A flexible pressure sensor and its preparation method

Abstract

The present invention relates to the field of pressure sensors, and specifically to a flexible pressure sensor and a preparation method thereof. The flexible pressure sensor comprises a first substrate and a second substrate located below the first substrate, a probe box being provided on the side of the first substrate away from the second substrate, a plurality of probe cavities being provided inside the probe box, a plurality of probes sliding in the probe cavities, the bottoms of the probes passing through the first substrate and being located between the first substrate and the second substrate; the plurality of probes are arranged in sequence, and the distance from the bottom of the probe to the second substrate gradually increases from the middle probe to the probes on both sides; the flexible pressure sensor also comprises a first electrode sheet and a second electrode sheet, the first electrode sheet and the probe are electrically connected, and the second electrode sheet is located on the upper surface of the second substrate and opposite to the bottom of the probe. The preparation method comprises the preparation of the first substrate, the second substrate, the probe and the probe box, and finally composite assembly. This solution improves the maximum pressure value detected by the flexible pressure sensor.

Description

Technical Field

[0001] The present invention relates to the field of pressure sensors, and in particular to a flexible pressure sensor and a preparation method thereof. Background Art

[0002] Flexible pressure sensor is a flexible electronic device that can convert pressure into electrical signals. It can be widely used in flexible touch screens, artificial intelligence, wearable electronics, mobile medical care and other fields.

[0003] The flexible pressure sensor in the prior art has the following structure (for example, a flexible pressure sensor and its manufacturing method disclosed in Chinese invention patent application No. 201610882536.X): the flexible pressure sensor includes two opposing flexible substrates, and a plurality of protruding balls are provided on the opposite sides of the two flexible substrates. The protruding balls are elastic and can undergo elastic deformation, and a conductive layer is provided on the surface of the protruding balls.

[0004] The detection principle of the flexible pressure sensor is as follows: when pressure is applied to one of the flexible substrates, the two flexible substrates approach each other, causing the two protruding balls on each substrate to contact and squeeze each other, and the conductive layers on the surfaces of the protruding balls on the two flexible substrates to come into contact with each other. Because the protruding balls are elastic, they deform under compression. As a result, the degree of deformation varies with the pressure, and the contact area of ​​the conductive layers on the two protruding balls also varies. This, in turn, causes the characteristic parameters of the flexible pressure sensor, such as resistance and current, to change accordingly, enabling detection of different pressures.

[0005] However, the protruding ball protrudes from the surface of the flexible substrate and has a certain elastic deformation limit. When the protruding ball is squeezed to the limit, it can no longer be compressed and further deformed. The protruding ball compressed to the limit is located between the two flexible substrates and hinders the deformation of the flexible substrates. At this time, although there is a gap between the two flexible substrates, since the protruding ball cannot be compressed any further, the two flexible substrates will not get closer. The pressure sensor reaches its detection limit of pressure and can no longer detect a larger pressure, thereby limiting the maximum pressure that the pressure sensor can detect.

[0006] Therefore, the detection range of the flexible pressure sensor of the above structure is relatively small, and the detection range of the flexible pressure sensor needs to be increased. Summary of the Invention

[0007] The present invention is intended to provide a flexible pressure sensor and a preparation method thereof, so as to increase the maximum pressure value that can be detected by the flexible pressure sensor compared with the flexible pressure sensor in the background art.

[0008] To achieve the above-mentioned object, the present invention adopts the following technical solution: a flexible pressure sensor comprising a first substrate and a second substrate located below the first substrate; a probe box is provided on a side of the first substrate away from the second substrate; a plurality of probe cavities are provided inside the probe box; a probe slides in each probe cavity; the bottom of the probe passes through the first substrate and is located between the first substrate and the second substrate; the plurality of probes are arranged in a transverse order, with the distance from the bottom of the probe to the second substrate gradually increasing from the middle probe to the probes on both sides;

[0009] It also includes a first electrode sheet and a second electrode sheet. The first electrode sheet is electrically connected to the probe, and the second electrode sheet is located on the upper surface of the second substrate and is opposite to the bottom of the probe.

