Underwater soft material interface contact in-situ observation device and method

Abstract

The invention discloses an underwater soft material interface contact in-situ observation device and method, and belongs to the field of interface observation equipment. According to the observation device provided by the invention, a bright domain interface contacted with gel and a dark domain interface of retained water are distinguished by utilizing the refractive index difference of two materials, namely water and hydrogel, passing through the transparent prism, so that the evolution process of the real contact area of the interface in the underwater bonding process of the hydrogel is clearly and accurately observed; and the influence mechanism of the interfacial retention water on the underwater hydrogel bonding performance can be conveniently explored. The underwater soft material interface contact in-situ observation device is simple in principle and low in manufacturing cost, and the problem that the real contact area is difficult to observe in an underwater hydrogel bonding experiment can be solved.

Description

Technical Field

[0001] The invention belongs to the field of interface observation equipment, and in particular relates to an underwater soft material interface contact in-situ observation device and method. Background Art

[0002] As a kind of intelligent flexible material, hydrogel material is composed of a three-dimensional polymer network and a large amount of water. This soft material not only has high water content and simple preparation method, but also can adjust mechanical properties through a variety of polymer network structures. In particular, its excellent biocompatibility and structural similarity have attracted widespread attention in the biomedical field.

[0003] For example, hydrogels can achieve rapid hemostasis on damaged tissues and accelerate wound healing through controlled drug release. As a cartilage replacement material, they provide stable structural support through strong adhesion to bone tissue. They can also be used to manufacture micro soft robots that can flexibly climb on smooth biological tissue surfaces. In flexible wearable devices, hydrogels can enhance skin contact and effectively manage sweat release issues.

[0004] The practical application of hydrogels often requires the synergistic effect of multiple materials. Therefore, for such a rich and diverse variety of hydrogels with various functions and broad application prospects, how to organically combine them, or form reliable connections with other interfaces, or even achieve controllable bonding, is of great significance.

[0005] Due to the high water content of the hydrogel material itself and the hydrophilicity of the polymer chain, at the mesoscopic scale, its surface is prone to permanent "water locking" phenomenon, resulting in the appearance of a water film layer at the contact interface. The existence of this water film layer not only increases the distance between molecules, but also greatly weakens the intermolecular forces between the adhesive materials due to the high dielectric constant of water molecules. Although some researchers have used some methods to enhance the interfacial forces, when these adhesive materials are used in underwater environment operations, their bonding effects are often greatly reduced. In order to gain more obvious advantages in service in water environments, it is necessary to accurately observe the evolution of hydrogel interface bonding in water environments.

[0006] A lot of research has been done on the application of underwater adhesion of hydrogel materials. The invention patent entitled: A method for improving the underwater adhesion ability of hydrogels and related hydrogels and their preparation methods, with publication number CN110358130A, discloses a dynamic hydrogel containing hydrophobic groups prepared by cross-linking with the assistance of a surfactant. The hydrogel can produce a hydrophobic effect underwater and can expel water molecules between interfaces when bonding with a substrate, thereby achieving underwater bonding. However, this method cannot accurately observe the evolution of the real contact area of ​​the interface during the hydrogel bonding process, and cannot quantify the drainage efficiency of the hydrophobic interface. The invention patent entitled: A barnacle bionic water-touch adhesion hydrogel and its preparation method and application, with publication number CN117402292A, also failed to observe the real contact area of ​​the bonding interface when characterizing the underwater adhesion performance.

[0007] Therefore, for hydrogels with high transparency, how to distinguish the contact area and non-contact area in their underwater contact interface is a technical problem that needs to be solved urgently. Summary of the invention

[0008] The purpose of the present invention is to solve the above problems existing in the prior art and to provide an underwater soft material interface contact in-situ observation device and method.

[0009] The specific technical solutions adopted by the present invention are as follows: In a first aspect, the present invention provides an underwater soft material interface contact in-situ observation device, which includes a transparent container, a transparent prism, a reflector, a level adjustment platform, a sensor pressure head and an imaging device; The transparent container is placed on a horizontal adjustment platform, and the horizontal adjustment platform is used to level the bottom plane of the inner cavity of the transparent container; The reflector and the transparent prism are built into the bottom of the inner cavity of the transparent container, the sensor pressure head and the imaging device are located outside the transparent container, the transparent prism is a quadrangular prism whose longitudinal sections are all isosceles trapezoids of the same size, and the isosceles trapezoids are placed inverted, the bottom surface of the prism where the upper base of the isosceles trapezoid is located is in contact with the bottom plane of the inner cavity of the transparent container, and the top surface of the prism where the lower base of the isosceles trapezoid is located is located directly below the sensor pressure head; the top surface of the prism and the two side surfaces of the isosceles trapezoid of the transparent prism are frosted surfaces, and the remaining surfaces are transparent surfaces; the bottom surface of the sensor pressure head is used to fix the hydrogel sample, and can enter the transparent container under the drive of the loading device and apply pressure to the top surface of the prism of the transparent prism; The reflector is flatly attached to the bottom plane of the inner cavity of the transparent container and is located between the transparent prism and the imaging device. The imaging device records the contact interface between the top surface of the prism and the hydrogel sample through the reflector.

