Rapid switch adhesion regulation and control method and application thereof

Abstract

The invention relates to a rapid switch adhesion regulation and control method and application thereof, and belongs to the technical field of adhesion regulation and control. According to the method, the characteristics that the strong viscoelasticity and the adhesion performance of an adhesion layer material in a phase transition region near the phase transition temperature of the adhesion layer material have strong and unique dependence on the pull-off rate are utilized, and the switch adhesion can be quickly regulated and controlled by adjusting the pull-off rate at a constant temperature; the remarkable adhesion enhancement can be realized; and when unloading and pulling open are carried out at the second critical pulling-open speed Vc2, zero adhesion can be realized. The method has the advantages of high adhesion strength, large on-off ratio and short on-off time at the same time, and the time period of adhesion opening and closing is also remarkably shortened, so that the adhesion switching efficiency can be remarkably improved, and the method can be widely applied to the emerging technical fields needing quick adhesion switching response, such as micro-transfer printing, robot wall climbing and soft tongs.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesion regulation, and in particular to a rapid switch adhesion regulation method and application thereof. Background Art

[0002] In order to meet the advanced application requirements of emerging technologies such as micro-transfer printing, robot or human wall climbing, robot soft gripper, flexible electronic skin and wearable monitoring equipment, a new generation of switch adhesion technology has been proposed. The so-called switch adhesion means that adhesion can be turned on when adhesion is required (corresponding to strong adhesion), and adhesion can be easily turned off when adhesion is not required (corresponding to weak adhesion). Adhesion strength, adhesion switch ratio (i.e. the ratio of strong adhesion to weak adhesion) and switch time (i.e. the time required to change from strong adhesion to weak adhesion) are three important indicators of switch adhesion technology.

[0003] In nature, the setae-type adhesive toe pads of geckos show the characteristics of strong adhesion (~100 kPa), easy detachment (adhesion and friction force change over 3 orders of magnitude) and fast adhesion-detachment transformation (15-20 ms), which enables them to climb stably and quickly on different natural or artificial walls. In order to achieve similar or even enhanced on-off adhesion as geckos, on-off adhesion technologies based on external stimuli have been developed. These on-off adhesion technologies have their own advantages in adhesion strength, adhesion-on-off ratio and on-off time. For example, on-off adhesion achieved by electrical or magnetic stimulation has a short adhesion-on-off time, but low adhesion strength; on-off adhesion achieved by light or heat stimulation has high adhesion strength and large adhesion-on-off ratio, but long adhesion-on-off time; on-off adhesion achieved by mechanical stimulation has a moderate adhesion-on-off ratio and on-off time. In particular, thermosensitive shape memory polymers (SMPs) are particularly outstanding in switch adhesion applications due to their excellent shape memory and significant variable stiffness properties. SMP adhesive materials show high adhesion strength and adhesion switch ratio on smooth or rough, dry or wet hard substrate surfaces. Thin layers of SMP adhesive materials also show good shape and bending dual adaptation and strong adhesive contact to flexible textiles. However, in order to achieve the adhesive on state, the temperature must first be actively raised to a temperature far above the SMP glass transition temperature (T g ) in the soft rubber state, contact is established by applying a pre-pressure, and then the pre-pressure is kept constant and the temperature is lowered to a temperature far below T g The rigid glass state at 100° is completed, and the shape is fixed and the stiffness is significantly increased (corresponding to a large contact area and uniform interfacial stress distribution), thereby enhancing adhesion; in order to achieve the adhesion-off state, the temperature must be raised again to a level far above T gThe soft rubber state at that time, through the elastic energy release accompanied by deformation recovery, the reduction of stiffness and the reduction of contact area, the adhesion performance is significantly reduced, but it usually does not reach the 0 adhesion level. The slow heating and cooling process makes the adhesion switch cycle longer. It usually takes 1-2 minutes or even longer to achieve adhesion opening, and it usually takes tens of seconds to achieve adhesion closing (i.e. adhesion switch time).

