WO2021116640A1

WO2021116640A1 - Pressure sensing device

Info

Publication number: WO2021116640A1
Application number: PCT/GB2020/000097
Authority: WO
Inventors: Xu Feng; Zhou Li; Wang SHICHAO; Li ZEFENG
Original assignee: Peratech Holdco Ltd
Priority date: 2019-12-12
Filing date: 2020-12-10
Publication date: 2021-06-17
Also published as: CN210863017U

Abstract

A pressure sensing device (401), comprises a first substrate (201) comprising a first conductive layer (202) and a second substrate (301) comprising a second conductive layer (302). A pressure sensitive layer (305) is electrically connected to the second conductive layer. The pressure sensitive layer and the second substrate comprise a substantially curved cross-sectional profile which protrudes towards the first substrate and the first conductive layer.

Description

Pressure Sensing Device

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Chinese Utility Model number ZL 2019 2 223 212 1 filed on 12 December 2019, the whole contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a pressure sensing device and method of manufacturing a pressure sensing device.

Existing pressure sensing devices are known in the art and typically comprise flexible substrates having first and second conductive layers and a third pressure sensitive layer which is responsive to mechanical interactions such as a force or pressure applied.

The flexible substrates are typically manufactured from substantially thin, flexible materials comprising PET (polyethylene terephthalate). This provides a pressure sensing device which is flexible, relatively small, lightweight, stable, and reliable at relatively low cost and straightforward integration.

Existing PET pressure sensing devices, however, are only capable of capturing applied pressures above around twenty grams and consequently are unsuitable for applied pressures below this amount. It is desirable to improve the pressure sensitivity of current pressure sensing devices to solve this problem.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a pressure sensing device, comprising: a first substrate comprising a first conductive layer; a second substrate comprising a second conductive layer; and a pressure sensitive layer electrically connected to said second conductive layer; wherein said pressure sensitive layer comprises a substantially curved cross-sectional profile which protrudes towards said first substrate and said first conductive layer.

According to a second aspect of the present invention, there is provided a method of manufacturing a pressure sensing device comprising the steps of: providing a first substrate; applying a first conductive layer to said first substrate; providing a second substrate; applying a second conductive layer to said second substrate; applying a pressure sensitive layer to said second substrate; and deforming said second substrate to form a substantially curved cross-sectional profile which protrudes towards said first substrate and said first conductive layer.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the invention as claimed. However, they are only exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide a teaching to those skilled in the art. Components and processes distinguished by ordinal phrases such as “first" and "second” do not necessarily define an order or ranking of any sort.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 shows an exploded schematic view of a pressure sensing device;

Figure 2 shows a cross-sectional exploded view of components forming part of a pressure sensitive device in accordance with the present invention;

Figure 3 shows a further cross-sectional exploded view of further components forming part of a pressure sensitive device in accordance with the present invention;

Figure 4 shows a pressure sensing device comprising the components of Figures 2 and 3;

Figure 5 shows the pressure sensing device of Figure 4 when a force or pressure is applied;

Figure 6 shows an exploded view of a pressure sensing device of the present invention.

Figure 7 shows a pressure detector including a pressure sensing device; and

Figure 8 shows a method of manufacturing a pressure sensing device.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1

An exploded schematic of a pressure sensing device 101 is shown in isolation in Figure 1 for illustrative purposes.

Pressure sensing device 101 comprises a first substrate comprising a first conductive layer 102 and a second substrate comprising a second conductive layer 103. Pressure sensing device 101 is further provided with a pressure sensitive layer 104 which is electrically connected to the second conductive layer. Pressure sensitive layer 104 is responsive to a mechanical interaction and is positioned between first conductive layer 102 and second conductive layer 103.

In use, the conductive layers 102, 103 and pressure sensitive layer 104 of pressure sensing device 101 are held in close proximity such that, when a mechanical interaction, such as a force or pressure, is applied to, for example, the top surface of the first substrate in the direction and manner of arrow 105, an electric current is transmitted through the first conductive layer 102 and pressure sensitive layer 104 to second conductive layer 103. In the absence of such a mechanical interaction, the conductive layers are held apart by the layer and an electric current is not transmitted. Thus, when connected to a suitable electric circuit known in the art, the response to the mechanical interaction can be utilised to calculate the magnitude of the mechanical interaction and, in some embodiments, the position of the mechanical interaction.

Figure 2

A cross-sectional exploded view of components forming part of a pressure sensitive device in accordance with the present invention is shown in Figure 2

In the embodiment, first substrate 201 is shown with first conductive layer 202. Together, first substrate 201 and first conductive layer 202 are combined to result in the first substrate comprising a first conductive layer 102 as illustrated in Figure 1.