[0010] As a preferred embodiment of the first aspect, the transparent prism is made of glass or other transparent materials.

[0011] As a preferred embodiment of the first aspect, the angle between the waist and the lower base of the isosceles trapezoid is 70°.

[0012] As a preferred embodiment of the first aspect, the horizontal adjustment platform adopts a three-axis balancing platform.

[0013] As a preferred embodiment of the first aspect, the loading device adopts a universal testing machine, and the sensor pressure head is driven by the universal testing machine to move up and down in the vertical direction.

[0014] As a preferred embodiment of the first aspect, the sensor pressure head has a stress sensor for detecting the stress value between the hydrogel sample and the transparent prism.

[0015] As a preferred embodiment of the first aspect above, the position of the imaging device can be moved and adjusted, and before conducting in-situ observation of underwater soft material interface contact, an observation point at which the contact interface between the hydrogel sample and the top surface of the prism can be observed as a bright area and the non-contact interface as a dark area is determined through preliminary experiments, and the imaging device is moved and adjusted to the observation point position.

[0016] In a second aspect, the present invention provides an underwater soft material interface contact in-situ observation method using the underwater soft material interface contact in-situ observation device according to any one of the solutions of the first aspect, comprising: S1, adding water to the transparent container until the water surface submerges the transparent prism and the liquid level is 4-5 cm above the top surface of the prism; at the same time, adjusting the bottom plane of the inner cavity of the transparent container through the horizontal adjustment platform to keep the bottom plane of the inner cavity horizontal; S2. Through a preliminary experiment, the hydrogel sample is attached to the top surface of the transparent prism, and an observation point is determined at which the contact interface between the hydrogel sample and the top surface of the prism is observed as a bright area and the contact interface between water and the top surface of the prism is observed as a dark area, and then the imaging device is moved and adjusted to the position of the observation point; S3, fix the hydrogel sample to be observed at the bottom of the sensor pressure head, start to perform in-situ observation of underwater soft material interface contact, first drive the sensor pressure head to move downward at a constant speed according to a preset first rate by the loading device, so that the hydrogel sample enters the transparent container and starts to fit the prism top surface of the transparent prism and apply pressure, after detecting that the stress value between the two reaches the preset stress value, keep the sensor pressure head still to maintain the pressure between the hydrogel sample and the transparent prism until the contact time meets the preset time value, and then drive the sensor pressure head to move upward at a constant speed according to a preset second rate by the loading device again, so that the hydrogel sample is gradually peeled off from the prism top surface of the transparent prism; during the lifting and lowering process of the sensor pressure head, the contact interface between the prism top surface and the hydrogel sample is recorded by the reflector to obtain contact interface image frames at different times; S4. Perform image recognition on the contact interface image frames at different times, and extract the bright area and dark area in the contact interface image frames. The bright area is the contact interface between the hydrogel sample and the top surface of the prism, and the dark area is the non-contact interface between the hydrogel sample and the top surface of the prism due to the presence of retained water. Finally, the evolution process of the contact interface of the hydrogel sample to be observed during the underwater bonding process is obtained.

[0017] As a preferred embodiment of the second aspect, during the lifting and lowering process of the sensor pressure head, it is also necessary to record the stress value between the hydrogel sample and the transparent prism in real time through a stress sensor installed on the sensor pressure head.