[0010] The principle and advantages of this solution are: the probe box in this solution is used to accommodate the probes and limit the probes so that the probes will not fall over when placed on the first substrate, and the probes are relatively stable when placed on the first substrate and slide vertically.

[0011] In this solution, the first and second substrates are arranged relative to each other, and the second substrate is used to sense pressure. When the second substrate senses pressure, it deforms and touches the bottoms of the probes. Different pressures acting on the second substrate cause different degrees of upward deformation of the second substrate, so that the second substrate contacts different numbers of probe bottoms (the greater the pressure, the greater the degree of upward deformation of the second substrate, and the second electrode sheet on the second substrate contacts more probe bottoms; conversely, the smaller the pressure, the smaller the degree of upward deformation of the second substrate, and the second electrode sheet on the second substrate contacts only the bottoms of probes that are closer, and the second electrode sheet on the second substrate contacts fewer probe bottoms). As a result, the second electrode sheet on the second substrate contacts different numbers of probes, and by having the second electrode sheet contact different numbers of probes, different pressures can be detected.

[0012] In this solution, when the second substrate is bent upward by pressure, when the bottom of the probe is squeezed by the second substrate, the probe will slide upward, so that the probe will not hinder the second substrate from bending upward until the second substrate has a maximum deformation. In this way, the second substrate can bend to the maximum extent. Compared with the existing technology, the probe is not fixed on the first substrate, and the probe will not hinder the upward movement of the second substrate. When the pressure is large enough, the second substrate can even move to the first substrate and contact the bottom of all the probes, thereby improving the maximum pressure detection value of the flexible pressure sensor, thereby improving the detection range of the flexible pressure sensor.

[0013] The flexible pressure sensor in this solution can be used in scenarios with higher pressure, such as some grippers and fixtures of industrial robots in the field of artificial intelligence. Since the maximum pressure value that can be detected is large, a larger clamping force can be applied as much as possible to ensure that the parts can be clamped stably. At the same time, the larger clamping force applied can be detected to avoid excessive clamping force and damage to the parts.

[0014] Preferably, as an improvement, the first electrode sheet is located at the top of the probe box, and a conductive wire is connected between the top of the probe and the first electrode sheet. Thus, the first electrode sheet and the top of the probe are connected via the conductive wire, thereby achieving an electrical connection between the first electrode sheet and the probe. The conductive wire is bendable and does not hinder the sliding of the probe.

[0015] Preferably, as an improvement, the conductive filament is a graphene fiber filament. There are two main reasons why the conductive filament is made of graphene fiber filament. On the one hand, graphene has good electrical conductivity, and graphene fiber has the good electrical conductivity of graphene, with low resistance, which can improve the sensitivity of the pressure sensor. On the other hand, the conductive filament is located in a smaller probe cavity and needs to have good flexibility, while graphene fiber filament has good softness and can bend and deform into any shape. Even if the conductive filament is located in a probe cavity with a smaller space, it is easy to bend and has very little effect on the vertical sliding of the probe. Therefore, the conductive filament in this solution takes into account both flexibility and conductivity. While conductive filaments made of other materials, such as metal materials, can also conduct electricity, the flexibility of metal materials is not as good as that of fibers.

[0016] Preferably, as an improvement, a magnetic layer is provided on the top of the probe box, and the top of the probe is magnetic, with the magnetic properties of the top of the probe being the same as those of the magnetic layer. Thus, a weak repulsive force exists between the top of the probe and the magnetic layer. When the pressure on the second substrate disappears, the probe is subjected to a downward repulsive force, thereby assisting the probe in moving downward and resetting.

[0017] Preferably, as an improvement, a gasket is connected between the first substrate and the second substrate. The gasket is provided to create a gap between the first substrate and the second substrate so as to accommodate the bottom end of the probe.

