Homogeneous integrated flexible proximity sense-force touch sensor and preparation method thereof

Abstract

The invention relates to a homogeneous integrated flexible proximity sense-force touch sensor and a preparation method thereof, and belongs to the technical field of sensors. The problems that an existing flexible proximity sense-force tactile sensor is complex in structure and inaccurate in measurement, the perceptible distance of proximity sense is too short, the measuring range of force tactile sense is too small, and the robustness and durability are reduced due to heterogeneous material packaging are solved. The sensor comprises a packaging layer and a functional layer, and the functional layer is sealed in the packaging layer; from top to bottom, the functional layer sequentially comprises a coil layer, an air gap layer and a piezoresistive layer, and the packaging layer comprises a coil layer substrate, a supporting frame and a packaging bottom surface which are bonded in sequence. According to the invention, the coil layer electrodes of the sensor are designed into a complementary labyrinth structure, so that the sensing distance of proximity sense is enlarged; the design of the air gap layer is matched, so that the measuring range and the response speed of haptic perception are improved; the structure is simple, the performance is reliable, and the robustness and durability of the sensor can be improved through the homogeneous integrated packaging design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a homogeneous integrated flexible proximity-force tactile sensor and a preparation method thereof. BACKGROUND

[0002] Compared with traditional rigid sensors, flexible sensors have good flexibility, bendability and conformability, and can better adapt to irregular surfaces and complex environments. Flexible force tactile proximity tactile dual-mode sensors are devices that can perceive and respond to external proximity and tactile stimuli, and are widely used in robots and smart homes to achieve precise force tactile feedback and environmental perception.

[0003] Existing flexible force tactile proximity tactile dual-mode sensors usually need to integrate multiple sensing elements and circuits in a limited space, which not only increases the structural complexity and manufacturing difficulty of the sensor, but also the complex structure may reduce the reliability of the sensor, and the signals of different sensing modalities may have crosstalk, resulting in inaccurate measurement results; the planar capacitors of existing flexible dual-mode sensors have a small perceivable distance, and the range of force tactile is also small; in addition, the use of heterogeneous glue packaging has poor interface stability and robustness, and is easily affected by external environment, resulting in performance degradation or failure of the sensor.

[0004] Therefore, in order to provide more rich and reliable sensing information for intelligent devices such as robots, and improve the motion control and human-computer interaction performance of intelligent devices, there is an urgent need for a flexible force tactile proximity tactile dual-mode sensor with better structure and performance. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a homogeneous integrated flexible proximity-force tactile sensor and a preparation method thereof, to solve at least one of the problems of existing flexible proximity-force tactile sensors, such as complex structure, inaccurate measurement, too close perceivable distance of proximity tactile (0-225mm) or too small range of force tactile (0-160kPa), and heterogeneous material packaging reducing robustness and durability.

[0006] In one aspect, the embodiments of the present application provide a homogeneous integrated flexible proximity-force tactile sensor, which comprises a packaging layer and a functional layer, and the functional layer is sealed inside the packaging layer; from top to bottom, the functional layer comprises a coil layer, an air gap layer and a piezoresistive layer in sequence, and the packaging layer comprises a coil layer substrate, a support frame and a packaging bottom surface bonded in sequence;

[0007] Wherein, the coil layer and the coil layer substrate are mutually embedded and have a planar complementary labyrinth structure, for providing an edge field capacitor to perceive a proximity object and form a capacitive proximity tactile of the sensor.

[0008] The air gap layer is provided by the support frame to provide space for the deformation of the coil layer when pressed to perceive the contact object by the capacitance between the coil layer plates, forming the capacitive tactile of the sensor;

[0009] The piezoresistive layer is fixed inside the support frame and has a porous structure to provide resistance to perceive the contact object, forming the resistive tactile of the sensor;

[0010] The material of the packaging layer is the same as the base material of the functional layer;

[0011] The support frame and the bottom surface of the packaging layer are designed as a whole or separated.

[0012] Further, the thickness of the plane complementary labyrinth structure of the coil layer is 0.8-1.5mm.

[0013] Further, the ratio of the coil width to the pitch is 5:1-1:1.

[0014] Further, the piezoresistive layer includes multiple layers of porous sponge layers, and the porosity of the porous sponge layers decreases from top to bottom.

[0015] Further, the thickness of the piezoresistive layer is 2-6mm.

[0016] Further, the piezoresistive layer includes 1-3 layers of porous sponge layers.

[0017] Further, the thickness of the porous sponge layer is 1-2mm.

[0018] Further, the porosity of the porous sponge layer is 45-80%.

[0019] Further, the thickness h of the air gap layer is 0.5mm

[0020] Further, the material of the packaging layer is polydimethylsiloxane.

[0021] Further, the material of the coil layer and the piezoresistive layer is conductive carbon-doped polydimethylsiloxane composite.

[0022] Further, the conductive carbon is at least one of nanotubes, carbon black, and graphene.

[0023] Further, the content of conductive carbon in the composite is 4-8wt% by weight percentage.

[0024] Further, the sensing distance of the sensor proximity is up to 250mm, the range of the sensor force tactile is up to 200kPa, and the response time of the piezoresistive layer force tactile is up to 166ms.

[0025] In another aspect, the present application also provides a method for preparing a sensor, the sensor being the sensor described above, the method comprising:

[0026] (1) according to the coil layer structure, a mold for preparing the coil layer substrate is obtained, polydimethylsiloxane is used for pouring, and the patterned coil layer substrate is obtained after curing;

[0027] The polydimethylsiloxane is mixed with conductive carbon, and the obtained mixed prepolymer I is filled into the pattern of the coil layer substrate, and the coil layer is obtained after curing, wherein the coil layer and the substrate are embedded into one whole;

[0028] (2) polydimethylsiloxane is mixed with conductive carbon and inorganic salt, the obtained mixed prepolymer II is mold poured, and the piezoresistive layer is obtained after soaking after curing;

[0029] (3) according to the piezoresistive layer structure and the air gap layer thickness design, a mold for preparing a support frame for fixing the piezoresistive layer and providing the air gap layer is obtained, the material prepolymer of the packaging layer is mold poured, and the support frame is obtained after curing, wherein the support frame has a cube structure with an open top surface or a cube structure with an open top surface and a bottom surface, the inner cavity size of the support frame is greater than the volume size of the piezoresistive layer, and the height difference constitutes the air gap layer of the sensor prepared after packaging;

[0030] (4) packaging, the specific steps are as follows: the cube structure support frame with an open top surface and a bottom surface prepared in step (3) is bonded on the packaging bottom surface with semi-cured polydimethylsiloxane or a cube structure support frame with an open top surface is directly used, the piezoresistive layer is placed in the reserved area of the support layer; semi-cured polydimethylsiloxane is applied on the top surface of the support frame, and the coil layer substrate is placed on the support layer and cured.