[0018] As a preferred embodiment of the above-mentioned second aspect, after obtaining the image recognition results of the contact interface image frames at different times, it is necessary to calculate the contact interface ratio of the hydrogel sample at each time, and generate a time domain curve of the contact interface ratio, wherein the contact interface ratio is the ratio of the area of ​​the bright domain region to the complete contact surface area of ​​the hydrogel sample; at the same time, it is necessary to calculate the nominal stress at each time, and generate a time domain curve of the nominal stress, and the negative maximum nominal stress in the extracted curve is the bonding strength of the hydrogel sample; the nominal stress is the ratio of the stress value recorded by the stress sensor to the complete contact surface area of ​​the hydrogel sample.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an underwater soft material interface contact in-situ observation device, which uses the refractive index difference between water and hydrogel through a transparent prism to distinguish the bright domain interface of gel contact from the dark domain interface of retained water, so as to clearly and accurately observe the evolution of the real contact area of ​​the interface during the underwater bonding process of the hydrogel, and facilitate the exploration of the mechanism of the influence of the retained water on the bonding performance of the underwater hydrogel. The underwater soft material interface contact in-situ observation device used in the present invention has a simple principle and low manufacturing cost, and can solve the problem that it is difficult to observe the real contact area in the underwater hydrogel bonding experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the in-situ observation device for underwater soft material interface contact; Figure 2 Schematic diagram of the interface observation principle of a transparent prism; Figure 3 Schematic diagram of the in-situ observation device for underwater soft material interface contact in use after water injection; Figure 4 The contact area ratio-contact time relationship curve obtained in the embodiment; Figure 5 : This is the nominal stress-time curve of the underwater bonding process of the hydrogel obtained in the embodiment.

[0021] The reference numerals in the figure are as follows: transparent container 1, transparent prism 2, reflector 3, level adjustment platform 4, sensor pressure head 5, imaging device 6, hydrogel sample 7, liquid surface 8, retained water 9, bright area A, dark area B. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0023] In the description of the present invention, it is to be understood that when an element is considered to be "connected" to another element, it may be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0024] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0025] In a preferred embodiment of the present invention, an underwater soft material interface contact in-situ observation device is provided, and the components of the device include a transparent container 1, a transparent prism 2, a reflector 3, a level adjustment platform 4, a sensor pressure head 5 and an imaging device 6. Based on the device, the evolution of the real contact area of ​​the interface during the underwater bonding process of the hydrogel can be clearly and accurately observed, and it can be used to explore the mechanism of the influence of the interface retained water on the bonding performance of the underwater hydrogel. The specific structure and working principle of the device are introduced in detail below.

[0026] In the in-situ observation device of the present invention, the transparent container 1 is a container made of transparent material with an open inner cavity. The transparent container 1 is placed on a level adjustment platform 4, and the level adjustment platform 4 is used to level the bottom plane of the inner cavity of the transparent container 1.

[0027] It should be noted that the specific form of the horizontal adjustment platform 4 is not limited, and any equipment capable of three-axis adjustment may be used. In the embodiment of the present invention, the horizontal adjustment platform 4 adopts a three-axis balancing platform.

[0028] The reflector 3 and the transparent prism 2 are built into the bottom of the inner cavity of the transparent container 1, while the sensor pressure head 5 and the imaging device 6 are located outside the transparent container 1. The transparent prism 2 is a quadrangular prism whose longitudinal sections are all isosceles trapezoids of the same size, and the isosceles trapezoids are placed inverted. According to the definition of an isosceles trapezoid, there are two bases and two waists, the shorter base is called the upper base, and the longer base is called the lower base. The upper base of the upright isosceles trapezoid is above the lower base, but the isosceles trapezoid in the present invention is placed inverted, so the lower base is above the upper base. Therefore, for the inverted transparent prism 2, the prism bottom surface where the upper base of the isosceles trapezoid is located is in contact with the plane of the bottom of the inner cavity of the transparent container 1, and the prism top surface where the lower base of the isosceles trapezoid is located is located directly below the sensor pressure head 5. In addition, the prism top surface and the two isosceles trapezoidal side surfaces of the transparent prism 2 are frosted surfaces, and the remaining surfaces (including the prism bottom surface and the two rectangular side surfaces) are transparent surfaces.

[0029] The sensor pressure head 5 is a test pressure head that can carry a sensor, and the sensor pressure head 5 can be connected to a loading device to work. The bottom surface of the sensor pressure head 5 is used to fix the hydrogel sample 7, and can enter the transparent container 1 under the drive of the loading device and gradually approach and adhere to the prism top surface of the transparent prism 2, thereby applying pressure to the prism top surface of the transparent prism 2.

[0030] In the embodiment of the present invention, the loading device for installing the sensor pressure head 5 can be a universal testing machine, which generally has a sensor pressure head 5. Of course, if necessary, the sensor pressure head 5 can also be installed. The sensor pressure head 5 is driven by the universal testing machine to move up and down in the vertical direction, thereby controlling the entire observation process.