[0004] The above-mentioned prior art has at least the following defects: (1) The switch adhesion technology based on a single stimulation mode cannot simultaneously have high adhesion strength, large adhesion switch ratio and short switch time; (2) The switch adhesion technology based on shape memory and variable stiffness characteristics has a long adhesion switch time and adhesion switch cycle at the macroscopic scale, and the adhesion switch response is slow; (3) The adhesion performance when the adhesion is turned off is difficult to reach the zero level, which makes the adhesion switch ratio not too large. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a rapid switch adhesion control method and applications based thereon.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention first provides a rapid switch adhesion control method, comprising the following steps:

[0008] Step 1: Prepare the switch adhesive;

[0009] The switch adhesive comprises an adhesive layer and a stimulation module, wherein the stimulation module is used to apply stimulation to the adhesive layer to thereby regulate the temperature of the adhesive layer;

[0010] The adhesion layer has phase change characteristics, at the phase transition temperature T trans The phase transition region near the trans The temperature range of the phase transition zone can be determined by a dynamic thermomechanical analysis (DMA) method, and the phase transition temperature can be determined by a differential scanning calorimeter (DSC) or a dynamic thermomechanical analysis (DMA) method.

[0011] Step 2: Determine the first critical pull-off rate V at temperature T through adhesion testing c1 and the second critical pull-off rate V c2 ;

[0012] The temperature T is not lower than T trans -10°C, and located in the phase change region of the adhesive layer, so that the adhesive layer has strong viscoelasticity;

[0013] The adhesion test is performed at the temperature T to obtain the adhesion force of the adhesion layer at different pulling-off rates. The adhesion force and the pulling-off rate have the following variation pattern: the adhesion force gradually increases with the increase of the pulling-off rate to a peak adhesion force, and then gradually decreases from the peak adhesion force to 0 with the continued increase of the pulling-off rate;

[0014] The first critical pull-off rate V c1 Corresponding to the peak adhesion force, the second critical pull-off rate V c2 Corresponding to 0 adhesion;

[0015] The second critical pull-off rate V c2 Obviously higher than the first critical pull-off rate V c1 ; Moreover, as the temperature T increases, the viscoelasticity of the adhesive layer tends to weaken, V c1 and V c2 As T increases, the overall value increases.

[0016] Step 3: At temperature T, the switch adhesive is in good contact with the adherend, and the first critical pull-off rate V c1 Uninstall and pull apart the switch adhesive to achieve sticky opening.

[0017] Step 4: At temperature T, the switch adhesive is in good contact with the adherend, and the second critical pull-off rate V c2 Uninstall and pull the switch adhesive away to achieve adhesive closure.

[0018] Preferably, the material used to prepare the adhesion layer in step 1 includes but is not limited to at least one of responsive amorphous or semi-crystalline polymers, hydrogels, liquid crystal elastomers, liquid metals and composite materials formed with other functional materials, as long as T in step 1 is satisfied. trans The material is not lower than room temperature and satisfies the variation law between the adhesion force and the pulling rate in step 2, and can be used as the material for preparing the adhesion layer.

[0019] More preferably, the surface of the adhesion layer in step 1 is smooth or has a bionic microstructure array.

[0020] Preferably, the stimulation module in step 1 adopts a direct or indirect stimulation method that can adjust the temperature of the adhesion layer, including but not limited to one of light, heat, electricity or magnetism.

[0021] Preferably, the adhesion test in step 2 includes at least one of a contact adhesion test, a peel test, a tensile test, a lap shear test and a burst pressure test, and when carrying out the adhesion test, other test parameters are fixed and only the pulling rate is changed.

[0022] The present invention further provides an application of the above switch adhesion control method, comprising the following steps:

[0023] Step 1: Apply stimulation through the stimulation module to make the temperature of the adhesion layer reach T and maintain it. At this time, the adhesion layer has strong viscoelasticity.

[0024] Step 2: Make sure the adhesive layer is in good contact with the adherend on the donor substrate surface.

[0025] Step 3: Pull apart at the first critical rate V c1 Unload and pull open the switch adhesive to open the adhesive and pick up the adherend stably.

[0026] Step 4: Transfer the adherend to a specific position on the surface of the target substrate so that the adherend on the surface of the adhesive layer forms good contact with the target substrate.