[0018] Preferably, as an improvement, the probe box includes a box body and a box cover located on the top of the box body, a wire hole is provided on the top of the box cover, a first electrode sheet is fixedly connected to the top of the box cover, and the top of the conductive wire passes through the wire hole and is connected to the first electrode sheet. Thus, the provision of the wire hole facilitates the conductive wire to pass through the box cover and be connected to the first electrode sheet. The box cover and the box body in this solution are provided separately, rather than as an integrated arrangement, in consideration of the convenience of the preparation operation, so that it is convenient for the probe to penetrate into the probe cavity of the probe box and for the conductive wire to pass through the wire hole.

[0019] Preferably, as an improvement, the tops of the multiple probes are flush. Thus, by selecting probes of different lengths, the distances between the bottoms of the probes and the second substrate can be different. Furthermore, since the tops of the probes are flush and the distances between the tops of the probes and the top of the probe box are the same, conductive wires of the same length can be used to connect the tops of the probes to the first electrode sheet.

[0020] To achieve the above object, the present invention also adopts the following technical solution: a method for preparing a flexible pressure sensor, comprising the following steps:

[0021] Step 1, preparing a first substrate: filling a flexible material into a cavity of a mold for preparing the first substrate to form the first substrate, and punching a plurality of pinholes on the first substrate by laser drilling;

[0022] Step 2, preparing a second substrate: filling a flexible material into the cavity of a mold for preparing the second substrate to form the second substrate, and coating a second electrode sheet on the middle of the surface of the second substrate;

[0023] Step 3, preparing the probe box and the probes: filling the flexible material into the cavity of the mold for preparing the probe box to form the probe box, and punching a plurality of probe cavities on the probe box by laser drilling;

[0024] Step 4, preparing probes: taking metal needles of the same length and cutting them by laser cutting to produce probes of different lengths;

[0025] Step 5, assembling: fixing and assembling the probe box, the first substrate, and the second substrate in order from top to bottom, with the probe cavity on the probe box and the pinhole on the first substrate facing each other;

[0026] Then, the tops of the multiple probes are electrically connected to the first electrode sheet. After the probes are connected to the first electrode sheet, the multiple probes are inserted into the probe cavity in sequence so that the tops of the multiple probes are flush. The multiple probes are arranged as follows: from the middle probe to the probes on both sides, the distance between the bottom of the probe and the second substrate gradually increases.

[0027] Thus, through this preparation method, a flexible pressure sensor with the structure of the present application can be prepared. After searching, no prior art discloses a flexible pressure sensor with this structure, let alone a preparation method for a flexible pressure sensor with this structure. Therefore, the preparation method is inventive and is also eligible for patent protection. Preferably, as an improvement, any two steps from step 1 to step 4 are interchangeable. Therefore, the order of steps 1 to step 4 is not unique, and any two steps can be interchanged.

[0028] Preferably, as an improvement, a conductive filament is connected between the first electrode sheet and the probe, and the conductive filament is a graphene fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a vertical cross-sectional structure of a flexible pressure sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following is further described in detail through specific implementation methods:

[0031] The reference numerals in the drawings of the specification include: first substrate 1, gasket 2, second substrate 3, second electrode sheet 4, box body 5, box cover 6, magnetic layer 7, first electrode sheet 8, probe 9, conductive wire 10, and probe cavity 11.

[0032] Example 1

[0033] Basically as attached Figure 1 As shown: A flexible pressure sensor includes a first substrate 1 and a second substrate 3 located below the first substrate 1, and the first substrate 1 and the second substrate 3 are connected (when the first substrate 1, the gasket 2 and the second substrate 3 are not integrated, the connection method is preferably bonding, and when the first substrate 1, the second substrate 3 and the gasket 2 are made of the same material, the three can be integrally formed) with a gasket 2, and the arrangement of the gasket 2 allows a gap to be formed between the first substrate 1 and the second substrate 3. The first substrate 1, the second substrate 3 and the gasket 2 are all flexible, and the materials of the first substrate 1, the second substrate 3 and the gasket 2 are all selected from any one of polydimethylsiloxane, polyvinyl alcohol, styrene-butadiene-styrene block copolymer, styrene-butadiene rubber, polyurethane elastomer, polyolefin elastomer and polyamide elastomer. In this embodiment, the first substrate 1, the second substrate 3 and the gasket 2 are made of the same material, preferably polydimethylsiloxane.