[0031] The reflector 3 is flatly attached to the bottom plane of the inner cavity of the transparent container 1 and is located between the transparent prism 2 and the imaging device 6. The imaging device 6 can be a camera, a high-speed industrial camera, etc., and its function is to record the contact interface between the top surface of the prism and the hydrogel sample 7 through the reflector 3. The purpose of setting the reflector 3 is to match the requirement of the transparent prism 2 being inverted, because

[0032] When the test is actually carried out, different microstructures can be processed on the surface of the hydrogel sample 7 to be tested. By pre-injecting water that submerges the top surface of the transparent prism 2 into the transparent container 1, an underwater bonding test environment for the hydrogel sample 7 can be created. The hydrogel sample 7 can be directly bonded to the bottom surface of the sensor pressure head 5, and then driven downward by the loading device to fit to the top surface of the prism of the transparent prism 2 in the water and gradually increase the pressure. During this bonding process, the water layer between the hydrogel sample 7 and the transparent prism 2 will be gradually squeezed out, but there may be retained water in the local area, so that the final contact interface may have a contact interface and a non-contact interface between the hydrogel sample 7 and the top surface of the prism. In this process, the imaging device 6 records the contact interface between the top surface of the prism and the hydrogel sample 7 through the reflector 3. In addition, after the pressure is maintained for a certain period of time, the transparent prism 2 can be reversed and lifted up to be peeled off from the top surface of the prism of the transparent prism 2. In this process, the imaging device 6 can continue to record the contact interface between the top surface of the prism and the hydrogel sample 7 through the reflector 3 to observe the changes in the release interface during the peeling process. The ideal contact state between the hydrogel sample 7 and the top surface of the prism is that the two are in full contact, and there is no retained water area, but it is often difficult for actual samples to achieve this state. Therefore, the observation device based on the present invention can observe the interface contact state of hydrogel samples 7 with different preparation processes or different surface microstructures underwater, and can be used to explore the mechanism of the influence of interface retained water on the bonding performance of underwater hydrogels.

[0033] In addition, in general hydrogel performance testing requirements, it is also necessary to record the stress value between the hydrogel sample 7 and the transparent prism 2. Therefore, a stress sensor for detecting the stress value between the hydrogel sample 7 and the transparent prism 2 can be further installed on the above-mentioned sensor pressure head 5.

[0034] It should be particularly noted that the position of the above-mentioned imaging device 6 should be movable and adjustable, and before conducting in-situ observation of underwater soft material interface contact, a preliminary experiment should be conducted to determine an observation point at which the contact interface between the hydrogel sample 7 and the top surface of the prism can be observed as a bright area A and the non-contact interface as a dark area B, and the imaging device 6 should be moved and adjusted to the position of the observation point.

[0035] exist Figure 2 In the figure, the transparent prism 2 is placed forward as an example to illustrate the principle schematic diagram of the transparent prism 2 being used for underwater in-situ observation of the evolution of the hydrogel contact interface. Since the refractive indexes of the hydrogel material and water are different, there is a slight difference in the refraction angle of the light refracted by these two materials to the glass prism 2. It is possible to distinguish whether the interface is water or hydrogel material. Figure 2 In, θ w is the critical refraction angle of water, θ g is the critical refraction angle of the hydrogel. When the observation point falls between the two angle areas, if the observed target point is in contact with the hydrogel sample 7, the light can be refracted into the human eye, so what is seen is the bright area A; on the contrary, if it is in contact with the retained water 9, due to the total reflection of the light, no light enters the human eye, and what is seen is the dark area B, thereby distinguishing the actual contact area of ​​the surface. Using this strategy, the imaging device 6 is set between the two angle areas and faces the glass prism 2 to record the evolution process of the entire underwater contact interface. Similarly, after the transparent prism 2 is inverted, the morphology in the transparent container 1 after adding water is as follows: Figure 3 As shown, the liquid level 8 exceeds the top surface of the transparent prism 2. At this time, the light path is changed due to the presence of the reflector 3. Therefore, the imaging device 6 can record the contact interface between the top surface of the prism and the hydrogel sample 7 through the reflector 3. The principle is the same as Figure 2 are similar.

[0036] The material of the transparent prism 2 of the present invention is glass. In addition, the angle between the waist and the lower base of the isosceles trapezoid needs to be optimized according to actual conditions. In the embodiment of the present invention, the angle between the waist and the lower base of the isosceles trapezoid is optimally 70°. Of course, the transparent prism 2 can also be replaced by other transparent materials besides glass, and the actual size can be adjusted to ensure that the side observable angle is greater than the angle between the critical refraction angle of water and the critical refraction angle of hydrogel.