[0027] Step 5: Pull apart at the second critical rate V c2 Unload and pull the switch adhesive to close the adhesive, allowing the adherend to be easily released onto the target substrate surface.

[0028] Preferably, the adherend may be a one-dimensional, two-dimensional or three-dimensional solid, may have different shapes, sizes and materials, and may have a dry or wet smooth or rough surface.

[0029] Preferably, the material of the donor substrate in step 2 and the target substrate in step 4 can be rigid or flexible.

[0030] More preferably, the target substrate in step 4 has a regular or irregular flat surface or curved surface.

[0031] Preferably, in steps 2 to 5, the switch adhesive can pick up, transfer and release the adherend manually or automatically.

[0032] Compared with the prior art, the present invention has the following advantages and outstanding effects:

[0033] The present invention utilizes the adhesion layer material at its phase transition temperature T trans The strong viscoelasticity and adhesion properties of the phase transition zone have a strong and unique dependence on the pull-off rate. Under constant temperature, the switch adhesion can be quickly regulated by adjusting the pull-off rate. During the unloading and pulling process, the first critical pull-off rate V c1 Significant adhesion enhancement can be achieved, with an adhesion strength of 700 kPa, while the second critical pull-off rate V c2Adhesion can be weakened to zero level, which makes the adhesion switch ratio approach infinity. Since adhesion opening (corresponding to strong adhesion) and closing (corresponding to zero adhesion) are achieved at a constant temperature, there is no need for a slow heating and cooling process. Compared with the switch adhesion technology based on shape memory and variable stiffness, this significantly shortens the adhesion opening time; and since zero adhesion requires a higher critical pull-off rate V c2 This is achieved by reducing the adhesion switch time from tens of seconds to tens of milliseconds. Obviously, the fast switch adhesion control method proposed in the present invention has high adhesion strength, large switch ratio and short switch time, and also significantly shortens the time period of adhesion opening and closing, thus significantly improving the adhesion switch efficiency. The present invention solves the shortcomings of the prior art well, the method is simple and easy to implement, and can be widely used in emerging technology fields that require fast adhesion switch response, such as micro-transfer printing, robot wall climbing and soft grippers. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the switch adhesive;

[0035] Figure 2 is the relationship between the normal adhesion force and the pulling rate;

[0036] Figure 3 It is a schematic diagram of using a switch adhesive to realize the picking up and releasing operation of the adherend.

[0037] The meanings of the numbers in the figure are: 1-adhesion layer, 21-electric heating plate, 22-temperature controller, 23-adjustable power supply, 24-temperature sensor, 3-adherend, 4-donor substrate, 5-target substrate. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. The equipment and reagents used in each embodiment and test example can be obtained from commercial sources unless otherwise specified. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] A rapid switch adhesion regulation method comprises the following steps:

[0040] Step 1: Prepare the switch adhesive

[0041] like Figure 1As shown, the switch adhesive includes an adhesive layer 1 made of a resin polymer material and a stimulation module, the stimulation module includes an electric heating plate 21, a temperature controller 22 connected in series with the electric heating plate 21, an adjustable power supply 23, and also includes a temperature sensor 24 electrically connected to the temperature controller 22; the temperature sensor 24 is used to detect the temperature value of the electric heating plate 21 and feed it back to the temperature controller 22, and the temperature controller 22 adjusts the temperature of the electric heating plate 21 through PID control.

[0042] First, a polydimethylsiloxane (PDMS) elastomer negative mold is prepared by a mold-transfer process, and the bottom surface of the negative mold is a smooth surface or has micro-pits; then, a resin mixture (resin monomer E44 and polyetheramine Jeffamine D230, the mass ratio of the two is 45:23) that is fully mixed and bubbled is poured into and filled with the PDMS negative mold, and then the mixture is kept at 100°C and 130°C for 1 hour respectively to complete the curing, and then the mold is removed after cooling, so that an adhesive layer 1 with a smooth surface or microstructure characteristics can be prepared. In this embodiment, a smooth surface is used.

