Sensor and method for bonding functional layers thereof

Abstract

This application discloses a sensor and a method for bonding its functional layers, belonging to the field of electronic technology. The sensor comprises a first functional layer and a second functional layer, each comprising the same polymer. The first and second functional layers are bonded together by a cross-linked structure formed by the polymers. In this application, a complete cross-linked network is formed between the first and second functional layers, forming a single integrated unit with high interfacial strength, thereby improving the stability and responsiveness of the sensor.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a bonding method for a sensor and its functional layer. Background Art

[0002] A sensor is a device that converts a measured physical or mechanical quantity into a change in electrical quantity. Generally, a sensor consists of multiple functional layers. Currently, related technologies place each functional layer in a sensor according to pre-defined structural rules and then package them together to form a complete sensor.

[0003] However, in related technologies, after the various functional layers are uniformly encapsulated, each functional layer remains a separate entity in the sensor, making the sensor prone to stratification under complex conditions, thereby affecting the stability and response performance of the sensor. Summary of the Invention

[0004] The present invention provides a sensor and a method for bonding its functional layers, which can improve the stability and response performance of the sensor. The technical solution is as follows:

[0005] According to one aspect of an embodiment of the present application, a sensor is provided, comprising a first functional layer and a second functional layer, wherein the first functional layer and the second functional layer comprise the same polymer;

[0006] The first functional layer and the second functional layer are bonded together by a cross-linked structure formed by the polymer.

[0007] According to one aspect of an embodiment of the present application, a method for bonding a functional layer of a sensor is provided, the method comprising:

[0008] Obtaining a first functional layer and a second functional layer required for preparing a sensor, wherein the first functional layer and the second functional layer both contain a first polymer;

[0009] Immersing the first functional layer and the second functional layer in a solvent solution; wherein the solvent solution includes a solvent and a second polymer, and during the immersion process, the second polymer diffuses into the first functional layer and the second functional layer along with the solvent, and the first polymer and the second polymer are the same polymer;

[0010] After the immersion is completed, taking out the first functional layer and the second functional layer from the solvent solution, and stacking the taken out first functional layer and second functional layer in order;

[0011] A cross-linking structure for bonding the first functional layer and the second functional layer is formed between the first polymer and the second polymer.

[0012] The technical solutions provided in the embodiments of the present application can bring the following beneficial effects:

[0013] The solvent solution allows the second polymer to enter the original network structure of the first functional layer and the second functional layer. The original network structure is the network structure formed inside the original polymer of the functional layer. Furthermore, a new network structure is formed between the first functional layer and the second functional layer. A topological cross-linked structure is generated between the new network structure and the original network structure of the functional layer. The first functional layer and the second functional layer are bonded together through the cross-linked structure. A complete cross-linked network is formed between the first functional layer and the second functional layer. The first functional layer and the second functional layer become a whole with high interface strength. During the application of the sensor, even under extreme conditions (high pressure, high friction, etc.), the first functional layer and the second functional layer will not be delaminated, thereby improving the stability and response performance of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] Figure 1 This is a flow chart of a sensor functional layer bonding method provided by one embodiment of the present application;

[0016] Figure 2 A schematic diagram illustrating a cross-linked structure formation process is shown;

[0017] Figures 3 to 5 A schematic diagram showing sensor signal test data is exemplified;

[0018] Figure 6 Schematic diagram showing the cone fracture at the crack tip between functional layers;

[0019] Figure 7 A schematic diagram showing a cross section of a capacitive sensor is exemplified;

[0020] Figure 8 A schematic diagram illustrating the effect of a cross-linked structure;

[0021] Figure 9 A schematic diagram showing an exemplary structure of a first functional layer;

[0022] Figure 10A schematic diagram showing a comparison of the interface strength and shear strength between the sensor prepared by the method provided in this application and the sensor prepared by other methods is shown;

[0023] Figure 11 A schematic diagram exemplarily shows the structure of a sensor;

[0024] Figure 12 A schematic diagram showing, by way of example, a curve showing changes over time of a capacitance signal of a capacitance sensor and a force applied by the gripper when a melon is gripped using the gripper equipped with the capacitance sensor;

[0025] Figure 13 The diagram exemplarily shows the capacitance response curve and resistance response curve of the sensor when grabbing a doll. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0027] Artificial Intelligence (AI) refers to the theories, methods, techniques, and application systems that use digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, to perceive the environment, acquire knowledge, and use that knowledge to achieve optimal results. In other words, AI is a comprehensive technology within computer science that seeks to understand the essence of intelligence and produce new intelligent machines that can respond in a manner similar to human intelligence. AI also studies the design principles and implementation methods of various intelligent machines, enabling them to possess the capabilities of perception, reasoning, and decision-making.

[0028] Artificial intelligence (AI) technology is a comprehensive discipline encompassing a wide range of fields, encompassing both hardware and software technologies. Foundational AI technologies generally include sensors, specialized AI chips, cloud computing, distributed storage, big data processing, operating / interaction systems, and mechatronics. AI software technologies primarily encompass computer vision, speech processing, natural language processing, and machine learning / deep learning.

[0029] With the research and advancement of artificial intelligence technology, artificial intelligence technology has been studied and applied in many fields, such as common smart homes, smart wearable devices, virtual assistants, smart speakers, smart marketing, unmanned driving, autonomous driving, drones, robots, smart medical care, smart customer service, etc. It is believed that with the development of technology, artificial intelligence technology will be applied in more fields and play an increasingly important role.

[0030] The solution provided in the embodiments of this application relates to artificial intelligence robotics technology. Solvent swelling bonding is used to bond the various functional layers in a sensor. This creates a stable cross-linked structure between the functional layers, making them not independent entities but tightly connected. In this case, when the sensor is applied to an artificial intelligence robot, the bonded functional layers improve the sensor's wear resistance and pressure resistance. Even when the robot operates in extreme environments, the sensor can still obtain data promptly and accurately, ensuring the robot's normal operation.