[0037] In the present invention, further based on the above Figure 1 The underwater soft material interface contact in-situ observation device shown provides an underwater soft material interface contact in-situ observation method, and the specific steps are as follows: S1, adding water to the transparent container 1 until the water surface submerges the transparent prism 2 and the liquid level 8 is located 4-5 cm above the top surface of the prism; at the same time, adjusting the bottom plane of the inner cavity of the transparent container 1 through the horizontal adjustment platform 4 to keep the bottom plane of the inner cavity horizontal; S2, attaching the hydrogel sample 7 to the top surface of the transparent prism 2 through a preliminary experiment, determining an observation point where the contact interface between the hydrogel sample 7 and the top surface of the prism can be observed as a bright area A and the contact interface between water and the top surface of the prism can be observed as a dark area B, and then moving the imaging device 6 to the observation point; S3, fix the hydrogel sample 7 to be observed at the bottom of the sensor pressure head 5, and start to perform in-situ observation of the underwater soft material interface contact. First, the sensor pressure head 5 is driven by the loading device to move downward at a constant speed according to a preset first rate, so that the hydrogel sample 7 enters the transparent container 1 and begins to fit the prism top surface of the transparent prism 2 and apply pressure. After it is detected that the stress value between the two reaches the preset stress value, the sensor pressure head 5 is kept stationary to maintain the pressure between the hydrogel sample 7 and the transparent prism 2 until the contact time meets the preset time value. Then, the sensor pressure head 5 is driven by the loading device to move upward at a constant speed according to a preset second rate again, so that the hydrogel sample 7 is gradually peeled off from the prism top surface of the transparent prism 2; during the lifting and lowering process of the sensor pressure head 5, the contact interface between the prism top surface and the hydrogel sample 7 is recorded by the reflector 3 to obtain contact interface image frames at different times; S4. Perform image recognition on the contact interface image frames at different times, and extract the bright area and dark area in the contact interface image frames. The bright area is the contact interface between the hydrogel sample 7 and the top surface of the prism, and the dark area is the non-contact interface between the hydrogel sample 7 and the top surface of the prism due to the presence of retained water 9. Finally, the evolution process of the contact interface of the hydrogel sample 7 to be observed during the underwater bonding process is obtained.

[0038] It should be noted that the above-mentioned first rate, preset stress value, and second rate can all be set according to the actual test plan requirements, and there is no limitation on this.

[0039] It should be noted that the observation point in the above step S2 can be determined by observation with the naked eye or an imaging device 6, or by theoretical calculation. w and θ g, and then determine the optional range of the observation point based on the geometric relationship, but the present invention preferably uses naked eye observation, which is more efficient. In addition, when conducting a preliminary experiment, when determining the observation point, it is necessary to attach the hydrogel sample 7 to the prism top surface of the transparent prism 2. At this time, the hydrogel sample 7 can be attached to the prism top surface of the transparent prism 2 alone, or the hydrogel sample 7 can be directly fixed on the sensor pressure head 5 and then driven by the sensor pressure head 5 to attach to the prism top surface of the transparent prism 2. Both methods are acceptable.

[0040] It should be noted that when performing image recognition on the contact interface image frames at different times, manual recognition can be used, or image processing software (such as Image-J) or automatic recognition program can be used for recognition, as long as the bright area and the dark area can be distinguished according to the brightness difference in the image.

[0041] In an embodiment of the present invention, according to test requirements, during the lifting and lowering process of the sensor pressure head 5, the stress value between the hydrogel sample 7 and the transparent prism 2 can be recorded in real time by a stress sensor installed on the sensor pressure head 5.

[0042] Based on the various recorded image information and stress information, corresponding analysis can be further carried out. An optional analysis method is as follows: after obtaining the image recognition results of the contact interface image frames at different times, it is necessary to calculate the contact interface ratio of the hydrogel sample 7 at each time, and generate a time domain curve of the contact interface ratio; at the same time, it is necessary to calculate the nominal stress at each time, and generate a time domain curve of the nominal stress, and extract the negative maximum nominal stress in the curve as the bonding strength of the hydrogel sample 7.

[0043] It should be noted that the above-mentioned contact interface ratio in the present invention is defined as the ratio of the bright area area in the contact interface image frame to the complete contact surface area of ​​the hydrogel sample 7. The complete contact surface area of ​​the hydrogel sample 7 here refers to the contact area corresponding to when the hydrogel sample 7 is completely attached to the prism top surface of the transparent prism 2, that is, the area of ​​the contact surface of the hydrogel sample 7 itself for attaching to the transparent prism 2. In addition, the above-mentioned nominal stress in the present invention is defined as the ratio of the stress value recorded by the stress sensor to the complete contact surface area of ​​the hydrogel sample 7.

[0044] The above-mentioned embodiment of the present invention is demonstrated below through a specific embodiment. Figure 1 The in-situ observation device for underwater soft material interface contact and the specific implementation and technical effects of the in-situ observation method for underwater soft material interface contact shown in S1 to S4.

