, vehicles driving in the rain (cars, trains, airplanes, etc.), water sprinkling for dust removal, inkjet printing, and liquid medicine packaging. Due to the microstructure on the solid surface, when they come into contact with liquid, the microstructure captures small bubbles and produces a thin film of air on the contact surface. This film can separate the solid and liquid surfaces, making the solid surface exhibit unique super-hydrophobic properties, and this property is the main reason for the rebound phenomenon caused by droplets hitting super-hydrophobic surfaces.

[0004] The present invention is based on the principle that spherical bounce occurs when a viscous droplet hits a super-hydrophobic surface. When the droplet to be tested is known to have a needle diameter d, a liquid-gas surface tension coefficient γ and a liquid density ρ, its kinematic viscosity can be obtained by measuring the droplet length L at the initial moment, the height h1 of the droplet bottom from the substrate surface and the maximum height h2 of the droplet bottom from the substrate surface during the first bounce. The present invention is mainly composed of a small computer, a microprocessor, a dropper mobile platform, an angle platform and a high-speed camera. The high-speed camera is used to capture the behavior of the droplet bouncing, and the captured image is processed by the small computer to obtain the height of the droplet bottom from the substrate twice, and finally the viscosity of the droplet is calculated. Summary of the invention

[0005] In view of the above problems existing in the prior art, an object of the present invention is to provide a droplet bouncing motion characteristic detection platform and a control method of the detection platform.

[0006] The present invention provides the following technical solutions: a droplet bouncing motion feature detection platform, comprising a base frame; the base frame is provided with a dropper moving arm and an angle platform; the dropper is provided on the dropper moving arm, and the dropper moving arm is controlled by a control module for moving the position of the dropper and squeezing the dropper; the angle platform comprises a bearing platform and a rotating mechanism for adjusting the angle of the bearing platform, and the rotating mechanism is controlled by the control module; the base frame is also provided with a camera device for detection and recording and a fluid storage tank for providing fluid for the dropper, and a data transmission link is provided between the control module and the camera device.

[0007] Furthermore, the dropper moving arm includes a horizontal moving component, a vertical moving component and a push-pull component. The horizontal moving component is used to drive the vertical moving component to move horizontally, the vertical moving component is used to drive the dropper to move vertically, and the push-pull component is used to squeeze the dropper so that the liquid in the dropper falls.

[0008] Furthermore, the angle platform includes an angle platform seat and a bearing platform movably arranged on the angle platform seat, and the bearing platform can be freely rotated and moved around the axis through the control of a rotating mechanism.

[0009] A control method for a droplet bouncing motion feature detection platform is used to determine the viscosity of a droplet to be measured. By fixing the distance between a dropper and a super-hydrophobic surface, a camera device is used to measure the length L of the droplet at the initial moment, the height h1 of the droplet bottom from the substrate surface, and the maximum height h2 of the droplet bottom from the substrate surface during the first bounce. The method specifically comprises the following steps:

[0010] S1. Power on the droplet bouncing motion feature detection platform and initialize the system of the control module, move the dropper moving arm and the angle platform to zero position, and place a certain amount of fluid to be tested in the fluid storage tank;

[0011] S2, controlling the dropper moving arm to move the dropper to the fluid storage tank, extracting a certain amount of fluid, and controlling the dropper moving arm to move the dropper to a specified position; and adjusting the angle platform to a set angle at the same time;

[0012] S3, when the position of the dropper and the angle of the angle platform are stable, the control module receives the data collected by the camera device for storage, and extracts the data for real-time detection; at the same time, the push-pull component squeezes the dropper to make the fluid drip; when the control module detects that there are drops of liquid dripping, and the data received from the camera device does not change, it stops receiving data and controls the angle platform to the maximum tilt angle, so that the drops on the carrying plane drip naturally;

[0013] S4. Finally, the dropper moving platform returns to the initial position; the control module processes the recorded data, extracts the required droplet motion characteristics, and finally calculates the fluid viscosity and displays the data on the display screen, and the program ends.

