Strain sensor and preparation method thereof

Abstract

A strain sensor (200), comprising: a substrate (210) on which a groove structure (211) is provided; the conductive thin film (220) is attached to the surface of the substrate (210), and cracks (221) are formed in the positions, right opposite to the groove structures (211), of the conductive thin film (220). The strain sensor (200) has a high sensitivity.

Description

Strain sensor and preparation method thereof Technical Field

[0001] The present application relates to the field of sensing equipment, and in particular to a strain sensor and a preparation method thereof. Background Art

[0002] Strain sensors, as sensors for measuring the deformation of objects under force, are widely used in various electronic devices. Current strain sensors mostly use resistive strain sensors, which convert mechanical strain into electrical signals through resistance strain gauges. The improvement of the sensitivity of resistive strain sensors is mainly achieved by improving the resistance material and optimizing the circuit. However, the R&D cycle involved in improving the resistance material and circuit optimization is long and the R&D cost is relatively high. In addition, in existing resistive strain sensors, cracks can be set in the resistance material through mechanical deformation to improve the sensitivity of the resistive strain sensor, but the position of the cracks generated by mechanical deformation is difficult to control, resulting in poor consistency in the performance of the prepared samples, which is not conducive to industrial applications.

[0003] Therefore, a strain sensor is needed that has a simple structure, low cost and high sensitivity.

[0004] Summary of the Invention

[0005] One embodiment of this specification provides a strain sensor, comprising: a substrate having a groove structure provided thereon; and a conductive film attached to a surface of the substrate, wherein a crack is provided on the conductive film at a position facing the groove structure.

[0006] In some embodiments, the groove structure penetrates the substrate.

[0007] In some embodiments, the groove structure does not penetrate the substrate, and the conductive film is located on a side of the substrate where the opening of the groove structure is located.

[0008] In some embodiments, a dimension of the groove structure in the second direction along the length of the substrate ranges from 1 μm to 50 μm.

[0009] In some embodiments, the groove structure does not penetrate the substrate, and the conductive film is located on a side of the substrate opposite to the opening of the groove structure.

[0010] In some embodiments, a dimension of the groove structure in the second direction along the length of the substrate ranges from 10 μm to 100 μm.

[0011] In some embodiments, the groove structure extends along a first direction of the substrate width, and a size of the groove structure in the first direction is larger than a size of the conductive film at a location of the groove structure in the first direction.

[0012] In some embodiments, the groove structure extends along a first direction of the width of the substrate, and a ratio of a size of the groove structure to a size of the substrate in the first direction may be within a range of 2 / 3-9 / 10.

[0013] In some embodiments, the groove structure extends along a first direction of the width of the substrate, and hole structures are respectively provided at both ends of the extending direction of the groove structure.

[0014] In some embodiments, the groove structure includes a first groove, a second groove, and a third groove sequentially arranged along the second direction of the substrate length, and a first spacing between the first groove and the second groove is the same as a second spacing between the second groove and the third groove.

[0015] In some embodiments, the groove structure includes a first groove, a second groove, and a third groove sequentially arranged along a second direction of the substrate length, and a first spacing between the first groove and the second groove is different from a second spacing between the second groove and the third groove.

[0016] In some embodiments, the resistivity of the substrate is higher than 1×10 7 Ω·m, the conductive film presents different resistances as the external stress changes.

[0017] In some embodiments, the conductive film is conductive carbon paste.

[0018] In some embodiments, the resistivity of the substrate is higher than 1×10 7 Ω·m, the conductive film is in two states of on or off under the action of external stress.

[0019] In some embodiments, the conductive film is conductive silver paste.

[0020] One of the embodiments of this specification provides a method for preparing a strain sensor, comprising: etching a groove structure on a non-conductive substrate; coating a conductive paste on the substrate and curing the paste to form a conductive film; and bending the substrate coated with the conductive film to form a crack, thereby obtaining the strain sensor.

[0021] One of the embodiments of this specification provides a pressure sensor, including: a strain sensor, wherein the strain sensor includes: a substrate, a groove structure is provided on the substrate, and a conductive film attached to the surface of the substrate, a crack is provided on the conductive film at a position opposite to the groove structure; and a supporting component for supporting the groove structure and the crack.

[0022] In some embodiments, the supporting component is disposed on the conductive film or on a side of the substrate where the conductive film is located.

[0023] In some embodiments, the pressure sensor is arranged in an earphone, which includes: a speaker for generating a sound signal, and a shell for carrying the speaker and the pressure sensor, wherein the pressure sensor is used to switch the pressure sensor from a path state to an off-path state in response to pressure applied by a user, and generate a corresponding electrical signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present application will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0025] FIG1 is an exemplary module diagram of a strain sensor according to some embodiments of this specification;

[0026] FIG2A is an exemplary structural diagram of a strain sensor according to some embodiments of this specification;

[0027] FIG2B is a cross-sectional view taken along line AA of the strain sensor of FIG2A according to some embodiments of the present specification;

[0028] FIG2C is an exemplary structural diagram of a strain sensor according to other embodiments of this specification;

[0029] FIG2D is a cross-sectional view taken along line BB of the strain sensor of FIG2C according to some embodiments of the present specification;

[0030] FIG3 is an exemplary structural diagram of a strain sensor according to other embodiments of this specification;

[0031] FIG4 is an exemplary structural diagram of a strain sensor according to other embodiments of this specification;

[0032] FIG5 is an exemplary structural diagram of a strain sensor according to other embodiments of this specification;

[0033] FIG6 is an exemplary flow chart of a method for preparing a strain sensor according to some embodiments of this specification;

[0034] FIG. 7 is an exemplary structural diagram of a pressure sensor according to some embodiments of the present specification. DETAILED DESCRIPTION

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0036] As used in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not refer to the singular but also include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0037] In the description of this specification, it should be understood that the terms "first," "second," "third," "fourth," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of such features. In the description of this specification, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0038] In this specification, unless otherwise specified or limited, terms such as "connected" and "fixed" should be interpreted broadly. For example, the term "connected" can refer to a fixed connection, a removable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; and can refer to internal communication between two components or an interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this specification based on the specific circumstances.