[0031] Further, in step (2), by changing the ratio of the inorganic salt to polydimethylsiloxane, batch pouring is carried out to prepare a piezoresistive layer with a gradient decrease in porosity from top to bottom;

[0032] And / or, the mass ratio of the inorganic salt to polydimethylsiloxane is 10:1-2:1.

[0033] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0034] 1. Compared with the existing flexible proximity tactile bimodal sensor, the overall structure and material composition of the flexible bimodal sensor are improved in the application: on the one hand, the coil layer is designed as a planar complementary maze structure, the piezoresistive layer is designed as a multi-layer sponge layer containing a gradient porosity, and an air gap layer is added in the sensor structure, which can expand the sensor proximity sensing distance, expand the force tactile sensing range, and improve the response speed and sensitivity of the resistance force tactile sensing; on the other hand, the material of the sensor packaging layer is the same as the base material of the functional layer, which improves the stability of the interface between the parts of the sensor, and makes the sensor have high robustness and durability.

[0035] 2. The application improves the sensitivity of the sensor to the deformation caused by pressure by adjusting the thickness of the coil layer, to improve the accuracy of measuring the size of the object contact force through the change of capacitance, wherein the thinner the thickness of the coil layer, the more sensitive the sensor to the deformation caused by pressure, and at the same time, the adjustment of the thickness of the coil layer should also consider the mechanical properties of the coil layer, so that it can maintain the integrity of the structure and performance when the sensor is deformed by pressure, and avoid affecting the accuracy of the sensor measurement results.

[0036] The application balances the strength and range of the edge field generated by the coil layer by adjusting the ratio of the width and spacing of the coil layer, to ensure the accuracy of measuring the proximity distance or position of the object through the change of the edge field of the coil layer, while expanding the proximity sensing distance of the sensor.

[0037] 3. The piezoresistive layer is designed as a multi-layer porous sponge layer in the application, and the porosity of the multi-layer sponge layer decreases from top to bottom, which improves the accuracy of measuring the size of the pressure of the sensor while expanding the force tactile sensing distance of the sensor.

[0038] 4. The air gap layer arranged between the coil layer and the piezoresistive layer in the application not only enables the sensor to accurately perceive the size of the object contact force through the change of capacitance, and widens the range of the force tactile sensing range of the sensor, but also enables the preloading of the piezoresistive layer when the sensor is pressed, to improve the response speed and accuracy of the piezoresistive layer in sensing pressure. At the same time, considering the whole sensor, the application adjusts the thickness of the air gap layer, so that the sensor can successfully switch between the capacitive sensing mode and the resistance sensing mode, avoid the discontinuity of the force tactile sensing of the sensor caused by the fact that the object does not fully contact the piezoresistive sponge after pressing the sensor to the range of capacitive sensing, and truly expand the range of force tactile sensing of the sensor.

[0039] 5、The application can improve the stability of the interface between each part of the sensor, the robustness and durability in the actual use process of the sensor, and realize the strengthening of the charge aggregation effect by increasing the micro tip and edge structure and specific surface area of the coil layer electrode; the content and size of the conductive particles can affect the sensitivity of the piezoresistive layer during deformation.

[0040] 6、The sensor proximity sense can perceive a distance of 250mm, such as 225-250mm; the sensor force sense can reach a range of 200kPa, such as 160-200kPa, and the response time of the piezoresistive layer force sense can reach 166ms, such as 160-240ms.

[0041] In the present application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification or by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0043] Figure 1 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0044] Figure 2 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0045] Figure 3 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0046] Figure 4 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0047] Figure 5 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0048] Figure 6 (a) is a structural schematic diagram of the flexible proximity sense and force sense bimodal sensor of the present application, (b) is a piezoresistive layer structure schematic diagram, and (c) is a coil layer structure schematic diagram;

[0049] Figure 7 Preparation flow chart of the flexible proximity tactile bimodal sensor of the present application;

[0050] Figure 8 Sensor proximity response result chart of the present application;

[0051] Figure 9 Sensor force tactile response result chart of the present application;

[0052] Reference signs:

[0053] 1 - encapsulation layer; 2 - coil layer; 3 - air gap layer; 4 - piezoresistive layer; 4-1 - first porous sponge layer; 4-2 - second porous sponge layer. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this description, and together with the embodiments of the present application illustrate the principles of the present application. The present application should not be limited to the embodiments disclosed in the drawings.

[0055] In terms of technical principles, the flexible force tactile sensor realizes the sensing function through special materials and structural design. It uses conductive materials with high flexibility, such as silver nanowires and hydrogel, and realizes the response to force tactile information based on piezoelectric, piezoresistive, optical, capacitive, electromagnetic field, etc. The flexible proximity sensor can perceive the existence or distance information of an object through the changes of light field, sound field, capacitive edge field, etc. and perceive the proximity of the object without direct contact. Existing research has developed a series of flexible sensors based on various working mechanisms for robots, enabling robots to interact with the environment more accurately, quickly and safely. These sensors are mainly based on one or two mechanisms, including capacitance, piezoresistance, triboelectricity, piezoelectricity and electromagnetism, etc.

[0056] The existing flexible force tactile proximity bimodal sensor mainly adopts triboelectric type, capacitive type sensor or hybrid scheme (such as combined with piezoresistive sensor), but in the actual manufacturing and application process of the sensor, the following problems exist: The bimodal flexible sensor usually needs to integrate multiple sensing elements and circuits in a limited space, increasing the structural complexity and manufacturing difficulty of the sensor. At the same time, the complex structure may also lead to a decrease in the reliability of the sensor, and the signals of different sensing modalities may exist crosstalk, resulting in inaccurate measurement results. In the existing research on flexible force tactile proximity sensors, the perceivable distance of the planar capacitive proximity sensor is small, the range of force tactile is small, and the packaging and combined interface stability and robustness are extremely poor, which is easily affected by the external environment, leading to a decrease or failure of the performance of the sensor.

