WO2019138153A1

WO2019138153A1 - A force and/or pressure sensor with at least two layers of electrodes

Info

Publication number: WO2019138153A1
Application number: PCT/FI2018/050953
Authority: WO
Inventors: Petri JÄRVINEN; Mikko Turunen; Pekka Iso-Ketola
Original assignee: Forciot Oy
Priority date: 2018-01-10
Filing date: 2018-12-20
Publication date: 2019-07-18
Also published as: FI20185027A1; FI128328B

Abstract

A sensor (900) suitable for use as a pressure and/or a force sensor. The sensor (900) comprises a first and second insulating layers (200, 100). The sensor (900) comprises on a primary side (201) of the first insulating layer (200) primary electrodes (300, 301, 302) and primary wiring (350), and on a secondary side (202) secondary electrodes (400, 401, 402) and secondary wiring (450). The sensor (900) comprises at least one controller (500) attached to the wirings (350, 450) and configured to measure capacitances from each one of the electrodes (300, 400). At least some of the electrically conductive primary wiring (350) or the electrically conductive secondary wiring (450) overlaps a secondary electrode (400) or a primary electrode (300), respectively. At least one of the first insulating layer (200) and the second insulating layer (100) is elastic and stretchable.

Description

A force and/or pressure sensor with at least two layers of electrodes

Technical field

The invention relates to force sensors. The invention relates to pressure sensors. The invention relates to capacitive force and/or pressure sensors. The invention relates to wearable capacitive force and/or pressure sensors.

Background

Interest in well-being has increased. This involves personal well-being as well as health care. This has resulted in many personal and medical monitoring devices, such as sensors. Such sensors can be embedded in clothing, such as gloves, mitts, footwear, helmets, etc. As for force or pressure sensors for garments, they may be e.g. piezo resistive, piezoelectric, or capacitive. A capacitive force/pressure sensor typically involves only easily available materials.

In capacitive sensors, the capacitance of an electrode is measured. The capacitance can be measured relative to surroundings or relative to another electrode, such a ground electrode. In general there are two working principles: (1 ) the dielectric material close to the electrode (e.g. in between two electrodes) changes, which changes the capacitance; and/or (2) the distance between two electrodes changes, which changes the capacitance in between these electrodes. These principles are known to a skilled person.

For example, the patent application DE102009055121 discloses a force sensor having multiple conductors and an elastic non-conductive layer in between. By applying force, the elastic non-conductive layer deforms, which results in a change of capacitance in between parts of the conductors (i.e. electrodes). Capacitances of different parts can only be measured subsequently.

In such sensors there are several interrelated problems. For example, the area of the electrodes should be reasonably large in order to measure the force accurately. Moreover, the measurement of the capacitance of an electrode should not affect the measurement result of the capacitance of another electrode. Furthermore, it would be beneficial that multiple capacitances can be measured in parallel, i.e. simultaneously or substantially simultaneously. For example, when monitoring the performance of a high jumper, one should be able to measure the pressure distribution under foot as function of time with reasonable high sampling rate. Moreover, the spatial resolution should be reasonably high, whereby the number of electrodes should be reasonably high. Still further, the sensor should be mechanically reliable, and, at least in some applications, comfortable to wear.

Summary

A force and/or pressure sensor that has a good balance between the aforementioned aspects is disclosed. The force and/or pressure sensor comprises a first and a second insulating layer. At least one of the insulating layers is elastic, i.e. compressible, whereby it is configured to be compressed and deform under pressure. In addition, the force and/or pressure sensor comprises electrodes on both sides of the first insulating layer. Because electrodes are arranged on both sides of the first insulating layer, electrodes can take up a great part of the cross sectional area of the sensor. Moreover, wiring on a primary side of the first insulating layer can be arranged on a location having electrodes on the secondary side of the first insulating layer and/or vice versa. Thus, reasonably wide wires can be used at the same time with large electrodes. Moreover, reasonably wide wiring has been found to be mechanically more reliable than narrow wires. The second insulating layer may ease manufacturing the sensor and enable use of a common potential electrode, which improves the accuracy of measurements. The invention is more specifically disclosed in the appended independent claim 1. Preferable embodiments are disclosed in the dependent claims. These and other embodiments and examples are disclosed also in appended numbered examples and in the description.

Brief description of the drawings

Figs. 1 a and 1 b show, as a side view, an embodiment of a sensor, the side view shown along the line la, lb of Fig 1 e,

Fig. 1 c shows, as a top view“lc” as indicated in Fig. 1 a or 1 b, the sensor of Fig. 1a or 1 b, Fig. 1d shows, as a bottom view“Id” as indicated in Fig. 1 a or 1 b, the sensor of Fig. 1 a or 1 b,

Fig. 1 e shows, as a top view, the electrodes of the sensor of Fig. 1 a or

1 b,

Figs. 2a to 2c show, as a side view, embodiments of a sensor,

Fig. 2d shows, as a top view“lid” as indicated in Figs. 2a to 2c, the sensor of Fig. 2a, 2b, or 2c,

Fig. 2e shows, as a top view“Me” as indicated in Figs. 2a to 2c, the sensor of Fig. 2a, 2b, or 2c,

Figs. 2f and 2g show, as a side view, embodiments of a sensor,

Figs. 3a and 3b show, as a side view, embodiments of a sensor having two elastic layers,

Figs. 4a and 4b show, as a side view, embodiments of a sensor having an electrically conductive layer,

Figs. 5a to 5j show, as a side view, embodiments of a sensor having two elastic layers and two electrically conductive layers,

Fig. 6 shows, as a top view, the electrodes of a sensor,

Figs. 7a and 7b show, as a side view, using some of the electrodes as ground electrodes,

Fig. 8a shows, as a top view, electrodes and wiring, wherein a part of the wiring, i.e. a dummy wire, can be used to compensate a capacitance of the wires,

Fig. 8b shows, as a top view, electrodes and wiring, the electrodes including overlapping electrodes to be used as supplemental common potential electrodes,

Figs. 9a and 9b shows, as a top view and a bottom view, respectively, a sensor having a circular cross section, and

Figs. 10a to 10c show, as a side view, embodiment of a sensor, having a deformable layer only in between the layers of electrodes.

In the figures, symbols Sx, Sy, and Sz indicate three orthogonal directions.

Detailed description

Figure 1 a shows a side view of a sensor 900. The sensor 900 is suitable for use as a pressure and/or a force sensor. The operating principle of the sensor is capacitive. In order for the measurable pressure and/or force to cause deformations to the structure, the sensor 900 comprises an elastic and stretchable layer that is configured to be compressed and deform under pressure in use. Moreover, because of the capacitive operational principle, the elastic and stretchable layer is also insulating. The sensor 900 comprises a first insulating layer 200 and a second insulating layer 100, as indicated in the Figures. At least one of the insulating layers 100, 200 serves as the elastic and stretchable layer. The other one of the insulating layers 200, 100 is used to make the manufacturing process of the sensor more easy and/or to insulate a common potential layer from the electrodes to improve measurement accuracy.