[0039] An embodiment of the present specification provides a strain sensor, comprising: a substrate having a groove structure disposed thereon; and a conductive film attached to a surface of the substrate, wherein a crack is disposed on the conductive film at a position facing the groove structure.

[0040] In some embodiments, the resistance value of the conductive film can change in response to the deformation of the strain sensor. At this time, by setting cracks on the conductive film, when the strain sensor is deformed by external stress, not only the resistance of the conductive film itself can be changed, but also the contact area between the conductive materials inside the conductive film can be changed accordingly, so that the conductive film produces a larger resistance value change under the same deformation amount, thereby achieving the effect of improving the sensitivity of the strain sensor, without the need to develop new materials and / or optimize the circuit, greatly reducing costs. In addition, by pre-setting a groove structure on the substrate, the stress can be highly concentrated at the position of the groove structure during the preparation of the crack, so that cracks are preferentially generated at the groove structure. By reasonably setting the position of the groove structure, the cracks on the conductive film can be generated in a controllable and orderly manner, thereby improving the consistency of the cracks on the prepared resistive strain sensor, which is beneficial to industrial applications. Again, by changing the width, number, conductivity of the conductive film, etc. of the groove structure, the sensitivity of the resistive strain sensor can be flexibly adjusted to make it suitable for scenarios with different sensitivity requirements.

[0041] In some embodiments, the resistance of the conductive film may not change with bending of the strain sensor, or the conductivity of the conductive film may be minimally affected by bending. In this case, by providing a crack in the conductive film, when the strain sensor is deformed by external stress, the crack can be closed or fully opened, thereby enabling or disconnecting the circuit in which the strain sensor resides, thereby achieving the function of a switch device. Furthermore, a support component can be provided to allow the groove structure and the crack to be suspended in the air. This allows the strain sensor to fully open and close the crack in response to external pressure, thus achieving pressure sensing.

[0042] FIG. 1 is an exemplary module diagram of a strain sensor according to some embodiments of the present specification.

[0043] As shown in FIG. 1 , the strain sensor 100 may include a substrate 110 and a conductive film 120 .

[0044] The substrate 110 can be used to support the conductive film 120. The substrate 110 can elastically deform under external stress. A groove structure is provided on the substrate 110. In some embodiments, the groove structure 211 can be a depression with a rectangular, circular, or other irregular cross-section. The shape of the groove structure 211 is designed to produce a stress concentration effect. The shape should be varied to facilitate processing, and this specification does not limit its shape.

[0045] In some embodiments, the substrate 110 can be made of a non-conductive material that has a certain mechanical strength and can undergo elastic deformation under external stress. For example, the substrate 110 can be made of materials such as polyvinyl alcohol, polyimide, and polydimethylsiloxane. In some embodiments, the substrate 110 can be a conductive material. For example, the substrate 110 can be a metal, graphene, etc. When the substrate 110 is a conductive material, there can be an insulating layer between the substrate 110 and the conductive film 120 to isolate the electrical conduction between the substrate 110 and the conductive film 120. Exemplary materials of the insulating layer may include polyethylene, rubber, etc. In some embodiments, the shape of the substrate 110 can be a regular shape such as a triangle, rectangle, circle, oval, or any other irregular shape. The width, thickness, length, etc. of the substrate 110 can be set according to specific needs.

[0046] The conductive film 120 can be attached to the surface of the substrate 110 or the insulating layer (if any) on the substrate 110, and a crack is provided at a position opposite the groove structure. The opening (including full opening and partial opening) or closing of the crack can affect the resistance in the circuit in which the strain sensor 100 is located. For example, when the crack is closed, the two sides of the crack are conductive (or the strain sensor 100 is in a conductive state). At this time, the resistance of the strain sensor 100 is only determined by the material of the conductive film 120 itself (for example, the resistivity of the material, the shape of the conductive film, etc.). As the crack gradually opens, the contact area of ​​the conductive film 120 at the crack will become smaller, and its conductivity will become worse. In other words, the greater the degree of crack opening, the greater the resistance of the strain sensor 100; conversely, the smaller the degree of crack opening, the smaller the resistance of the strain sensor 100. When the crack is fully opened (ie, the two conductive films formed by the crack are disconnected), there is no conduction between the two sides of the crack, and the strain sensor 100 is in an open circuit state.

[0047] It should be noted that, in this specification, when the strain sensor 100 is in its natural state, the crack can be in an open state (e.g., fully open or partially open) or a closed state, and the state of the crack is not limited herein. If the crack is in an open state when the strain sensor 100 is in its natural state, the crack can gradually close during the bending process of the strain sensor 100; if the crack is in a closed state when the strain sensor 100 is in its natural state, the crack can gradually open during the bending process of the strain sensor 100.

[0048] In some embodiments, the conductive film 120 can be formed by curing a conductive paste. In some embodiments, the conductive paste can be formed by mixing conductive particles and a resin base. Exemplary conductive particles can include carbon black, carbon nanotubes, graphene, silver powder, copper powder, etc. Exemplary resin bases can include epoxy resin, polyvinyl chloride (PVC), polyimide resin, phenolic resin, etc. In some embodiments, in this specification, the terms conductive paste and conductive film can be used interchangeably. For example, conductive carbon paste can also refer to a conductive film formed by curing the conductive carbon paste.

