A rapid switchable adhesion regulation method and applications thereof

Abstract

The present application relates to a kind of quick switch adhesion regulation method and its application, belong to adhesion regulation technical field.The method utilizes the strong viscoelasticity and adhesion performance of adhesion layer material in its phase transition temperature vicinity phase transition region to the strong and unique dependence characteristics of pull-off rate, at constant temperature, by adjusting pull-off rate can realize the quick regulation of switch adhesion: when with the first critical pull-off rate V c1 Unload and pull-off, can realize significant adhesion enhancement;And when with the second critical pull-off rate V c2 Unload and pull-off, can realize 0 adhesion.The method of the present application has high adhesion strength, large switch ratio and short switch time, and also significantly shortens the time period of adhesion opening and closing, so it can significantly improve the adhesion switch efficiency, can be widely applied in micro transfer printing, robot wall climbing and soft gripper and other emerging technical fields requiring fast adhesion switch response.

Description

Technical Field

[0001] This invention relates to the field of adhesion control technology, specifically to a rapid on / off adhesion control method and its application. Background Technology

[0002] To meet the advanced application needs of emerging technologies such as micro-transfer printing, robot or human wall climbing, robotic soft grippers, flexible electronic skin, and wearable monitoring devices, a new generation of switch-adhesion technology has been proposed. Switch-adhesion refers to the ability to enable adhesion when needed (corresponding to strong adhesion) and easily disable adhesion when not needed (corresponding to weak adhesion). Adhesion strength, adhesion-to-onset ratio (i.e., the ratio of strong adhesion to weak adhesion), and switching time (i.e., the time required to transition from strong adhesion to weak adhesion) are three important indicators of switch-adhesion technology.

[0003] In nature, geckos' bristle-like adhesive toe pads exhibit strong adhesion (~100 kPa), easy detachment (adhesion and friction changes exceeding three orders of magnitude), and rapid adhesion-detachment switching (15-20 ms), enabling them to climb stably and quickly on various natural or artificial surfaces. To achieve similar or even enhanced on / off adhesion to geckos, externally stimulated on / off adhesion techniques have been developed. These techniques each have advantages in terms of adhesion strength, adhesion-to-on ratio, and on / off time. For example, on / off adhesion achieved through electrical or magnetic stimulation has a short on / off time but lower adhesion strength; on / off adhesion achieved through light or heat stimulation has high adhesion strength and a large adhesion-to-on ratio but a longer on / off time; and on / off adhesion achieved through mechanical stimulation has a moderate adhesion-to-on ratio and on / off time. In particular, thermosensitive shape memory polymers (SMPs) excel in switch-on adhesive applications due to their excellent shape memory and significant variable stiffness properties. SMP adhesive materials exhibit high adhesion strength and adhesion-on ratio on both smooth and rough, dry and wet hard substrates. Thin-layer SMP adhesive materials also demonstrate excellent shape and bending adaptability and strong adhesive contact with flexible textiles. However, to achieve the adhesion-on state, it is necessary to actively heat the material to a temperature much higher than the SMP glass transition temperature (T0). g In its soft rubber state, contact is formed by applying pre-pressure, then the pre-pressure is kept constant, and the temperature is lowered to a level far below T. g At this point, the rigid glassy state achieves shape fixation and significantly increased stiffness (corresponding to a large contact area and uniform interfacial stress distribution), thereby enhancing adhesion; however, to achieve the adhesion-closed state, the temperature must be raised again to a level much higher than T. gWhen the rubber is in its soft rubber state, the adhesive properties are significantly reduced due to the release of elastic energy, decrease in stiffness, and reduction in contact area accompanying deformation recovery, but it usually does not reach a zero adhesion level. The slow heating and cooling process makes the adhesion switching cycle long. The time to achieve adhesion on usually takes 1-2 minutes or even longer, and the time to achieve adhesion off (i.e., adhesion switching time) usually takes tens of seconds.