[0057] Therefore, the application provides a flexible proximity-force tactile sensor with homogeneity and integrity, a structural schematic diagram of which is shown in the figure Figure 1 The sensor comprises a packaging layer and a functional layer, the functional layer is sealed inside the packaging layer, and from top to bottom, the functional layer comprises a coil layer, an air gap layer and a piezoresistance layer in sequence, and the packaging layer comprises a coil layer substrate, a support frame and a packaging bottom surface bonded in sequence.

[0058] The coil layer and the coil layer substrate are mutually embedded and have a planar complementary labyrinth structure for providing an edge field capacitance to perceive a proximity object and form a capacitive proximity of the sensor.

[0059] The air gap layer is provided by the support frame to provide a space for deformation of the coil layer when subjected to pressure, so as to perceive a contact object by using an inter-plate capacitance of the coil layer and form a capacitive tactile of the sensor.

[0060] The piezoresistance layer is fixed inside the support frame and has a porous structure for providing a resistance to perceive a contact object and form a resistive tactile of the sensor.

[0061] The material of the packaging layer is the same as the base material of the functional layer.

[0062] It should be noted that the capacitive sensor perceives proximity by an edge field of a capacitor, and the method for improving the proximity sensing distance and accuracy of the edge field is to increase the tip and edge area of the capacitor electrode. Currently, researchers design parallel electrodes into cross-shaped, disc-shaped and spiral-shaped to enhance the strength of the edge field. Although this improves the relative performance of proximity perception to some extent, this enhancement is at the expense of the pressure sensing capability. Unbalanced or insufficient dual-mode sensing performance limits the practical application of the dual-mode sensor, and often requires trade-off and compromise between the range and performance of proximity and force tactile, and cannot simultaneously expand the performance of proximity and force tactile in the flexible sensor.

[0063] It should be noted that compared with the existing flexible proximity-force tactile dual-mode sensor, the application improves the flexible dual-mode sensor in terms of material and structural composition, simultaneously improves the proximity and force tactile sensing performance of the dual-mode sensor, simplifies the structure, reduces the manufacturing difficulty, and solves the problems of the existing flexible dual-mode sensor, such as complex structure, unreliable performance, and inability to simultaneously expand the proximity sensing distance and the force tactile sensing range.

[0064] Specifically, the coil layer in the sensor has a planar complementary labyrinth structure, as shown in the figure Figure 2 .

[0065] It should be noted that the coil layer with the planar complementary labyrinth structure can not only expand the sensing distance of the sensor's proximity sense, but also, in cooperation with the air gap layer structure design of the sensor, can expand the range of the sensor's force touch sense, and the specific reason is that:

[0066] On the one hand, the capacitive electrode structure with a complementary labyrinth structure can increase the area of the electrode edge in a limited space, release more internal fields through the edge to the outside of the electrode plate plane, obtain a more dense and wider distributed edge electric field, and thus obtain a farther proximity sense sensing distance and improve the proximity sense sensing sensitivity, as shown in Figure 3 、 4 .

[0067] On the other hand, in the initial stage of the contact between the object and the sensor, although the contact pressure from the object makes the flexible sensor begin to produce compression deformation, the coil layer does not directly contact the piezoresistive layer due to the existence of the air gap layer between the coil layer and the piezoresistive layer. At this time, the sensor is still in a capacitive working mode. In this stage, the greater the contact force, the closer the coil layer to the piezoresistive layer, and the coil layer capacitance also increases. After the capacitive change is converted into an electric signal, the pressure on the system in the initial process of the object contacting the sensor, i.e., the pressure-capacitance effect of the sensor, can be calculated. The response working principle of the sensor in the initial stage of contacting the object is shown in Figure 5 . It can be seen that the coil layer of the present application can expand the sensing range of the sensor's force touch.

[0068] It should be noted that in order to balance the diffusion range and intensity of the edge field of the coil layer capacitance, the ratio of the width of the coil layer electrode plate to the distance between adjacent electrode plates needs to be limited.

[0069] More specifically, the ratio of the width of the coil layer electrode plate to the distance between adjacent electrode plates is limited to the range of 5:1-1:1. The higher the ratio of the width of the electrode plate to the distance between adjacent electrode plates, the higher the intensity of the edge electric field. However, too high a ratio will cause the edge electric field to be concentrated around the coil, affecting the expansion of the sensor's proximity sense sensing distance.

[0070] According to some preferred embodiments of the present application, the ratio of the width of the coil layer electrode plate to the distance between adjacent electrode plates can be any value within the range of 5:1-1:1, such as 5:1, 4:1, 3:1, 2:1, and 1:1.

[0071] It should be noted that in order to ensure the mechanical properties of the coil layer, improve the sensitivity and sensing range of the sensor's force touch by using the pressure-capacitance effect generated in the capacitive sensing mode, the thickness of the coil layer needs to be limited.

[0072] More specifically, the thickness of the coil layer is 0.8-1.5 mm, preferably 1-1.5 mm. The thinner the thickness of the coil layer, the more sensitive the sensor is to the deformation caused by pressure, and the higher the force tactile sensitivity of the sensor. However, considering the limitations of the existing preparation process and the mechanical properties, the thickness of the coil layer cannot be too low.

[0073] According to some preferred embodiments of the present application, the thickness of the coil layer is any value in the range of 0.8-1.5 mm, such as 0.8 mm, 0.9 mm, 1 mm, 1.2 mm, 1.3 mm, 1.4 mm, and 1.5 mm.

[0074] It should be noted that in order to enable the air gap layer to achieve the sensor force tactile sensing range in cooperation with the coil layer, to enable the sensor to achieve seamless switching from capacitive sensing to resistive sensing, and to improve the reliability of sensor measurement, the thickness of the air gap layer needs to be limited.

[0075] Specifically, the thickness h of the air gap layer is 0.5 mm < h < 1.5 mm. The present application needs to enable the coil layer to fully contact the porous piezoresistive layer before the pressure sensor reaches the range of pressure-capacitance effect sensing, or at least when the sensor reaches the range of pressure-capacitance effect sensing, to enable the coil layer to fully contact the porous piezoresistive layer, convert the working mode of the sensor to piezoresistive mode, avoid the discontinuity of sensor force tactile sensing, and improve the reliability of the dual-mode sensor.

[0076] According to some preferred embodiments of the present application, the thickness h of the air gap layer can be any value in the range of 0.5 mm < h < 1.5 mm, such as 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, and 1.4 mm.

[0077] It should be noted that in order to enable the pressure sensor to achieve force tactile sensing under greater pressure through the resistive sensing mode after reaching the range of pressure-capacitance effect sensing, and to expand the range of sensor force tactile sensing, the present application provides a piezoresistive layer below the air gap layer to continue detecting the contact force information of the object through resistive response.