[0034] A probe box (integrally formed or bonded) is provided on the side of the first substrate 1 away from the second substrate 3. The material of the probe box is the same as that of the first substrate 1. A plurality of probe cavities 11 are provided inside the probe box. A probe 9 slides vertically in each probe cavity 11. The probe 9 in this embodiment is made of metal. A plurality of pinholes are provided on the first substrate 1. The pinholes and the probe cavity 11 are opposite. The bottom of the probe 9 passes through the pinholes on the first substrate 1 and is located between the first substrate 1 and the second substrate 3. The plurality of probes 9 are arranged horizontally in sequence, and the tops of the plurality of probes 9 are flush with each other. Figure 1 As shown, for ease of explanation and understanding, this embodiment takes 11 probes 9 as an example (in actual production, more probes 9 can be set to improve the sensitivity of the pressure sensor). From the middle probe 9 to the probes 9 on both sides, the distance from the bottom of the probe 9 to the second substrate 3 gradually increases, that is, from the middle probe 9 to the probes 9 on both sides, the length of the probe 9 gradually becomes shorter.

[0035] The probe box in this embodiment includes a box body 5 and a box cover 6 located on the top of the box body 5. The box cover 6 is provided with a plurality of wire holes, the aperture of the wire holes is smaller than the aperture of the probe cavity 11, and the top side of the box cover 6 is covered with a first electrode sheet 8. A conductive wire 10 is connected between the first electrode sheet 8 and the top of the probe 9. The conductive wire 10 passes through the wire hole and is located in the probe cavity 11. The conductive wire 10 in this embodiment is a graphene fiber. The graphene fiber is filamentous and woven from graphene fibers. Graphene fibers are prior art and will not be described here. For example, a method for preparing graphene fibers disclosed in patent announcement number CN103388197B and a method for preparing graphene conductive composite fibers disclosed in patent announcement number CN103966844B are provided. The conductive wire is made of graphene fiber because graphene fibers have high electrical conductivity and high flexibility, and can be used in flexible electronic products, sensors and other fields.

[0036] The middle of the upper surface of the second substrate 3 is covered with a second electrode sheet 4, which is opposite to the bottom of the probe 9. The first electrode sheet 8 and the second electrode sheet 4 are made of any one of gold, silver, aluminum, copper, nickel and carbon.

[0037] In this embodiment, the thickness of the first substrate 1 and the second substrate 3 is between 0.01mm and 1mm, preferably 0.5mm. The thickness of the gasket 2 is between 0.1mm and 1mm, preferably 1mm. The height of the probe box body 5 is 1-3mm, preferably 2mm in this embodiment. The lengths of the probes 9 from the center to the probes 9 on both sides are 2mm, 1.84mm, 1.68mm, 1.52mm, 1.36mm, and 1.2mm, respectively. Of course, the dimensional parameters of each part will vary depending on the size of the actual pressure sensor.

[0038] This embodiment also discloses a method for preparing a flexible pressure sensor, comprising the following steps:

[0039] Step 1, preparing the first substrate 1: filling the flexible material into the cavity of the mold for preparing the first substrate 1 to form the first substrate 1, and punching a plurality of pinholes on the first substrate 1 by laser, with a diameter of 0.15 mm.

[0040] Step 2, preparing the second substrate 3: filling the flexible material into the cavity of the mold for preparing the second substrate 3 to form the second substrate 3, and connecting and setting the second electrode sheet 4 in the middle of the surface of the second substrate 3, and fixing the second electrode sheet 4 on the upper surface of the second substrate 3 by bonding.

[0041] Step 3, preparing the probe box and probe 9: Fill the cavity of the mold for preparing the probe box with flexible material to form the probe box. The probe box includes a box body 5 and a box cover 6. Multiple probe cavities 11 are punched out on the box body 5 by laser. In this embodiment, the number of probe cavities 11 is 11, and the diameter of the probe cavity 11 is 0.15mm. Wire holes are punched out on the box cover 6 by laser. The hole diameter of the wire hole is smaller than that of the probe cavity 11. The diameter of the conductive wire 10 is smaller than that of the wire hole.