In the embodiment, substrate 201 comprises polyethylene terephthalate (PET) although it is appreciated that in alternative embodiments, other suitably flexible substantially thin materials may be utilised. In the embodiment, substrate 201 has a thickness 205. In the embodiment, the thickness is between seventy and eighty micrometres (70-80 pm). In a specific embodiment, thickness 205 is seventy-five micrometres (75pm). This thickness range provides a thickness which is large enough to ensure support for the layers while being small enough to allow for relatively easy deformation when pressure is applied.

In the embodiment, conductive layer 202 comprises a first conductive material 203 and a second conductive material 204. In the embodiment, conductive material 202 comprises a metallic material such as silver and specifically may comprise a silver-based printable ink. In contrast, conductive material 203 comprises carbon or a carbon-based material such as a carbon- based printable ink.

In the embodiment, conductive material 203 has a thickness 206. In the embodiment, thickness 205 is between four and seven micrometres (4-7 pm). In a specific embodiment, thickness 205 is five micrometres (5pm). This thickness provides a suitable thickness which ensures that a stable transmission of force through the conductive layer while avoiding unnecessary thickness to the pressure sensing device.

Similarly, in the embodiment, conductive material 204 has a thickness 207 In the embodiment, thickness 206 is also between four and seven micrometres (4-7 pm). In a specific embodiment, thickness 206 is five micrometres (5pm). Thus, the thicknesses of each material may be substantially similar, although it is appreciated that, as required, the thicknesses of each conductive material may differ from each other.

Figure 3

In combination with the components illustrated in previous Figure 2 a pressure sensing device in accordance with the present invention comprises a further plurality of components which are again illustrated in a cross-sectional exploded schematic view of Figure 3.

In the embodiment, second substrate 301 is shown with second conductive layer 302. Together, second substrate 301 and second conductive layer 302 are combined to result in the second substrate comprising a second conductive layer 103 as illustrated in Figure 1.

In the embodiment, substrate 301 again comprises polyethylene terephthalate (PET) although it is appreciated that in alternative embodiments, other suitably flexible substantially thin materials may be utilised. Thus, in this way, the material of substrate 301 is substantially similar to the material of substrate 302. In the embodiment, substrate 301 has a thickness 303 In the embodiment, the thickness is between seventy and eighty micrometres (70-80 pm). In one embodiment, thickness 303 is seventy-five micrometres (75pm). Again, this thickness range provides a thickness which is large enough to ensure support for the layers while being small enough to allow for relatively easy deformation when pressure is applied.

In the embodiment, conductive layer 302 comprises a third conductive material. In this embodiment, the conductive material comprises carbon or a carbon-based material such as a carbon-based printable ink. In the embodiment, the conductive material has a thickness 303. In the embodiment, thickness 303 is between four and seven micrometres (4-7 pm), and in one embodiment, is five micrometres (5pm).

Pressure sensitive layer 305 is configured to be electrically connected to conductive layer 302 in use, and, in the embodiment comprises a substantially curved cross-sectional profile as shown. In this embodiment, conductive layer 302 and substrate 301 further comprise a similar substantially curved cross-sectional profile, and this will be described further with respect to Figures 4 and 5.

Pressure sensitive layer 305 comprises a pressure sensitive material. In the embodiment, the pressure sensitive material comprises a quantum tunnelling material. In an embodiment the pressure sensitive material comprises a printable ink. Examples of suitable materials can be obtained from the present applicant, Peratech Holdco Limited, Brompton-on-Swale, United Kingdom.

Quantum tunnelling materials of this type are responsive to a mechanical interaction in that, when a force is applied, they exhibit a change in electrical resistance which can be used to measure the nature of the force applied.

In the embodiment, pressure sensitive layer 305 has a thickness 306 In this embodiment, thickness 306 is between seven and ten micrometres (7- 10 pm). In an embodiment, thickness 306 is eight point five micrometres (8 8 pm).

Figure 4

The components shown in cross-sectional view in Figures 2 and 3 can be effectively combined to form a pressure sensing device 401. Pressure sensing device 401 is shown in Figure 4 in cross-sectional view.

Pressure sensing device 401 comprises first substrate 201 comprising conductive layer 202, which, as shown in this embodiment, comprises first and second conductive materials 203 and 204. Pressure sensing device 401 further comprises second substrate 301 which comprises conductive layer 302. Pressure sensitive layer 305 is electrically connected to conductive layer 302 as shown in Figure 4, which illustrates conductive layer 302 and pressure sensitive layer 305 in electrical contact.