In the figures, the direction Sz refers to the direction of the thickness of a planar force and/or pressure sensor 900. The sensor is preferably deformable. Therefore, in use, the sensor need not to be planar. However, a non-planar sensor may be deformable to a planar shape. In non-planar sensors, the direction Sz of the thickness of the sensor depends on the point of observation. Moreover, the term thickness of a planar sensor refers to the smallest of three orthogonal dimensions of the planar sensor. In general, the sensor extends in the direction of thickness a shorter distance that in other two directions that are perpendicular to the thickness and to each other. Other directions Sx and Sy are perpendicular to Sz and to each other. Herein below the force and/or pressure sensor 900 is referred to as a sensor 900.

The sensor 900 comprises a first insulating layer 200 having a primary side 201 and a secondary side 202. The sensor 900 has measurement areas M, denoted in the figures by M,, wherein i is a number, such as 301 or 401 (see e.g. Fig. 1 c) of a corresponding electrode. A measurement area M, is a part of the sensor 900 extending through the sensor 900 in the direction of thickness t2oo of the first insulating layer 200. Within a measurement area M,, at least one electrode (300, 400) is arranged. More precisely, a measurement area M, includes the whole of at least one electrode (300, 400). Depending on the position of the electrode, the electrode within the measurement area M, may be a primary electrode 300, which is on a primary side of the layer 200, or a secondary electrode 400, which is on a secondary side of the layer 200. Correspondingly, a measurement area M, is defined by an electrode i. The measurement area M, defined by the electrode i is the area, from which capacitance is configured to be measured by the electrode i. Thus, the electrode which is in full comprised by the measurement area M, defines the measurement area M, such that measurement area M, equals the effective area of that electrode i. The effective area will be discussed later. A measurement area M, may comprise, in addition to the one electrode it comprises, at least a part of another electrode, e.g. a part of an electrode arranged in another layer than that electrode that the measurement area M, comprises.

A controller 500 is configured to measure a capacitance of each one of the measurement areas M, using the electrodes, of which each electrode i define one, and only one, of the measurement areas. Figures 1 c and 9a illustrate a measurement area M301 defined by the electrode 301 ; and Figures 1d and 9b illustrate a measurement area M₄OI defined by the electrode 401. The measurement areas M, are used to measure deformation, in particular compression, of the elastic and stretchable layer (i.e. at least one of the insulating layers 200, 100) in the measurement areas M,.

At least a first primary electrode 300, 301 and a second primary electrode 300, 302 are arranged on the primary side 201 of the first insulating layer 200. Moreover, electrically conductive primary wiring 350 is arranged on the primary side 201 of the first insulating layer 200 and coupled to the first primary electrode 300, 301 and the second primary electrode 302. The sensor 900 has, on the secondary side 202 of the first insulating layer 200, a first secondary electrode 400, 401 and a second secondary electrode 400, 402. Moreover, electrically conductive secondary wiring 450 is arranged on the secondary side 202 of the first insulating layer 200 and coupled to the first secondary electrode 400, 401 and the second secondary electrode 400, 402. In order to have a large area covered by electrodes and still have the possibility for wider wiring, wiring and electrodes are provided on both sides of the first insulating layer 200. It is also noted, that in some applications, also the areas near the boundaries should comprise electrodes in order to measure pressure also in these areas. Thus, is not necessary possible to arrange the wiring only outside the area of all electrodes. Moreover, in an embodiment, all the electrodes 300, 400 are left on a same side of the second insulating layer 100, as indicate e.g. in Fig. 1 a. As for the term “measurement area”, electrodes of two different measurement areas are not an a galvanic contact with each other. For example, the in Fig. 1 c and 1 d, each one of the electrodes 300, 400 form a separate measurement area. Such electrodes may be temporarily coupled e.g. by the controller 500 to a common potential, but in such a case, they are also electrically isolatable by the controller 500.

Thus, the sensor 900 comprises, on the primary side 201 of the first insulating layer 200 at least a first primary electrode 300, 301 and electrically conductive primary wiring 350 coupled to the first primary electrode 300, 301. The sensor 900 further comprises, on the secondary side 202 of the first insulating layer 200 at least a first secondary electrode 400, 401 and electrically conductive secondary wiring 450 coupled to the first secondary electrode 400, 401. Flerein the primary electrodes are commonly denoted by the reference number 300; and the individual primary electrodes are denoted by the numerals 301 , 302, 303, ... 312 (see e.g. Fig. 1 c) and 313 and 314 (see Fig. 8a). Flerein the secondary electrodes are commonly denoted by the reference number 400; and the individual secondary electrodes are denoted by the numerals 401 , 402, 403, ... 412 (see e.g. Fig. 1d). The number of primary electrodes 300 need not to be equal to the number of secondary electrodes 400.

Each electrode (300, 400) is connected by a wire (351 , 451 ) to the controller 500. For example, the electrically conductive primary wiring 350 comprises a first primary wire 351a coupled to the first primary electrode 300, 301 and a second primary wire 351 b coupled to the second primary electrode 300, 302. Moreover, the electrically conductive secondary wiring 450 comprises a first secondary wire 451 a coupled to the first secondary electrode 400, 401 and a second secondary wire 451 b coupled to the second secondary electrode 400, 402. Such wires 351 a, 351 b, 351 c, 451 a, 451 b, 451 c are indicated in Figs. 8a, 9a, and 9b. Each electrode (300, 400), which is connected by a wire (351 , 451 ) to the controller 500, and not connected by a wire (351 , 451 ) to another electrode defines a measurement area M,. The measurement area Mi defined by the electrode i may be exactly the area covered by the electrode. Flowever, if e.g. perforated electrodes are used, the measurement area defined by the electrode is the effective area of the electrode. Such an effective area is discussed in detail below. Moreover, the controller 500 is configured to measure a capacitance from each one of the measurement areas M,. Correspondingly, if two electrically conductive areas were connected by a wire, they would define only one measurement area (or electrode), since capacitance could only be measured from the area covered by the two electrically conductive areas. As for the terminology in this description, such connected electrically conductive areas will form only one electrode.

The sensor 900 comprises a controller 500. The controller is configured to measure a capacitance from each one of the measurement areas M,. More specifically, the controller 500 is configured to measure a capacitance from the whole area (or effective area) of each one of the electrodes (300, 400) used for measurements. However, as will be discussed below, the sensor 900 may further comprise ground electrodes (e.g. 313, 314 in Fig. 8b), of which capacitance is not measured. By measuring the capacitance of a whole area (or effective area) of the electrodes, there is no need, e.g. for measuring different parts of the electrodes in sequence, which improves the temporal accuracy of the measurements. Thus, in an embodiment, the controller 500 is attached to the first primary wire 351 a, the second primary wire 351 b, the first secondary wire 451 a, and the second secondary wire 451 b. Moreover, the controller 500 is configured to measure capacitances from the whole area of the first primary electrode 301 , the whole area of the second primary electrode 302, the whole area of the first secondary electrode 401 , and the whole area of the second secondary electrode 402. Thus, the controller 500 is configured to measure a capacitance from each one of the measurement areas M, individually.