[0014] Furthermore, the calculation of the fluid viscosity is based on the droplet bouncing motion characteristic detection platform to conduct experiments to find the relationship between the droplet viscosity and related physical quantities; the relationship between the physical quantities is determined by the dimensional analysis method, and the coefficients are determined based on experimental data and nonlinear regression on Matlab; the specific steps of the calculation are as follows:

[0015] 1) Assume that the process from the dropper dripping to the bottom surface bouncing up is a single-degree-of-freedom damped linear vibration, and the relationship is as follows:

[0016] Displacement: x = Ae -tξ ω0sin(ωd+θ) (1)

[0017] speed:

[0018] The ratio of the velocity v1 when it hits the base when it falls and the velocity v2 when it leaves the base when it jumps is:

[0019]

[0020] definition:

[0021] T1 = t1-t2 is the contact time between the droplet and the substrate;

[0022] K2=-K1ω0 is a new constant;

[0023] Take the logarithm of both sides:

[0024]

[0025] In order to calculate T1, by referring to the article "Contact time of a bouncing drop" published by Richard and Quere in Nature, it is known that the expression of the contact time between the droplet and the substrate obtained by experiment is:

[0026]

[0027] Substituting into formula (5), according to dimensional analysis method, we can get:

[0028]

[0029] 2) The surface tension coefficient is:

[0030]

[0031] Where X i is the molar fraction, V i is the molar volume, γ i is the surface tension coefficient, and X1 and X2 satisfy X1+X2=1);

[0032] 3) According to the volume ratio formula, the viscosity of the new solution is deduced. If the volume fraction of the first liquid is x1, then the volume fraction of the second liquid is 1-x1, μ i is the viscosity of each liquid:

[0033] μ=x1μ1+(1-x1)μ2 (9)

[0034] 4) According to the relationship between dynamic viscosity and kinematic viscosity, the corresponding kinematic viscosity ν can be obtained. Then, according to the inner diameter of the needle tube, the needle tube diameter d, surface tension γ, liquid density ρ, drop length L, falling height h1, rising height h2 and liquid viscosity ν of the fluid under different volume fractions are calculated, and the optimal value k is fitted.

[0035] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1) Based on the setting of the detection platform, the present invention can control the movement of the dropper, the dripping of the droplet, the angle adjustment of the angle platform, and the collection and processing of image data, thereby realizing the centralized collection of droplet-related data; and adopts the principle of spherical bounce when the viscous droplet hits the super-hydrophobic surface, that is, when the droplet to be measured is in the condition of known needle diameter d, liquid-gas surface tension coefficient γ and liquid density ρ, its kinematic viscosity can be obtained by measuring the droplet length L at the initial moment, the height h1 of the droplet bottom from the substrate surface and the maximum height h2 of the droplet bottom from the substrate surface during the first bounce; non-contact measurement is realized, and the measurement speed and measurement accuracy can be effectively improved compared with the falling body viscometer;

[0037] 2) In the present invention, the angle of the angle platform is fed back by the gyroscope and controlled in real time by the control module. The angle platform can automatically stabilize its own angle and has a certain resistance to external interference. When studying the influence of the droplet collision angle on the droplet motion characteristics, the requirements for the environment can also be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the layout of the detection platform of the present invention;

[0039] Figure 2 It is a schematic diagram of the structure of the detection platform of the present invention;

[0040] Figure 3 It is a schematic diagram of the structure decomposition of the dropper moving arm of the present invention;

[0041] Figure 4 It is a schematic diagram of the angle platform structure decomposition of the present invention;

[0042] Figure 5 is a system control flow chart of the present invention;

[0043] Figure 6 These are four situations in which the liquid droplets of the present invention fall. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments of the specification. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0046] See also Figure 1-6 A droplet bouncing motion feature detection platform includes a control module, a dropper moving arm 3, an angle platform 4, a high-speed camera 5 and a base frame 6. The dropper moving arm 3 and the angle platform 4 are fixed on the base frame 6; the control module includes a small computer 1 and a microprocessor 2; the small computer 1 receives data transmitted by the high-speed camera 5; the microprocessor 2 controls the movement of the dropper moving arm 3 and the angle of the angle platform 4; the dropper is placed on the dropper moving arm 3, and the dripping of the fluid in the dropper is controlled by the dropper moving arm 3; the small computer 1 is connected to the microprocessor 2 for data transmission.