[0049] In some embodiments, the shape of the conductive film 120 may or may not match the shape of the substrate 110. For example, when the substrate 110 is circular, the conductive film 120 may be elliptical. For another example, when the substrate 110 is rectangular, the conductive film 120 may also be rectangular. For ease of description, this specification uses the example of both the substrate 110 and the conductive film 120 being rectangular, which does not limit the scope of this application.

[0050] The conductive film 120 can be deformed accordingly with the deformation of the substrate 110. In some embodiments, the conductive film 120 can be formed by curing a conductive paste with a higher resistivity, and the resistance value of the conductive film 120 can change in response to the deformation (for example, bending) of the strain sensor 100. In this case, the strain sensor 100 can also be called a resistive strain sensor. The resistive strain sensor can generate an electrical signal in response to the deformation of the strain sensor 100. Specifically, when the strain sensor 100 is deformed (for example, bent) by an external force, the surface of the substrate 110 can be stretched or compressed, thereby causing the conductive film 120 provided on its surface to be deformed accordingly, thereby causing the resistance value of the conductive film 120 to change (for example, increase or decrease), and ultimately generating an electrical signal. Exemplary electrical signals may include resistance signals, current signals, voltage signals, etc.

[0051] In some embodiments, the conductive film 120 can be formed by curing a low-resistivity conductive paste. The resistance of the conductive film 120 does not substantially change with bending of the strain sensor 100. In this case, when the strain sensor 100 is deformed by an external force, cracks in the conductive film 120 can open or close under the external stress, thereby causing the circuit in which the strain sensor 100 resides to be open or closed. Further description of the strain sensor can be found elsewhere in this specification, such as Figures 2A-7 and their descriptions, and will not be repeated here.

[0052] In some embodiments, the strain sensor 100 may further include a processor (not shown). The processor may be used to further process the electrical signal. For example, when the strain sensor 100 is placed on a target object, the processor may determine the degree of bending of the strain sensor 100 (or the target object) based on the change in the resistance value of the strain sensor 100. For another example, the processor may determine whether the user has applied pressure (e.g., whether the user has tapped or long-pressed) based on the difference between the electrical signals generated by the strain sensor 100 when it is in a circuit and when it is in an open circuit, and may then perform a corresponding operation.

[0053] FIG2A is an exemplary structural diagram of a strain sensor according to some embodiments of this specification. FIG2B is a cross-sectional view taken along line AA of the strain sensor shown in FIG2A according to some embodiments of this specification. FIG2C is an exemplary structural diagram of a strain sensor according to other embodiments of this specification. FIG2D is a cross-sectional view taken along line BB of the strain sensor shown in FIG2C according to some embodiments of this specification.

[0054] As shown in FIG2A or FIG2C , strain sensor 200 may include substrate 210 and conductive film 220. Substrate 210 may be used to support conductive film 220. Substrate 210 is provided with a groove structure 211. Conductive film 220 is attached to the surface of substrate 210, and cracks 221 are provided on conductive film 220 directly opposite groove structure 211.

[0055] The provision of the groove structure 211 can generate orderly and controllable cracks 221 during the preparation of the strain sensor 200. In other words, the cracks 221 can be generated in the area corresponding to the groove structure 211. It is understood that during the preparation of the strain sensor 200, after the conductive paste is coated on the substrate 210 and cured to form the conductive film 220, when the substrate 210 coated with the conductive film 220 is bent, due to the stress concentration effect, the deformation of the substrate 210 will be preferentially generated at the portion of the substrate 210 where the shape of the substrate 210 changes sharply (such as the location of the groove structure 211 of the substrate 210). Therefore, when the substrate 210 coated with the conductive film 220 is bent by an external force, the groove structure 211 can cause the stress on the substrate 210 to be mainly concentrated at the location of the groove structure 211, thereby generating cracks 221 on the conductive film 220 corresponding to the location of the groove structure 211. Thus, by pre-arranging groove structures 211 on substrate 210 according to a certain rule, the stress concentration effect of groove structures 211 can be used to create cracks 221 at locations corresponding to groove structures 211, thereby achieving controllable crack generation according to the predetermined rule. Specifically, as shown in FIG2A or FIG2C , groove structures 211 can extend along a first direction of substrate 210 (e.g., the width direction of substrate 210).

[0056] In some embodiments, the groove structure 211 can penetrate the substrate 210 in a direction perpendicular to the paper. By arranging the groove structure 211 to penetrate the substrate 210, the stress on the strain sensor 200 is concentrated at the crack 221 and the processing of the substrate 210 is facilitated. In some embodiments, the groove structure 211 may not penetrate the substrate 210. For example, as shown in Figure 2A or Figure 2B, when the groove structure 211 does not penetrate the substrate 210, the conductive film 220 can be located on the side of the substrate 210 where the opening of the groove structure 211 is located. For another example, as shown in Figure 2C or Figure 2D, the conductive film 220 can be located on the other side of the substrate 210 opposite to the side where the opening of the groove structure 211 is located. By setting the groove structure 211 so as not to penetrate the substrate 210 and setting the conductive film 220 on the side where the groove structure 211 opens (i.e., corresponding to the structure shown in FIG2B ), further protection of the circuit structure of the strain sensor 200 (such as the conductive film 220) can be achieved, thereby preventing the conductive film 220 from being exposed to the outside and impurities (such as conductive impurities) from entering and affecting the stability of the circuit.