More specifically, the controller 500 is configured to measure: the capacitance from the whole area of the first primary electrode 301 at one instance of time; the capacitance from the whole area of the second primary electrode 302 at one instance of time; the capacitance from the whole area of the first secondary electrode 401 at one instance of time; and the capacitance from the whole area of the second secondary electrode 402 at one instance of time. These instances of times may be the same or they may be different. However, in an embodiment, subsequent measurements are not performed to measure the capacitance from the whole area of the aforementioned electrode. Thus, a measurement area comprises at least one electrode (300, 400) that is connected by a wire 351 , 451 to the controller M,. Moreover, a wire 351 , 451 connects only one electrode 300, 400 to the controller 500. Thus, separate wires 351 , 451 connect each measurement area M, to the controller. Thus, for each measurement area, the sensor comprises a wire 351 , 451 that is attached in an electrically conductive manner to an electrode 300, 400. This has the beneficial effect that a capacitance is measurable from each measurement area simultaneously.

As indicated in the summary, electrically conductive primary wiring 350 on the primary side 201 of the first insulating layer can be arranged on a location having a secondary electrode 400 on the second side 202 of the first insulating layer and/or vice versa. Thus, the first primary electrode 301 may overlap with a part of the secondary wiring 450 and/or vice versa: the first secondary electrode 401 may overlap with a part of the primary wiring 350. This is particularly feasible, when the cross sections of the measurement areas M and the cross-section of the controller 500, in combination, cover a large part of the cross-sectional area of the sensor and/or boundary areas cannot be used for wiring. The spaces in between electrodes provide for space for the wiring.

More specifically [A] at least some of the electrically conductive primary wiring 350 overlaps, in a direction Sz of a thickness t2oo of the first insulating layer 200, the first secondary electrode (400, 401 ) or [B] at least some of the electrically conductive secondary wiring 450 overlaps, in a direction Sz of a thickness t2oo of the first insulating layer 200, the first primary electrode (300, 301 ).

Even more specifically, referring to Figs. 1 b, 5b, and 10a, in an embodiment, the electrically conductive primary wiring 350 and the first secondary electrode 401 are arranged relative to each other in such a way that a first imaginary straight line S_wi that is parallel to a direction Sz of the thickness t2oo of the first insulating layer 200 and penetrates the electrically conductive primary wiring 350 penetrates also the first secondary electrode 401. Referring to Figs. 1 b and 5b, in addition or alternatively, a second imaginary straight line S_W2 that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates the electrically conductive secondary wiring 450 penetrates also the first primary electrode 301. For clarity, the primary wiring 350 and/or the secondary wiring 450 is not shown in all the figures.

This has the effect that even if the electrodes 300, 400 in combination take up substantially all the cross-sectional area of the first insulating layer 200, as they may, the electrodes 300, 400 may still be connected to a controller 500 by the wirings 350, 450, since both the electrodes 300, 400 and the wirings 350, 450 are arranged in at least two layers.

Since some of the wiring (350, 450) overlaps with some of the electrodes (400, 300, respectively), in order to have accurate measurements, the wires of the wiring are preferably narrow. As an alternative to narrow wires, the wires may be wide, when their effect on the capacitive measurements are compensated for.

In the former case, the primary wiring 350 and/or the secondary wiring 450 comprises wires 351 , 451 of which width is at most 700 mΐti, at most 500 mΐti, such as at most 200 mΐti. For example, on a flexible and essentially non- stretchable material, such as material from the material group A or C (see below), a width of the wires may today be as low as 50 mhh, and most likely even narrower in the future. In an embodiment, the primary wiring 350 and the secondary wiring 450 only comprise such wires 351 , 451 , of which width is at most 700 mhh, preferably at most 500 mhh, or at most 200 mΐti.

In the latter case, the wiring 300, 400 may comprise dummy wires 352 as will be detailed later. Such dummy wires may be used to compensate for the capacitance of the wires. In such a case, the primary wiring 350 and/or the secondary wiring 450 may comprise wires 351 , 451 of which width is more than 200 mΐti, such as more than 500 mΐti, such as at least 700 mΐti.

For example, on a flexible and stretchable material, such as material from the material group B (see below), a width of the wires may today be about 700 mΐti. While narrow wires may provide for accurate measurements and easy implementation, wide wires may provide for better long term mechanical reliability. The applicable width of the wiring 350, 450 depends on the material on which the wires are manufactured. E.g. in the embodiment of Fig. 2a, the wiring 350 may be manufactured on the layer 200 (e.g. material from group A), but could be manufactured on the layer 100 (e.g. material from group B).

As indicated above, in an embodiment, a width of each one of a first primary wire 351 a coupled to the first primary electrode 300, 301 , a second primary wire 351 b coupled to the second primary electrode 300, 302, a first secondary wire 451 a coupled to the first secondary electrode 400, 401 , and a second secondary wire 451 b coupled to the second secondary electrode 400, 402 is at most 700 mhh, such as at most 500 mhh, or at most 200 mΐti.

As indicated above, in an embodiment, a width of each one of a first primary wire 351 a coupled to the first primary electrode 300, 301 , a second primary wire 351 b coupled to the second primary electrode 300, 302, a first secondary wire 451 a coupled to the first secondary electrode 400, 401 , and a second secondary wire 451 b coupled to the second secondary electrode 400, 402 is more than 200 mΐti, such as more than 500 mΐti; and the wirings 350, 450 comprise dummy wires 352, 452, as detailed elsewhere.

As indicated above, the sensor 900 comprises, on the primary side 201 of the first insulating layer 200 at least a first primary electrode 300, 301 and electrically conductive primary wiring 350 coupled to the first primary electrode 300, 301. In general, an electrode is electrically conducting. For example, a resistivity of an electrically conducting material (e.g. that of the electrodes 3000, 400 and/or the wirings 350, 450) may be at most 1 Qm at a temperature of 23 °C, preferably at most 0.1 Qm at a temperature of 23 °C. As indicated in Figs. 1 c and 6, in general, an electrode has a such a shape, that its length Le is of the same order of magnitude as its width We, wherein the length Le and the width We are measured along the surface of the first insulating layer 200 and are perpendicular to each other. Examples of such measures are given in Fig. 6. In an embodiment, a ratio Le/W_eof the length L_e of an electrode 300, 400 (in particular the first primary electrode 301 and the first secondary electrode 401 ) to its width We is less than 10, such as less than 5. As is conventional, length and width are defined so that the width is not greater than the length.

On the other hand, wiring, such as the primary wiring 350 and the secondary wiring 450, comprises wires (e.g. a wire 351 as indicated in Fig. 6). For clarity, the primary wiring 350 comprises primary wires 351 , 351 a, 351 b, 351 c; and the secondary wiring 450 comprises secondary wires 451 a, 451 b, 451 c (see Figs. 9a and 9b; commonly denoted by reference 451 ). A wire 351 , 451 , as known to a skilled person, is a reasonably long and thin conductive object. In general, an wire has a such a shape, that its length L_w is much larger than its width W_w, wherein the length L_w and the width W_w are measured along the surface of the first insulating layer 200 and are perpendicular to each other. In an embodiment, the primary wiring 350 comprises such a primary wire that the length L_w of the wire is at least five times the width W_w of the wire (i.e. L_w ³ 5*Ww). In an embodiment, the primary wiring 350 comprises such a primary wire that the length L_w of the wire is at least ten times the width W_w of the wire (i.e. L_w ³ 10xW_w). What has been said about the primary wiring 350 applies to the secondary wiring 450; in particular to an aspect ratio (i.e. ratio on length to width) of a secondary wire 451 a, 451 b, 451 c.

