Low-cost free-clamp hydrogel tensile property testing method

Abstract

A low-cost clamping-free hydrogel tensile property testing method, the clamping plate used is an integrated structure, including A end, B end and bottom. When testing, the bonding plate is fixed respectively in the space between B end and A end and on the A face of B end, the hydrogel sample is bonded with glue between the bonding plates and is placed between the two B ends of the clamping plate, then the A end of the clamping plate is clamped by the clamp of the tensile testing machine to carry out the test. The hydrogel sample is fixed by using the friction force provided by the glue parallel to the tensile direction, and almost no clamping force is generated during testing, so that the accuracy of the test is greatly improved. And the force is transmitted through the intermediate clamping plate, so that no modification is needed for the clamp of the tensile testing machine during testing, and it can be directly adapted to most of the tensile testing machines on the market, and the operation is convenient. The clamping plate is low in manufacturing cost, can be directly disassembled and reused after testing, and can greatly reduce the testing cost on the basis of ensuring the accuracy of the test data.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogel tensile test, in particular to a low-cost free-clamping hydrogel tensile test method. BACKGROUND

[0002] Hydrogel material is a kind of gel material with water as dispersion medium, which has the properties of high water absorption and high water retention, and is widely used in tissue engineering, biological bionics and flexible electronic devices. Compared with rubber and plastic materials, hydrogel material has low elastic modulus and strong deformation ability, and due to the presence of water, the surface of the material is smoother. As a special kind of polymer material, when performing tensile test, the existing tensile testing machine is generally equipped with a clamp made of traditional polymer material (i.e. ordinary rubber and plastic), which applies clamping force perpendicular to the tensile direction of the hydrogel to fix the hydrogel sample for testing. However, for soft and smooth, strong deformation and high toughness hydrogel material, if the clamping force applied by the clamp is too small, the hydrogel sample will slip off the clamp and cannot be fixed, and vice versa, if a large clamping force is applied, the sample will be deformed to a large extent or even broken before testing. These two situations are a pair of contradictions when testing the tensile properties of hydrogel, and either of them will seriously affect the accuracy of the test.

[0003] Chinese patents CN208999202U and CN111487130A respectively disclose two kinds of hydrogel tensile test clamps with reduced clamping force. However, in actual use, the design of the two clamps is relatively complex, and the cost of clamp manufacturing and hydrogel sample testing is high. More importantly, the design of the two clamps is more suitable for testing hydrogel materials with large modulus, relatively low deformation ability and small surface smoothness. However, when testing the tensile properties of soft and smooth, strong deformation and high toughness hydrogel (such as acrylamide), due to the small friction along the parallel direction to the tensile direction, the two clamps still cannot prevent the hydrogel sample from slipping off the clamp, thereby adversely affecting the test. SUMMARY

[0004] The present application aims to solve the above-mentioned problems in the prior art, and provides a low-cost free-clamping hydrogel tensile test method. The device used in the present application has a simple structure and low manufacturing cost, and the isolation of the hydrogel sample and the tensile testing machine clamp is realized by the clamp plate, which can realize the uniaxial tensile test of the hydrogel sample under the condition of almost no clamping force. And in the testing process, some smooth, strong deformation and high toughness hydrogels (such as acrylamide) can be fixed well, which can minimize the slipping of the hydrogel sample, thereby ensuring the accuracy of the test.

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] A low-cost clamping-free hydrogel tensile property testing method, force transmission is achieved by using a clamping plate and an adhesive plate, the clamping plate is an integrated structure, including two clamping plate B ends standing in front, a clamping plate A end standing in back, and two clamping plate bottoms under the two clamping plate B ends in front; the two clamping plate bottoms are connected with the clamping plate A end in back and symmetrically distributed on both sides of the clamping plate A end; the two clamping plate B ends are respectively above the two clamping plate bottoms, a space for inserting the adhesive plate is provided between the clamping plate B end and the clamping plate A end, and the spacing between the two clamping plate B ends is greater than the width of the hydrogel sample strip; during testing, the two ends of the hydrogel sample strip are respectively fixed on the two clamping plates through the adhesive plates, and the two clamping plates are respectively connected with the clamps of the tensile testing machine.

[0007] When the clamping plate is used, two adhesive plates that can be used to bond the hydrogel sample strip are prepared first. When the hydrogel sample strip and the clamping plate are assembled, first, an adhesive plate is inserted into the space between the clamping plate B end and the clamping plate A end, glue is applied to the exposed part of the adhesive plate between the two clamping plate B ends, and one end of the hydrogel sample strip is bonded to the exposed part; then double-sided tape or other glue is adhered to the outside of the two clamping plate B ends, glue is applied to the other side of the hydrogel sample strip, and the second adhesive plate is adhered to the hydrogel sample strip and the two clamping plate B ends; at this time, due to the effect of the glue on the surface of the hydrogel, the hydrogel sample strip can be bonded between the two adhesive plates, and due to the presence of the double-sided tape, the second adhesive plate can be well fixed with the clamping plate, and during testing, the part of the clamping plate A end that is higher than the front clamping plate B end can be clamped by the clamp to perform stretching.