[0042] Step 4, preparing probes 9: Take metal needles of the same length, align one end of the needles, and use laser cutting to uniformly cut the other ends of the needles to produce probes 9 of varying lengths. Connect the conductive wire 10 to the aligned end of the probes 9.

[0043] Step 5, combination: fix and composite the box body 5, the first substrate 1, the gasket 2 and the second substrate 3 in sequence from top to bottom (if the box body 5, the first substrate 1, the gasket 2 and the second substrate 3 are integrally formed, there is no need to composite and fix them; if the probe box, the first substrate 1, the gasket 2 and the second substrate 3 are not integrally formed, they can be composite and fixed by bonding), and the probe cavity 11 on the box body 5 and the pinhole on the first substrate 1 are opposite to each other.

[0044] Then, the conductive wires 10 on the tops of the plurality of probes 9 are passed through the wire holes on the box cover 6 , the first electrode sheet 8 is adhered to the top of the box cover 6 , and the tops of the conductive wires 10 are soldered to the first electrode sheet 8 .

[0045] Then, multiple probes 9 are sequentially inserted into the probe cavity 11 , and the tops of the multiple probes 9 in the box body 5 are flush; the multiple probes 9 are arranged as follows: from the middle probe 9 to the probes 9 on both sides, the distance between the bottom of the probe 9 and the second substrate 3 gradually increases.

[0046] Finally, the box cover 6 and the top of the box body 5 are bonded and fixed.

[0047] In this embodiment, the second substrate 3 is used to sense pressure. When the second substrate 3 senses upward pressure, it touches the bottom of the probe 9 and pushes the probe 9 upward. The second electrode sheet 4 contacts the bottom of the probe 9, and an electrical signal is transmitted between the second electrode sheet 4, the probe 9, the conductive wire 10, and the first electrode sheet 8, detecting the pressure. When the pressure disappears, the second substrate 3 recovers its deformation downward, and the probe 9 moves downward under the action of gravity and resets. The probe 9 is pulled and limited by the conductive wire 10, so that the probe 9 does not break away and fall onto the second electrode sheet 4.

[0048] Different pressures acting on the second substrate 3 cause the second substrate 3 to deform upward to different degrees, resulting in the second electrode sheet 4 on the second substrate 3 contacting different numbers of the bottoms of the probes 9. For example, when the pressure is low, the second substrate 3 bends upward to a lesser extent, only touching the bottoms of the middle probe 9. When the pressure increases, the second substrate 3 bends upward to a greater extent, and after contacting the middle probe 9, it continues to deform upward, pushing the middle probe 9 upward. The second substrate 3 will then contact the bottoms of the other probes 9 on either side of the middle probe 9. Thus, the greater the pressure, the greater the upward deformation of the second substrate 3, and the second electrode sheet 4 on the second substrate 3 will contact the bottoms of more probes 9. Conversely, the lower the pressure, the second electrode sheet 4 on the second substrate 3 will only contact the bottoms of the closer probes 9, and the second electrode sheet 4 on the second substrate 3 will contact the bottoms of fewer probes 9. This results in the second electrode sheet 4 on the second substrate 3 contacting different numbers of probes 9. By having the second electrode sheet 4 contact different numbers of probes 9, detection of different pressures is achieved.

[0049] In this embodiment, when the bottom of the probe 9 is squeezed by the second substrate 3, the probe 9 will slide upward, so that the probe 9 will not hinder the second substrate 3 from bending upward. The second substrate 3 can bend upward to the maximum extent according to the applied pressure. Compared with the existing technology, the probe 9 is not fixed on the first substrate 1, and the probe 9 will not hinder the upward movement of the second substrate 3. When the pressure is large enough, the second substrate 3 can even move to the first substrate 1 and contact the bottom of all the probes 9, thereby improving the maximum pressure detection value of the flexible pressure sensor, thereby improving the detection range of the flexible pressure sensor.

[0050] Therefore, according to the working principle of the pressure sensor in this embodiment, the more probes 9 there are, the smaller the length difference between each probe 9 will be, and the greater the accuracy of the pressure sensor will be. Therefore, in actual application, different numbers of probes 9 can be set according to actual intensive reading requirements, such as 20, 30, 40, etc.