In particular, in an embodiment, an aspect ratio l__e/W_e of the first primary electrode 301 (i.e. the length L_e of the first primary electrode 301 divided by the width W_e of the first primary electrode 301 ) is less than an aspect ratio Lw/Ww (i.e. the length L_w of a primary wire 351 ,351 a, 351 b, 351 c divided by the width W_w of the primary wire 351 , 351a, 351 b, 351 c) of a primary wire 351 , 351 a, 351 b, 351 c of the electrically conductive primary wiring 350. In an embodiment, an aspect ratio L_w/W_w of a primary wire 351 , 351 a, 351 b, 351 c of the electrically conductive primary wiring 350 is more than twice the aspect ratio Le/We of the first primary electrode 301 ; i.e. L_w/W_w > 2* l_e/W_e. In particular, in an embodiment, an aspect ratio L_w/W_w of such a primary wire 351 , 351 a, 351 b, 351 c of the electrically conductive primary wiring 350 that overlaps the first secondary electrode 401 is more than, e.g. more than twice, the aspect ratio of the first secondary electrode 401.

Moreover, in an embodiment, an aspect ratio of the first secondary electrode 401 (i.e. a length of the first secondary electrode 401 divided by a width of the first secondary electrode 401 ) is less than an aspect ratio (i.e. a length of a wire of the secondary wiring 450 divided by a width of the wire of the secondary wiring 450) of the electrically conductive secondary wiring 450. In an embodiment, an aspect ratio of a wire of the electrically conductive secondary wiring 450 is more than twice the aspect ratio of the first secondary electrode 401. In particular, in an embodiment, an aspect ratio of such a secondary wire 451 , 451 a, 451 b, 451 c of the electrically conductive secondary wiring 450 that overlaps the first primary electrode 301 is more than, e.g. more than twice, the aspect ratio l_e/W_e of the first primary electrode 301.

As indicated above, the electrodes 300, 400 are used to measure a capacitance. As known to a skilled person, a capacitance is proportional to an area. Thus, for complex shaped objects comprising both an electrode and the wire that connects the electrode to the controller, such a part of the object that constitutes 25 % of its area and is closest to the controller 500 may be called as a“wire”, while the rest of the object may be called as the“electrode” that is comprised by the object. Also other definitions are possible, depending on the length and width of the wires of the wiring. For example, such a part of the object that constitutes 50 % of its area and is closest to the controller 500 may be called as a“wire”, while the rest may be called as an“electrode”. In normal cases, however, a skilled person realizes what is a wire as opposed to an electrode, e.g. following the definitions related to aspect ratios, as detailed above. The definitions (a) related to aspect ratios and (b) to the areas are not mutually exclusive.

In an embodiment, the sensor 900 comprises the first primary electrode 301 and a second primary electrode 302, which primary electrodes 301 , 302 do not belong to the same primary measurement area (i.e. they are not in galvanic contact, as explained above), the primary wiring 350 comprises a first primary wire 351a electrically connected to the first primary electrode 301 and a second primary wire 351 b electrically connected to the second primary electrode 302, and both the first primary wire 351 a and the second primary wire 351 b overlap, in a direction of a thickness t2oo of the first insulating layer 200, the first secondary electrode 400, 401. In the alternative or in addition, in an embodiment, the sensor 900 comprises the first secondary electrode 401 and a second secondary electrode 402, which secondary electrodes 401 , 402 do not belong to the same secondary measurement area (i.e. they are not in galvanic contact, as explained above), the secondary wiring 450 comprises a first secondary wire 451 a electrically connected to the first secondary electrode 401 and a second secondary wire 452b electrically connected to the second secondary electrode 402, and both the first secondary wire and the second secondary wire overlap, in a direction of a thickness t2oo of the first insulating layer 200, the first primary electrode 300, 301.

As an example, in Fig. 1 c, three primary wires overlap with the secondary electrode 410; and other three primary wires overlap with the secondary electrode 409. In addition, three secondary wires overlap with the primary electrode 310; and other three secondary wires overlap with the primary electrode 309. In Figs. 9b the numbering of the electrodes is such that:

- the primary wires 351 a, 351 b, and 351 c of the primary wiring 350 overlap with the first secondary electrode 401 ,

- the primary wires 351 b and 351 c of the primary wiring 350 overlap with the second secondary electrode 402,

- the primary wire 351 c of the primary wiring 350 overlaps with the third secondary electrode 402,

- the secondary wires 451a, 451 b, and 451 c of the secondary wiring 450 overlap with the first primary electrode 301 ,

- the secondary wires 451 b and 451 c of the secondary wiring 450 overlap with the second primary electrode 302, and

- the secondary wire 451 c of the secondary wiring 450 overlaps with the third primary electrode 302.

It is also noted that Fig. 9a is a top view of the layer 200, while a Fig. 9b, is a bottom view of the layer 200, as indicated by the direction arrows of the figures 9a and 9b. To better notice the aforementioned overlapping, Fig. 9b may be mirrored about a line that is parallel to the longer edge of figure page 9/12 and propagates through a centre of Fig. 9b. Moreover, also in the embodiments of Figs. 1 c and 1 d, three wires overlap such an electrode, of which capacitance is configured to be measured by the controller 500. Thus, by renumbering the electrodes in these Figs, also therein at least two (in Figs. 1 c and 1 d, exactly three) primary wires 351 of the primary wiring 350 overlap with the first secondary electrode; and at least two (in Figs. 1 c and 1 d, exactly three) secondary wires 451 of the secondary wiring 450 overlap with the first primary electrode.

As indicated in Figs. 1 c to 1 e, preferably the sensor comprises multiple primary electrodes 300 (see Fig. 1 c) and multiple secondary electrodes 400 (see Fig. 1d). This improves the spatial accuracy of the measurements. In Figs. 1 c, 1 d, 9a, and 9b there are twelve electrodes 300, 400 on both sides 201 , 202. As all of them are electrically isolated from other electrodes, the twenty-four electrodes define twenty-four measurement areas, as discussed above. Moreover, the primary wiring 350 comprises twelve wires 351 , each wire connected to a primary electrode 300 and insulated from another wire. Furthermore, the secondary wiring 450 comprises twelve wires 451 , each wire connected to a secondary electrode 400 and insulated from another wire. As is evident, the number of primary electrodes 300 and the number of second electrodes may selected according to needs. The number of primary electrodes 300 may be e.g. at least five, at least ten, at least fifteen, or at least twenty. The number of secondary electrodes 400 may be e.g. at least five, at least ten, at least fifteen, or at least twenty. The number of primary electrodes 300 may different from the number of secondary electrodes 400.