[0078] Specifically, the piezoresistive layer has a porous structure. When the contact force of the object increases, the deformation of the sensor causes the coil layer to fully contact the piezoresistive layer, the porous structure of the piezoresistive layer deforms, causing the internal conductive circuit path to change, increasing the contact area of the conductive path, and reducing the resistance. By continuously increasing the contact force of the object, the resistance of the piezoresistive layer continues to decrease, converting the resistance change into an electrical signal, so that the greater pressure received by the sensor can be calculated, i.e., the piezoresistive effect. The principle of realizing sensor force tactile sensing through piezoresistive response is as follows: Figure 6as shown.

[0079] It should be noted that, in order to improve the sensitivity and accuracy of the sensor, the thickness of the porous piezoresistive layer needs to be limited.

[0080] Specifically, the thickness of the piezoresistive layer is 1-6mm. If the thickness of the piezoresistive layer is too large, it will lead to a decrease in sensitivity and accuracy. Based on the limitations of existing preparation processes, the thickness of the piezoresistive layer according to the present application cannot be too small.

[0081] According to some preferred embodiments of the present application, the thickness of the piezoresistive layer according to the present application can be any value within the range of 1-6mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, or 6mm.

[0082] It should be noted that, in order to improve the sensitivity and increase the force tactile perception range, the porosity of the piezoresistive layer needs to be limited.

[0083] Specifically, the porosity of the piezoresistive layer is 45-80%. If the porosity is too high, the required object contact force when the sensor switches from capacitive sensing to resistive sensing is too small, which is not conducive to the expansion of the force tactile perception range of the sensor. If the porosity is too small, it is easy to cause the coil layer to not be able to fully contact the piezoresistive layer after the sensor is pressed to the limit of the capacitive sensing range, i.e., the sensor cannot achieve seamless switching from capacitive sensing to resistive sensing.

[0084] It should be noted that, in order to expand the range of the sensor's resistive force tactile, the porosity of the porous piezoresistive layer according to the present application is gradiently changed.

[0085] More specifically, the piezoresistive layer includes multiple layers of porous sponge layers. From top to bottom, i.e., in the direction of the contact object exerting contact pressure on the sensor, the porosity of the porous sponge layers decreases in turn. Preferably, the piezoresistive layer includes 1-6 layers of the porous sponge layers, and more preferably 1-3 layers.

[0086] According to some preferred embodiments of the present application, the number of layers of the porous sponge layers can be 1, 2, 3, 4, 5, or 6. The more layers of the porous sponge layers, the more conducive to expanding the range of the sensor's force tactile. However, increasing the number of layers of the porous sponge layers will increase the size of the sensor, which is not conducive to the practical application of the sensor.

[0087] It should be noted that, due to the large number of pores of the upper sponge layer constituting the piezoresistive layer, the conductive material forms an incomplete conductive network in the matrix material, and when subjected to slight pressure, the originally far apart CNTs will contact each other, resulting in a significant change in resistance value, thereby achieving high sensitivity sensing of slight pressure; the lower layer has fewer pores, and the conductive material forms a relatively stable conductive network in the matrix material, which itself has a relatively low resistance value under low pressure, but because the slope of the resistance-pressure response curve is relatively small, it can withstand greater pressure without being quickly saturated, thereby enabling the sensor to sense a larger pressure range.

[0088] It should be noted that, in order to maximize the extension of the force touch sensing range while reducing the thickness of the piezoresistive layer, the present application needs to limit the thickness of each sponge layer.

[0089] Specifically, the thickness of the porous sponge layer is 1-2 mm.

[0090] According to some preferred embodiments of the present application, the thickness of the porous sponge layer can be 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, or 2 mm.

[0091] It should be noted that, in order to increase the range of force touch sensing, the present application needs to limit the porosity difference between adjacent porous sponge layers.

[0092] Specifically, the porosity difference between adjacent porous sponge layers is 25-45%. If the porosity difference is too large, it will result in discontinuity of the force touch response interval of the piezoresistive layer; if the porosity is too small, it will result in insignificant improvement in sensitivity and force touch sensing range.

[0093] According to some preferred embodiments of the present application, the porosity difference between adjacent porous sponge layers can be 25%, 27%, 30%, 32%, 35%, 38%, 40%, 42%, or 45%.

[0094] It should be noted that the piezoresistive sponge layer itself has a certain viscoelasticity, and the deformation and recovery process thereof is not completed instantaneously during the loading and unloading of external force. The viscoelasticity leads to a relatively slow response speed (~200 ms) of the piezoresistive sponge in force touch. The sensor designed in the scheme realizes force touch perception through the relatively fast (60 ms) response speed of the capacitor in the initial stage of small contact force (such as 0-60 kPa). Although the contact force from the outside causes the deformation of the overall system in this stage, the coil layer cannot contact the piezoresistive layer, and the external force applied to the sensor acts on the entire sensor, including the piezoresistive layer below, so the piezoresistive sponge also deforms to a certain extent, which is the preloading process. When the contact pressure continues to rise to a certain degree (such as 60 kPa or more), the piezoresistive sponge has been preloaded and no longer needs to go through the initial viscoelastic deformation process. Therefore, the sensor designed in the scheme has a high response speed in the piezoresistive sensing stage of force touch.

[0095] It should be noted that in order to improve the mechanical adaptability of the sensor package and promote the close connection between the layers, the material of each part and functional layer constituting the sensor needs to be limited.

[0096] Specifically, in order to promote the combination and close and stable packaging of the layers of the sensor, improve the robustness and durability of the sensor, and improve the ability to resist external environmental interference, the flexible proximity force touch sensor is designed as a homogeneous integrated structure.

[0097] More specifically, the material of the packaging layer of the sensor is the same as the base material of the functional layer.

[0098] It should be noted that in order to make the sensor have softness and deformability and improve the ability to apply robot motion control and human-computer interaction, the material of the packaging layer needs to be limited.

[0099] Specifically, the material of the packaging layer is polydimethylsiloxane (PDMS), which has high flexibility, low Young's modulus (close to skin), high chemical stability, good biocompatibility, good environmental resistance, good tensile adaptability, excellent resilience, can be worn for a long time, can improve human-computer interaction performance, and has low cost.