[0008] After testing, the adhesive plates are detached from the clamping plate, the double-sided tape on the clamping plate and the glue on the adhesive plate are scraped off, and the clamping plate and the adhesive plate are reused.

[0009] The width of the space between the clamping plate B end and the clamping plate A end is slightly greater than the thickness of the adhesive plate to be inserted, so that the adhesive plate can be inserted and will not be loose after insertion.

[0010] Further, in order to better fix the adhesive plate on the clamping plate, the length of the adhesive plate is equal to the length of the clamping plate A end.

[0011] Further, the height of the adhesive plate is not less than the length of the bonded part of the hydrogel sample strip, and the height of the clamping plate B end is not less than the height of the adhesive plate.

[0012] Further, under the condition that the strength of the clamping plate permits, the height of the clamping plate bottom is as small as possible compared to the length of the tested part of the hydrogel sample strip, and the total width of the clamping plate bottom is greater than the sum of the thicknesses of the clamping plate B end and the two adhesive plates.

[0013] Further, the height of the end A of the clamping plate is higher than the height of the end B of the clamping plate, and the height and the thickness of the end A of the clamping plate are convenient for the clamp of the tensile testing machine to clamp the clamping plate.

[0014] Further, in order to better bond the hydrogel sample between the two bonding plates, the thickness of the end B of the clamping plate is slightly smaller than the thickness of the hydrogel sample.

[0015] Further, the end B of the clamping plate and the end A of the clamping plate are both cuboid.

[0016] The principle of force transmission of the clamping plate of the present application is that when the tensile testing machine clamps the clamping plate, the hydrogel sample is fixed on the bonding plate by glue, and as the tensile process proceeds, the shrinkage tension of the hydrogel sample will be transmitted to the bonding plate in the form of friction, and since the bonding plate is clamped by the bottom of the clamping plate, the force on the bonding plate can be transmitted to the tensile testing machine through the clamping plate, and finally the detection of the tensile force is realized.

[0017] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0018] 1. The hydrogel sample is bonded to the bonding plate by glue, the friction parallel to the tensile direction generated by the glue and the hydrogel sample is used to fix the hydrogel sample, and the force is transmitted through the clamping plate, which can prevent the slipping of the hydrogel sample with smooth surface, large deformation ability and strong toughness during the tensile test, and realize the detection of the hydrogel sample without applying any clamping force, so that the accuracy of the data is greatly increased.

[0019] 2. The clamping plate used can be manufactured by the most common 3D printer on the market, and is low in cost and can be reused. The assembly process of the clamping plate and the hydrogel sample is simple, and the cleaning after testing is convenient, which reduces the testing cost and improves the testing efficiency.

[0020] 3. The design of the clamping plate can match any tensile testing machine on the market, and no change is needed for the clamp of the tensile testing machine before testing the hydrogel sample, which simplifies the preparation work before testing. DETAILED DESCRIPTION

[0021] Figure 1 It is a schematic view of the overall structure of the clamping plate.

[0022] Figure 2 It is a three-view schematic view of the clamping plate.

[0023] Figure 3 It is a schematic view of the structure of the hydrogel sample.

[0024] Figure 4 It is a schematic view of the structure of the bonding plate.

[0025] Figure 5 The schematic diagram for assembling the clamp and the hydrogel sample and testing with the clamp of the tensile testing machine, including the front view and the left view.

[0026] Figure 6 The detailed flow chart for assembling the clamp and the hydrogel sample, taking the assembly of one end of the hydrogel sample as an example. DETAILED DESCRIPTION

[0027] The application will be further described below in conjunction with the drawings, in which only a part of the embodiments of the application are described instead of all. The hydrogel sample used in the embodiments is a rectangular sample with the size of 45x8x2mm 3 , but the test scheme is also applicable to other sizes of rectangular and dumbbell-shaped samples.

[0028] As Figure 1 shown, the clamp structure described in the embodiments can be integrally made by a 3D printer, and the model built is imported into the 3D printer for processing and manufacturing, and the material is selected as PLA. The clamp includes two bottoms, a rear large cuboid (clamp A end) connected with the two bottoms, and two small cuboids (two clamp B ends) located in the front and seated on the clamp bottoms, and the dimensions of the parts of the clamp are referred to Figure 2 .

[0029] Specifically, the clamp B end is 1.8mm thick, 15mm high, and 8mm long. The clamp A end is 25mm long, 6mm thick, and 50mm high. The clamp bottom is 6mm wide, 3mm high, and 8mm long. The gap width between the A end and the B end is 1mm.

[0030] The hydrogel sample uses an acrylamide sample with a mass fraction of 28%, and the total length is 45mm, the width is 8mm, and the thickness is 2mm. The length of the part used for bonding on the glass sheet is 15mm, and the length of the part used for testing is also 15mm, as shown in Figure 3 .