[0031] Optionally, the sensor in this application can be applied to electronic skin. Electronic skin is a device that can respond to mechanical stimuli and enable intelligent robots to perceive the surrounding environment. In related technologies, electronic skin mostly adopts a multi-layer structure. Due to mechanical mismatch and weak adhesion, the interface between the layers is often poor, resulting in unstable performance of the electronic skin under harsh mechanical conditions. However, in this application, the functional layers of the sensor are bonded by swelling bonding, and then when the sensor is applied to the electronic skin, the sensor can exhibit mechanical matching and strong adhesion between the layers, realizing a seamless interface between the sensor and the robot.

[0032] Please refer to Figure 1 , which shows a flow chart of a sensor functional layer bonding method provided by an embodiment of the present application. The method may include the following steps (101-104):

[0033] Step 101: Obtain a first functional layer and a second functional layer required for preparing a sensor.

[0034] A sensor refers to a conversion device that converts environmental information into electrical information. The environmental information includes, but is not limited to, at least one of the following: light intensity, pressure intensity, friction intensity, movement speed, rotation angle, etc., which is not limited in the embodiments of the present application. Optionally, the environmental information received by sensors on different devices is different. For example, the environmental information received by the sensor on the photosensitive device is light intensity, the environmental information received by the sensor on the mobile device is movement speed, and so on. In an exemplary embodiment, the same device contains multiple sensors, which can be the same sensor or different sensors.

[0035] Optionally, the sensor includes multiple functional layers, and the functional layers included in different types of sensors may have different functions and types. In an embodiment of the present application, before preparing the sensor, the first functional layer and the second functional layer required for preparing the sensor are obtained. Wherein, the first functional layer and the second functional layer both contain a first polymer, and the first polymer includes a first polymer monomer and a curing agent. Exemplarily, the above-mentioned sensor is a capacitive sensor, the above-mentioned first functional layer is an electrode layer, and the above-mentioned second functional layer is a dielectric layer. Wherein, the electrode layer includes an upper electrode layer and a lower electrode layer, and the dielectric layer is a functional layer between the upper electrode layer and the lower electrode layer for improving the response and relaxation speed of the capacitive sensor.

[0036] In one possible embodiment, the functional layer is a pre-prepared functional layer. Optionally, to ensure rapid sensor production, personnel pre-prepare functional layers of various types and functions and store them by category. Before producing the sensor, the functional layers required for the sensor are determined based on the sensor's intended function, and the first and second functional layers are then obtained.

[0037] In another possible embodiment, the functional layer is prepared in real time. Optionally, because the expected function of the sensor may be slightly adjusted in different situations, to ensure sensor accuracy, personnel determine the functional layer required for the sensor based on the expected function, prepare the required functional layer, and then obtain the first and second functional layers.

[0038] It should be noted that in the embodiments of the present application, different sensors correspond to different functional layers. For example, in a capacitive sensor, the first functional layer is the upper electrode layer or the lower electrode layer, and the second functional layer is the dielectric layer; in a resistive sensor, the first functional layer is the upper electrode layer, and the second functional layer is the lower electrode layer; and so on.

[0039] Optionally, the first functional layer is an electrode layer, and the second functional layer is a dielectric layer. Optionally, in an embodiment of the present application, the conductive particles and the first polymer are mixed in a first mass ratio to generate the first functional layer; the conductive particles and the first polymer are mixed in a second mass ratio to generate the second functional layer; wherein the first mass ratio is greater than the second mass ratio, thereby ensuring the conductivity of the first functional layer and the dielectric properties of the second functional layer. In this case, the first functional layer and the second functional layer are prepared using the same material, so that the polymer network formed by the first functional layer and the second functional layer has the same chemical properties, thereby ensuring mechanical matching between the functional layers. Moreover, doping the dielectric layer with conductive particles can improve the sensing characteristics and signal stability of the sensor. Of course, in an exemplary embodiment, since the dielectric layer has dielectric properties, the pure first polymer can also be directly used to generate the second functional layer.

[0040] Optionally, the first polymer is a macromolecular polymer. In the embodiment of the present application, the first polymer is any macromolecular polymer capable of producing a swelling effect. Optionally, the first polymer includes any one of the following: polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polypropylene, rubber, polyoxymethylene, etc.

[0041] Optionally, the conductive particles include, but are not limited to, at least one of the following: metal nanowires (such as silver nanowires, gold nanowires, and copper nanowires), carbon nanotubes, graphite, graphene, carbon black, and metal conductive powders (such as gold powder, silver powder, and copper powder). In the embodiments of the present application, the conductive particles can be made of any conductive material. It should be noted that the conductive particles can refer to conductive particles composed of a single material or a conductive network composed of multiple materials, and the embodiments of the present application are not limited thereto.

[0042] Optionally, in an embodiment of the present application, the first polymer is an elastic-based polymer, and correspondingly, the sensor is a flexible sensor.

[0043] Optionally, in an embodiment of the present application, a plurality of microstructure units are arranged protruding from the bonding surface of the first functional layer. This bonding surface refers to the side of the first functional layer that is bonded to the second functional layer. The presence of microstructures in the sensor can, on the one hand, improve the sensor's sensing characteristics and signal stability; on the other hand, for flexible sensors, enable the sensor to quickly relax energy when pressure is released.

[0044] Step 102: Immerse the first functional layer and the second functional layer in a solvent solution.

[0045] In an embodiment of the present application, after obtaining the first and second functional layers, the first and second functional layers are immersed in a solvent solution. The solvent solution includes a solvent and a second polymer. During the immersion process, the second polymer diffuses into the first and second functional layers along with the solvent. The second polymer includes a second polymer monomer and a curing agent. Optionally, in this embodiment of the present application, both the second polymer and the first polymer are elastomeric-based polymers.