Substrate 201 is attached to substrate 301 and each of their layers by means of an adhesive layer 402. Adhesive layer 402 comprises a thickness 403 between substrate 201 and substrate 301. In the embodiment, thickness 403 is between twenty-five and fifty-five micrometres (25-55 pm) with the adhesive providing a suitable mechanism to hold each of the layers together to ensure stability of the pressure sensing device. In one embodiment, thickness 403 is thirty micrometres (30 pm). In an alternative embodiment, thickness 403 is fifty micrometres (50 pm). These thicknesses are determined as the most suitable thickness in which to minimise the overall thickness of the pressure sensing device while providing sufficient adhesive to ensure a good connection of the two substrates.

In the embodiment, when constructed, conductive layer 202 and pressure sensitive layer 305 are separated by a distance 404. In the embodiment, distance 403 is between eight and twenty-four micrometres (8- 24 pm). In a first embodiment, the distance is ten micrometres (10pm). In an alternative embodiment, the distance is twenty micrometres (20 pm).

In the embodiment, pressure sensitive layer 305, conductive layer 302 and substrate 301 each comprise a substantially curved cross-sectional profile which protrudes towards substrate 201 and conductive layer 202. Thus, layers 302, 305 and substrate 301 each illustrate a corresponding curved cross- sectional profile.

The curved cross-sectional profile provides a curvature defined by a curvature ratio which is defined as the ratio between the distance or radius measured between the bottom and the top of the arc and the length or diameter of that arc. Specifically, referring to substrate 301, distance 405 extends between the highest point 406 of the arc-shaped cross-section and the lowest point 407 of the same arc. The length of this lower arc 408 extends between the two ends of the arc along the lowest point 407. Thus, it is the ratio between dimension 405 and dimension 408 which defines the curvature ratio. In the embodiment, this curvature ratio is between 0.016 and 0.0179. It is appreciated that any other suitable curvature ratios may be utilised, however, the curvature ratio is intended to provide a sufficient curve to increase sensitivity while being small enough to allow for large-scale processing.

In the embodiment, a substantially similar curvature ratio is present in the substrate 301, conductive layer 302 and pressure sensitive layer 305. However, it is further appreciated, and will be shown in the example of Figure 7, that each of these layers and substrate may not always utilise substantially similar curvature ratios.

In the embodiment, the pressure sensing device is manufactured by a process of coating or printing each of the conductive materials on the respective substrates. In order to obtain the substantially curved cross- sectional profile, the pressure sensitive layer and second conductive layer, once printed onto the second substrate can be deformed by a suitable process such as an embossing process along with the substrate. In one embodiment, the embossing process utilises hot embossing technology.

Figure 5

In the embodiment of Figure 4, force sensing device 401 is shown at rest, without any force being applied thereto. In the absence of an applied force or pressure, the conductive layer does not contact the pressure sensitive layer and the pressure sensing device is considered in an open circuit state. When a force or pressure is applied, force sensing device 401 deforms to the position shown in Figure 5.

In the embodiment, when force 501 is applied, substrate 201 bends in response to force 501 which consequently causes conductive material 204 to bend and contact pressure sensitive layer 305. This consequently creates an electrical contact and closure of the electrical circuit from which a resistance can be measured and consequently processed into an applied force by means of a processor.

Thus, in this way, a magnitude or positional data of an applied force can be processed to provide an output to a user in, for example, an electronic device or detector in which the pressure sensing device is utilised.

The construction of the aforesaid pressure sensing device has indicated a high level of sensitivity with forces of as little as one gram being measured and detected in practice. This is due to the small change in deformation of the substrate and conductive layer required to contact the curved cross-sectional profile which means that low forces can be detected. Thus, the arrangement increases the sensitivity in comparison to convention pressure sensing devices.

An example of a pressure detector which utilises the aforesaid described pressure sensing device 401 will now be described with reference to Figure 6.

Figure 6

An exploded view of pressure sensing device 401 is shown in Figure 6

Pressure sensing device 401 comprises first substrate 201 comprising conductive layer 202, which comprises first and second conductive materials 203 and 204. Pressure sensing device 401 further comprises second substrate 301 which comprises conductive layer 302.

Pressure sensing device 401 further comprises adhesive layer 402.

In addition to the previously described layers, pressure sensing device 401 also comprises an adhesive to provide a means in which to fix pressure sensing device 401 into a position in use. A further adhesive 602, which may take the form of adhesive tape, is also provided for this purpose.

Pressure sensing device 401 also comprises a gasket 603 positioned above substrate 201 and attached to substrate 201 by means of an adhesive 604

In addition, pressure sensing device 401 also comprises a reinforcing element 605 which is positioned above substrate 201. Reinforcing element 605 is offset from substrate 201 , conductive layer 202, pressure sensitive layer 305, conductive layer 302 and substrate 301 when viewed from plan view. This ensures that the reinforcing element 605 does not contribute to any false readings from the pressure sensing device while providing reinforcement for the substantially thin pressure sensing device.