As indicated above, the sensor also comprises the second insulating layer 100. In an embodiment, the second insulating layer 100 is an elastic and stretchable layer 100. In an embodiment, at least the layer 100 is configured to be compressed and deform under pressure. In addition, the first primary electrode 300, 301 is arranged in between the elastic and stretchable layer 100 and the first insulating layer 200 in a direction Sz of a thickness of the sensor 900. In other words, both the primary electrodes 300 and the secondary electrodes 400 are arranged on the same side of the first elastic and stretchable layer 100. This has the effect that the first insulating layer 200 need not be compressible. It suffices that the second insulating layer 100 deforms. This increases the spectrum of available materials for the first insulating layer 200 and may ease the process of manufacturing the sensor. Typically, electrodes are not easy to manufacture directly on thick layers of elastic and stretchable material (such as the layer 100), but is more easily applicable on a thinner layer, such as an insulating layer 200, 205, 210, 220.

When the elastic and stretchable layer 100, 200 is compressed (i.e. one or both of the insulating layers is/are compressed), the capacitance of the primary electrodes 300 and the secondary electrodes 400 change. Conversely, from the capacitances of the primary electrodes 300 and the secondary electrodes 400, the compression of the first elastic and stretchable layer 100 at a location near the corresponding electrode 300, 400 can be determined.

As known in the field of capacitive sensors, the capacitance of an electrode 300, 400 can be measured relative to any object. For example, the capacitance of the first primary electrode 301 can be measured relative to a common potential, such as a ground potential. As an example, a secondary electrode 400, such as the first secondary electrode 401 or all the secondary electrodes may be connected — by the controller 500 and at the time measuring a capacitance of a primary electrode 300 — to the common potential in order to make the measurements. In addition or alternatively, another part of the sensor 900, such as any wiring, may serve as the common potential. In particular, when the sensor 900 comprises an electrically conductive layer (510 or 520), as shown in Figs. 4a, 4b, 5a to 5j, 10b, and 10c the capacitance(s) of the electrode(s) 300, 400 may be measured relative to such an electrically conductive layer (510 or 520). In particular, when the sensor comprises two electrically conductive layers (510 and 520), as shown in Figs. 5a to 5j, the capacitance(s) of the electrode(s) 300, 400 may be measured relative to either of the electrically conductive layers (510, 520) or both the electrically conductive layers (510, 520). Preferably in such a case the capacitance in measured relative to both electrically conductive layers (510, 520). The capacitance may be measured relative to both the electrically conductive layers (510, 520) simultaneously or subsequently. In the former case, both the electrically conductive layers (510, 520) may be simultaneously connected to the common potential. In the latter case, the capacitance is first measured relative to only one of the electrically conductive layers (510 or 520) by connecting the electrically conductive layer (510 or 520) to the common potential and disconnecting from the common potential the other the electrically conductive layer (520 or 510, respectively); and thereafter the capacitance is measured relative to the other electrically conductive layer (520 or 510) by connecting the other electrically conductive layer (520 or 510) to the common potential and disconnecting from the common potential the rest of the electrically conductive layers (510 or 520, respectively).

As for suitable materials of the insulating layer or layers that is/are configured to be compressed and deform under pressure in use, i.e. an elastic and stretchable layer, the layer is elastic in the sense that the Young’s modulus Y of the layer is less than 1 GPa. A sensor has at least one such an elastic and stretchable layer. The sensor may have at least two elastic and stretchable layers, i.e. layers configured to be compressed and deform under pressure. In an embodiment, the Young’s modulus Y of the elastic and stretchable layer is from 0.05 MPa to 15 MPa, such as from 0.2 MPa to 5 MPa. Such values ensure reasonable deformation in typical applications, such as an insole or a scale. However, in other applications, materials with a different Young’s modulus may be applicable. Moreover, the material of the elastic and stretchable layer has preferably a yield strain of at least 10 per cent. This ensures that the material can be stretched without breaking in use. Thus, this ensures good comfort in use. In an embodiment, the elastic and stretchable layer is made of at least one of: polyurethane, polyethylene, poly(ethylene- vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel. These materials a referred to as materials belonging to material group B (see below). Moreover, in order to have reasonable deformations, in an embodiment, a thickness t of the elastic and stretchable layer is at least 0.5 mm. The Young’s modulus Y and the thickness t are shown in Figs. 1 a and 10a.

As indicated above, the second insulating layer 100 may be an elastic and stretchable layer. The Young’s modulus Y100 and the thickness tioo of the second insulating layer 100 is shown in Fig. 1 a. As indicated above, in the alternative or in addition, the second insulating layer 200 may be an elastic and stretchable layer. Materials suitable for the insulating layers 100, 200 which do not serve as the elastic and stretchable layer are discussed below (material groups A and C).

In an embodiment, the elastic and stretchable layer 100, 200 is conformable. Herein the term conformable refers to material that is flexible, compressible, and stretchable. A planar flexible material can be bent to a radius of curvature of 10 mm (or less) without breaking the material at a temperature of 20 °C. Moreover, the flexible material can be thereafter turned back to the planar form at a temperature of 20 °C without breaking the material. A compressible material can be compressed by at least 10 % in a reversible manner. In particular, a layer of compressible material can be compressed by at least 10 % in a reversible manner in the direction of thickness of the layer. The reversibility of the compression is spontaneous, i.e. elastic. A stretchable material can be stretched by at least 10 % in a reversible manner. In particular, a layer of stretchable material can be stretched by at least 10 % in a reversible manner a direction that is perpendicular to the direction of thickness of the layer. The reversibility of the stretching is spontaneous, i.e. elastic. Thus, a planar conformable material is flexible as indicated above, compressible in the direction of its thickness as detailed above, and stretchable in a direction of the plane of the planar conformable material. A planar conformable material can be arranged to conform a surface of a sphere having a radius of 10 cm (or less) at a temperature of 20 °C without introducing plastic (i.e. irreversible) deformations to the material. Thus, a planar conformable material can be arranged to conform a surface of a foot.

As for suitable materials for the insulating layers 100, 200, a purpose of the insulating layers is to act as a support for the electrodes 300, 400 and the wirings 350, 450 without forming short-circuits. Therefore, the material for the layers 100 and 200 should be electrically insulating. E.g. its resistivity may be at least 10 Qm at a temperature of 23 °C.

Preferably, the first insulating layer 200 is flexible in the aforementioned sense. Moreover, preferably, the Young’s modulus of the first insulating layer 200 is at most 3.0 GPa. Either of these features and both of them improve the comfort of wear of the sensor. This is particularly beneficial in wearable solutions, such as garments, such as footwear. Furthermore, the first insulating layer 200 may be conformable in the aforementioned sense.

The first insulating layer 200 may act only as a flexible support, as in Fig. 1 a, or it may form another deformable layer, as in Fig. 1 b. Suitable materials for these purposes include materials from the material groups A and B, wherein the material group A consists of polyimide, polyethylene naphthalate, polyethylene terephthalate, and polyetheretherketone; and the material group B consists of polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile- butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel.