[0045] Example In this embodiment, in order to solve the problem that the contact interface between the hydrogel and the adhesive in the water environment is difficult to observe, a Figure 1The in-situ observation device for underwater soft material interface contact is shown. The transparent container 1 is a rectangular transparent experimental box. The rectangular transparent experimental box is a box-shaped structure without a lid surrounded by 5 acrylic plates. The bottom is a square acrylic plate with a thickness of 5 mm and a side length of 210 mm. The four sides are surrounded by rectangular acrylic plates with a size of 210 mm*100 mm*5 mm. The transparent prism 2 is an isosceles trapezoidal glass prism, which is a quadrangular prism glass prism with an isosceles trapezoidal cross section. The glass prism is made of borosilicate glass. The dimensions of the isosceles trapezoid are: upper base 50 mm, lower base 66 mm, height 22.08 mm, angle 70°, of which the prism bottom surface where the 50 mm upper base is located and the two trapezoidal side surfaces are frosted, and the remaining surfaces are all smooth. The reflector 3 is a rectangular reflector with a size of 150 mm*80 mm*3 mm. The horizontal adjustment platform 4 is a three-axis adjustable horizontal platform. The three-axis adjustable horizontal platform is a commercial xyz three-axis adjustable platform with a table size of 200mm*200mm. The hydrogel sample 7 is a pre-prepared polyampholyte hydrogel. The universal material testing machine uses instron 5965. The sensor pressure head 5 uses the sensor pressure head provided by the universal material testing machine, and the pressure head is provided with a stress sensor, which is controlled by the universal material testing machine and records the stress data of the sensor. The imaging device 6 uses an industrial camera.

[0046] The construction sequence of the above-mentioned underwater soft material interface contact in-situ observation device is as follows: first, place the three-axis adjustable horizontal platform under the force arm of the instron 5965 test machine, and then place the rectangular transparent experimental box on the three-axis adjustable horizontal platform. Place the rectangular reflector flat on the bottom of the experimental box and align it with the side. Then invert the isosceles trapezoidal glass prism (with the large square bottom facing up), with the rectangular side facing the reflector, and place it 1~2cm away from the reflector to ensure that the refracted light of the glass prism can be reflected by the reflector, which is convenient for the experimenter to observe. Adjust the xyz axis of the horizontal platform so that the upper surface of the isosceles trapezoidal glass prism is perpendicular to the force sensor of the test machine. According to the needs of the test environment, water can be injected into the experimental box to explore the underwater contact situation.

[0047] like Figure 2 As shown in the in-situ observation device for underwater soft material interface contact, due to the refractive index of water n w ≈1.33, and the refractive index of the hydrogel n g ≈1.35. When light is refracted from water or hydrogel into a glass prism (nglass ≈1.52), according to the law of refraction shown in formula (1), the refracted light will deviate toward the normal line of the prism interface.

[0048] n1*sinθ1 = n2*sinθ2 (1) Therefore, when the incident angle of the light is greater than the critical angle θ cTherefore, the difference in the refractive index of water and hydrogel can be used to calculate the difference in the critical angle between the two materials to determine the best observation angle.

[0049] sinθ c = n2 / n1 (2) In this embodiment, the critical angle θ of water can be calculated w ≈ 62°, while the critical angle θ of the hydrogel g ≈ 64°, and then use a glass prism to refract the light from the underwater contact interface to the side of the isosceles trapezoid, so that the experimenters can observe the evolution of the underwater contact interface in situ from the side. Figure 2 As shown, θ w Critical refraction angle of water, θ g is the critical refraction angle of the hydrogel. The camera’s observation point is placed at θ w and θ g In the area between the two angles, if the observed target point is in contact with the hydrogel, the light can be refracted into the human eye, so what is seen is the bright area; on the contrary, if it is in contact with water, due to total reflection of the light, no light enters the human eye, and what is seen is the dark area, thereby distinguishing the actual contact area of ​​the surface.

[0050] Using the above-built underwater soft material interface contact in-situ observation device, the specific experimental steps for in-situ observation of underwater soft material interface contact are as follows: First, adjust the direction of the rectangular experimental box so that the rectangular reflector at the bottom of the box is in front of the experimenter, ensuring that the upper surface of the isosceles trapezoidal glass prism can be observed through the reflector; Then add water to the experimental box, and pour the water along the side wall of the experimental box to prevent the isosceles trapezoidal glass prism and the rectangular reflector from being displaced by the impact of the water flow. Stop adding water when the liquid level is 4-5 cm above the upper surface of the isosceles trapezoidal glass prism. Note that the liquid level should not be too high to prevent the subsequent experiment from submerging the entire stress sensor and causing damage to the instrument;