[0004] The above-mentioned prior art has at least the following defects: (1) the switching and adhesion technology based on a single stimulation mode cannot simultaneously possess high adhesion strength, large adhesion-on-off ratio and short switching time; (2) the switching and adhesion technology based on shape memory and variable stiffness characteristics has a long adhesion-on-off time and adhesion-on-off cycle on a macroscopic scale, and the adhesion-on-off response is slow; (3) the adhesion performance when the adhesion is off is difficult to reach the 0 level, which makes the adhesion-on-off ratio not very large. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a rapid switching and adhesion control method and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention first provides a rapid on / off adhesion control method, comprising the following steps:

[0008] Step 1: Prepare the switch adhesive;

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

[0010] The adhesive layer exhibits phase transition characteristics at a phase transition temperature T. trans The nearby phase transition region exhibits strong viscoelasticity, T trans Not lower than room temperature. The temperature range of the phase transition region can be determined by dynamic thermomechanical analysis (DMA), and the phase transition temperature can be determined by differential scanning calorimetry (DSC) or dynamic thermomechanical analysis (DMA).

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

[0012] The temperature T is not lower than T trans -10℃, and located in the phase transition region of the adhesive layer, giving the adhesive layer strong viscoelasticity;

[0013] At the temperature T, the adhesion force of the adhesive layer at different pull-out rates is obtained through the adhesion test. The adhesion force and the pull-out rate have the following variation law: the adhesion force gradually increases to the peak adhesion force as the pull-out rate increases, and then gradually decreases from the peak adhesion force to 0 as the pull-out rate continues to increase.

[0014] 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 force;

[0015] The second critical pull-off rate V c2 Significantly higher than the first critical pull-off rate V c1 Furthermore, the viscoelasticity of the adhesive layer tends to decrease as the temperature T increases, V c1 and V c2 It increases as T increases.

[0016] Step 3: At temperature T, ensure good contact between the switch adhesive and the adhered object, and then apply the first critical pull-off rate V. c1 Unload and pull the switch to open / close the adhesive attachment.

[0017] Step 4: At temperature T, ensure good contact between the switch adhesive and the adhered object, and then apply the second critical pull-out rate V. c2 Unload and pull the switch to open / close the adhesive attachment, thus achieving adhesive closure.

[0018] Preferably, the material used to prepare the adhesive 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 the T condition in step 1 is met. trans If the material meets the requirement of being at or above room temperature, and also satisfies the variation law between the adhesive force and the pull-off rate in step 2, it can be used as a material for preparing the adhesive layer.

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

[0020] Preferably, the stimulation module in step 1 uses a direct or indirect stimulation method with adjustable adhesion layer temperature, 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 contact adhesion test, peel test, tensile test, lap shear test and burst pressure test. When conducting the adhesion test, other test parameters are fixed and only the pull-off rate is changed.

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

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

[0024] Step 2: Ensure good contact between the adhesive layer and the substrate on the donor substrate surface.

[0025] Step 3: At the first critical pull-out rate V c1 Unload and pull the switch to open the adhesive attachment, enabling stable pickup of the object to be adhered.

[0026] Step 4: Transfer the material to be adhered to a specific location on the surface of the target substrate, so that the material on the surface of the adhesive layer can form good contact with the target substrate.

[0027] Step 5: At the second critical pull-out rate V c2 Unload and pull the switch to turn off the adhesive attachment, allowing the object to be adhered to be easily released onto the target substrate surface.

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

[0029] Preferably, the materials 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 picking up, transferring, and releasing of the adhered object by the switch adhesive can be performed manually or automatically.

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

[0033] This invention utilizes the adhesive layer material at its phase transition temperature T trans The strong viscoelasticity and adhesion properties of the nearby phase transition region exhibit a strong and unique dependence on the pull-out rate. At a constant temperature, the adhesion of the switch can be rapidly controlled by adjusting the pull-out rate. During unloading and pull-out, the first critical pull-out rate V is used. c1 Significant adhesion enhancement can be achieved, with an adhesion strength reaching 700 kPa, while using the second critical pull-off rate V c2This allows adhesion to be reduced to zero, making the adhesion-to-once ratio approach infinity. Since adhesion on (corresponding to strong adhesion) and off (corresponding to zero adhesion) are achieved at a constant temperature, eliminating the need for slow heating and cooling processes, this significantly reduces the adhesion on-time compared to shape memory and variable stiffness-based on-off adhesion techniques; while zero adhesion requires a higher critical pull-off rate V. c2 This reduces the adhesion switching time from tens of seconds to tens of milliseconds. Clearly, the fast-switching adhesion control method proposed in this invention simultaneously possesses high adhesion strength, a large on / off ratio, and a short switching time, and also significantly shortens the adhesion on / off time cycle. Therefore, it can significantly improve adhesion switching efficiency. This invention effectively addresses the shortcomings of existing technologies; the method is simple and easy to implement, and can be widely applied in emerging technology fields requiring rapid adhesion switching responses, such as micro-transfer printing, robot wall climbing, and soft grippers. Attached Figure Description

[0034] Figure 1 This is a structural diagram of the switch adhesive attachment;

[0035] Figure 2 This is a graph showing the relationship between normal adhesion force and pull-off rate;

[0036] Figure 3 This diagram illustrates the use of a switch adhesive attachment to pick up and release the attached object.