[0046] Optionally, the solvent is used to swell the first and second functional layers. Optionally, in embodiments of the present application, when the functional layer is immersed in the solvent solution, the solvent causes the functional layer to swell and expand in volume. At this point, the second polymer monomers and the curing agent diffuse into the existing polymer network of the functional layer. The existing polymer network of the functional layer refers to the network generated by the first polymer. It should be noted that the volume of the functional layer after immersion is expanded compared to the original functional layer.

[0047] Optionally, to improve the bonding effect between the functional layers, the ratio of the mass of the second polymer to the mass of the solvent is 1 wt% to 50 wt%, such as 1 wt%, 5 wt%, 17 wt%, 28 wt%, 39 wt%, 45 wt%, etc. Of course, in exemplary embodiments, personnel can flexibly set and adjust the ratio of the mass of the second polymer to the mass of the solvent based on actual conditions, and this embodiment of the application is not limited thereto.

[0048] In the embodiments of the present application, to improve the bonding effect between the functional layers, the first functional layer and the second functional layer are immersed in the solvent solution for a period of more than 4 hours. Of course, in exemplary embodiments, personnel can flexibly set and adjust the immersion time of the functional layers based on actual conditions, and the embodiments of the present application are not limited to this.

[0049] Optionally, the solvent includes any one of the following: chloroform, dichloromethane, and n-hexane, etc. Of course, in actual use, the selection of the solvent can be flexibly set and adjusted according to the different materials of the functional layer, and the embodiment of the present application does not limit this.

[0050] Step 103 : After the immersion is completed, the first functional layer and the second functional layer are taken out from the solvent solution, and the taken out first functional layer and the second functional layer are stacked in order.

[0051] In an embodiment of the present application, after the functional layers are immersed, the first and second functional layers are removed from the solvent solution, and the removed first and second functional layers are stacked in order. Optionally, the stacking order of the functional layers is different for different types of sensors. For example, if the sensor is a capacitive sensor, the stacking order of the functional layers is, from bottom to top, the lower electrode layer, the dielectric layer, and the upper electrode layer; if the sensor is a resistive sensor, the stacking order of the functional layers is, from bottom to top, the lower electrode layer, the upper electrode layer, and so on.

[0052] Optionally, in order to reduce the effect of the solvent on the bonding effect of the functional layer, after removing the first functional layer and the second functional layer from the solvent solution, the first functional layer and the second functional layer can be stacked in order after the solvent evaporates. In an exemplary embodiment, the above step 103 includes the following steps:

[0053] 1. Performing surface solvent volatilization treatment on the first functional layer and the second functional layer;

[0054] In a possible implementation, when performing the surface solvent volatilization treatment on the functional layer, the process is to simply wait for the solvent on the surface of the first functional layer and the solvent on the surface of the second functional layer to be completely evaporated.

[0055] In another possible embodiment, in order to increase the solvent evaporation rate, when performing surface solvent volatilization treatment on the functional layer, the environment in which the first functional layer and the second functional layer are located is adjusted according to the solvent volatilization conditions; then, in the adjusted environment, the solvent on the surface of the first functional layer and the solvent on the surface of the second functional layer are waited for to evaporate completely.

[0056] Optionally, the aforementioned environmental adjustment includes, but is not limited to, at least one of the following: pressure adjustment, temperature adjustment, wind speed adjustment, etc., which is not limited in the present embodiment. Of course, in exemplary embodiments, since the material of the functional layer may affect the volatilization of the solvent, different environments can be used for surface solvent volatilization treatment for different functional layers that have been immersed in the same solvent solution.

[0057] 2. Stack the first functional layer and the second functional layer in order.

[0058] Optionally, in the embodiment of the present application, in order to improve the solvent evaporation effect, the solvent on the surface of the functional layer evaporates for a time longer than 20 minutes. Of course, in the exemplary embodiment, the evaporation time can be flexibly set and adjusted according to actual conditions, and the embodiment of the present application does not limit this.

[0059] Step 104 : forming a cross-linking structure between the first polymer and the second polymer for bonding the first functional layer and the second functional layer.

[0060] In the embodiments of the present application, after the functional layers are stacked, a crosslinked structure is formed between the first polymer and the second polymer using the curing agent in the solvent solution. The crosslinked structure serves to bond the first and second functional layers. The curing agent, under swelling, enters the interior of the functional layers. In the embodiments of the present application, the curing agent and the second polymer monomer in the solvent solution are collectively referred to as the second polymer.

[0061] Optionally, under the action of a curing agent, a new network structure is formed between the second polymer monomers in the gaps of the first functional layer and the second polymer monomers in the gaps of the second functional layer. Furthermore, the original network structure formed by the first polymer monomers exists in the first functional layer, and the original network structure formed by the first polymer monomers exists in the second functional layer. The new network structure and the original network structure are topologically cross-linked, that is, the new network structure connects the original network structure in the first functional layer and the original network structure in the second functional layer. In this way, a cross-linked structure is formed between the first functional layer and the second functional layer, and the first functional layer and the second functional layer are bonded together. At this time, from the perspective of the cross-linked network, the first functional layer and the second functional layer belong to the same cross-linked network, and the first functional layer and the second functional layer can be regarded as a whole. In this way, the first functional layer and the second functional layer are bonded by solvent swelling bonding, which can alleviate the high viscosity of the sensor compared to the related art of encapsulating the sensor with tape.

[0062] For example, Figure 2 As shown, during the immersion process, the second polymer 21 diffuses with the solvent into the existing network 22 (indicated by the solid line) of the functional layer. The functional layer comprises a first functional layer and a second functional layer, and the existing network of the functional layer refers to the first polymer network generated by the first polymer. Subsequently, under the action of the curing agent, the second polymer 21 forms a second polymer network 23 (indicated by the dotted line). At this point, a cross-linked structure is formed between the second polymer network 23 and the existing network 22 of the functional layer.