[0051] Then adjust the xyz axis of the three-axis horizontal platform so that the upper surface of the isosceles trapezoidal glass prism is completely perpendicular to the pressure head of the stress sensor, ensuring that only positive stress but no shear stress is generated on the upper surface during the subsequent downward pressure process; Then fix the hydrogel sample to be investigated on the sensor pressure head of the universal material testing machine. After determining the observation point where the contact interface between the hydrogel sample and the top surface of the prism is observed as a bright area and the contact interface between water and the top surface of the prism is a dark area through the above-mentioned preliminary experiment, place the industrial camera at the observation point position and record the interface image through the rectangular reflector. The hydrogel sample on the sensor pressure head is controlled by the universal material testing machine to slowly approach the isosceles trapezoidal glass prism at a rate of 10μm / s and fit the top surface of the prism until the stress detected by the stress sensor on the sensor pressure head reaches the preset load of 15N, stop pressing down, and maintain a certain contact time;

[0052] The sensor head is then reversely stretched at a speed of 10 μm / s to peel the hydrogel from the adhered substrate. The experiment is completed when the hydrogel is completely separated from the top surface of the prism.

[0053] It should be noted that during the experiment, the industrial camera was set at the observation point and kept the viewing angle, focal length and other parameters unchanged, so as to maintain clear video recording in the whole process from contact to peeling, so as to facilitate the subsequent analysis and calculation of the images using Image-J software to quantify the evolution process of the contact interface.

[0054] The data of the stress sensor is read from the universal material testing machine, and the contact interface image frames at different times are read from the industrial camera. Image recognition is performed on the contact interface image frames at different times, and the bright domain area and the dark domain area in the contact interface image frame are extracted. The bright domain area is the contact interface between the hydrogel sample 7 and the top surface of the prism, and the dark domain area is the non-contact interface between the hydrogel sample 7 and the top surface of the prism due to the presence of retained water 9. Finally, the evolution process of the contact interface of the hydrogel sample 7 to be observed during the underwater bonding process is obtained. At the same time, after obtaining the image recognition results of the contact interface image frames at different times, it is necessary to calculate the contact interface proportion of the hydrogel sample 7 at each time, and generate a time domain curve of the contact interface proportion; at the same time, it is necessary to calculate the nominal stress at each time, and generate a time domain curve of the nominal stress, and extract the negative maximum nominal stress in the curve as the bonding strength of the hydrogel sample 7.

[0055] It should be noted that in order to achieve better underwater bonding effect, different microstructures are usually designed on the hydrogel surface to improve the interface drainage efficiency. Therefore, if there are multiple groups of hydrogel samples, the above experimental process can be repeated.

[0056] In this embodiment, the contact area in the contact image at different time points is calculated using Image-J software, and the contact area A is divided by the complete contact surface area A0 to obtain the contact area ratio A / A0. The contact area ratio is plotted over time to clarify the interface drainage efficiency. Taking the hydrogel with a hexagonal microstructure designed on the surface as an example, in order to compare the bonding strength of different microstructures, a regular hexagonal protrusion pattern with a height of 0.5 mm and a side length of 8 mm, 4 mm, and 3 mm is designed on the surface of the hydrogel (recorded as 8mm-0.5mm, 4mm-0.5mm, and 3mm-0.5mm, respectively). Figure 4 The contact area ratio-contact time relationship curve between the surface microstructured gel and the non-microstructured gel obtained in this embodiment is shown. Figure 5 The nominal stress-time curve of the hydrogel underwater bonding process obtained in this example is shown, thereby allowing for an intuitive comparison of the underwater interface bonding performance of hydrogels with different microstructure designs.

[0057] The above-described embodiments are only some preferred implementations of the present invention, but are not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. An underwater soft material interface contact in-situ observation device, characterized in that: It comprises a transparent container (1), a transparent prism (2), a reflector (3), a level adjustment platform (4), a sensor pressure head (5) and an imaging device (6); The transparent container (1) is placed on a horizontal adjustment platform (4), and the horizontal adjustment platform (4) is used to level the bottom plane of the inner cavity of the transparent container (1); The reflector (3) and the transparent prism (2) are built into the bottom of the inner cavity of the transparent container (1); the sensor pressure head (5) and the imaging device (6) are located outside the transparent container (1); the transparent prism (2) is a quadrangular prism whose longitudinal sections are all isosceles trapezoids of the same size, and the isosceles trapezoids are placed upside down, the prism bottom surface where the upper base of the isosceles trapezoid is located is in contact with the bottom plane of the inner cavity of the transparent container (1), and the prism top surface where the lower base of the isosceles trapezoid is located is located directly below the sensor pressure head (5); the prism top surface and two isosceles trapezoidal side surfaces of the transparent prism (2) are frosted surfaces, and the remaining surfaces are transparent surfaces; the bottom surface of the sensor pressure head (5) is used to fix the hydrogel sample (7), and can enter the transparent container (1) under the drive of a loading device and apply pressure to the prism top surface of the transparent prism (2); The reflector (3) is flatly attached to the bottom plane of the inner cavity of the transparent container (1) and is located between the transparent prism (2) and the imaging device (6). The imaging device (6) records the contact interface between the top surface of the prism and the hydrogel sample (7) through the reflector (3).

2. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The transparent prism (2) is made of glass or other transparent materials.

3. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The angle between the waist and the lower base of the isosceles trapezoid is 70°.

4. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The horizontal adjustment platform (4) adopts a three-axis balancing platform.

5. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The loading device is a universal testing machine, and the sensor pressure head (5) is driven by the universal testing machine to move up and down in the vertical direction.

6. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The sensor pressure head (5) is provided with a stress sensor for detecting the stress value between the hydrogel sample (7) and the transparent prism (2).

7. The underwater soft material interface contact in-situ observation device according to claim 1, characterized in that: The position of the imaging device (6) can be moved and adjusted, and before performing in-situ observation of underwater soft material interface contact, an observation point at which the contact interface between the hydrogel sample (7) and the top surface of the prism can be observed as a bright area (A) and the non-contact interface as a dark area (B) is determined through preliminary experiments, and the imaging device (6) is moved and adjusted to the observation point position.

8. A method for in-situ observation of underwater soft material interface contact using the underwater soft material interface contact in-situ observation device according to any one of claims 1 to 7, characterized in that: include: S1, adding water to the transparent container (1) until the water surface submerges the transparent prism (2) and the liquid surface (8) is located 4 to 5 cm above the top surface of the prism; at the same time, adjusting the bottom plane of the inner cavity of the transparent container (1) through the horizontal adjustment platform (4) so ​​that the bottom plane of the inner cavity remains in a horizontal state; S2. Through a preliminary experiment, the hydrogel sample (7) is attached to the top surface of the transparent prism (2), and an observation point is determined at which the contact interface between the hydrogel sample (7) and the top surface of the prism is observed as a bright area (A) and the contact interface between water and the top surface of the prism is observed as a dark area (B), and then the imaging device (6) is moved and adjusted to the position of the observation point; S3, fixing the hydrogel sample (7) to be observed at the bottom of the sensor pressure head (5), and starting to perform underwater soft material interface contact in-situ observation, first, the sensor pressure head (5) is driven by the loading device to move downward at a constant speed according to a preset first rate, so that the hydrogel sample (7) enters the transparent container (1) and begins to fit the prism top surface of the transparent prism (2) and apply pressure, after detecting that the stress value between the two reaches a preset stress value, the sensor pressure head (5) is kept stationary to maintain the pressure between the hydrogel sample (7) and the transparent prism (2) until the contact time meets the preset time value, and then the sensor pressure head (5) is driven by the loading device to move upward at a constant speed according to a preset second rate, so that the hydrogel sample (7) is gradually peeled off from the prism top surface of the transparent prism (2); during the lifting and lowering process of the sensor pressure head (5), the contact interface between the prism top surface and the hydrogel sample (7) is recorded by the reflector (3), and contact interface image frames at different times are obtained; S4. Perform image recognition on the contact interface image frames at different times, and extract the bright area and dark area in the contact interface image frames, wherein the bright area is the contact interface between the hydrogel sample (7) and the top surface of the prism, and the dark area is the non-contact interface between the hydrogel sample (7) and the top surface of the prism due to the presence of retained water (9), and finally obtain the evolution process of the contact interface of the hydrogel sample (7) to be observed during the underwater bonding process.

9. The in-situ observation method of underwater soft material interface contact according to claim 8, characterized in that: During the lifting and lowering process of the sensor pressure head (5), it is also necessary to record the stress value between the hydrogel sample (7) and the transparent prism (2) in real time through a stress sensor installed on the sensor pressure head (5).

10. The in-situ observation method of underwater soft material interface contact according to claim 9, characterized in that: After obtaining the image recognition results of the contact interface image frames at different times, it is necessary to calculate the contact interface ratio of the hydrogel sample (7) at each time, and generate a time domain curve of the contact interface ratio, wherein the contact interface ratio is the ratio of the bright domain area to the complete contact surface area of ​​the hydrogel sample (7); at the same time, it is necessary to calculate the nominal stress at each time, and generate a time domain curve of the nominal stress, and the negative maximum nominal stress in the extracted curve is the bonding strength of the hydrogel sample (7); the nominal stress is the ratio of the stress value recorded by the stress sensor to the complete contact surface area of ​​the hydrogel sample (7).

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