[0100] It should be noted that the material constituting the packaging layer of the sensor is not conductive. According to the homogeneous integrated structure design of the present application, in order to meet the requirement of electrical conductivity of the functional layer, the material needs to be compounded with a conductive material when it is used as the base material of the functional layer.

[0101] Specifically, in order to make the composite polymer material have conductivity while maintaining the inherent flexibility and deformability of PMDS, meet the needs of wearable and foldable electronic products, and meet the structural design of the homogenization of the sensor of the application, the application dopes conductive carbon particles into the PDMS base material, so that the sensor packaging layer material which does not have conductive properties obtains good conductivity to be used as the material for forming the functional layer of the sensor.

[0102] More specifically, the material forming the functional layer of the sensor of the application is a conductive carbon-doped PDMS composite material, wherein the conductive carbon is at least one of carbon nanotubes (CNT), carbon black (CB), and graphene (GO), has a large specific surface area, is easy to disperse, and can provide a high-conductive network; preferably CNT or graphene.

[0103] It should be noted that the one-dimensional (CNTs) or two-dimensional (graphene) structure has extremely high inherent flexibility and aspect ratio / high specific surface area, can form a reversible percolation network inside the PDMS; and the carbon material has excellent chemical inertness and oxidation resistance, ensuring the performance stability and reliability of the sensor in long-term use.

[0104] It should be noted that in order to make the coil layer with a planar complementary labyrinth structure not only have high conductivity and capacitance strength and range, but also have excellent mechanical properties, ensure that the sensor has softness and deformability, and meet the design of the homogenization of the sensor of the application, the application needs to limit the content of each component in the composite material forming the coil layer of the functional layer.

[0105] Specifically, the content of conductive carbon in the composite material forming the coil layer is 4-8% by weight. If the carbon content is too low, the conductivity of the composite material is less than the percolation threshold, resulting in poor or even no conductivity of the coil layer, affecting the edge electric field strength and range; if the content is too high, it is easy to form stress concentration points in the composite material, reducing the conductivity and flexibility of the material.

[0106] According to some preferred embodiments of the application, the content of conductive carbon in the composite material forming the coil layer can be any value within the range of 4-8%, such as 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0107] It should be noted that in order to make the piezoresistive layer with a porous structure not only have high piezoresistive tactile sensitivity, but also have excellent mechanical properties, ensure that the sensor has softness and deformability, and meet the design of the homogenization of the sensor of the application, the application needs to limit the content of each component in the composite material forming the piezoresistive layer of the functional layer.

[0108] Specifically, the content of the conductive carbon in the composite material constituting the piezoresistive layer is 4-8% by weight. If the carbon content is too low, the conductive network is sparse, the initial resistance is high and the signal is weak, which is easy to cause the piezoresistive layer to be activated when it is subjected to a small pressure, and the piezoresistive effect is easy to perceive the force touch; if the content is too high, the conductive network is too dense, the deformation contributes little to the resistance change, the sensitivity decreases, and the brittleness increases and the cycle stability deteriorates.

[0109] According to some preferred embodiments of the present application, the content of the conductive carbon in the composite material constituting the piezoresistive layer can be any value within the range of 4-8%, such as 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0110] The material of the sensor packaging layer of the present application is the same as the base material of the functional layer, by limiting the composition, size and content of the conductive particles in the sensor functional layer, not only the stability of the interface between the parts of the sensor can be improved, the robustness and durability of the sensor can be improved, but also the strengthening of the charge aggregation effect can be realized by increasing the microstructure of the coil layer electrode tip and edge structure and the specific surface area; the change of the internal conductive particle network contact path caused by the deformation of the piezoresistive layer under pressure, the content and size of the conductive particles will affect the sensitivity of the piezoresistive layer during deformation.

[0111] The sensor proximity sensing distance of the present application can reach 250mm, the sensor force touch range can reach 200kPa, and the piezoresistive layer force touch response time can reach 166ms.

[0112] The present application also discloses a method for preparing the above-mentioned sensor, and the specific preparation process is shown in Figure 7 The method comprises the following steps:

[0113] (1) According to the structure of the coil layer, a mold for preparing the coil layer substrate is obtained, and polydimethylsiloxane is used for pouring, and after curing, a patterned coil layer substrate is obtained;

[0114] The polydimethylsiloxane is mixed with conductive carbon, and the obtained mixed prepolymer I is filled into the pattern of the coil layer substrate, and after curing, the coil layer is obtained, wherein the coil layer and the substrate are embedded into one whole;

[0115] (2) The polydimethylsiloxane is mixed with conductive carbon and inorganic salt, and the obtained mixed prepolymer II is poured into a mold, and after curing, it is soaked to obtain the piezoresistive layer;

[0116] (3) According to the piezoresistive layer structure and the air gap layer thickness design, a mold for preparing a support frame for fixing the piezoresistive layer and providing the air gap layer is obtained, and a prepolymer of the encapsulation layer material is mold-cast to obtain the support frame after curing, wherein the support frame has a square structure with an open top surface or a square structure with open top and bottom surfaces.

[0117] (4) Encapsulation, the specific steps are as follows: the square structure support frame with open top and bottom surfaces prepared in step (3) is adhered to the encapsulation bottom surface using semi-cured polydimethylsiloxane or directly using a square structure support frame with an open top surface, the piezoresistive layer is placed in the reserved area of the support layer, and the coil layer substrate is placed on the support layer after smearing the semi-cured encapsulation layer material on the top surface of the support frame.

[0118] Specifically, in step (1), the specific steps for preparing the coil layer substrate are as follows: according to the planar complementary labyrinth structure of the sensor, a polylactic acid (PLA) mold for the capacitive coil layer substrate is obtained by 3D printing technology, a prepolymer (such as PDMS prepolymer) for preparing a sensor encapsulation layer material and a PDMS curing agent are mixed in a mass ratio of 5:1-20:1 (such as 10:1), and after degassing in a vacuum, they are poured into the PLA mold, and then cured at a certain temperature of 40-60°C (such as 50°C) for 70-100 min (such as 80 min) to obtain the patterned coil layer substrate.