[0063] In the embodiment of the present application, the sensor has high signal stability through solvent swelling bonding, which enables the sensor to work in harsh mechanical environments. Taking the capacitive sensor as an example, the test shows that Figure 3 As shown in Figure 1, when the sensor is rubbed with sandpaper for 100,000 cycles under a normal pressure of 10 kPa and a reciprocating displacement of 2 mm, the sensor's signal waveform or amplitude does not change significantly; Figure 4 As shown, the sensor was subjected to a repeated shear stress of 5 kPa and a torsional stretch with a torsion angle of 180° and a maximum strain of 50%, 10,000 times per cycle, and no significant changes in signal amplitude or mechanical failure were observed. In addition, sensors were installed on the tire tread of a car to test the stability of the sensor under extreme mechanical conditions during driving. During the test, the sensor signal was collected by the data acquisition module, and the measurement data was transmitted to the computer via Bluetooth. When the test car was running, the tire tread was subjected to a normal pressure of about 300 kPa and a shear stress of about 60 kPa. Generally speaking, under such complex mechanical conditions, sensors with poor interfaces between functional layers will fail quickly. However, in this application, when the car travels a long distance on an asphalt road, Figure 5As shown, even if the car's speed reaches 15 km / h -1 , the sensor signal remains stable within a distance of 1km.

[0064] In addition, the solvent swelling bonding between the functional layers improves the toughness and shear strength of the interface between the functional layers. According to the test, if the functional layer does not contain microstructures, the interface toughness between the first functional layer and the second functional layer is 420 J·m -2 , the shear strength is 90kPa; and although the microstructure makes the interface contain abundant voids and pores, the interface toughness is 390J·m -2 , and the shear strength is 88 kPa. The topological interconnection formed by the solvent swelling effect is crucial for high interfacial toughness and shear strength. For example, when a thin layer (a few micrometers) of the second polymer base liquid and the curing agent (volume ratio of 10:1) is applied as an adhesive between the unswollen first and second functional layers, because the second polymer precursor is viscous and hardly penetrates into the polymer network of the functional layer, the interfacial toughness of the cured interface is much lower, about 96 J·m -2 , which is only 1 / 4 of the interface obtained after swelling bonding. Similarly, the shear strength of the non-interconnected interface is only 39 kPa, which is also much lower than the shear strength of the interface with a cross-linked structure.

[0065] In the presence of microstructures in the functional layers, the interface between the functional layers obtained by solvent swelling bonding can be referred to as a microstructured interface. The high interfacial toughness of this microstructured interface lies in its significant elastic dissipation and the discrete fracture pattern of the cone. The high elastic dissipation can be attributed primarily to the strong adhesion of the cone-dielectric interface (i.e., the microstructured interface) and the large stretchability of the cone. At the cone tip-dielectric interface, the newly formed polymer network interconnects the two adherent networks of the electrode and dielectric layers. This interface is so strong that debonding results in cohesive fracture of the cone rather than failure at the cone-dielectric layer joint. Furthermore, the cone can be significantly elongated to large strains to dissipate significant energy, thus achieving high interfacial toughness. It is important to note that the strain distribution within the cone is non-uniform, with the elongation of the structure primarily contributed by its tip. Analysis shows that the strain at the cone tip can reach at least 500%. This high stretchability can be attributed to the fact that small-scale structures have far fewer defects than bulk materials.

[0066] Second, the microstructural interface enables a discrete fracture mode that locally stabilizes the interface and protects it from continuous catastrophic brittle failure. Although the bulk first polymer is soft and stretchable, it becomes brittle and easily breaks once a crack forms and propagates. In contrast, at the microstructural interface, the cones are elongated together and break one by one. When the cones at the crack tip break, they dissipate the stored strain energy and relax the local strain on the adjacent cones, while the remaining cones ahead of the crack tip deform and maintain overall integrity, as shown in Figure 2. Figure 6 As shown in Figure 6, when the sensor is pulled by an external force 61, the cone 64 at the crack tip between the first functional layer 62 and the second functional layer 63 breaks, while the remaining cones 65 deform and maintain overall integrity. This failure mode is called "discrete fracture," which is similar to the delocalized fracture of a two-dimensional nanomesh electrode on an elastic substrate. Due to the elastic dissipation and discrete fracture mode characteristics of the bulk first polymer, the microstructure interface exhibits a near 400 J·m -2 High interface toughness.

[0067] Optionally, in the embodiment of the present application, in order to increase the bonding speed between the functional layers, the stacked first functional layer and the second functional layer are cured. In an exemplary embodiment, the above step 104 includes the following steps:

[0068] 1. Curing the stacked first functional layer and the second functional layer, wherein the curing process includes: pressurizing curing process and / or heating curing process;

[0069] 2. During the curing process, a cross-linked structure is formed between the first polymer and the second polymer.

[0070] Optionally, the applied pressure of the pressurized curing treatment is greater than 20 kPa, and the pressurization time is greater than 4 hours. It should be noted that in order to ensure the integrity of the functional layer, the above-mentioned pressure, while being greater than 20 kPa, needs to be less than the maximum pressure that the functional layer can withstand. Optionally, different functional layers can withstand different maximum pressures. Of course, in exemplary embodiments, the applied pressure can be flexibly set and adjusted according to actual conditions, and the embodiments of the present application are not limited to this.

[0071] Optionally, the heating temperature of the heat curing process is greater than 60° C. and less than 80° C., and the heating time is greater than 2 hours. Of course, in exemplary embodiments, the heating temperature and heating time can be flexibly set and adjusted according to actual conditions, and the embodiments of the present application are not limited thereto.

[0072] It should be noted that, in the embodiments of the present application, the first polymer and the second polymer are the same polymer.

[0073] It should also be noted that in the embodiment of the present application, the volume of the functional layer after immersion is larger than the volume of the original functional layer, but after the above operation, the volume of the functional layer after bonding will return to its initial size.