[0051] In addition, according to actual conditions, the distance between the first substrate 1 and the second substrate 3 may be increased, and the number of probes 9 may be increased, thereby further improving the maximum detection value of the flexible sensor.

[0052] Example 2

[0053] Combine Figure 1 As shown, in this embodiment, the bottom of the box cover 6 is provided with a magnetic layer 7, and the top of the probe 9 is magnetic, and the magnetic properties of the top of the probe 9 are the same as those of the magnetic layer 7. Thus, when the pressure on the second substrate 3 disappears, a weak repulsive force is generated between the top of the probe 9 and the magnetic layer 7, which helps the probe 9 move downward and reset.

[0054] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A flexible pressure sensor, characterized in that: The invention comprises a first substrate and a second substrate located below the first substrate, wherein a probe box is provided on a side of the first substrate away from the second substrate, wherein a plurality of probe cavities are provided inside the probe box, wherein a probe slides in each probe cavity, and the bottom of the probe passes through the first substrate and is located between the first substrate and the second substrate; wherein the plurality of probes are arranged transversely in sequence, and the distance between the bottom of the probe and the second substrate gradually increases from the middle probe to the probes on both sides; It also includes a first electrode sheet and a second electrode sheet, wherein the first electrode sheet is electrically connected to the probe, and the second electrode sheet is located on the upper surface of the second substrate and is opposite to the bottom of the probe.

2. The flexible pressure sensor according to claim 1, characterized in that: The first electrode sheet is located on the top of the probe box, and a conductive wire is connected between the top of the probe and the first electrode sheet.

3. The flexible pressure sensor according to claim 2, characterized in that: The conductive filaments are graphene fiber filaments.

4. The flexible pressure sensor according to claim 1, characterized in that: A magnetic layer is provided on the top of the probe box, and the top of the probe is magnetic, and the magnetism of the top of the probe is the same as that of the magnetic layer.

5. The flexible pressure sensor according to claim 1, characterized in that: A gasket is connected between the first substrate and the second substrate.

6. The flexible pressure sensor according to claim 2, characterized in that: The probe box includes a box body and a box cover located on the top of the box body. The top of the box cover is provided with a wire hole. The top of the box cover is fixedly connected to a first electrode sheet. The top of the conductive wire passes through the wire hole and is connected to the first electrode sheet.

7. The flexible pressure sensor according to claim 1, characterized in that: The tops of the multiple probes are flush.

8. A method for preparing a flexible pressure sensor according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, preparing a first substrate: filling a flexible material into a cavity of a mold for preparing the first substrate to form the first substrate, and punching a plurality of pinholes on the first substrate by laser drilling; Step 2, preparing a second substrate: filling a flexible material into the cavity of a mold for preparing the second substrate to form the second substrate, and coating a second electrode sheet on the middle of the surface of the second substrate; Step 3, preparing the probe box and the probes: filling the flexible material into the cavity of the mold for preparing the probe box to form the probe box, and punching a plurality of probe cavities on the probe box by laser drilling; Step 4, preparing probes: taking metal needles of the same length and cutting them by laser cutting to produce probes of different lengths; Step 5, assembling: fixing and assembling the probe box, the first substrate, and the second substrate in order from top to bottom, with the probe cavity on the probe box and the pinhole on the first substrate facing each other; Then, the tops of the multiple probes are electrically connected to the first electrode sheet. After the probes are connected to the first electrode sheet, the multiple probes are inserted into the probe cavity in sequence so that the tops of the multiple probes are flush. The multiple probes are arranged as follows: from the middle probe to the probes on both sides, the distance between the bottom of the probe and the second substrate gradually increases.

9. The method for preparing a flexible pressure sensor according to claim 8, wherein: Interchange any two steps from step 1 to step 4.

10. The method for preparing a flexible pressure sensor according to claim 8, characterized in that: A conductive wire is connected between the first electrode sheet and the probe, and the conductive wire is a graphene fiber.

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