[0037] The labels in the diagram represent: 1-Adhesive layer, 21-Heating plate, 22-Temperature controller, 23-Adjustable power supply, 24-Temperature sensor, 3-Substrate to be adhered, 4-Donor substrate, and 5-Target substrate. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Unless otherwise specified, the equipment and reagents used in the embodiments and experimental examples are commercially available. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0039] A rapid on / off adhesion control method includes the following steps:

[0040] Step 1: Prepare switch adhesive

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

[0042] First, a polydimethylsiloxane (PDMS) elastomer negative mold is prepared using a copy-transfer process. The bottom surface of this negative mold is either smooth or has micro-pits. Next, a thoroughly mixed and de-air-degassed resin mixture (resin monomer E44 and polyetheramine Jeffamine D230, in a mass ratio of 45:23) is poured into and fills the PDMS negative mold. The mold is then cured at 100°C and 130°C for 1 hour each, respectively. After cooling, the mold is demolded, yielding an adhesive layer 1 with a smooth surface or microstructural features. In this embodiment, a smooth surface is used.

[0043] In the curing step of adhesive layer 1, the heating plate 21 is placed flat on the PDMS negative mold, and the temperature sensor 24 is placed between the heating plate 21 and the resin mixture. After curing, demolding is performed to achieve the integral fabrication of the resin polymer adhesive layer 1, the heating plate 21, and the temperature sensor 24. Of course, the resin polymer adhesive layer 1 can also be fixed together with the heating plate 21 and the temperature sensor 24 using thermally conductive adhesives or mechanical clamps.

[0044] Adhesive layer 1 exhibits glass-rubber transition characteristics, with a phase transition temperature T. trans (that is, the glass transition temperature T) g The temperature is approximately 40°C, at T g In the nearby phase transition region (i.e., the glass-rubber transition region, spanning a temperature range of approximately 20°C, i.e., 30-50°C), the adhesive layer 1 exhibits strong viscoelasticity.

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

[0046] The normal adhesion properties between adhesive layer 1 and the rigid glass hemispherical indenter (9 mm in diameter) were characterized using an adhesion testing device. The temperature of the heating plate 21 was set to T = 37°C (slightly lower than T). gAfter the temperature of adhesive layer 1 stabilized, adhesion tests were conducted. With fixed loading rates (20 μm / s), loading displacements (500 μm), and holding times (~5 s), the normal adhesive force was obtained at different unloading and pull-off rates (2 μm / s to 6000 μm / s). Additionally, a top-down video image of the adhesion test process was observed using a high-speed CCD electron microscope in the vertical direction to obtain the contact area. The adhesive strength was calculated by dividing the adhesive force by the contact area.

[0047] Figure 2 This shows the relationship between normal adhesive force (pull-offforce) and 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), while 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. This indicates the existence of a first critical pull-off rate V. c1 (40 μm / s) causes the normal adhesion force to reach a maximum value (~3215 mN), and there exists a second critical pull-off rate V. c2 (6000 μm / s) reduces the normal adhesion force to zero. Clearly, the second critical pull-off rate V... c2 Significantly higher than the first critical pull-off rate V c1 .

[0049] Step 3: At temperature T, ensure good contact between the switch adhesive and the adhered object, and then apply the first critical pull-off rate V. c1 Unload and pull the switch to open / close the adhesive attachment.

[0050] Slightly below T g At a temperature T(37℃) of (~40℃), the adhesive layer 1 has strong viscoelasticity. In the load-bearing section of the adhesion test, it will lose some of the elastic strain energy stored in the loading section due to the relaxation of the peak load force, and will also increase the contact area due to creep, thereby strengthening the viscoelastic deformation hysteresis.