[0074] For example, taking a capacitive sensor as an example, Figure 7 As shown, the capacitive sensor 70 includes an upper electrode layer 71, an interface layer 72, and a lower electrode layer 73. When preparing the capacitive sensor, the upper electrode layer 71, the dielectric layer 72, and the lower electrode layer 73 are immersed in a solvent solution, and the immersed upper electrode layer 71, the dielectric layer 72, and the lower electrode layer 73 are stacked in order. The stacked upper electrode layer 71, the dielectric layer 72, and the lower electrode layer 73 are then cured. Afterwards, in the completed capacitive sensor, a cross-linked structure exists between the upper electrode layer 71 and the dielectric layer 72, and a cross-linked structure exists between the dielectric layer 72 and the lower electrode layer 73.

[0075] To sum up, in the technical solution provided in the embodiment of the present application, the second polymer is enabled to enter the original network structure of the first functional layer and the second functional layer through the solvent solution. The original network structure is the network structure formed inside the original polymer of the functional layer. Furthermore, a new network structure is formed between the first functional layer and the second functional layer. A topological cross-linked structure is generated between the new network structure and the original network structure of the functional layer. The first functional layer and the second functional layer are bonded together through the cross-linked structure. A complete cross-linked network is formed between the first functional layer and the second functional layer. The first functional layer and the second functional layer become a whole with high interface strength. During the application of the sensor, even under extreme conditions (high pressure, high friction, etc.), the first functional layer and the second functional layer will not be delaminated, thereby improving the stability and response performance of the sensor.

[0076] For example, Figure 8 As shown, if the first functional layer and the second functional layer are simply stacked together without introducing cross-linking, stratification is likely to occur between the first functional layer and the second functional layer during use; however, if the bonding method provided in the present application bonds the first functional layer and the second functional layer together through a cross-linking structure, then, during use, the first functional layer and the second functional layer are tightly bonded together through the cross-linking structure, and the first functional layer and the second functional layer are not separated.

[0077] In addition, in an embodiment of the present application, conductive particles are doped into the first polymer to generate a dielectric layer (second functional layer), and a plurality of microstructure monomers are protruding and arranged on the bonding surface of the first functional layer and the second functional layer, which can improve the sensing characteristics and signal stability of the sensor. Taking a capacitive sensor as an example, when the dielectric layer doped with conductive particles is replaced by a dielectric layer of a pure first polymer, the normalized change in capacitance is reduced to ~0.90 under a pressure of 450kPa, which is only 1 / 33 of the dielectric layer doped with conductive particles. That is, after doping with conductive particles to generate a dielectric layer, the sensor can detect tiny pressure signals or weights as low as a few milligrams. Moreover, the effect of conductive particle doping on capacitance can be well explained by the relationship between the dielectric constant and the applied pressure. The capacitance of the sensor can be expressed as C~εS / d, where ε is the effective dielectric constant, S is the sensor area, and d is the thickness of the dielectric layer. It should be noted that the air gap is also used as a dielectric. In this application, the microstructure monomer makes the sensor consist of many micro-conical capacitors and meshed air gap capacitors connected in parallel. When the sensor is in use, the change in S is negligible. Due to the thin air gap, the change in d is also very limited. Therefore, the sensor response is mainly contributed by the micro-conical capacitor, whose dielectric constant can change dramatically with the applied pressure. That is, when pressure is applied to the sensor, the compressive stress and the ε of the underlying dielectric layer will be significantly amplified by the conical tip. Since the capacitance C is proportional to the effective dielectric constant ε, the response performance of the sensor is improved at this time.

[0078] Moreover, in the related art, due to the high viscosity between the functional layers, the functional layers of the flexible sensor usually exhibit very low response and relaxation speeds. However, in the embodiment of the present application, the first functional layer and the second functional layer are bonded by solvent swelling bonding to alleviate the high viscosity caused by sealing the sensor with tape; by using a functional layer with a microstructure in the flexible sensor, the microstructure and the air gap can restore mechanical energy with a high elastic energy density when in use, and can quickly relax the energy when released, thereby improving the response and relaxation speed of the sensor. Here, a homemade test system is used to measure the response and relaxation time of the sensor by applying, maintaining and removing a pressure of 1.1kPa. The test system has a sub-millisecond time resolution (~0.68ms) to measure the response and relaxation time, which are 0.68ms and 2.75ms, respectively. It should be noted that in actual use, the response speed of the sensor should be even faster, because 0.68ms is the time limit of the above-mentioned test system. In addition, the high response and relaxation speeds imply that the sensor with the bonded microstructure interface has high elasticity. Tests show that the energy dissipated by the sensor during loading and unloading at a pressure of 100 kPa is negligible.

[0079] It should be noted that the first functional layer and the second functional layer mentioned above are only exemplary and explanatory. In actual situations, there may be functional layers that need to be bonded in the sensor, and there may also be functional layers that do not need to be bonded. For the functional layers that need to be bonded, the following methods can be used: Figure 1 In the embodiment, the functional layers are bonded to form a whole.

[0080] Below, taking the first functional layer as an example, the preparation method of the functional layer is briefly introduced.

[0081] In an exemplary embodiment, the first functional layer is prepared as follows:

[0082] 1. Mixing a first polymer into a solution to obtain a first mixed solution.

[0083] The first polymer refers to any macromolecular polymer capable of swelling, wherein the first polymer includes a first polymer monomer and a curing agent.

[0084] In the embodiment of the present application, when preparing the first functional layer, the first polymer is mixed into a solution to obtain a first mixed solution.

[0085] 2. Pour the first mixed solution into the microstructure template and wait for the first mixed solution to solidify to obtain the first functional layer.

[0086] In an embodiment of the present application, after obtaining the first mixed solution, the first mixed solution is poured into a microstructure template and allowed to solidify to form a first functional layer. A plurality of microstructure units are formed on the side where the first functional layer and the second functional layer are bonded. Optionally, the height of each microstructure unit is 300 nm to 200 μm, and the spacing between adjacent microstructure units is 300 nm to 500 μm.

[0087] For example, Figure 9 As shown, a plurality of microstructure units 91 are provided on one side of the first functional layer 90 that is bonded to the second functional layer.