[0047] The dropper moving arm 3 includes a horizontal moving arm 101, a vertical moving arm 103, a horizontal stepping motor 102, a motor seat, a coupling, a slider guide module, a gear rack module, a lead screw, a lead screw nut, a dropper, and a push-pull block.

[0048] The three stepper motors in the dropper moving arm 3 respectively control the horizontal movement, vertical movement and squeezing action of the dropper 107; the horizontal moving arm 101 is arranged on the base frame 6, the vertical moving arm 103 is arranged on the horizontal moving arm 101, and the dropper 107 and the push-pull mechanism are arranged on the vertical moving arm 103.

[0049] The structure of the dropper moving arm 3 is as follows:

[0050] The horizontal moving arm 101 is connected to the base trestles 6 through two slider guide mechanisms, and the horizontal moving arm 101 can freely move in the horizontal direction relative to the base trestles 6. The horizontal stepping motor 102 is installed on the horizontal moving arm 101, and is connected to the base trestles through a gear rack mechanism, and the horizontal stepping motor 102 can control the horizontal movement of the horizontal moving arm 101. The vertical moving arm 103 is connected to the horizontal moving arm through two slider guide mechanisms, and the vertical moving arm 103 can freely move in the vertical direction relative to the horizontal moving arm 101. The vertical stepping motor 104 is installed on the horizontal moving arm 101, and is connected to the vertical moving arm 103 through a gear rack mechanism, and the vertical stepping motor 104 can control the up and down movement of the vertical moving arm 103. The push-pull mechanism includes a push-pull block 105, and the push-pull block 105 is connected to the vertical moving arm 103 through a slider guide mechanism, and the push-pull block 105 can freely move in the vertical direction relative to the slider guide mechanism. The push-pull stepper motor 106 is fixed on the vertical moving arm 103 and connected to the push-pull block 105 through a screw nut mechanism. The push-pull stepper motor 106 can control the push-pull action of the push-pull block 105. Finally, the dropper 107 is fixed to the bottom of the vertical moving arm, and the push-pull block 105 can control the action of the dropper 107 to extract and drip fluid.

[0051] Specifically, the angle platform includes an angle platform seat 108, a rotating stepper motor 112, an arc guide rail 111, an arc guide rail baffle 109, a platform 110, a rocker arm 113 and a connecting rod 114. The angle platform seat 108 is fixed to the base frame 6, and the arc guide rail baffle 109 is fixed to the angle platform seat 108. The bearing platform 110 is connected to the arc guide rail 111, and the bearing platform 110 can rotate freely around the axis relative to the angle platform 108. The rotating stepper motor 112 is fixed to the angle platform seat 108, and the angle of the bearing platform is controlled by the rocker arm 113 and the connecting rod 114.

[0052] A control method for a droplet bouncing motion feature detection platform, the specific steps are as follows:

[0053] First, power on the instrument and initialize the system;

[0054] The small computer will check whether it can successfully receive the data sent by the high-speed camera. If it cannot, the system will be initialized again.

[0055] At the same time, the dropper moving arm is moved to the zero position by the horizontal moving arm and the angle platform; and a certain amount of fluid to be tested is placed in the fluid storage tank;

[0056] Then the dropper moving arm moves the dropper to the fluid storage tank, the 28 stepper motors on the vertical moving arm control the push-pull block to extract a certain amount of fluid, and finally the dropper moving arm controls the dropper to move to the specified position;

[0057] At the same time, the gyroscope fixed on the carrier collects the angle of the carrier and feeds the angle back to the microprocessor, which determines whether the carrier reaches the specified angle. If it does not reach the specified angle, the microprocessor controls the motor 28 to make the carrier reach the set angle.