[0043] In the curing step of the adhesive layer 1, the electric heating plate 21 is placed flat on the PDMS negative mold, and the temperature sensor 24 is placed between the electric heating plate 21 and the resin mixture. After curing, demolding is performed to realize the integrated preparation of the resin polymer adhesive layer 1, the electric heating plate 21, and the temperature sensor 24. Of course, the resin polymer adhesive layer 1, the electric heating plate 21, and the temperature sensor 24 can also be fixed together by a thermally conductive adhesive or a mechanical clamp.

[0044] The adhesive layer 1 has glass-rubber transition characteristics, and its phase transition temperature T trans (also known as the glass transition temperature T g ) is about 40℃, at T g In the nearby phase transition region (ie, glass-rubber transition region, spanning a temperature range of about 20° C., ie, 30-50° C.), the adhesive layer 1 has strong viscoelasticity.

[0045] Step 2: Determine the first critical pull-off rate V at temperature T through adhesion testing c1 and the second critical pull-off rate V c2

[0046] The adhesion test equipment was used to characterize the normal adhesion performance between the adhesive layer 1 and the rigid glass hemispherical indenter (diameter 9 mm). The temperature of the electric heating plate 21 was set to T = 37 ° C (slightly lower than T g), and after the temperature of the adhesive layer 1 stabilizes, the adhesion test is started. The loading rate (20μm / s), loading displacement (500μm) and holding time (~5s) are fixed, and the normal adhesion force under different unloading and pulling rates (2μm / s to 6000μm / s) is tested. In addition, a vertical high-speed CCD electron microscope is used to observe the top-view video image of the adhesion test process to obtain the contact area. The adhesion strength is calculated by dividing the adhesion force by the contact area.

[0047] Figure 2 Shows the relationship between the normal adhesion force (pull-off force) and the detaching speed (detaching speed).

[0048] Depend on Figure 2 It can be seen that when the pull-off rate increases from 2 μm / s to 40 μm / s, the normal adhesion force gradually increases from ~1170 mN to a maximum value (~3215 mN), and when the pull-off rate increases from 40 μm / s to 6000 μm / s, the normal adhesion force gradually decreases from the maximum value to 0, which indicates that there is a first critical pull-off rate V c1 (40 μm / s) makes the normal adhesion force reach a maximum value (~3215 mN), and there is a second critical pulling rate V c2 (6000 μm / s) reduces the normal adhesion force to 0. Obviously, the second critical pull-off rate V c2 Obviously higher than the first critical pull-off rate V c1 .

[0049] Step 3: At temperature T, the switch adhesive is in good contact with the adherend, and the first critical pull-off rate V c1 Uninstall and pull apart the switch adhesive to achieve sticky opening.

[0050] At slightly below T g At a temperature T (37°C) (~40°C), the adhesion layer 1 has strong viscoelasticity. During the load-holding stage of the adhesion test, the elastic strain energy stored in the loading stage will be partially lost due to the relaxation of the peak load force, and the contact area will be increased due to creep, thereby enhancing the viscoelastic deformation hysteresis.

[0051] When the first critical pull-off rate V c1(40μm / s) When the switch adhesive is unloaded and pulled apart, the time from the beginning of unloading to the final desorption is about 6.94s, which is close to the relaxation time of the adhesive layer 1 (7.437s). At this time, the resistance to the movement of the molecular segments is relatively large, but the molecular segments can still adjust the structure and orient, so the internal friction is large, which makes the viscoelasticity very strong, while the rigidity is moderate, which further leads to the development of greater tensile stress in the area near the crack tip between the adhesive layer 1 and the glass hemisphere indenter (i.e., the cohesive zone), and the range of action of the tensile stress is also wider, which will have a greater inhibitory or weakening effect on the crack propagation, and ultimately lead to significant viscoelasticity and adhesion hysteresis. Therefore, the adhesion performance is significantly enhanced (adhesion strength is about 700kPa).

[0052] Step 4: At temperature T, the switch adhesive is in good contact with the adherend, and the second critical pull-off rate V c2 Uninstall and pull the switch adhesive away to achieve adhesive closure.