[0088] It should be noted that in the embodiments of the present application, the heights of the microstructure units on different functional layers in the same sensor can be the same or different; and the spacing between adjacent microstructure units on different functional layers in the same sensor can be the same or different. However, on the same functional layer, the heights of the microstructure units are the same, and the spacing between adjacent microstructure units is the same.

[0089] Optionally, in an embodiment of the present application, the above-mentioned microstructure template has a microstructure. After the first mixed solution is poured into the microstructure template, under the action of the curing agent, a polymer network is formed between the first polymer monomers, thereby forming a first functional layer. At this time, based on the shape of the template, the first functional layer has multiple microstructure monomers on the side where the second functional layer is bonded.

[0090] For example, the above-mentioned microstructure mold is made based on a leaf. The leaf is cleaned and cut into rectangular blocks (area: 50mm×80mm), and then fixed to a glass substrate using double-sided tape to form a leaf template. The first polymer monomer and curing agent (weight ratio of 5:1) are cast on the surface of the leaf template. After curing at 70°C for 1 hour, the first polymer sheet with a microporous structure is peeled off and used as a microstructure mold. Each microstructure mold is then subjected to air plasma treatment (TS-PL05, Dongxingaoke Co., Ltd) at 50W for 3 minutes.

[0091] Optionally, the microstructures can be pyramidal, hemispherical, ellipsoidal, conical, triangular pyramidal, cylindrical, wavy, or the like. Within the same sensor, different functional layers can have microstructures of the same or different shapes. However, within the same functional layer, the shapes of the individual microstructures are identical. Methods for preparing the microstructures include etching, 3D printing, biomimetic replication, laser engraving, casting, and electroplating. Workers can select the appropriate microstructure preparation method based on actual conditions to prepare the microstructure templates.

[0092] To sum up, in the technical solution provided in the embodiment of the present application, there are multiple microstructure monomers on the bonding surface of the first functional layer and the second functional layer. Since the microstructure monomers can affect the distance between the functional layers, the functional layers affect the effect performance of the sensor, thereby improving the response performance of the sensor.

[0093] It should be noted that the above description of the preparation method of the functional layer is only exemplary and explanatory. In actual practice, the preparation method of the second functional layer may be the same as or different from the preparation method of the first functional layer. Figure 7 As shown, the first functional layer (upper electrode layer 71) has multiple microstructure units, the second functional layer (dielectric layer 72) does not have any microstructure units, and the third functional layer (lower electrode layer 73) also does not have any microstructure units. In other words, the surfaces of the dielectric layer 72 and the lower electrode layer 73 are smooth.

[0094] Another point that needs to be explained is that since the microstructure monomers will affect the bonding area between the functional layers, if there are multiple microstructure monomers on the bonding surface between the first functional layer and the second functional layer, the bonding strength of the functional layers will be weak; if there are multiple microstructure monomers on the bonding surface of the first functional layer and there are no microstructure monomers on the bonding surface of the second functional layer, the bonding strength of the functional layers will be moderate; if there are no microstructure monomers on the bonding surface between the first functional layer and the second functional layer, the bonding strength of the functional layers will be strong. In other words, Figure 7 In the embodiment, the bonding strength between the upper electrode layer 71 and the dielectric layer 72 is smaller than the bonding strength between the dielectric layer 72 and the lower electrode layer 73 .

[0095] In addition, the interface strength (also called interface toughness) of the sensor prepared by the solvent swelling bonding method provided by this application is higher than that of the sensor prepared by other methods. The experimental data are as follows: Figure 10 As shown in the figure: when only the functional layers are stacked together, the sensor interface strength is zero; the sensor interface strength prepared by bonding the first polymer itself with a crosslinker is 96 J·m -2 , the shear strength is 39kPa; the interface strength of the sensor prepared by the solvent swelling bonding method provided by this application and having a microstructure on the functional layer is 390J·m -2 , the shear strength is 88kPa; the interface strength of the sensor prepared by the improved solvent swelling bonding method of the present application and without microstructure on the functional layer exceeds 400J·m -2 , and the shear strength is 90 kPa. Therefore, the interface strength of the sensor prepared by the solvent swelling bonding method provided by this application is much higher than the interface strength of the sensor prepared by other methods.

[0096] Below, taking a capacitive sensor as an example, the complete preparation method of the sensor is introduced.

[0097] In an exemplary embodiment, the electrode layers (upper electrode layer and lower electrode layer) are made of conductive polymers of polydimethylsiloxane and carbon nanotubes, the dielectric layer is made of carbon nanotubes and polydimethylsiloxane, the solvent is chloroform, and the first polymer and the second polymer are polydimethylsiloxane.

[0098] To prepare the top electrode layer, carbon nanotubes and polydimethylsiloxane are weighed to a ratio of 7 wt% carbon nanotubes, with the polydimethylsiloxane monomer and curing agent at a mass ratio of 10:1. The polydimethylsiloxane and carbon nanotubes are then mixed uniformly using mechanical stirring. The resulting mixed solution of polydimethylsiloxane and carbon nanotubes is then poured into a microstructure template containing microstructures. After curing by heating at 80°C for 4 hours, the resulting microstructured top electrode layer is 80-200 μm thick.

[0099] When preparing the lower electrode layer, the mixed solution of polydimethylsiloxane and carbon nanotubes is spin-coated on a clean and flat glass plate by spin coating, and heated at 80°C for 4 hours to solidify to obtain a flat lower electrode with a thickness of 80-200 μm.

[0100] When preparing the dielectric layer, carbon nanotubes are weighed according to a ratio of 2wt% of the carbon nanotube mass fraction, wherein the mass ratio between the polydimethylsiloxane monomer and the curing agent is 10:1. Similarly, the polydimethylsiloxane and the carbon nanotubes are evenly mixed by mechanical stirring. The mixed solution of the polydimethylsiloxane and the carbon nanotubes is spin-coated on a clean and flat glass plate by spin coating. After heating at 80°C for 2h and curing, a flat dielectric layer with a thickness of 50-150μm is obtained.