[0051] When the first critical pulling rate V c1When unloading and pulling the switch adhesive at (40 μm / s), the time from the start of unloading to the final desorption is about 6.94 s, which is close to the relaxation time of adhesive layer 1 (7.437 s). At this time, the movement of molecular chain segments is subject to greater resistance, but the molecular chain segments can still adjust their structure and orientation, resulting in large internal friction. This makes the viscoelasticity very strong while the rigidity is moderate. This further leads to the development of greater tensile stress in the region near the crack tip of adhesive layer 1 and the glass hemispherical indenter (i.e., the cohesive zone), and the range of the tensile stress is also wider. This will have a greater inhibitory or weakening effect on crack propagation, ultimately leading to significant viscoelasticity and adhesive hysteresis. Therefore, the adhesive performance is significantly enhanced (adhesive strength is about 700 kPa).

[0052] Step 4: At temperature T, ensure good contact between the switch adhesive and the adhered object, and then apply the second critical pull-out rate V. c2 Unload and pull the switch to open / close the adhesive attachment, thus achieving adhesive closure.

[0053] When the second critical pulling rate V c2 When unloading and pulling the switch adhesive at (6000μm / s), the time from the start of unloading to the final desorption is about 0.1s, which is very small compared to the relaxation time of adhesive layer 1 (7.437s). Corresponding to the high vibration frequency, the molecular chain segments do not have time to adjust their structure and orientation, and exhibit pure elastic deformation. Therefore, the internal friction is very small, and the viscoelasticity in the region near the crack tip is very weak. This region even transitions from the glass-rubber mixed state (glass state is dominant) in the glass-rubber transition zone to the rigid glass state, which causes the tensile stress in the region near the crack tip to almost disappear, and the inhibitory effect on crack propagation is significantly weakened. In addition, the elastic strain energy released by the recovery of the hysteretic deformation in the compression deformation zone when desorption occurs will also have a destructive effect on the interfacial adhesion, ultimately leading to the adhesion performance being reduced to 0 level.

[0054] Due to the first critical pull-off rate V c1 The adhesion strength at that time was approximately 700 kPa, while the second critical pull-off rate V c2 The adhesion strength is as low as 0, which makes the adhesion-to-switching ratio approach infinity.

[0055] Since adhesion on (corresponding to strong adhesion) and off (corresponding to zero adhesion) are achieved at a constant temperature, without the need for slow heating and cooling processes, this significantly shortens the adhesion on time compared to shape memory and variable stiffness-based on-off adhesion techniques. Furthermore, since zero adhesion requires a higher second critical pull-off rate V... c2This reduces the adhesion switching time from tens of seconds to tens of milliseconds. Using pull-off time to approximate the adhesion switching time, with a critical pull-off rate of 6000 μm / s and a pull-off displacement of 500 μm, the adhesion switching time is only about 83 ms. For higher temperature conditions, the pull-off rate required to achieve zero adhesion will be even greater, which will further shorten the adhesion switching time and improve adhesion switching efficiency.

[0056] Figure 3 This diagram illustrates how a switch adhesive attachment is used to pick up and release an object.

[0057] like Figure 3 As shown, an application based on a fast on / off adhesion control method is provided, including the following steps:

[0058] Step 1: Apply stimulation through the stimulation module to bring the temperature of the adhesive layer 1 to T (37℃) and maintain it. At this time, the adhesive layer 1 has strong viscoelasticity.

[0059] Step 2: Ensure good contact between the adhesive layer 1 and the substrate 3 on the surface of the donor substrate 4. Figure 3 (a));

[0060] Step 3: At the first critical pull-out rate V c1 Unload and pull the switch to open the adhesive layer 1 and heating plate 21 of the adhesive attachment, so that the adhesion can be turned on, and the object to be adhered 3 can be picked up stably. Figure 3 (b));

[0061] Step 4: Transfer the adherend 3 to a specific location on the surface of the target substrate 5, so that the adherend 3 on the surface of the adhesive layer 1 and the target substrate 5 form good contact. Figure 3 (c));

[0062] Step 5: At the second critical pull-out rate V c2 Unload and pull the switch to open the adhesive layer 1 and heating plate 21, closing the adhesive and allowing the object to be adhered 3 to be easily released onto the surface of the target substrate 5. Figure 3 (d)).

[0063] In practice, the object to be adhered to 3 can be a one-dimensional, two-dimensional, or three-dimensional solid, and can have different shapes, sizes, and materials, and can have a smooth or rough surface, whether dry or wet.

[0064] In 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 practice, steps 2 to 5 can be performed manually or automatically to pick up, transfer, and release the object 3 attached to the switch adhesive.