[0057] In some embodiments, when the groove structure 211 is configured not to penetrate the substrate 210 and the conductive film 220 is disposed on the side where the opening of the groove structure 211 is located (i.e., corresponding to the structures shown in Figures 2A and 2B), during the preparation of the corresponding strain sensor 200, after the conductive paste is applied to the substrate 210, the conductive paste will fill the groove structure 211 due to its fluidity. In this case, after the conductive paste cures to form the conductive film 220, a main crack may be generated on the conductive film 220 at a location corresponding to the groove structure 211 during bending to generate cracks 221. The main crack may extend into the interior of the groove structure 211 along the thickness direction of the substrate 210 (i.e., the ZZ' direction in Figure 2B) (as shown in Figure 2B). In this case, the depth of the main crack along the thickness direction of the substrate 210 may be greater than or substantially equal to the depth of the groove structure 211.

[0058] In some embodiments, when the strain sensor 200 having the structure shown in Figures 2A and 2B is in a natural state, the crack surfaces of the crack 221 (i.e., the side surfaces of the conductive film on both sides of the crack) can partially contact each other (i.e., there is a contact surface between the conductive films 220 on both sides of the crack 221). When the strain sensor 200 is bent and arched in the Z direction due to external pressure, the crack surfaces gradually lose contact, and the resistance value of the strain sensor 200 increases; when the strain sensor 200 is bent and arched in the Z' direction due to external pressure, the crack surfaces gradually come into close contact, and the resistance value of the strain sensor 200 decreases. Different external stresses can produce different contact areas between the conductive films 220 on both sides of the crack 221. The different contact areas between the conductive films 220 on both sides of the crack 221 can correspond to different resistance values ​​of the strain sensor 200, thereby outputting different electrical signals.

[0059] It is understandable that when the strain sensor 200 has the structure shown in Figures 2A and 2B, the size of the groove structure 211 in the second direction along the substrate 210 (i.e., the width of the groove structure 211) may affect the formation of the crack 221 and / or the performance of the strain sensor 200. The width of the groove structure 211 cannot be too wide or too narrow. When the width of the groove structure 211 is too narrow, during the process of preparing the strain sensor 200, the conductive paste may not be able to fill into the groove structure 211, thereby reducing the depth of the main crack and the crack surface contact area of ​​the main crack, affecting the performance of the strain sensor 200. When the width of the groove structure 211 is too wide, during the process of preparing or using the strain sensor 200, the conductive paste filled in the groove structure 211 is easily broken after curing, thereby causing the strain sensor 200 to be in an open circuit state and unable to be used normally. Therefore, in some embodiments, in order to make the generated crack 221 (eg, main crack) thin and deep so that the crack surfaces are easily closed or contacted under bending, the width of the groove structure 211 may be in the range of 1 μm-50 μm.

[0060] In some embodiments, when the groove structure 211 is configured not to penetrate the substrate 210 and the conductive film 220 is disposed on the side opposite the opening of the groove structure 211 (i.e., corresponding to the structures shown in Figures 2C and 2D), during the preparation of the corresponding strain sensor 200, after the conductive paste is coated on the substrate 210 and cured to form the conductive film 220, multiple cracks 221 may be generated on the conductive film 220 at locations corresponding to the groove structure 211 during bending to generate cracks 221. In this case, the depth of the cracks 221 along the thickness direction of the substrate 210 may be equal to or substantially equal to the thickness of the conductive film 220.

[0061] It is understandable that when the strain sensor 200 has the structure shown in Figures 2C and 2D, the width of the groove structure 211 may affect the formation of the crack 221. The width of the groove structure 211 cannot be too wide or too narrow. When the width of the groove structure 211 is too narrow, during the preparation of the strain sensor 200, when the substrate 210 is bent by an external force, the stress concentration effect at the groove structure 211 will be deteriorated, which may result in the inability to generate the crack 221. When the width of the groove structure 211 is too wide, the deformation of the uncarved portion of the substrate 210 during bending may be too large, causing the conductive film 221 to break or peel off, thereby affecting the performance of the strain sensor 200. In addition, when the width of the groove structure 211 is too wide, the mechanical strength of the substrate 210 and the conductive film 220 will be adversely affected, and the substrate 210 may be irreversibly fractured when bent by an external force. Therefore, in some embodiments, in order to generate the cracks 221 in a controllable manner (for example, to generate multiple fine cracks that run across the substrate 210) without affecting the supporting performance of the substrate 210, the size range of the groove structure 211 along the second direction of the substrate 210 (for example, the length direction of the substrate 210) can be 10μm to 100μm.

[0062] In some embodiments, the ratio of the dimensions of the groove structure 211 to the substrate 210 in the first direction can affect the performance of the strain sensor. For example, the larger the ratio of the dimensions of the groove structure 211 to the substrate 210 in the first direction, the weaker the mechanical strength of the substrate 210 at the location of the groove structure 211. In this case, the strain sensor is more likely to bend, resulting in a more sensitive response. Therefore, in some embodiments, the ratio of the dimensions of the groove structure 211 to the substrate 210 in the first direction can be within a range of 2 / 3 to 9 / 10.