[0101] One thing that needs to be explained is that during the preparation of the upper electrode layer, the lower electrode layer and the dielectric layer, the heating temperature and the heating time can be flexibly set and adjusted, and the heating temperature and the heating time corresponding to different functional layers may be different.

[0102] The prepared top electrode, dielectric layer, and bottom electrode were then immersed in a mixed solution of chloroform and polydimethylsiloxane (PDMS) for 6 hours, using mechanical stirring and ultrasonic mixing. The top electrode, dielectric layer, and bottom electrode were then removed. After the chloroform on their surfaces evaporated completely, the bottom electrode, dielectric layer, and top electrode were stacked in that order. A pressure of 20 kPa was then applied and maintained for 4 hours. After curing by heating for 2 hours, a capacitive sensor with a firmly bonded interface was obtained.

[0103] One thing that needs to be explained is that during the bonding process of the upper electrode, dielectric layer and lower electrode, the magnitude of the applied pressure, the duration of the pressure, the heating temperature and the heating duration can all be flexibly set and adjusted according to the range provided above, and the embodiments of the present application do not limit this.

[0104] Among them, the above-mentioned polydimethylsiloxane is an elastic-based macromolecular polymer. Therefore, the capacitive sensor prepared according to the above method is a flexible sensor. This flexible sensor can be used in smart clothing, electronic textiles, electronic skin, human health monitoring, environmental monitoring, human-computer interaction, and flexible displays, creating an era of the Internet of Things where devices and the human body work closely together. For example, wearable sensors have the potential to continuously detect the vital signs of the subject's health and can transmit this data to relevant personnel for further analysis to detect any health hazards early. In addition, in addition to health monitoring applications, wearable sensors are also used in other fields, including environmental monitoring, human motion monitoring, prosthetics, construction and security, human-computer interaction, sports, intelligent robots, and so on.

[0105] In an exemplary embodiment, the present application further provides a sensor comprising a first functional layer and a second functional layer; wherein the first functional layer and the second functional layer contain the same polymer, and the first functional layer and the second functional layer are bonded by a cross-linked structure formed by the polymer. For example, Figure 11 As shown, the sensor 110 includes a first functional layer 111 and a second functional layer 112 , and the first functional layer 111 and the second functional layer 112 are bonded via a cross-linking structure 113 . Both the first functional layer 111 and the second functional layer 112 contain a first polymer 114 .

[0106] Optionally, the above polymer is an elastic-based polymer.

[0107] Optionally, a plurality of microstructure units are arranged protrudingly on the bonding surface of the first functional layer, where the bonding surface is the side where the first functional layer is bonded to the second functional layer. For example, the height of the microstructure units is 300 nm to 200 μm, and the spacing between adjacent microstructure units is 300 nm to 500 μm.

[0108] Optionally, the first functional layer is an electrode layer, and the second functional layer is a dielectric layer. The first functional layer and the second functional layer both contain conductive particles and polymers, and the mass ratio of the conductive particles to the polymer in the first functional layer is greater than the mass ratio of the conductive particles to the polymer in the second functional layer. Optionally, the conductive particles include but are not limited to at least one of the following: metal nanowires, carbon nanotubes, graphite, graphene, carbon black, metal conductive powder, etc., which is not limited in the embodiments of the present application. Optionally, the polymer includes any one of the following: polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polypropylene, rubber, and polyoxymethylene.

[0109] In addition, regarding the above-mentioned sensor, any details not described in detail can be found in the above-mentioned method embodiment.

[0110] Next, the application of the sensor in this application in soft robots is introduced.

[0111] One requirement for soft robotics is the integration of electronic skin with sensory capabilities, enabling them to interact with humans and the environment. However, existing electronic skin and robots are often made of different materials, so their integration suffers from a poor sensor-robot interface due to significant differences in mechanical properties. Consequently, such integration requires complex designs, such as embedding sensors within the robotic matrix.

[0112] However, in the embodiment of the present application, the sensor is made of an elastic-based polymer-conductive particle composite material. The sensor is applied to the electronic skin, so that the electronic skin and the soft robot can be made of the same composite material, and there is no problem of mechanical mismatch. At the same time, through the solvent swelling and bonding effect, the interface between the various functional layers of the sensor is made strong. In this way, the soft robot can be used for grasping objects and detecting the pressure distribution on the gripper surface.

[0113] Taking the gripper used to grasp a mesh melon (weight: 1250 grams) and a stuffed doll (weight: 180 grams) as examples, when grasping heavy objects, the soft robot generates tens of kilopascals of pressure and shear stress on the gripper surface. When grasping the relatively heavy and rigid melon, the gripper surface does not fully conform to the melon's curvature, and the pressure is concentrated primarily at the gripper's base, where the melon tends to slide and come into closer contact with the bottom sensor. When grasping a softer and lighter stuffed doll, the contact point between the doll and the gripper is elevated to a higher position compared to the melon, and due to the doll's lighter weight, the observed pressure distribution on the gripper surface changes more slowly. Furthermore, after multiple grasping experiments with the soft robot, the sensor signals can accurately identify the specific operation phase during the soft robot's cyclic manipulation of the melon, and the sensor exhibits high stability after at least 1000 cycles. This high stability is due to the interconnectedness between all functional layers of the sensor; without this strong topological adhesion, the sensor would not be able to function properly and stably under harsh mechanical conditions. Correspondingly, in the test, if no interconnection results were introduced between the functional layers, that is, no cross-linked structure was formed at the interface between the functional layers, the sensor delaminated and failed when grasping the melon in the 137th cycle. Taking the capacitive sensor as an example, when the gripper grasps the melon, the curve of the capacitance signal of the capacitive sensor and the curve of the force applied by the gripper over time are shown as follows: Figure 12 shown.