In an embodiment, the first insulating layer 200 acts also a the elastic and stretchable layer, and the material of the first insulating layer 200 is selected from the material group B. In such a case the material of the second insulating layer 100 may be relatively freely chosen. As an example, it may be a flexible circuit board material, in particular a material selected from the material group A. As an alternative, in such a case, the second insulating layer 100 need not be flexible. Referring to Figs. 10a to 10c, in such a case, the second insulating layer 100 may be e.g. a regular (e.g. hard) printed circuit board. Thus, suitable material for the second insulating layer 100 includes also materials comprising a material from a material group C consisting of epoxy and phenolic resin. Examples include FR-4 glass epoxy and cotton paper impregnated with phenolic resin. In the embodiments of Fig. 10b and 10c, the second insulating layer 100 may be e.g. a double-sided printed circuit board (flexible or non-flexible; material group A or C), wherein electrodes 300 are arranged on one side and the other side forms an electrically conductive layer 510.

The materials of the material group A are flexible and have a reasonably high Young’s modulus, whereby they may be used at least when the insulating layer 100, 200 acts only or mainly as a support. In this case, the material is essentially non-stretchable. In this case, the thickness of the layer 200 may be selected freely; however, is may be e.g. less 1 mm, or less than 0.5 mm, e.g. down to 50 mΐti. Fig. 1a shows an embodiment, wherein the thickness t2oo of the first insulating layer 200 is small. Thus, in Fig. 1 a, the deformations do not significantly affect the capacitance between the primary electrodes 300 and the secondary electrodes 400. In this embodiment, the second insulating layer 100 is elastic and stretchable. The second insulating layer 100 comprises material that has a second Young’s modulus Y100, and the first insulating layer 200 has a first Young’s modulus Y200, wherein the second Young’s modulus Y100 is less than the first Young’s modulus Y200. In this embodiment, the ratio Y100/Y200 of the second Young’s modulus Y100 to the first Young’s modulus Y200 may be less than 0.5, less than 0.2, or less than 0.1. The materials of the group B are flexible and have such a Young’s modulus, that the layer 100, 200 is also compressed in typical use by at least 1 %. Such a layer is also stretchable. Thereby, they may be used at least when the first insulating layer 200 acts as a deformable layer (the only deformable layer or an additional deformable layer). In this case, the thickness of the layer 100, 200 should be reasonable, such as at least 0.5 mm. Fig. 1 b shows an embodiment, wherein the thickness t2oo of the first insulating layer 200 is large. Moreover, the material of the first insulating layer 200 is elastic. Therefore, in Fig. 1 b, the pressure, which is measured, has also the effect that the first insulating layer 200 is compressed. In this way, the pressure affects also the capacitance between the primary electrodes 300 and the secondary electrodes 400. What has been said about the Young’s modulus of the second insulating layer 100 applies, in this embodiment, to the Young’s modulus of the first insulating layer 200.

As for suitable materials for the primary electrodes 300, the secondary electrodes 400, the primary wiring 350, or the secondary wiring 450, preferably the material is stretchable. In an embodiment, the first primary electrode 301 is made of such material that is stretchable by at least 5 % without breaking and the first secondary electrode 401 is made of such material that is stretchable by at least 5 % without breaking. In an embodiment, all the primary electrodes 300 and all the secondary electrodes 400 are made of such material that is stretchable by at least 5 % without breaking. Such material may be e.g. ink or paste. In an embodiment, the first primary electrode 301 comprises electrically conductive particles, such as flakes or nanoparticles, attached to each other in an electrically conductive manner. In an embodiment, the first primary electrode 301 comprises electrically conductive particles comprising at least one of carbon, copper, silver, and gold. In an embodiment, the first primary electrode 301 comprises electrically conductive particles comprising carbon. What has been said about the material of the first primary electrode 301 applies, in an embodiment, to all primary electrodes 300. What has been said about the material of the first primary electrode 301 applies, in an embodiment, to first secondary electrode 401. What has been said about the material of the first primary electrode 301 applies, in an embodiment, to all secondary electrodes 400. What has been said about the material of the first primary electrode 301 applies, in an embodiment, to the primary wiring 350. What has been said about the material of the first primary electrode 301 applies, in an embodiment, to the secondary wiring 450.

Fig. 1 c shows as a top view a sensor 900. The top view is seen from the top of the primary electrodes 300 towards the secondary electrodes, as indicated in Figs. 1a and 1 b. Fig. 1d shows as a bottom view a sensor 900. The bottom view is seen from the bottom of the secondary electrodes 400 towards the primary electrodes, as indicated in Figs. 1 a and 1 b. Fig. 1 e shows as a top view the sensor 900 of Figs. 1 c and 1d as seen from the top of the primary electrodes 300 towards the secondary electrodes. In Fig. 1 e, also the secondary electrodes 400 are shown, even if they remain behind the insulating layer 200 (compare to Figs. 1 a and 1 b). The cross section of Figs. 1 a and 1 b is shown by the dotted line la, lb of Fig. 1 e.

The sensor may be shaped according to the intended application. As indicated in Figs. 1 c to 1 d, in an embodiment, the sensor 900 has such a shape, as seen from a direction Sz of the thickness of the sensor 900, that the sensor 900 is suitable for use as an insole for footwear. Figures 9a and 9b, as well as Fig. 6, show an alternative shape for another application. Other possible electrode configurations resulting from a combination of two layers are e.g. those detailed for a single layer e.g. in the international application PCT/FI2017/050462 corresponding to a Finnish patent application FI20165581 , both incorporated herein by reference. Some of the electrodes shown therein may be placed on the primary side 201 of the first insulating layer 200, to for primary electrodes 300, and the remaining electrodes shown therein may be placed on the secondary side 202 of the first insulating layer 200 to form secondary electrodes 400; to form a sensor according to an embodiment of the present invention.

As motivated above, preferably the area of the electrodes 300, 400 is large. In an embodiment, a total effective cross-sectional area åA_ei,i or a total cross- sectional area åA_ei,i of the primary electrode or primary electrodes 300, 301 , 302 and the secondary electrode or secondary electrodes 400, 401 , 402 is at least 75 % of the total cross-sectional area A200 of the first insulating layer 200. Referring to Fig. 1 e, in an embodiment, the total cross-sectional area åA_ei,i of the electrodes 300, 400 is at least 85 % of the total cross-sectional area A200 of the first insulating layer 200. Flowever, the controller 500 may take up some space. Thus, preferably the cross sections of the measurement areas M, (i.e. the electrodes or their effective area) and the cross-section of the controller 500, in combination, cover at least 80 % such as at least 90 % of the cross-sectional area of the sensor. Such an embodiment is shown in Figs 1 c, 1 d, and 1 e; as well as in Figs. 9a and 9b.