[0066] In summary, the fast-switching adhesive control method proposed in this invention possesses high adhesion strength, a large on / off ratio, and a short switching time, and also significantly shortens the time cycle of adhesive opening and closing. Therefore, it can significantly improve adhesive switching efficiency and can be widely applied in fields requiring fast adhesive switching response, such as micro-transfer printing, robot wall climbing, and soft grippers.

[0067] The above description is merely 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 within the protection scope of the present invention.

Claims

1. A rapid on / off adhesion control method, characterized in that, Includes the following steps: Step 1: Prepare the switch adhesive; The switch adhesive attachment includes an adhesive layer and a stimulation module, the stimulation module being used to apply stimulation to the adhesive layer to regulate the temperature of the adhesive layer; the adhesive layer is made of a responsive amorphous or semi-crystalline polymer material; The adhesive layer exhibits phase transition characteristics at the phase transition temperature. T trans The nearby phase transition region exhibits strong viscoelasticity. T trans Not lower than room temperature; Step 2: Determine the temperature through adhesion testing T The first critical pull-off rate at time V C1 Second critical pull-off rate V C2 ; The temperature T Not less than T trans -10℃, and located in the phase transition region of the adhesive layer, giving the adhesive layer strong viscoelasticity; At the temperature T The adhesion force of the adhesive layer at different pull-out rates was obtained through the adhesion test. The adhesion force and the pull-out rate showed the following variation: the adhesion force gradually increased to the peak adhesion force as the pull-out rate increased, and then gradually decreased from the peak adhesion force to 0 as the pull-out rate continued to increase. First critical pull-off rate V C1 Corresponding to peak adhesion force, the second critical pull-off rate V C2 Corresponding to 0 adhesion force; Second critical pull-off rate V C2 Significantly higher than the first critical pull-off rate V C1 ,and V C1 and V C2 Follow T Increases in size and the whole increases; Step 3: Temperature T When the switch adhesive makes good contact with the object being adhered, at the first critical pull-out rate V C1 Unload and pull the switch to open / remove the adhesive attachment; Step 4: Temperature T At this time, the adhesive attachment of the switch forms good contact with the object being adhered, at the second critical pull-out rate. V C2 Unload and pull the switch to open / close the adhesive attachment, thus achieving adhesive closure.

2. The rapid switching and adhesion control method as described in claim 1, characterized in that: The material used to prepare the adhesive layer in step 1 satisfies the requirements of step 1. T trans The temperature must be no lower than room temperature, and the variation between the adhesive force and the pull-off rate in step 2 must also be satisfied.

3. The rapid switching and adhesion control method as described in claim 1, characterized in that: The surface of the adhesive layer described in step 1 is smooth or has a biomimetic microstructure array.

4. The rapid switching and adhesion control method as described in claim 1, characterized in that: The stimulation module described in step 1 employs a direct or indirect stimulation method with adjustable adhesion layer temperature, including one of light, heat, electricity, or magnetism.

5. The rapid switching and adhesion control method as described in claim 1, characterized in that: The adhesion test described in step 2 includes at least one of the following: contact adhesion test, peel test, tensile test, lap shear test, and burst pressure test. During the adhesion test, other test parameters are fixed, and only the pull-off rate is changed.

6. The application of the rapid switching and adhesion control method according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Apply stimulation through the stimulation module to raise the temperature of the adhesion layer to [a certain level]. T And it remains so that the adhesive layer has strong viscoelasticity; Step 2: Ensure good contact between the adhesive layer and the substrate on the donor substrate surface; Step 3: At the first critical pull-out rate V C1 Unload and pull the switch to open the adhesive attachment, enabling stable pickup of the object to be attached; Step 4: Transfer the material to be adhered to a specific location on the surface of the target substrate, so that the material on the surface of the adhesive layer and the target substrate can form good contact; Step 5: At the second critical pull-out rate V C2 Unload and pull the switch to turn off the adhesive attachment, allowing the object to be adhered to be easily released onto the target substrate surface.

7. The application as described in claim 6, characterized in that: The adherend is a one-dimensional, two-dimensional, or three-dimensional solid with different shapes, sizes, and materials, and has a smooth or rough surface, whether dry or wet.

8. The application as described in claim 6, characterized in that: The donor substrate in step 2 and the target substrate in step 4 are made of rigid or flexible materials, and the target substrate has a regular or irregular flat or curved surface.

9. The application as described in claim 6, characterized in that: Steps 2 through 5 can be performed manually or automatically to pick up, transfer, and release the object being glued.

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