[0114] Furthermore, the sensor in the present application can act as a dual-mode sensor by responding sensitively to both pressure and strain. For example, Figure 13 Figure 2 shows the sensor's capacitance and resistance response curves during the dynamic process of grasping, lifting, holding, and releasing a doll. In the initial state, the gripper is fully open to grasp a large object, applying tensile strain to the sensor. During touching and grasping the doll, the capacitance increases dramatically, while the resistance decreases due to the reduced strain on the gripper surface. The doll is then lifted and held for approximately 2 seconds, dropping upon release. Correspondingly, the capacitance signal remains constant during the holding process, then abruptly drops to its initial value upon release. The resistance signal also exhibits a relatively stable value while the doll is being grasped, returning to its original value upon release.

[0115] In addition, the sensors in the present application do not require encapsulation. Encapsulated sensors or electronic skins are typically achieved by stacking the functional layers of the device and sealing them with a layer of tape. Such sensors work stably under normal compression, but fail in other mechanical modes that produce planar shear stress. Taking a capacitive sensor as an example, in a capacitive sensor sealed and fixed to a soft robotic gripper with a thin layer of polyimide tape, the top functional layer bends during concave bending due to the much higher stiffness of the tape and the non-adhesive interface. As a result, the capacitive signal becomes negative during the bending and release cycles due to the thick air gap created between the electrode and the dielectric layer doped with conductive particles. In contrast, the capacitive sensor obtained by solvent swelling bonding provided by the present application did not show any structural damage or signal attenuation during the bending and release cycles. All these results confirm that the sensor provided by the present application is an ideal choice for soft robots with integrated sensors.

[0116] It should be understood that the "multiple" mentioned in this article refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship. In addition, the step numbers described in this article only illustrate a possible execution sequence between the steps. In some other embodiments, the above steps may not be executed in the order of the numbers, such as two steps with different numbers are executed at the same time, or two steps with different numbers are executed in the opposite order to the diagram. The embodiments of the present application do not limit this.

[0117] The above description is merely an exemplary embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A sensor, characterized in that: The sensor includes a first functional layer and a second functional layer, wherein the first functional layer and the second functional layer contain a first polymer, the first polymer being a macromolecular polymer capable of producing swelling, and the first functional layer and the second functional layer further contain a second polymer, the second polymer being diffused into the first functional layer and the second functional layer through a solvent solution; The first functional layer and the second functional layer are bonded by a cross-linked structure formed between the first polymer and the second polymer by curing, and the first polymer and the second polymer are the same polymer; The cross-linked structure includes an original network structure formed by the first polymer and a new network structure formed by the second polymer extending into the first functional layer and the second functional layer, and the original network structure and the new network structure are topologically cross-linked.

2. The sensor according to claim 1, characterized in that The first polymer is an elastomeric-based polymer.

3. The sensor according to claim 1, wherein A plurality of microstructure units are protrudingly arranged on the bonding surface of the first functional layer, and the bonding surface refers to a side where the first functional layer and the second functional layer are bonded.

4. The sensor according to claim 1, characterized in that The first functional layer is an electrode layer, and the second functional layer is a dielectric layer.

5. The sensor according to claim 4, characterized in that The first functional layer and the second functional layer both contain conductive particles and the first polymer; wherein the mass ratio of the conductive particles to the first polymer in the first functional layer is greater than the mass ratio of the conductive particles to the first polymer in the second functional layer.

6. The sensor according to claim 5, characterized in that The conductive particles include at least one of the following: metal nanowires, carbon nanotubes, graphite, graphene, carbon black, and metal conductive powder.

7. The sensor according to any one of claims 1 to 6, characterized in that The first polymer includes any one of the following: polydimethylsiloxane, polyurethane, polyimide, epoxy resin, polyethylene, polyvinylidene fluoride, polypropylene, rubber, and polyoxymethylene.

8. A bonding method for a sensor functional layer, characterized in that: The method comprises: Obtaining a first functional layer and a second functional layer required for preparing a sensor, wherein the first functional layer and the second functional layer both contain a first polymer; Immersing the first functional layer and the second functional layer in a solvent solution; wherein the solvent solution includes a solvent and a second polymer, and during the immersion process, the second polymer diffuses into the first functional layer and the second functional layer along with the solvent, and the first polymer and the second polymer are the same polymer; After the immersion is completed, taking out the first functional layer and the second functional layer from the solvent solution, and stacking the taken out first functional layer and second functional layer in order; A cross-linked structure for bonding the first functional layer and the second functional layer is formed between the first polymer and the second polymer through curing treatment. The cross-linked structure includes an original network structure formed by the first polymer and a new network structure formed by the second polymer extended to the inside of the first functional layer and the second functional layer. The original network structure and the new network structure are topologically cross-linked.

9. The method according to claim 8, characterized in that The cross-linking structure for bonding the first functional layer and the second functional layer is formed between the first polymer and the second polymer through a curing process, comprising: Performing the curing treatment on the stacked first functional layer and the second functional layer, wherein the curing treatment includes: pressurizing curing treatment and / or heating curing treatment; During the curing process, the cross-linked structure is formed between the first polymer and the second polymer.

10. The method according to claim 8 or 9, characterized in that A plurality of microstructure units are protrudingly arranged on the bonding surface of the first functional layer, and the bonding surface refers to a side where the first functional layer and the second functional layer are bonded.

11. The method according to claim 10, characterized in that The method further comprises: mixing the first polymer into a solution to obtain a first mixed solution; pouring the first mixed solution into the microstructure template, and waiting for the first mixed solution to solidify to obtain the first functional layer; Wherein, the plurality of microstructure units are formed on one side where the first functional layer and the second functional layer are bonded.

12. The method according to claim 11, characterized in that The method further comprises: mixing the conductive particles and the first polymer in a first mass ratio to form the first functional layer; mixing the conductive particles and the first polymer in a second mass ratio to form the second functional layer; Wherein, the first mass ratio is greater than the second mass ratio.

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