[0063] In some embodiments, the resistivity of the substrate 210 may be higher than 1×10 7Ω·m (for example, the substrate 210 can be made of an insulating material or the substrate 210 can be a conductor with an outer layer coated with an insulating material) to prevent electrical conduction between the substrate 210 and the conductive film 220. The cracks 221 in the conductive film 220 can open to varying degrees as the external stress changes, generating different resistances. For example, the conductive film 220 can be made of a conductive carbon paste. In this case, the strain sensor 200 can sense the magnitude of the external stress and generate a corresponding electrical signal. For example, when the strain sensor 200 is free of external stress, the conductive film 220 can be in a natural state. At this time, the crack 221 can be in a closed state, the conductive films 220 on both sides of the crack 221 can be in the best contact, and the resistance of the conductive film 220 can be at a minimum. When the strain sensor 200 is subjected to external stress, the substrate 210 can deform, causing the conductive film 220 (for example, at the location of the crack 221) to deform, thereby changing the contact area between the conductive film 220 on both sides of the crack 221. Different external stresses can produce different contact areas between the conductive films 220 on both sides of the crack 221. The different contact areas between the conductive films 220 on both sides of the crack 221 can correspond to different degrees of opening of the crack 221, thereby causing the strain sensor 200 to produce different resistance changes and output different electrical signals. The strain sensor 200 can determine the stress magnitude (or degree of deformation) of the external stress through the electrical signal (e.g., resistance signal) it generates, thereby achieving sensing of the external stress (or deformation). For example, when the strain sensor 200 is applied to a wearable device such as headphones, the strain sensor 200 (or substrate 210) can be sheet-shaped and disposed in the back-hook component between the two speakers of the headphones. The strain sensor 200 can generate an electrical signal in response to changes in the degree of bending of the back-hook component to determine the degree of bending of the back-hook component, thereby determining whether the headphones are in a wearing state. Furthermore, one or more components of the headphones (e.g., battery, Bluetooth module) can be controlled to perform corresponding operations based on the wearing state of the headphones. For another example, the strain sensor 200 can be attached to the touch area of ​​the product. When the user touches the area, the strain sensor 200 can generate an electrical signal in response to the force applied by the user, thereby determining the user's touch operation. In some embodiments, the strain sensor 200 can determine the stress magnitude of the external stress based on the electrical signal output by the strain sensor 200 using a preset electrical signal-stress value relationship table. In some embodiments, the electrical signal-stress value relationship table can be determined through experiments. During the process of sensing external stress, the presence of the crack 221 can cause the conductive film 220 to produce a greater change in resistance value under the same deformation, thereby achieving the effect of improving the sensitivity of the strain sensor 200.

[0064] In some embodiments, the resistivity of the substrate 210 is higher than 1×10 7Ω·m (for example, the substrate 210 can be made of an insulating material or the substrate 210 can be a conductor with an outer layer wrapped with an insulating material) to avoid electrical conduction between the substrate 210 and the conductive film 220. The conductive film 220 can be made of a material with very low resistivity, and its resistance value can basically not change with changes in external stress. For example, the conductive film 220 can be a conductive silver paste. At this time, the conductive film can be in two states of on or off under the action of external stress. The strain sensor 200 can be used as a switching device. For example, when the strain sensor 200 is not affected by external stress, the conductive film 220 can be in a natural state, at which time the conductive films 220 on both sides of the crack 221 contact each other, and the crack 221 is in a closed state (it can also be called the conductive film 220 is in a conductive state). Correspondingly, the circuit in which the strain sensor 200 is located can be in a path state. When the strain sensor 200 is subjected to external stress, the substrate 210 can be deformed, and the conductive film 220 (for example, the location of the crack 221) can be deformed, thereby causing the crack 221 to be in an open state (it can also be referred to as the conductive film 220 being in a disconnected state). Correspondingly, the circuit in which the strain sensor 200 is located can be in an open state. Thus, the circuit in which the strain sensor 200 is located can be in an open or disconnected state by external stress, thereby achieving the effect of a switching device. By using conductive silver paste as the conductive film 220, it is possible to determine whether the conductive film is open or closed, avoiding problems such as resistance creep and noise generated by measuring the resistance value.

[0065] Furthermore, by providing a support component, the groove structure 211 and the crack 221 can be suspended, and the strain sensor can cause the crack to open and close under the action of external pressure, thereby achieving pressure sensing. For a description of the pressure sensor, please refer to Figure 7 of this specification and its description, which will not be repeated here.

[0066] FIG3 is an exemplary structural diagram of another strain sensor according to some embodiments of this specification.

[0067] In some embodiments, as shown in FIG3 , the groove structure 211 extends along the first direction of the width of the substrate 210, and a hole structure 212 is provided at both ends of the groove structure 211 in the extension direction. Exemplary hole structures 212 may include circular holes, elliptical holes, square holes, etc. In some embodiments, the aperture of the hole structure 212 may be 1 μm to 100 μm. In some embodiments, the aperture of the hole structure 212 may be larger than the width of the groove structure 211 (i.e., its size along the second direction). The provision of the hole structure 212 can avoid stress concentration at both ends of the groove structure 211 in the first direction, thereby preventing the groove structure 211 from continuing to expand along the first direction and causing the substrate 210 to break at the groove structure 211, thereby improving the mechanical strength of the strain sensor.

[0068] FIG. 4 is an exemplary structural diagram of another strain sensor according to some embodiments of this specification.

[0069] In some embodiments, as shown in FIG4 or FIG5 , the groove structure 211 may include multiple grooves. Each groove may correspond to one or more cracks 221, that is, a crack 221 is provided on the conductive film 220 corresponding to each groove. In some embodiments, to ensure that the cracks 221 corresponding to the multiple grooves remain consistent (for example, the length of the cracks), the size of the groove structure 211 in the first direction may be larger than the size of the conductive film 220 in the first direction at the location of the groove structure 211. In this case, the conductive film 220 covers at least a portion of the area between the two end edges of the groove structure 211 in the first direction.