[0119] Specifically, in step (1), the specific steps for preparing the coil layer are as follows: according to the formula of the composite material constituting the coil layer, conductive particles (such as CNT powder, carbon black, graphene, etc.) are added to isopropyl alcohol (IPA) in a certain mass ratio, wherein the mass ratio of IPA to conductive particles is 60:1-30:1 (such as the mass ratio of IPA to CNT is 50:1); a small amount of surfactant sodium dodecyl benzene sulfonate (SDBS) (such as the mass ratio of CNT:SDBS is 3:1) is added, and the suspension is formed by ultrasonic treatment for 20-60 min (such as 30 min). Then, a proper amount of PDMS prepolymer is added to the suspension, and the mixture is mechanically stirred at a stirring paddle speed of 500-1500 rpm (such as 80°C, 1500 rpm) until the IPA in the mixture is completely volatilized at a temperature of 60-100°C; after sufficient cooling, PDMS curing agent is added in a mass ratio of PDMS prepolymer: curing agent of 5:1-20:1 (such as 10:1) and stirred thoroughly to obtain a CNT / PDMS composite with 4-8 wt% CNT (such as 8 wt%), and the mixture is filled and coated into the pattern of the prepared coil layer substrate; finally, the mixture is cured at a temperature of 100-120°C for 4-8 h (such as 8 h at 120°C) to obtain the coil layer.

[0120] Specifically, in step (2), the specific steps for preparing the piezoresistive layer are as follows: according to the formula of the composite material constituting the porous sponge layer in the piezoresistive layer, inorganic salt (such as NaCl), PDMS prepolymer and CNT powder are added into a proper amount of IPA in a certain proportion of 100-20:10:0.8 (such as 20:10:0.8), ultrasonic oscillation is performed for 20-60 min (such as 30 min), and the mixture is mechanically stirred at a stirring paddle speed of 500-1500 rpm (such as 80°C, 1500 rpm) at a temperature of 60-100°C until the IPA in the mixture is completely volatilized; after cooling, PDMS curing agent is added in a mass ratio of PDMS prepolymer to curing agent of 5:1-20:1 (such as 10:1) and fully stirred to obtain a CNT / PDMS / NaCl composite of inorganic salt (such as NaCl) and CNT; then, the composite is injected into a customized PTFE mold, and the first layer of sponge layer is obtained by pressure coating; subsequently, by changing the proportion of the inorganic salt and the material of the encapsulation layer, inorganic salt (such as NaCl), PDMS prepolymer and CNT powder are added into a proper amount of IPA in a proportion different from that for preparing the first layer of sponge layer, i.e. 100-20:10:0.8 (such as 100:10:0.8), and the above process is repeated to obtain a CNT / PDMS / NaCl composite of inorganic salt and CNT (8wt%), which is pressure coated on the first layer of sponge layer to obtain a second layer of sponge layer; the proportion of the inorganic salt and the material of the encapsulation layer is continuously changed, and the third, fourth, fifth and sixth layers of sponge layer are continuously obtained by the same preparation method, and finally, the piezoresistive layer with a gradient decrease in porosity from top to bottom is obtained by curing at a temperature of 80-120°C for 4-8h (such as 80°C for 4h).

[0121] It should be noted that, in order to obtain a porous piezoresistive layer, the inorganic salt doped in the piezoresistive layer after curing needs to be removed by solvent soaking.

[0122] According to some preferred embodiments of the present application, the piezoresistive sponge layer can be repeatedly immersed in hot water (such as 90°C) at a temperature of 70-90°C (such as 90°C) to dissolve the inorganic salt (such as NaCl) therein.

[0123] Specifically, in step (3), the specific steps for preparing the support frame are as follows: according to the structure of the piezoresistive layer and the thickness design of the air gap layer, a PLA mold for preparing the support frame is obtained by 3D printing, a prepolymer (such as PDMS prepolymer) and a curing agent (such as) for preparing the sensor encapsulation layer material are fully mixed in a mass ratio of PDMS prepolymer to curing agent of 5:1-20:1 (such as 10:1), and then poured into the PLA mold after degassing in a vacuum, and cured at a temperature of 45-60°C (such as 50°C) for 60-120 min (such as 80 min) to obtain a piezoresistive sponge support layer.

[0124] Specifically, in step (4), a polymer film (such as a PDMS film with a thickness of 300 μm) with a thickness of 200-500 μm is taken, and a semi-solid polymer prepolymer (such as a PDMS prepolymer) with a certain viscosity is applied on the film, the support frame is placed on the film, and the piezoresistive layer is placed in the reserved area of the support layer; finally, a semi-solid polymer prepolymer (such as a PDMS prepolymer) with a certain viscosity is applied on the top surface of the support frame, and the coil layer substrate embedded with the coil layer is placed on the support frame, and the flexible force tactile sensor is obtained by curing at 45-60°C (such as 50°C) for 60-120 min (such as 80 min).

[0125] Compared with the existing method for preparing a dual-mode sensor, the method of the present application improves the overall structure and material composition of the sensor: on the one hand, the coil layer is designed as a planar complementary labyrinth structure, and an air gap layer is added between the coil layer and the piezoresistive layer, which can expand the sensing distance of the sensor while expanding the force tactile sensing range, and improving the response speed and sensitivity of the resistive force tactile sensor; on the other hand, the material of the sensor packaging layer is the same as the base material of the functional layer, which improves the stability of the interface between the parts of the sensor, and makes the sensor have high robustness and durability.

[0126] Compared with the existing method for preparing a dual-mode sensor, the method of the present application improves the overall structure and material composition of the sensor: on the one hand, the coil layer is designed as a planar complementary labyrinth structure, and an air gap layer is added between the coil layer and the piezoresistive layer, which can expand the sensing distance of the sensor while expanding the force tactile sensing range, and improving the response speed and sensitivity of the resistive force tactile sensor; on the other hand, the material of the sensor packaging layer is the same as the base material of the functional layer, which improves the stability of the interface between the parts of the sensor, and makes the sensor have high robustness and durability.

[0127] The present application controls the height difference between the inner cavity of the support frame and the piezoresistive layer by a mold casting process, so that an air gap layer of the dual-mode sensor is formed between the coil layer and the piezoresistive layer after packaging each component, the process flow is simple, and the height difference is easy to control; the air gap layer plays a crucial role in improving the contact tactile and force tactile range of the dual-mode sensor, and improving the response speed and sensitivity of the resistive force tactile sensor.

[0128] The present application controls the height difference between the inner cavity of the support frame and the piezoresistive layer by a mold casting process, so that an air gap layer of the dual-mode sensor is formed between the coil layer and the piezoresistive layer after packaging each component, the process flow is simple, and the height difference is easy to control; the air gap layer plays a crucial role in improving the contact tactile and force tactile range of the dual-mode sensor, and improving the response speed and sensitivity of the resistive force tactile sensor.