[0053] When the second critical pull-off rate V c2 (6000μm / s) unload and pull the switch adhesive apart, the time from the beginning of unloading to the final desorption is about 0.1s, which is very small compared with the relaxation time (7.437s) of the adhesive layer 1. Corresponding to the high vibration frequency, the molecular chain segments have no time to adjust the structure and orientation, showing pure elastic deformation. Therefore, the internal friction is very small, and the viscoelasticity of the area near the crack tip is very weak. This area even enters the rigid glass state from the glass-rubber mixed state (dominated by the glass state) in the glass-rubber transition zone, resulting in the almost disappearance of the tensile stress in the area near the crack tip, and the inhibition of crack propagation is significantly weakened. In addition, the elastic strain energy released by the recovery of the delayed deformation in the compression deformation zone when desorption occurs will also have a destructive effect on the interfacial adhesion, eventually causing the adhesion performance to drop to 0 level.

[0054] Since the first critical pull-off rate V c1 The adhesion strength is about 700 kPa, and the second critical pull-off rate V c2 The adhesion strength is as low as 0, which makes the adhesion switching ratio tend to infinity.

[0055] Since the adhesion opening (corresponding to strong adhesion) and closing (corresponding to zero adhesion) are achieved at a constant temperature, there is no need for a slow heating and cooling process. Compared with the switch adhesion technology based on shape memory and variable stiffness, this significantly shortens the adhesion opening time. c2This reduces the adhesion switching time from tens of seconds to tens of milliseconds. The adhesion switching time is approximated by the pull-off time. With a critical pull-off rate of 6000μm / s and a pull-off displacement of 500μm, the adhesion switching time is only about 83ms. For higher temperature conditions, the pull-off rate required to achieve zero adhesion will be greater, which will further shorten the adhesion switching time and improve the adhesion switching efficiency.

[0056] Figure 3 A schematic diagram showing the use of a switch adhesive to achieve the pick-up and release operations of an adherend.

[0057] like Figure 3 As shown, an application based on a rapid switch adhesion regulation method is provided, comprising the following steps:

[0058] Step 1: applying stimulation through the stimulation module to make the temperature of the adhesive layer 1 reach T (37° C.) and maintain it, at which time the adhesive layer 1 has strong viscoelasticity;

[0059] Step 2: Make the adhesive layer 1 form good contact with the adherend 3 on the surface of the donor substrate 4 ( Figure 3 (a));

[0060] Step 3: Pull apart at the first critical rate V c1 Unload and pull apart the adhesive layer 1 and the heating plate 21 of the switch adhesive, so that the adhesive is turned on and the adherend 3 can be stably picked up ( Figure 3 (b));

[0061] Step 4: Transfer the adherend 3 to a specific position on the surface of the target substrate 5 so that the adherend 3 on the surface of the adhesive layer 1 forms good contact with the target substrate 5 ( Figure 3 (c));

[0062] Step 5: Pull apart at the second critical rate V c2 Unload and pull apart the adhesive layer 1 and the heating plate 21 of the switch adhesive, so that the adhesive is closed, and the adherend 3 is easily released to the surface of the target substrate 5 ( Figure 3 (d)).

[0063] In a specific implementation, the adherend 3 may be a one-dimensional, two-dimensional or three-dimensional solid, may have different shapes, sizes and materials, and may have a dry or wet smooth or rough surface.

[0064] In a specific implementation, the materials of the donor substrate 4 in step 2 and the target substrate 5 in step 4 can be rigid or flexible, and the target substrate 5 can have a regular or irregular flat surface or curved surface.

[0065] In a specific implementation, in step 2 to step 5, the switch adhesive can pick up, transfer and release the adherend 3 manually or automatically.

[0066] In summary, the fast switching adhesion control method proposed in the present invention has high adhesion strength, large switching ratio and short switching time, and also significantly shortens the time period of adhesion opening and closing. Therefore, it can significantly improve the adhesion switching efficiency and can be widely used in micro-transfer printing, robot wall climbing, soft grippers and other fields that require fast adhesion switching response.