[0070] In some embodiments, the density of cracks 221 on the conductive film 220 can affect the sensitivity of the strain sensor 200. A greater density of cracks 221 on the conductive film 220 indicates a higher sensitivity of the corresponding location to external stress; a lower density of cracks 221 on the conductive film 220 indicates a lower sensitivity of the corresponding location to external stress. In some embodiments, different locations on the strain sensor 200 can have the same sensitivity to external forces. For example, the groove structure 211 can include multiple grooves, which can be evenly spaced. In other words, the spacing between adjacent grooves is equal. For example, as shown in FIG4 , the groove structure 211 includes multiple grooves 2111, 2112, 2113, 2114, and 2115, spaced evenly along the second direction. By evenly distributing the grooves, the strain sensor 200 can simultaneously sense external stress at one or more locations. For example, in the circuit of the strain sensor 200, the multiple cracks 221 corresponding to the multiple grooves can be equivalent to multiple switches or multiple resistors connected in series. When one of the cracks 221 is fully open due to external stress, the circuit of the strain sensor 200 can be in an open circuit state, thereby being able to measure whether external stress is acting on a larger area, thereby increasing the scope of application of the strain sensor. For example, in the circuit of the strain sensor 200, the crack 221 corresponding to each groove can be equivalent to a switch or resistor. By providing leads (or wires) on the conductive film 220 on both sides of the crack 221 corresponding to each groove, the cracks 221 corresponding to each groove can be connected in parallel. Cracks 221 at different locations can be in different states (corresponding to different resistance values) depending on the external stress they are subjected to, thereby allowing the strain sensor 200 to simultaneously detect the magnitude of external stress at multiple locations, thereby increasing the scope of application of the strain sensor.

[0071] FIG. 5 is an exemplary structural diagram of another strain sensor according to some embodiments of this specification.

[0072] In some embodiments, different locations of the strain sensor 200 can have different responsiveness to external forces. In some embodiments, the responsiveness of different locations of the strain sensor 200 to external forces can be adjusted by adjusting the dimensions of the groove structure 211 in the first and / or second directions, the distance between adjacent groove structures 211, the number of groove structures 211, and the like. For example, as shown in FIG5 , the groove structure 211 includes multiple grooves distributed along the second direction. The grooves at different locations can have different dimensions in the second direction and / or the spacing between adjacent groove structures 211 can be different (that is, the distribution density of the groove structures at different locations varies). This allows different locations of the strain sensor 200 to have different responsiveness to external forces. For example, the spacing between grooves 2111 and 2112 can be different from the spacing between grooves 2113 and 2114.

[0073] In some embodiments, the tighter the groove structure 211 is arranged, the higher its sensitivity to external stress. For example, more groove structures 211 can be set in the sensitive parts of the target object, and fewer groove structures 211 can be set in the non-sensitive parts to adapt to different application scenarios and improve device utilization. For example, when the strain sensor 200 is applied to a wearable device such as an earphone, the shape of the strain sensor 200 (or substrate 210) can be sheet-shaped and arranged in the earphone back-hanging component between the two speakers of the earphone. Since the degree of curvature of the middle position of the earphone back-hanging component is more obvious than the position close to the two speakers, it can be determined that the middle position of the earphone back-hanging component or its vicinity is a sensitive part, and its position close to the two speakers is a non-sensitive part. In this case, more groove structures 211 (or corresponding cracks 221) can be set in the middle position of the earphone back-hanging component or its vicinity to improve the sensitivity of the strain sensor 200 and the device utilization.

[0074] In some embodiments, to achieve different levels of sensitivity in response to external stress at different locations on the strain sensor 200, conductive pastes of varying resistivity may be applied to different locations on the substrate 210. For example, conductive carbon paste may be applied to a certain area of ​​the strain sensor 200, while conductive silver paste may be applied to the remaining areas. This allows different locations on the strain sensor 200 to have different levels of sensitivity or response patterns in response to external stress. The sensitivity settings for different locations on the strain sensor 200 can vary depending on the specific application scenario of the strain sensor and are not limited in this specification.

[0075] FIG6 is an exemplary flow chart of a method for preparing a strain sensor according to some embodiments of the present disclosure. As shown in FIG6 , process 600 may include the following steps.

[0076] Step 610: Etch a groove structure on the substrate. The substrate is non-conductive. In some embodiments, the substrate can be made of a non-conductive material that has a certain mechanical strength and can undergo elastic deformation under external stress. For example, the substrate 110 can be made of materials such as polyvinyl alcohol, polyimide, and polydimethylsiloxane. In some embodiments, the substrate can also be a conductive material with an insulating layer wrapped around the surface. The insulating layer can make the substrate non-conductive. Exemplary materials of the insulating layer may include polyethylene, rubber, etc.

[0077] Exemplary etching methods include ion beam etching, laser etching, gas etching, etching liquid etching, mechanical etching, and the like. In some embodiments, when the groove structure penetrates the substrate, the etching process may be through-etching the substrate (e.g., mechanical etching) to form the groove structure. In some embodiments, when the groove structure does not penetrate the substrate, the etching process may be non-through-etching the substrate (e.g., gas etching) to form the groove structure. In some embodiments, to prevent the groove structure from expanding further due to tip stress concentration during subsequent crack formation in the conductive film, thereby affecting the performance (e.g., mechanical strength) of the resulting strain sensor, hole-like structures may be etched at both ends of the groove structure.

[0078] In some embodiments, the groove structure can extend along the first direction of the substrate width. To produce relatively uniform cracks in the conductive film, the groove structure can be larger in the first direction than the conductive film at the location of the groove structure. In other words, the groove structure 211 is not completely covered by the conductive film 220.

[0079] Step 620: coating a conductive paste on the substrate and curing the paste to form a conductive film.

[0080] In some embodiments, the conductive paste can be formed by mixing conductive particles and a resin base. Exemplary conductive particles can include carbon black, carbon nanotubes, graphene, silver powder, copper powder, etc. Exemplary resin bases can include epoxy resin, polyvinyl chloride (PVC), polyimide resin, phenolic resin, etc. In some embodiments, different conductive pastes can achieve different sensing effects of strain sensors. For example, when the conductive paste is a conductive carbon paste, the opening and closing of the cracks prepared subsequently can cause the resistance of the conductive film to change, and the strain sensor thus prepared can be a resistive strain sensor for sensing the magnitude of external stress. For another example, when the conductive paste is a conductive silver paste, the opening and closing of the cracks can reflect the on-off state of the circuit in which the strain sensor is located, and the strain sensor thus prepared can be used as a switching device. In some embodiments, the thickness of the conductive paste can be 1um to 100um. In some embodiments, the curing process can include sintering, low-temperature curing, self-drying thermoplasticity, etc.