[0129] The application can control the size and gradient change arrangement structure of the porosity in the piezoresistive layer by regulating the addition amount of inorganic salt in the piezoresistive layer casting raw material, adopting the batch casting mode in the same mold, further improving the sensing sensitivity and sensing range of the piezoresistive layer to external pressure, and improving the force tactile sensing ability of the sensor.

[0130] The flexible sensor prepared by the method of the application can realize bimodal response of proximity sense and force tactile sense, Figure 8 The proximity sense response result graph of the flexible sensor prepared for the embodiment 1 of the application; Figure 9 The force tactile response result graphs of the sensor designed for the embodiment 1 of the application in the capacitance mode and the resistance mode are shown in Figures 6 and 7, respectively. Figure 9 It can be seen that when the contact force increases to 60kPa, the mode of the sensor for force tactile sensing is switched from the capacitance mode to the resistance mode. The sensor designed by the application has a far proximity sense response range and a wide force tactile response range, and has good segmented linearity in the range.

[0131] The following examples and comparative examples further explain the technical solutions of the application.

[0132] The type of the PDMS prepolymer used in the embodiment is Sylgard 184.

[0133] Embodiment 1

[0134] The method for preparing a flexible proximity sense-force tactile sensor of homogeneous integration specifically comprises the following steps:

[0135] (1) According to the planar complementary square maze structure of the sensor coil layer, a polylactic acid (PLA) mold of the capacitance coil layer substrate is obtained by 3D printing technology, PDMS prepolymer and PDMS curing agent (containing hydrogen silicone oil crosslinking agent and platinum gold catalyst) are fully mixed in a mass ratio of 10:1, and after degassing in vacuum, the mixture is cast into the PLA mold, and the patterned coil layer substrate is obtained by curing at 50℃ for 80min, wherein the thickness of the coil layer is 1mm, and the ratio between the electrode width and the electrode spacing of the planar complementary square maze structure is 3:1;

[0136] The CNT powder is added to isopropyl alcohol (IPA) at a mass ratio of 1:50, a small amount of surfactant sodium dodecyl benzene sulfonate (SDBS) is added (for example, the mass ratio of CNT:SDBS is 3:1), and ultrasonic treatment is performed for 30 min to form a suspension; then, the PDMS prepolymer (with a content of 11.5:1 of CNT powder) is added to the suspension, and mechanical stirring is performed at a temperature of 80°C and a rate of 1500 rpm until the IPA in the mixture is completely volatilized; after sufficient cooling, the PDMS curing agent (containing hydrogen silicone oil crosslinking agent and platinum gold catalyst) is added at a mass ratio of PDMS prepolymer: curing agent = 10:1 and stirred thoroughly to obtain a CNT / PDMS composite with 8wt% CNT, and the mixture is filled and coated into the pattern of the prepared coil layer substrate; curing is performed at a temperature of 120°C for 8h to obtain a coil layer; wherein the coil layer is embedded into the prepared coil layer substrate;

[0137] (2) The inorganic salt NaCl, PDMS prepolymer and CNT powder are added to an appropriate amount of IPA at a mass ratio of 20:10:0.8, ultrasonic oscillation is performed for 30 min, and mechanical stirring is performed at a temperature of 80°C and a rate of 1200 rpm until the IPA in the mixture is completely volatilized; after cooling, the PDMS curing agent is added at a mass ratio of PDMS prepolymer: curing agent = 10:1 and stirred thoroughly to obtain a CNT / PDMS / NaCl composite with 2 times inorganic salt and 8wt% CNT; then, the composite is injected into a customized PTFE mold, and a first sponge layer is obtained by pressure coating;

[0138] The inorganic salt NaCl, PDMS prepolymer and CNT powder are added to an appropriate amount of IPA at a mass ratio different from that for preparing the first layer of sponge layer, and the above process is repeated to obtain a CNT / PDMS / NaCl composite with 10 times inorganic salt and 8wt% CNT, which is pressure coated on the first layer of sponge layer to obtain a second layer of sponge layer;

[0139] Curing is performed at 80°C for 4h, and the piezoresistive sponge layer is repeatedly immersed in hot water (90°C) to dissolve the inorganic salt NaCl therein, obtaining a piezoresistive layer composed of a second layer of sponge layer and a first layer of sponge layer, which are arranged from top to bottom with a gradient decrease in porosity, wherein the thickness of the second layer of sponge layer is 1mm and the porosity is 80%; the thickness of the first layer of sponge layer is 1mm and the porosity is 45%;

[0140] (3) A PLA mold for preparing a support frame is obtained by 3D printing, the PDMS prepolymer and the curing agent are thoroughly mixed at a mass ratio of 10:1, degassed in vacuum, and then poured into the PLA mold, and curing is performed at a temperature of 50°C for 80 min to obtain a support frame, wherein the support frame is 1mm thicker than the piezoresistive layer (i.e. the thickness of the air gap layer in the prepared sensor after packaging);

[0141] (4) Take a PDMS film with a thickness of 300 μm, apply semi-cured PDMS prepolymer on the film, and place the support frame prepared in step (3) on the film; place the piezoresistive layer prepared in step (2) in the reserved area of the support layer; apply semi-cured PDMS prepolymer on the top surface of the support frame, and place the coil layer substrate with the embedded coil layer prepared in step (1) on the support frame, and cure at 80°C for 1 h to obtain a flexible force tactile and proximity sensor 1.

[0142] Example 2

[0143] The same method as in Example 1 was used, except that in step (2), the prepared piezoresistive layer only included one sponge layer, and the mass ratio of raw materials, inorganic salt NaCl, PDMS prepolymer and CNT powder, was 100:10:0.8. After curing, the piezoresistive layer had a thickness of 1 mm and a porosity of 80%. Finally, a flexible force tactile and proximity sensor 2 was obtained.

[0144] Example 3

[0145] The same method as in Example 1 was used, except that in step (2), the prepared piezoresistive layer included three sponge layers, and the mass ratio of raw materials, inorganic salt NaCl, PDMS prepolymer and CNT powder, was 100:10:0.8, 50:10:0.8 and 20:10:0.8, respectively. A piezoresistive layer composed of a third sponge layer, a second sponge layer and a first sponge layer from top to bottom, with a gradient decrease in porosity, was obtained, wherein the third sponge layer had a thickness of 1 mm and a porosity of 80%; the second sponge layer had a thickness of 1 mm and a porosity of 70%; and the first sponge layer had a thickness of 1 mm and a porosity of 45%. Finally, a flexible force tactile and proximity sensor 3 was obtained.