[0067] 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 fast switch adhesion control method, characterized in that: The following steps are involved: Step 1: Prepare the switch adhesive The switch adhesive comprises an adhesive layer and a stimulation module, wherein the stimulation module is used to apply stimulation to the adhesive layer to thereby regulate the temperature of the adhesive layer; The adhesion layer has phase change characteristics, at the phase transition temperature T trans The phase transition region near the trans Not lower than room temperature; Step 2: Determine the first critical pull-off rate V at temperature T through adhesion testing c1 and the second critical pull-off rate V c2 The temperature T is not lower than T trans -10°C, and located in the phase change region of the adhesive layer, so that the adhesive layer has strong viscoelasticity; The adhesion test is performed at the temperature T to obtain the adhesion force of the adhesion layer at different pulling-off rates. The adhesion force and the pulling-off rate have the following variation pattern: the adhesion force gradually increases with the increase of the pulling-off rate to a peak adhesion force, and then gradually decreases from the peak adhesion force to 0 with the continued increase of the pulling-off rate; The first critical pull-off rate V c1 Corresponding to the peak adhesion force, the second critical pull-off rate V c2 Corresponding to 0 adhesion; The second critical pull-off rate V c2 Obviously higher than the first critical pull-off rate V c1 , and V c1 and V c2 As T increases, it increases overall; Step 3: At temperature T, the switch adhesive is in good contact with the adherend, and the first critical pull-off rate V c1 Unload and pull away the switch adhesive to achieve sticky opening; Step 4: At temperature T, the switch adhesive is in good contact with the adherend, and the second critical pull-off rate V c2 Uninstall and pull the switch adhesive away to achieve adhesive closure.

2. A fast switch adhesion control method as claimed in claim 1, characterized in that: The material used to prepare the adhesive layer in step 1 satisfies T in step 1. trans The temperature should not be lower than room temperature, and at the same time, the variation law between the adhesion force and the pulling rate in step 2 should be met.

3. A fast switch adhesion control method as claimed in claim 1, characterized in that: The material used to prepare the adhesion layer in step 1 includes at least one of responsive amorphous or semi-crystalline polymers, hydrogels, liquid crystal elastomers, liquid metals, and composite materials formed with other functional materials.

4. A fast switch adhesion control method as claimed in claim 1, characterized in that: The surface of the adhesion layer in step 1 is smooth or has a bionic microstructure array.

5. A fast switch adhesion control method as claimed in claim 1, characterized in that: The stimulation module in step 1 uses a direct or indirect stimulation method that can adjust the temperature of the adhesion layer, including one of light, heat, electricity or magnetism.

6. A fast switch adhesion control method as claimed in claim 1, characterized in that: The adhesion test in step 2 includes at least one of a contact adhesion test, a peel test, a tensile test, a lap shear test and a burst pressure test. During the adhesion test, other test parameters are fixed and only the pulling rate is changed.

7. An application of the rapid switch adhesion control method according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Apply stimulation through the stimulation module to make the temperature of the adhesion layer reach T and maintain it. At this time, the adhesion layer has strong viscoelasticity; Step 2: Make the adhesive layer form good contact with the adherend on the surface of the donor base; Step 3: Pull apart at the first critical rate V c1 Unload and pull open the switch adhesive to open the adhesive and pick up the adhered object stably; Step 4: Transfer the adherend to a specific position on the surface of the target substrate so that the adherend on the surface of the adhesive layer forms good contact with the target substrate; Step 5: Pull apart at the second critical rate V c2 Unload and pull the switch adhesive to close the adhesive, allowing the adherend to be easily released onto the target substrate surface.

8. The use according to claim 7, characterized in that: The adherend may be a one-dimensional, two-dimensional or three-dimensional solid, may have different shapes, sizes and materials, and may have a dry or wet smooth or rough surface.

9. The use according to claim 7, characterized in that: The material of the donor substrate in step 2 and the target substrate in step 4 can be rigid or flexible, and the target substrate has a regular or irregular flat surface or curved surface.

10. The use according to claim 7, characterized in that: In step 2 to step 5, the switch adhesive can pick up, transfer and release the adherend manually or automatically.

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