Referring to Fig. 6, the total cross-sectional area åA_ei,i of the electrodes 300, 400 refers to the sum of the cross sectional areas A_ei,i of the electrodes i. In Fig. 6, the cross sectional areas A_ei,3oi , A_ei,302, A_ei,4oi , and A_ei,402 are depicted for the electrodes 301 , 302, 401 , and 402. As indicated in the figure, the cross sectional area is the area of the cross section of the electrode 300, 400 with a plane having a normal in the direction of the thickness of the sensor 900. It is also noted that in the figures, the direction Sz is parallel to a direction of a thickness of the sensor 900.

An electrode 300, 400 may be formed as a uniform layer of some conductive material. In this case, the cross sectional area A_eu of the electrode is well defined. These areas are shown in the figure 6 for the values 301 , 302, 401 , and 402 of i. Flowever, in an embodiment, an electrode 300, 400 may be made as a mesh, e.g. of conductive yarns or conductive ink. In such a case the electrode 300, 400 is configured to detect the changes of capacitance in an area that is substantially the same as the area limited by the outer edge of the electrode. Thus, the effective area A_ei,i (see Fig. 6 for i = 301 , 302, 401 , or 402) from which such an electrode is configured to measure pressure, is equal to the area limited by the outer edge of the electrode 300, 400; even if the area of the conductive yarns may be less. Correspondingly, since the electrode i is configured to measure pressure from the effective area, the measurement area M, defined by the electrode i is the effective area. As indicated above, in an embodiment, the total effective cross-sectional area åA_ei,i is preferably large. Flerein the total effective cross-sectional area refers to the sum of the effective cross sectional areas A_ei,i of the electrodes i, wherein each effective cross sectional area is the cross sectional area limited by an outer edge of the electrode.

In an embodiment, such as in the embodiments of Figs. 8a and 8b, the total cross-sectional area of the wirings 350, 450 form a significant portion of the total cross-sectional area A200 of the first insulating layer 200. In an embodiment, the total cross-sectional area of the electrically conductive primary wiring 350 and the electrically conductive secondary wiring 450 is at least 5 % or at least 15 % of the total cross-sectional area A200 of the first insulating layer 200. Having wide wires in the wiring 350, 450 has been observed to improve the mechanical reliability of the wiring. Moreover, wide wires imply a large area occupied by the wiring.

As indicated in Figs. 8a and 8b, in an embodiment, the total cross-sectional area åA_ei,i of the electrodes 300, 400 is at least 85 % of the total cross- sectional area A200 of the first insulating layer 200. Moreover, the total cross- sectional area of the wirings 350, 450 form a significant portion of the total cross-sectional area A200 of the first insulating layer 200. Thus, in an embodiment, a sum of [i] the total effective cross-sectional area åA_ei,i or the total cross-sectional area åA_ei,i of the primary electrodes 300, [ii] the total effective cross-sectional area åA_ei,i or the total cross-sectional area åA_ei,i of the secondary electrodes 400, [iii] the total cross-sectional area of the electrically conductive primary wiring 350, and [iv] the total cross-sectional area of the electrically conductive secondary wiring 450 is more than the total cross-sectional area A200 of the first insulating layer 200. This illustrates the benefits of using both sides of the layer 200 for electrodes and wirings. If only one side was used, the available area would be only equal to the total cross- sectional area A200 of the first insulating layer 200.

As indicated above, the sensor 900 comprises a controller 500. In an embodiment, the controller 500 is configured to measure the capacitances from at least the whole area of the first primary electrode 301 , the whole area of the second primary electrode 302, the whole area of the first secondary electrode 401 , and the whole area of the second secondary electrode 402 relative to a common potential.

The controller may be configured to measure the capacitance from a whole area of an electrode (301 , 302, 401 , 402) relative to environment, typically called as ground potential (or herein a common potential). However, to improve accuracy of the measurements, the sensor 900 may comprise a first electrically conductive layer 510. The first electrically conductive layer 510 may be electrically coupled to a common potential, such as a ground potential, and the capacitances of the electrodes 300, 400 may be configured to be measured by the controller relative to the common potential. In particular, in an embodiment, the controller 500 is configured to measure the capacitances from at least the whole area of the first primary electrode 301 , the whole area of the second primary electrode 302, the whole area of the first secondary electrode 401 , and the whole area of the second secondary electrode 402 relative to the first electrically conductive layer 510. For proper functionality, the first electrically conductive layer 510 overlaps in the direction of thickness of the sensor with [i] the whole area of the a first primary electrode 301 , [ii] the whole area of the a second primary electrode 302, [iii] the whole area of the a first secondary electrode 401 , and [iv] the whole area of the a second secondary electrode 402. When the sensor comprises further electrodes, preferably, the first electrically conductive layer 510 overlaps in the direction of thickness of the sensor with all the electrodes.

However, referring to Fig. 7a, it has been realized, that some or all of the primary electrodes 300 may be electrically connected to the common potential while the capacitances of the secondary electrodes 400 are measured (this may be done at a first time t1 ). When the primary electrodes 300 are electrically connected to the common potential also those wires 351 of the primary wiring 350 that are used to connect the primary electrodes 300 to the common potential are electrically connected to the common potential. Moreover, referring to Fig. 7b, it has been realized, that some or all of the secondary electrodes 400 may be electrically connected to the common potential while the capacitances of the primary electrodes 300 are measured (this may be done at a second time t2). When the secondary electrodes 400 are electrically connected to the common potential also those wires of the secondary wiring 450 that are used to connect the secondary electrodes 400 to the common potential are electrically connected to the common potential. This may improve the measurement accuracy, in particular if the wires of the wirings 350, 450 is reasonably large.

The controller 500 may be so configured. Thus, in an embodiment, the controller 500 is configured to [A] at the second time t2, connect the first secondary electrode 401 to a common potential G and measure the capacitance of at least the first primary electrode 301 relative to the common potential G; and [B] at the first time t1 , connect the first primary electrode 301 to a common potential G and measure the capacitance of at least the first secondary electrode 401 relative to the common potential G. Moreover, in an embodiment, the controller 500 is configured to [A] at the second time t2, connect all the secondary electrodes 400 to a common potential G and measure the capacitance of at least the first primary electrode 301 relative to the common potential G; and [B] at the first time t1 , connect the all primary electrodes 300 to a common potential G and measure the capacitance of at least the first secondary electrode 401 relative to the common potential G.

Preferably, in such an embodiment, the first insulating layer 200 is also elastic (i.e. compressible). This is, because then the capacitance change in between the sides 201 and 202 of the first insulating layer 200 can be employed. E.g. in an embodiment, the material of the first insulating layer 200 comprises material selected from the material group B (see above). However, it may further comprise substantially incompressible material (e.g. selected from material group A), as indicated in Figs. 5h and 5i. For example, in the embodiment of Fig. 5h the first insulating layer 200 is a layer of a material from the material group B. In Fig. 5i, the layers 200 and 205 in combination form an insulating layer in between the electrode layers. The layer 200 comprises material from material group B and the layer 205 comprises material from group material A. Moreover, preferably, in this embodiment, the thickness of the first insulating layer 200 is at least 0.1 mm. In this way, also the compression of the first insulating layer 200 can be sensed. The first insulating layer 200 may be made of a material selected from the material group B.