[0146] Example 4

[0147] The same method as in Example 1 was used, except that in step (1), the ratio between the width of the electrode with a planar complementary square maze structure and the electrode spacing was 5:1. Finally, a flexible force tactile and proximity sensor 4 was obtained.

[0148] Example 5

[0149] The same method as in Example 1 was used, except that in step (1), the ratio between the width of the electrode with a planar complementary square maze structure and the electrode spacing was 1:1. Finally, a flexible force tactile and proximity sensor 5 was obtained.

[0150] Example 6

[0151] The same method as in Example 1 was adopted, except that in step (3), the thickness of the supporting frame was 0.55 mm (i.e. the thickness of the air gap layer in the sensor after packaging), and finally a flexible force tactile sensor 6 with homogeneous integration was obtained.

[0152] Example 7

[0153] The same method as in Example 1 was adopted, except that in step (3), the thickness of the supporting frame was 1.45 mm (i.e. the thickness of the air gap layer in the sensor after packaging), and finally a flexible force tactile sensor 7 with homogeneous integration was obtained.

[0154] Comparative Example 1

[0155] The same method as in Example 1 was adopted, except that in step (1), the sensor coil layer adopted an interdigital electrode structure, and finally a flexible force tactile sensor 8 with homogeneous integration was obtained.

[0156] Comparative Example 2

[0157] The same method as in Example 1 was adopted, except that steps (2) and (3) were not included, and finally a flexible force tactile sensor 11 with homogeneous integration was obtained.

[0158] Comparative Example 3

[0159] The same method as in Example 1 was adopted, except that the mass ratio of the PDMS prepolymer to the CNT powder was 10:0.1, and finally a flexible force tactile sensor 9 with homogeneous integration was obtained.

[0160] Comparative Example 4

[0161] The same method as in Example 1 was adopted, except that in step (3), the thickness of the supporting frame was 1.55 mm (i.e. the thickness of the air gap layer in the sensor after packaging), and finally a flexible force tactile sensor 10 with homogeneous integration was obtained.

[0162] The structural parameters of the sensors obtained in the above examples and comparative examples are shown in Table 1:

[0163]

[0164]

[0165] Test Example

[0166] The sensors 1-11 obtained in the examples and comparative examples were tested, and the details are as follows:

[0167] First, the sensor to be tested is placed directly below the Mark-10 F105 metal pressure head, and the metal pressure head is moved from 300 mm to 0 mm at a speed of 200 mm / min. The Keysight E4980 is used to collect the capacitance signal of the sensor to be tested during this process, and the Mark-10 F105 is used to record the distance signal to obtain the proximity response of the sensor to be tested.

[0168] Then, the metal pressure head is moved downward at a speed of 3 mm / min, and the sensor to be tested is subjected to pressure. The Keysight E4980 and Keithley 2450 are used to record the capacitance signal and resistance signal of the sensor to be tested during the pressure, respectively, and the Mark-10 F105 is used to record the pressure signal to obtain the force tactile response of the sensor to be tested.

[0169] The results obtained after testing the sensors prepared in the examples and comparative examples are shown in Table 1.

[0170] Table 2 shows the performance parameters of the sensors prepared in the examples and comparative examples.

[0171]

[0172] The above description is only a preferred embodiment of the present application, and the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A homogeneous and integrated flexible proximity-force tactile sensor, characterized by, The sensor comprises a packaging layer and a functional layer, the functional layer is sealed inside the packaging layer; from top to bottom, the functional layer comprises a coil layer, an air gap layer and a piezoresistive layer in sequence, and the packaging layer comprises a coil layer substrate, a support frame and a packaging bottom surface which are bonded in sequence; The coil layer and the coil layer substrate are mutually embedded and have a planar complementary labyrinth structure for providing an edge field capacitance to sense a close object and form a capacitive proximity sense of the sensor; The air gap layer is provided by the support frame for providing a space for the deformation of the coil layer when it is pressed to sense a contact object by using the inter-plate capacitance of the coil layer and form a capacitive force sense of the sensor; The piezoresistive layer is fixed inside the support frame and has a porous structure for providing a resistance to sense a contact object and form a resistive force sense of the sensor; The material of the packaging layer is the same as the base material of the functional layer; The support frame and the packaging bottom surface are designed as a whole or separated.

2. The sensor of claim 1, wherein, The thickness of the planar complementary labyrinth structure of the coil layer is 0.8-1.5 mm; And / or, the ratio of the coil width to the pitch is 5:1-1:

1.

3. The sensor of claim 1, wherein, The piezoresistive layer comprises a plurality of porous sponge layers, and the porosity of the porous sponge layers decreases in sequence from top to bottom; And / or, the thickness of the piezoresistive layer is 2-6 mm.

4. The sensor of claim 3, wherein, The piezoresistive layer comprises 1-3 porous sponge layers; And / or, the thickness of the porous sponge layer is 1-2 mm; And / or, the porosity of the porous sponge layer is 45-80%.

5. The sensor of claim 1, wherein, The thickness h of the air gap layer is 0.5 mm 6. The sensor of claim 1, wherein, The material of the packaging layer is polydimethylsiloxane; And / or, the material of the coil layer and the piezoresistive layer is a conductive carbon-doped polydimethylsiloxane composite.

7. The sensor of claim 6, wherein, The conductive carbon is at least one of nanotubes, carbon black and graphene; And / or, the content of the conductive carbon in the composite is 4-8 wt% in terms of weight percentage.

8. The sensor according to any one of claims 1 to 7, characterized in that The sensing distance of the proximity sense of the sensor reaches 250 mm, the range of the force sense of the sensor reaches 200 kPa, and the response time of the force sense of the piezoresistive layer reaches 166 ms.

9. A method of making a sensor, characterized by, The sensor is the sensor of any one of claims 1-7, and the method comprises: (1) obtaining a mold for preparing a coil layer substrate according to the structure of the coil layer, pouring, and curing to obtain a patterned coil layer substrate; filling and coating the pattern of the coil layer substrate, and curing to obtain the coil layer, wherein the coil layer and the substrate are mutually embedded as a whole; (2) mold pouring and curing to obtain the piezoresistive layer; (3) mold pouring and curing to obtain the support frame, wherein the inner cavity size of the support frame is greater than the volume size of the piezoresistive layer, and the height difference constitutes the air gap layer of the sensor prepared after packaging; (4) packaging.

10. The method of claim 9, wherein, In step (2), the pouring is carried out in batches.

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