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EP-4158295-B1 - CAPACITIVE PRESSURE SENSOR WITH A COMPRESSIBLE ELECTRODE

EP4158295B1EP 4158295 B1EP4158295 B1EP 4158295B1EP-4158295-B1

Inventors

  • VANFLETEREN, JAN
  • DE PAUW, HERBERT
  • WILLOCKX, Matthias
  • DE WINTER, HUGO
  • MOORKENS, Sofie

Dates

Publication Date
20260506
Application Date
20210526

Claims (13)

  1. A capacitive pressure sensor (10) comprising a compressible electrode (1) comprising - a stably deformable polymer layer (2) comprising a first outer surface (2a), a second outer surface (2b), at least one deformed portion (3) formed as at least one indentation (3a) in said first outer surface (2a) and at least one corresponding protrusion (3b) in said second outer surface (2b), and at least one non-deformed portion (2c), - at least one stretchable conductor layer (4) arranged on or within said stably deformable polymer layer (2) at said at least one deformed portion (3) and/or at said at least one non-deformed portion (2c); and wherein said stably deformable polymer layer (2) is stably deformed at said at least one deformed portion (3); and - an elastic material (5) arranged on said first outer surface (2a) such that said elastic material (5) fills said at least one indentation (3a) of said at least one deformed portion (3), the compressible electroce being arranged over an additional electrode (7) and with the second outer surface (2b) facing said additional electrode (7), wherein the second outer surface (2b) is between the first outer surface (2a) and the additional electrode (7); and at least one dielectric medium (9, 8) arranged between said second outer surface (2b) and said additional electrode (7); and wherein the compressible electrode (1) and additional electrode (7) are arranged such that compression of the at least one deformed portion (3) of the compressible electrode (1) changes the capacitance of the capacitive pressure sensor (1).
  2. A capacitive pressure sensor (10) according to claim 1, wherein said at least one stretchable conductor layer (4) is arranged at least at said at least one deformed portion (3) and wherein said at least one stretchable conductor layer (4) is stably deformed at said at least one deformed portion (3).
  3. A capacitive pressure sensor (10) according to claim 1 or 2, wherein said at least one stretchable conductor layer (4) is arranged on said first outer surface (2a) of said stably deformable polymer layer (2).
  4. A capacitive pressure sensor (10) according to claim 1 or 2, wherein said at least one stretchable conductor layer (4) is arranged on said second outer surface (2b) of said stably deformable polymer layer (2).
  5. A capacitive pressure sensor (10) according to any previous claim, wherein the stably deformable polymer layer (2) comprises a plurality of deformed portions (3), and wherein one stretchable conductor layer (4) is arranged on or within said stably deformable polymer layer (2) at said plurality deformed portions (3).
  6. A capacitive pressure sensor (10) according to any previous claim, wherein said elastic material (5) has a volume that is larger than the volume of the stably deformable polymer layer (2).
  7. A capacitive pressure sensor (10) according to any previous claim, wherein the thickness of the stably deformable polymer layer (2) is less than 100 µm, such as less than 55 µm.
  8. A capacitive pressure sensor (10) according to any one of the preceding claims, wherein said at least one deformed portion (3) of the compressible electrode (1) abuts said additional electrode (7) or an additional dielectric layer (8) arranged on top of said additional electrode (7).
  9. A capacitive pressure sensor (10) according to any one of the preceding claims, wherein the at least one stretchable conductor layer (4) is arranged on the first outer surface (2a) of said stably deformable polymer layer (2) of the compressible electrode (1), and wherein the at least one dielectric medium (9) is air.
  10. A capacitive pressure sensor (10) according to any one of the preceding claims, wherein the at least one stretchable conductor layer (4) is arranged on the second outer surface (2b) of said stably deformable polymer layer (2) of the compressible electrode (1), and further wherein the said sensor (10) comprises an additional dielectric layer (8) arranged on top of said additional electrode (7), such that the at least one dielectric comprises both air (9) and said additional dielectric layer (8).
  11. A capacitive pressure sensor (10) according to any one of the preceding claims, wherein the capacitive pressure sensor (10) is configured to be integrated into an arrangement for receiving and supporting at least a part of a body of a person.
  12. An array of capacitive pressure sensors (10), said array comprising: a plurality of capacitive pressure sensors (10) according to any one of claims 1-11, wherein the plurality of capacitive pressure sensors (10) are formed by a plurality of separate first strips (11), each first strip (11) comprising the compressible electrode (1) of a subset of the plurality of capacitive pressure sensors (10) and being configured to extend in a first direction, wherein each first strip (11) comprises a plurality of deformed portions (3); and a plurality of separate second strips (12), each second strip (12) comprising the additional electrode (7) of a subset of the plurality of capacitive pressure sensors (10) and being configured to extend in a second direction, which is not parallel to the first direction; the plurality of first strips (11) and the plurality of second strips (12) being arranged so as to form crossings (13) between the first strips (11) and the second strips (12) wherein the first (11) and the second strips (12) overlap, wherein each crossing (13) defines one of the plurality of capacitive pressure sensors (10) in the array.
  13. A sit or sleep arrangement, comprising: at least one capacitive pressure sensor (10) according to any one of claims 1-11, an output device (14), which is configured to be controlled based at least on an input from the at least one capacitive pressure sensor (10) for controlling at least one property of the sit or sleep arrangement in a group of properties comprising a hardness of one or more zones of the sit or sleep arrangement, a shape of the sit or sleep arrangement, a temperature of the sit or sleep arrangement, and air circulation of the sit or sleep arrangement.