[0058] When the position of the dropper and the angle of the angle platform are stable, the microprocessor sends a start signal to the minicomputer;

[0059] When the minicomputer receives the start signal, it starts to receive data from the high-speed camera and stores the received data in the SD card, while extracting a small number of frames for real-time detection;

[0060] At the same time, the push-pull block starts to slowly squeeze the dropper to make the fluid drip;

[0061] When the minicomputer detects a drop of liquid falling, it sends a message to the microprocessor to stop squeezing the dropper;

[0062] The microprocessor controls the dropper moving arm to stop squeezing the dropper, and the small computer stops receiving and storing the data from the high-speed camera when it detects that there is no obvious change in the data received from the high-speed camera;

[0063] Then the small computer sends information to the microprocessor to clean the carrying surface, and the microprocessor controls the angle platform to the maximum tilt angle so that the droplets on the carrying surface drip naturally;

[0064] The dropper then moves the platform back to its initial position;

[0065] The minicomputer processes the recorded data, extracts the droplet motion characteristics required by the user, calculates the viscosity of the droplet and displays the data on the display, and the program ends.

[0066] The calculation of fluid viscosity is done through experiments to find the relationship between droplet viscosity and physical quantities such as droplet length, nozzle diameter, surface tension coefficient, density, the height of the droplet bottom from the substrate surface at the initial moment, and the maximum height of the droplet bottom from the substrate surface during the first bounce. The relationship between physical quantities is determined using dimensional analysis methods, and the coefficients are determined using experimental data and nonlinear regression on Matlab.

[0067] The calculation method of fluid viscosity is as follows:

[0068] First, assume that the process from the droplet dripping out of the dropper to the dropper bouncing up after it contacts the bottom layer is a single-degree-of-freedom damped linear vibration, and the relationship is as follows:

[0069] Displacement: x = Ae -tξ ω0sin(ωd+θ) (1)

[0070] speed:

[0071] Since the same system vibration frequency omega ω, the initial phase θ and the amplitude A will not change, and ξ is proportional to ν, and for the same liquid, ν remains unchanged. Therefore, the ratio of the velocity v1 when hitting the base when falling and the velocity v2 when leaving the base when jumping is:

[0072]

[0073] definition:

[0074] T1 = t1-t2 is the contact time between the droplet and the substrate;

[0075] K2=-K1ω0 is a new constant;

[0076] Take the logarithm of both sides:

[0077]

[0078] In order to calculate T1, by referring to the article "Contact time of a bouncing drop" published by Richard and Quere in Nature, we know that the expression of the contact time between the droplet and the substrate obtained by their experiment is:

[0079]

[0080] Substitute into formula (5):

[0081]

[0082] According to dimensional analysis, we can get:

[0083]

[0084] The outline of the hanging drop can be displayed using the Bashforth-Adams equation with the help of MATLAB.

[0085] At the same time, the surface tension coefficient is derived from the simplified formula of the surface tension coefficient of the ideal binary mixed liquid in Lu Yigang's "Surface Tension Coefficient of Ideal Mixed Liquid" (where X i is the molar fraction, V i is the molar volume, γ i is the surface tension coefficient, and X1 and X2 satisfy X1+X2=1):

[0086]

[0087] The viscosity of the new solution can be deduced based on the volume ratio formula, where the volume fraction of the first liquid is x1, then the volume fraction of the second liquid is 1-x1, μ i is the viscosity of each liquid:

[0088] μ=x1μ1+(1-x1)μ2 (9)

[0089] The corresponding kinematic viscosity ν can be obtained from the relationship between dynamic viscosity and kinematic viscosity. Then, the needle diameter d, surface tension γ, liquid density ρ, drop length L, falling height h1, rising height h2 and liquid viscosity ν of glycerol aqueous solution at volume fractions of 30%, 40%, 50%, 60% and 70% are calculated based on the inner diameter of the needle tube of 0.52mm and 0.21mm respectively. The optimal value k=13.156 is fitted by a series of data related to (d, γ, ρ, L, h1, h2, ν) with the help of matlab's multivariate nonlinear fitting method.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A droplet bouncing motion feature detection platform, comprising a base frame (6); characterized in that: The base frame (6) is provided with a dropper moving arm (3) and an angle platform (4); the dropper (107) is provided on the dropper moving arm (3), and the dropper moving arm (3) is controlled by a control module for moving the position of the dropper (107) and squeezing the dropper (107); the angle platform (4) comprises a bearing platform (110) and a rotating mechanism for adjusting the angle of the bearing platform (110), and the rotating mechanism is controlled by the control module; the base frame (6) is also provided with a camera device (5) for detecting and recording, and a fluid storage tank for providing fluid for the dropper (107), and a data transmission link is established between the control module and the camera device (5).