[0081] In step 630, the substrate coated with the conductive film is bent to form cracks, thereby obtaining a strain sensor. In some embodiments, after the cracks are formed, the resulting device may be subjected to other operations to obtain a strain sensor. For example, external leads may be soldered to the resulting device to facilitate connection of the resulting strain sensor to an external circuit. In another example, the resulting device may be packaged to improve the stability and mechanical reliability of the resulting strain sensor.

[0082] According to the method for preparing a strain sensor described in some embodiments of this specification, by pre-setting (for example, uniformly or non-uniformly setting) a groove structure on a substrate, stress can be highly concentrated at the position of the groove structure during the crack preparation process, thereby preferentially generating cracks at the groove structure. By rationally setting the position of the groove structure, orderly cracks can be controllably generated on the conductive film, thereby improving the consistency of the performance of the prepared strain sensor. The process flow is simple and is conducive to industrial application. In addition, the sensitivity of the prepared strain sensor can be flexibly adjusted by changing the groove width, the number of arrays, and the conductivity of the slurry, thereby improving the adaptability of the strain sensor.

[0083] FIG. 7 is an exemplary structural diagram of a pressure sensor according to some embodiments of the present specification.

[0084] As shown in FIG. 7 , the pressure sensor 700 may include a strain sensor and a support member 730 .

[0085] The strain sensor may include a substrate 710 and a conductive film 720. The substrate 710 is provided with a groove structure 711. The conductive film 720 is attached to the surface of the substrate 710, and a crack 721 is provided on the conductive film 720 directly opposite the groove structure 711. For more information about the strain sensor, please refer to other places in this specification, such as Figures 2A-5 and their descriptions, and will not be repeated here.

[0086] The support component 730 can be used to support the groove structure 711 and the crack 721. For example, as shown in Figure 7, the support component 730 can allow the groove structure 711 and the crack 721 to be suspended. In some embodiments, the suspended positions corresponding to the groove structure 711 and the crack 721 (i.e., the area between the support components 730 on the left and right sides of Figure 7) can be provided with supports such as sponge and foam to make the overall structure of the pressure sensor 700 more stable. It should be noted that in this specification, there is no restriction on the support material, as long as it does not affect the deformation of the conductive film 720 under external force. In some embodiments, the substrate 710 can be located between the conductive film 720 and the support component 730. External pressure can act directly on the conductive film 720. In some embodiments, as shown in Figure 7, the conductive film 720 can be located between the support component 730 and the substrate 710. The support component 730 can be provided on at least a portion of the conductive film 720. In some embodiments, the support component 730 can be directly provided on the substrate 710. For example, the support member 730 may be disposed on one side of the substrate 710 where the conductive film 720 is located. External pressure may act directly on the substrate 710 .

[0087] In some embodiments, when the pressure sensor 700 is in its natural state, its crack 721 can be closed. At this point, the two conductive film sections 722 and 724 formed by the crack 721 are in optimal contact, the resistance of the conductive film 220 can be at its minimum, and the circuit within which the pressure sensor 700 resides can be in an open state. In other words, when the pressure sensor 700 is not subject to external pressure, the circuit within which the pressure sensor 700 resides can be in an open state and can generate electrical signals. When the pressure sensor 700 is subjected to external pressure, the substrate 710 can deform in response to the external pressure, driving the conductive film 720 to deform as well, thereby separating the two conductive film sections 722 and 724 (this can also be referred to as the crack 721 being in an open state). At this point, the circuit within which the pressure sensor 700 resides is in an open state. Therefore, based on the difference between the electrical signals generated by the pressure sensor 700 in the open and open states within the circuit, it can be determined whether a user has applied pressure (e.g., whether the user has tapped or long-pressed), and the corresponding operation can be performed. For example, the pressure sensor 700 can be used as a touch or tap button to activate or close an application. Another example is that the pressure sensor 700 can be used as an electrical switch, thereby achieving a structural surface without protrusions or the effect of a hidden switch. Furthermore, the user's touch gesture can be determined by the signal changes between two or more pressure sensors 700.

[0088] As an example only, the pressure sensor 700 can be used as a touch component (e.g., a touch screen) in headphones (e.g., TWS headphones). Specifically, the headphones may include a speaker, a pressure sensor 700, and a housing. The speaker can be used to generate sound signals. The housing can be used to carry the speaker and the pressure sensor 700. The pressure sensor 700 can switch from a path state to an open-circuit state in response to pressure applied by the user, thereby causing the electrical signal of the circuit where the pressure sensor 700 is located to change. The processor (not shown) can determine whether the user applies pressure based on the change pattern of the electrical signal.

[0089] The shell may include a contact surface. When the user wears the headset, the contact surface is used to contact the user's face, and at least a portion of the pressure sensor 700 is arranged on the contact surface. When the user wears the headset, the pressure on the contact surface can cause the pressure sensor 700 to switch from a path state to an off-circuit state and generate a corresponding electrical signal. The processor (not shown) can determine that the user has completed wearing the headset based on the electrical signal. Further, the processor can control one or more electronic components of the headset (for example, a Bluetooth module, a battery, etc.) to enter a working state. For example, the processor can control the headset to turn on and play music. When the headset is no longer worn, the pressure on the contact surface disappears, the pressure sensor 700 is in a path state, and the processor can determine that the user has released the headset in response to the path state of the pressure sensor 700. Further, the processor can control one or more electronic components of the headset (for example, a Bluetooth module, a battery, etc.) to enter a standby state.