Description

Technical field The present inventive concept relates to a capacitive pressure sensor comprising a compressible electrode. Background A basic capacitive pressure sensor consists of two electrodes with a dielectric in between the electrodes. By applying force/pressure on the sensor, either the dielectric, and/or at least one of the electrodes are deformed, resulting in a measurable change of capacitance value of the sensor. For achieving a high sensitivity and high values of capacitance per unit area, compressible electrodes are usually used in the sensors. A compressible electrode may consist of an electrically non-conductive, deformable polymer with electrically conductive fillers making the deformable polymer electrically conductive, resulting in an electrically conductive polymer composite. The compressible electrode may also, as an alternative, be a non-conductive polymer coated with a conductive layer. An example of a compressible electrode is disclosed in US 9,752,940, in which the electrode has a single polymer layer with embedded conductive particles or a conductive layer arranged onto the single polymer layer. However, there are several technical problems associated with existing solutions First of all, adding conductive fillers to produce an electrically conductive polymer composite may increase the hardness of the deformable polymer and thereby reduce the sensitivity of the whole compressible electrode. Secondly, when forming the compressible electrode as a conductive coating on a non-conductive polymer, there are generally requirements that need to be fulfilled but, in reality, may prove to be incompatible with each other. As an example, in order to have a sufficient sensitivity of the electrode, the non-conductive polymer used should be soft, e.g. a silicone rubber material or a gel, but problems often arise with adhesion capacity of the conductive coating to such soft polymers. Further, the adhesion process itself may need to be performed on non-flat surfaces that are not standard within the art. US 2017/362083 A1 discloses a MEMS device formed by disposing a sacrificial layer, such as photoresist, on a substrate. A first flexible support layer is disposed on the substrate, and a first conductive layer is disposed over a portion of the first support layer. A liquid or gel separator, e.g., silicone oil, is disposed on an internal region of the first conductive layer. A second flexible support layer encapsulates the first conductive layer and the separator. US 2017/075467 A1 discloses a force sensor including a first substrate, a first electrode installed in a pattern on an upper surface of the first substrate, a second substrate disposed above and spaced apart from the first substrate, a second electrode installed in a pattern on a lower surface of the second substrate, facing the first electrode, and a dielectric interposed between the first substrate and the second substrate. US 2019/305139 A1 discloses thin-film transistor-based pressure sensor including a gate electrode; a gate dielectric layer provided on the gate electrode; a semiconductor layer provided on the gate dielectric layer; and a source electrode and a drain electrode provided on the semiconductor layer. Thus, there is a need in the art for improved compressible electrodes that may be used in capacitive pressure sensors. Summary It is an object of the invention to at least partly overcome one or more limitations of the prior art. In particular, it is an object to provide a compressible electrode and a capacitive pressure sensor that are both sensitive and easy to transfer to a production environment. As a first aspect of the invention, there is provided a capacitive pressure sensor as defined in claim 1. The compressible electrode further comprises at least one stretchable conductor layer arranged on or within the stably deformable polymer layer at the at least one deformed portion and at least one non-deformed portion; and wherein the stably deformable polymer layer is stably deformed stably deformed at the at least one deformed portion. The compressible electrode further comprises an elastic material arranged on the first outer surface such that the elastic material fills the at least one indentation of said at least one deformed portion. The stably deformable polymer layer may be in the form of a sheet or layer and may form a substrate or a carrier for the stretchable conductor layer during e.g. deposition and printing of the stretchable conductor layer onto the stably deformable polymer layer. However, as an alternative, the stretchable conductor layer may be arranged within the stably deformable polymer layer, i.e. be embedded in the stably deformable polymer layer. The stably deformable polymer layer may be any polymer layer that may be deformed into a stable, deformed shape. The stably deformable polymer layer will retain the stable, deformed shape in the absence of any external force on the stably deformable polymer laye