[0031] The bonding plate uses a glass sheet with the size of 25x15x0.92mm 3 , as shown in Figure 4 .

[0032] The tensile property test method of the hydrogel sample of the application is as follows:

[0033] Before testing, a glass sheet is inserted into the gap between the A end and the B end, then glue (502 glue) is applied on the glass sheet between the two B ends, one end of the hydrogel sample strip is adhered to the glue, then the other side of the sample strip at the end is continuously applied with glue, a small amount of double-sided tape is adhered to the A face of the two clamps B ends, then another glass sheet is attached to the hydrogel sample strip, and the glass sheet is lightly pressed to make the glass sheet contact the two clamp B ends and be adhered to the two clamp B ends by the double-sided tape, and the detailed process is referred to Figure 6 When the one end of the hydrogel sample strip is assembled, the other end of the hydrogel sample strip is repeated Figure 6 The assembled combination of the clamp and the hydrogel sample strip shown in the figure can be obtained. Figure 5 After the hydrogel sample strip and the clamp are assembled, the upper half of the two clamp A ends (the part of the A end that is higher than the B end) can be clamped by the tensile testing machine clamp to perform the tensile test, as shown in Figure 5

[0034] After testing, the bonding plate is detached from the clamp, the double-sided tape on the clamp and the glue on the bonding plate are scraped off, and the clamp and the bonding plate can be reused.

[0035] The principle of the test method of the present application is that the hydrogel sample strip is adhered to two glass sheets by glue, the shrinkage tension generated by the sample strip during the tensile test is transmitted to the glass sheets through the friction force between the glue and the glass sheets, since the glass sheets are clamped by the bottom of the clamp, the shrinkage tension can be continuously transmitted to the clamp through the glass sheets, and finally transmitted to the tensile testing machine clamp by the clamp.

[0036] The present application fixes the hydrogel sample strip by using the friction force parallel to the tensile direction provided by the glue, and almost no clamping force is generated during testing, so that the accuracy of the test is greatly improved. Moreover, the force is transmitted by the intermediate clamp, so that no modification is needed for the clamp of the tensile testing machine during testing, and it can be directly adapted to most of the tensile testing machines on the market, which is convenient to operate. The clamp is cheap to manufacture, and can be directly detached and reused after testing, which greatly reduces the test cost on the basis of ensuring the accuracy of the test data.​

Claims

1. A low-cost, clamp-free method for testing the tensile properties of hydrogels, characterized in that: Force transmission is achieved using clamps and adhesive plates. The clamps are an integrated structure, including two upright clamps (B ends) at the front, one upright clamp (A end) at the rear, and two clamp bottoms located below the two clamps (B ends). The two clamp bottoms are connected to the clamp (A end) at the rear and are symmetrically distributed on both sides of the clamp (A end). The two clamps (B ends) are located above the two clamp bottoms. A space is provided between the clamps (B ends) and the clamps (A ends) for inserting the adhesive plates. The distance between the two clamps (B ends) is greater than the width of the hydrogel specimen. During testing, both ends of the hydrogel specimen are fixed to the two clamps using adhesive plates, and the two clamps are connected to the clamps of the tensile testing machine. When assembling the hydrogel specimen and the clamp, first insert an adhesive plate into the space between end B of the clamp and end A of the clamp. Apply adhesive to the exposed part of the adhesive plate between the two ends B of the clamp, and then attach one end of the hydrogel specimen to the exposed part. Then, apply double-sided tape or adhesive to the outside of the two ends B of the clamp, apply adhesive to the other side of the hydrogel specimen, and then attach the second adhesive plate to the hydrogel specimen and the two ends B of the clamp.

2. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: After testing, the adhesive board is removed from the clamp, and the double-sided tape or adhesive on the clamp and the adhesive board are scraped off, so that the clamp and adhesive board can be reused.

3. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: The width of the space between end B of the clamping plate and end A of the clamping plate is slightly greater than the thickness of the adhesive plate to be inserted, so that the adhesive plate can be inserted and will not become loose after insertion. The length of the adhesive plate is equal to the length of end A of the clamping plate.

4. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: The height of the bonding plate is not less than the length of the bonding portion of the hydrogel strip, and the height of end B of the clamp is not less than the height of the bonding plate.

5. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: If the strength of the clamp allows, the height of the bottom of the clamp is less than the length of the hydrogel strip test section, and the total width of the bottom of the clamp is greater than the sum of the thicknesses of the clamp B end and the two adhesive plates.

6. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: The height of end A of the clamping plate is higher than the height of end B of the clamping plate. The height difference and the thickness of end A of the clamping plate should be such that the clamping fixture of the tensile testing machine can easily hold the clamping plate.

7. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: The thickness of the clamp at end B is less than the thickness of the hydrogel strip.

8. The low-cost, clamp-free method for testing the tensile properties of hydrogels as described in claim 1, characterized in that: Both end B and end A of the clamping plate are rectangular parallelepipeds.

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