[0090] In some embodiments, the conductive film 720 can be formed by solidifying a conductive paste with a higher resistivity, and the resistance value of the conductive film 720 can change in response to the deformation of the pressure sensor 700. Different external pressures can cause the conductive film 720 to deform to different degrees (for example, the crack 721 opens to different degrees), thereby causing the resistance value of the conductive film 720 to be different, and thus generating different electrical signals. In this way, the effect of the pressure sensor 700 sensing the magnitude of the external pressure can be achieved. For example, the pressure sensor 700 (or the processor) can determine the magnitude of the external pressure based on the electrical signal output by the pressure sensor 700 through a preset electrical signal-pressure value relationship table. In some embodiments, the electrical signal-pressure value relationship table can be determined by experiment.

[0091] The pressure sensor 700 described in some embodiments of this specification can be used to detect whether the earphone is being worn or not by arranging the pressure sensor 700 on one or more contact surfaces between the earphone and the human body.

[0092] The beneficial effects that may be brought about by the embodiments of this specification include but are not limited to: (1) when conductive carbon paste is used as the conductive film material, the sensitivity of the resistive strain sensor is improved by setting a crack structure on the conductive film, and the structure is simple and the cost is low; (2) when conductive silver paste is used as the conductive film material, a stress switch is realized by setting a crack structure on the conductive film; (3) by pre-setting a groove structure on the substrate, the cracks on the conductive film can be generated in a controllable and orderly manner, thereby improving the consistency of the performance of the prepared strain sensor, which is beneficial to industrial application; (4) the use of a hole structure avoids stress concentration in the groove structure of the substrate and ensures the mechanical strength of the substrate; (5) by changing the groove structure width, number, conductivity of the conductive film, etc., the sensitivity of the strain sensor can be flexibly adjusted to make it suitable for scenarios with different sensitivity requirements; (6) by setting a support component so that the groove structure and crack are suspended in the air, pressure sensing can be realized. It should be noted that different embodiments may have different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other possible beneficial effects.

[0093] The basic concepts have been described above. It will be apparent to those skilled in the art that the detailed disclosure above is merely illustrative and does not limit the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and amendments to the present application. Such modifications, improvements, and amendments are suggested in the present application and remain within the spirit and scope of the exemplary embodiments of the present application.

Claims

1. A strain sensor comprising: a substrate, wherein a groove structure is provided on the substrate; as well as A conductive film is attached to the surface of the substrate, and a crack is provided on the conductive film at a position facing the groove structure.

2. The strain sensor according to claim 1, wherein The groove structure penetrates the substrate.

3. The strain sensor according to claim 1, wherein The groove structure does not penetrate the substrate, and the conductive film is located on a side of the substrate where the opening of the groove structure is located.

4. The strain sensor according to claim 3, wherein: The size of the groove structure in the second direction along the length of the substrate ranges from 1 μm to 50 μm.

5. The strain sensor according to claim 1, wherein The groove structure does not penetrate the substrate, and the conductive film is located on a side of the substrate opposite to the opening of the groove structure.

6. The strain sensor according to claim 5, wherein: The groove structure has a size ranging from 10 μm to 100 μm in a second direction along the length of the substrate.

7. The strain sensor according to claim 1, wherein The groove structure extends along a first direction of the width of the substrate, and a size of the groove structure in the first direction is larger than a size of the conductive film at a position of the groove structure in the first direction.

8. The strain sensor according to claim 1, wherein The groove structure extends along a first direction of the width of the substrate, and a ratio of a size of the groove structure to a size of the substrate in the first direction may be within a range of 2 / 3-9 / 10.

9. The strain sensor according to claim 1, wherein The groove structure extends along a first direction of the width of the substrate, and hole structures are respectively provided at both ends of the groove structure in the extending direction.

10. The strain sensor according to claim 1, wherein The groove structure includes a first groove, a second groove and a third groove sequentially arranged along a second direction of the substrate length, and a first distance between the first groove and the second groove is the same as a second distance between the second groove and the third groove.

11. The strain sensor according to claim 1, wherein The groove structure includes a first groove, a second groove, and a third groove sequentially arranged along a second direction of the substrate length, and a first distance between the first groove and the second groove is different from a second distance between the second groove and the third groove.

12. The strain sensor according to claim 1, wherein The resistivity of the substrate is higher than 1×10 7 Ω·m, the conductive film presents different resistances as the external stress changes.

13. The strain sensor according to claim 12, wherein: The conductive film is conductive carbon paste.

14. The strain sensor according to claim 1, wherein The resistivity of the substrate is higher than 1×10 7 Ω·m, the conductive film is in two states of on or off under the action of external stress.

15. The strain sensor according to claim 14, wherein: The conductive film is conductive silver paste.

16. A method for preparing a strain sensor, comprising: etching a groove structure on a substrate, wherein the substrate is non-conductive; Coating a conductive paste on the substrate and curing the paste to form a conductive film; as well as The substrate coated with the conductive film is bent to form cracks, thereby obtaining the strain sensor.

17. A pressure sensor comprising: A strain sensor, wherein the strain sensor comprises: a substrate, wherein a groove structure is provided on the substrate, and a conductive film attached to the surface of the substrate, wherein a crack is provided on the conductive film at a position facing the groove structure; and A supporting component is used to support the groove structure and the crack.

18. The pressure sensor according to claim 17, wherein: The supporting component is arranged on the conductive film or on a side of the substrate where the conductive film is located.

19. The pressure sensor according to claim 17, wherein: The pressure sensor is arranged in an earphone, and the earphone comprises: a speaker for generating an audible signal, and A housing for carrying the speaker and the pressure sensor, wherein: The pressure sensor is used to switch the pressure sensor from a circuit state to a circuit breaker state in response to pressure applied by a user, and generate a corresponding electrical signal.

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