2. A droplet bouncing motion feature detection platform according to claim 1, characterized in that: The dropper moving arm (3) comprises a horizontal moving component, a vertical moving component and a push-pull component, wherein the horizontal moving component is used to drive the vertical moving component to move horizontally, the vertical moving component is used to drive the dropper (107) to move vertically, and the push-pull component is used to squeeze the dropper (107) so that liquid drops in the dropper (107) fall.

3. A droplet bouncing motion feature detection platform according to claim 2, characterized in that: The angle platform (4) comprises an angle platform seat (108) and a bearing platform (110) movably arranged on the angle platform seat (108); the bearing platform (110) is capable of freely rotating and moving around an axis through the control of a rotating mechanism.

4. A control method for a droplet bouncing motion feature detection platform, characterized in that: The method is used to measure the viscosity of a droplet to be measured, by fixing the distance between the dropper and the super-hydrophobic surface, and measuring the length L of the droplet at the initial moment, the height h1 of the bottom of the droplet from the substrate surface, and the maximum height h2 of the bottom of the droplet from the substrate surface during the first bounce by using a camera device (5); specifically comprising the following steps: S1, power on the droplet bouncing motion characteristic detection platform and perform system initialization of the control module, move the dropper moving arm (3) and the angle platform (4) to zero position, and place a certain amount of fluid to be tested in the fluid storage tank; S2, controlling the dropper moving arm (3) to move the dropper (107) to the fluid storage tank, extracting a certain amount of fluid, and controlling the dropper moving arm (3) to move the dropper (107) to a specified position; and adjusting the angle platform (4) to a set angle at the same time; S3, when the position of the dropper and the angle of the angle platform are stable, the control module receives the data collected by the camera device (5) for storage, and extracts the data for real-time detection; at the same time, the push-pull component squeezes the dropper (107) to make the fluid drip; when the control module detects that a drop of liquid is dripping, and the data received from the camera device (5) is unchanged, it stops receiving data, and controls the angle platform (4) to the maximum tilt angle, so that the drop of liquid on the carrying plane drips naturally; S4. Finally, the dropper moving platform returns to the initial position; the control module processes the recorded data, extracts the required droplet motion characteristics, and finally calculates the fluid viscosity and displays the data on the display screen, and the program ends.

5. The control method of a droplet bouncing motion characteristic detection platform according to claim 4, characterized in that: The calculation of the fluid viscosity is based on an experiment conducted on a droplet bouncing motion feature detection platform to find the relationship between the droplet viscosity and related physical quantities; the relationship between the physical quantities is determined by a dimensional analysis method, and the coefficients are determined based on experimental data and nonlinear regression on Matlab; the specific steps of the calculation are as follows: 1) Assume that the process from the dropper dripping to the bottom surface bouncing up is a single-degree-of-freedom damped linear vibration, and the relationship is as follows: Displacement: x = Ae -tξω 0sin(ω d +θ) (1) speed: The ratio of the velocity v1 when it hits the base when it falls and the velocity v2 when it leaves the base when it jumps is: definition: T1 = t1-t2 is the contact time between the droplet and the substrate; K2=-K1ω0 is a new constant; Take the logarithm of both sides: Substituting into formula (5), according to dimensional analysis method, we can get: 2) The surface tension coefficient is: Where X i is the molar fraction, V i is the molar volume, γ i is the surface tension coefficient, and X1 and X2 satisfy X1+X2=1); 3) According to the volume ratio formula, the viscosity of the new solution is deduced. If the volume fraction of the first liquid is x1, then the volume fraction of the second liquid is 1-x1, μ i is the viscosity of each liquid: μ=x1μ1+(1-x1)μ2 (9) 4) According to the relationship between dynamic viscosity and kinematic viscosity, the corresponding kinematic viscosity ν can be obtained. Then, according to the inner diameter of the needle tube, the needle tube diameter d, surface tension γ, liquid density ρ, drop length L, falling height h1, rising height h2 and liquid viscosity ν of the fluid under different volume fractions are calculated, and the optimal value k is fitted.

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