Figure 7

Tiie pressure sensing device described herein can be utilised with a pressure detector as will be described with respect to Figure 7.

Pressure detector 701 comprises a pressure sensing device 702 which is substantially similar to any of the embodiments described previously. Pressure detector 701 further comprises a processor 703 which is electrically connected to pressure sensing device 702. Processor 703 is configured to receive a resistance output from pressure sensing device 702 and convert the resistance output to a pressure value. Processor 703 is further connected to a display device 704 which is configured to provide a visual output to a user as necessary. In an embodiment, pressure sensing device 701 forms part of display device 704 such that display device 704 can receive pressure inputs of minimal force and provide appropriate outputs to a user. Figure 8

A method of manufacturing a pressure sensing device in accordance with the present invention is show in schematic form in Figure 8.

At step 801, a substrate is provided and at step 802 a conductive layer is applied to the substrate. This conductive layer, as described previously may comprise two conductive materials which are coated or printed onto the substrate.

At step 803, a further substrate is provided and at step 804 this second substrate is provided with the application of a second conductive layer, which in the example described previously, comprises a layer of conductive material. A pressure sensitive material is applied at step 805 to form a pressure sensitive layer.

At step 806, the second substrate, and consequently the second conductive layer and pressure sensitive layer thereon are deformed to form a substantially curved cross-sectional profile which protrudes towards the first substrate and its corresponding conductive layer.

At step 807, the two substrates are secured together by means of the application of an adhesive forming an adhesive layer.

Claims

CLAIMS The invention claimed is:

1. A pressure sensing device, comprising: a first substrate comprising a first conductive layer; a second substrate comprising a second conductive layer; and a pressure sensitive layer electrically connected to said second conductive layer; wherein said pressure sensitive layer and said second substrate comprise a substantially curved cross-sectional profile which protrudes towards said first substrate and said first conductive layer.

2. The pressure sensing device of claim 1, wherein at least one of said first substrate or said second substrate comprises polyethylene terephthalate.

3. The pressure sensing device of claim 1 or claim 2, wherein said first conductive layer comprises a first conductive material and a second conductive material.

4. The pressure sensing device of claim 3, wherein said first conductive material comprises silver.

5. The pressure sensing device of claim 3 or claim 4, wherein said second conductive material comprises carbon.

6. The pressure sensing device of any one of claims 3 to 5, wherein at least one of said first conductive material or said second conductive material has a thickness of between four and seven micrometres.

7. The pressure sensing device of any preceding claim, wherein said pressure sensitive layer comprises a pressure sensitive material.

8. The pressure sensing device of claim 7, wherein said pressure sensitive material comprises a quantum tunnelling material.

9. The pressure sensing device of claim 7 or claim 8, wherein said pressure sensitive material has a thickness of between seven and ten micrometres.

10. The pressure sensing device of any preceding claim, wherein said second conductive layer comprises a third conductive material.

11. The pressure sensing device of any claim 10, wherein said third conductive material comprises carbon.

12. The pressure sensing device of claim 10 or claim 11, wherein said third conductive material has a thickness of between four and seven micrometres.

13. The pressure sensing device of any preceding claim, wherein said substantially curved cross-sectional profile has a curvature ratio of between 0 01(5 a no 0 0179.

14. The pressure sensing device of any preceding claim, wherein at least one of said first substrate or said second substrate have a thickness of between seventy and eighty micrometres.

15. The pressure sensing device of any preceding claim, wherein said first conductive layer and said pressure sensitive layer are separated by a 0.'stance of between eight and twenty-four micrometres.

16. The pressure sensing device of any preceding claim, further comprising an adhesive layer between said first substrate and said second substrate.

17. The pressure sensing device of claim 16, wherein said adhesive layer has a thickness of between twenty-five and fifty-five micrometres.

18. A pressure detector comprising the pressure sensing device of any preceding claim, in which said pressure detector comprises: a display device; and a processor connected to said pressure sensing device and said display; wherein said processor is configured to convert a resistance output from said pressure sensing device to a pressure value.

19. A method of manufacturing a pressure sensing device comprising the steps of; providing a first substrate; applying a first conductive layer to said first substrate; providing a second substrate; applying a second conductive layer to said second substrate; applying a pressure sensitive layer to said second substrate; and deforming said second substrate to form a substantially curved cross- sectional profile which protrudes towards said first substrate and said first conductive layer.

20. The method of claim 18. wherein said step of deforming further comprises the step of: embossing said second substrate to form said substantially curved cross-sectional profile.

21. The method of claim 19 or claim 20, wherein said step of applying said first conductive layer to said substrate comprises the step of: coating a surface of said first substrate with a first conductive material and a second conductive material.

22. The method of any one of claims 19 to 21 , further comprising the step of: applying an adhesive layer; and securing said first substrate to said second substrate.