Referring to Figs. 2a and 2b the sensor 900 may be a layered structure, in which the primary electrodes 300, 301 , 302 are applied on the primary side 201 of the first insulating layer 200 and the secondary electrodes 400, 401 , 402 are applied on a primary side of a third insulating layer 210. Moreover, the first insulating layer 200 and the third insulating layer 210 are arranged relative to each other in such a way that the primary electrodes 300 are arranged on the primary side 201 of the first insulating layer 200 and the secondary electrodes 400 are arranged on the secondary side 202 of the first insulating layer 200. The layers may be bonded together with suitable adhesive. What has been said about the thickness of the first insulating layer 200 applies to the thickness of the third insulating layer 210. What has been said about the material of the first insulating layer 200 applies to the material of the third insulating layer 210. However, referring to Figs. 2b, 2c, and 10c, the material of the third insulating layer 210 need not be flexible. Thus, the material of the third insulating layer 210 may be selected from the material group C, as detailed above for the second insulating layer 100. For example, both the first and third insulating layers 200, 210 may be thin and substantially only insulating, as shown in Fig. 2a. For example, both the first and third insulating layers 200, 210 may be thick and both insulating and elastic (see Fig. 5b having a third insulating layer 110). For example, the first insulating layer 200 may be thin and substantially only insulating, and the third insulating layer 210 may be thick and both insulating and elastic (see Fig. 5b having a third insulating layer 110). For example, the third insulating layer 210 may be thin and substantially only insulating, and the first insulating layer 200 may be thick and both insulating and elastic, as shown in Fig. 2b.

This has the technical benefit that the conductive areas (wiring and electrodes) can be applied onto only one side of an insulating layer (the first and the third layer). This may be easier from the point of view of manufacturing the sensor. Moreover, as indicated in Figs. 2d and 2e, in such a case, both the primary electrodes 300 and the secondary electrodes 400 can be designed as a top view, since neither of them need to be turned around during manufacturing, whereby the design may be slightly easier. Still further, both the first insulating layer 200 and the third insulating layer 210 may be thin, e.g. less than 0.5 mm in thickness, which simplifies the manufacturing process, since then the electrode material needs not to be applied on a thick and elastic structure.

However, referring to Fig. 2f it is possible to turn the third insulating layer 210 upside down when assembling the sensor. In Fig. 2f, the combination of the first and third insulating layers 200, 210 serves as the first insulating layer 200 of Fig. 1 a, but, as for manufacturing, electrodes and wiring may be applied only on one side of a layer; electrodes 300 on a side of the layer 200 and electrodes 400 on a side of the layer 210. Referring to Fig. 2c it is possible to apply the primary electrodes 300, 301 , 302 on a primary side of a fourth insulating layer 205 and apply the secondary electrodes 400, 401 , 402 on the primary side of the third insulating layer 210. Moreover, the fourth insulating layer 205 and the third insulating layer 210 are arranged relative to each other in such a way that the primary electrodes 300 are arranged on the primary side 201 of the first insulating layer 200 and the secondary electrodes 400 are arranged on the secondary side 202 of the first insulating layer 200. As for the solution of Fig. 2c, an embodiment needs not to comprise the third insulating layer 210 even if it comprises the fourth insulating layer 205. In such an embodiment, the layer 205 could be called as the third insulating layer 205.

What has been said about the thickness of the first insulating layer 200 applies to the thickness of the fourth insulating layer 205. What has been said about the material of the first insulating layer 200 applies to the material of the fourth insulating layer 205.

Moreover, referring to Fig. 2g, the secondary electrodes 400 need not to be on same side of each insulating layer. As indicated in the figure, in an embodiment, some of the secondary electrodes 400 are arranged on a primary side of a third insulating layer 210 and the rest of the secondary electrodes 400 are arranged on a secondary, different, side of the third insulating layer 210. In order to avoid applying conductive material on two sides of the third insulating layer 210, a fourth insulating layer 220 may be used as indicated in Fig. 2g.

As indicated above with reference to Figs. 2a to 2g, in an embodiment, the sensor 900 comprises a third insulating layer (205, 210), wherein

[A]

- the first secondary electrode 401 is arranged in between the first insulating layer 200 and the third insulating layer 210 in a direction Sz of a thickness of the sensor 900 (see Figs. 2a and 2b), OR

[B]

- a part of the third insulating layer 205 is left in between the first secondary electrode 401 and the second insulating layer 100 in a direction Sz of a thickness of the sensor 900 (see Fig. 2c). As for the option [B] for example at least a part of the third insulating layer 205 is left in between the first insulating layer 200 and the second insulating layer 100 in a direction Sz of a thickness of the sensor 900.

Referring to Figs. 3a and 3b, in an embodiment, the sensor 900 comprises a second elastic and stretchable layer 110, which is also an insulating layer. The third insulating layer 210 may serve as the second elastic and stretchable layer 110. What has been said above about the material of the elastic and stretchable layer applies to the material of the second elastic and stretchable layer 110. What has been said above about the thickness of an elastic and stretchable layer applies to the thickness of the second elastic and stretchable layer 110. What has been said above about the Young’s modulus Y of an elastic and stretchable layer applies to the Young’s modulus Y1 10 of the second elastic and stretchable layer 110. Thus, in an embodiment, the Young’s modulus Yno of the second elastic and stretchable layer 110 is at most 1 GPa, such as from 0.05 MPa to 15 MPa, such as from 0.2 MPa to 5 MPa. It is also noted that the second elastic and stretchable layer 110 is electrically insulating, whereby it forms an insulating layer.

In an embodiment, the first secondary electrode 401 is left in between the second elastic and stretchable layer 110 and the first insulating layer 200 in a direction Sz of a thickness of the sensor 900. As indicated in Figs. 3a and 3b, in an embodiment, the primary electrode(s) 300 and the secondary electrode(s) 400 are left in between the second insulating layer 100 and the second elastic and stretchable layer 110 in a direction Sz of a thickness of the sensor 900. Also the wirings 350, 450 are left in between the second insulating layer 100 and the second elastic and stretchable layer 110 in the direction Sz of the thickness of the sensor 900.

Because of the two elastic layers the capacitive measurement in this embodiment is more accurate. The two elastic layers may be e.g. the pairs of layers: 100 and 200; 100 and 110; or 200 and 110. When pressure is applied, both the elastic and stretchable layers (i.e. 100 and/or 200; and 110) deform. In this way the capacitance changes because of two layer are compressed. Compared to only one layer being deformed, this improves accuracy. Thus, preferably, the sensor comprises at least two layers (e.g. at least two of the layers 100, 200, 110, 205, 210) that are elastic and stretchable; in such a way that at least some of the electrodes 300, 400 are arranged in between the two layers that are elastic and stretchable.

Any one of the embodiments of Figs. 2a to 2g may be equipped with a second elastic and stretchable layer 110 to form an embodiment of a sensor 900.

The second elastic and stretchable layer 110 can be further utilized to increase the range of measurable pressures or forces. For example, the Young’s modulus Y of a first elastic and stretchable layer (e.g. the layer 100; or the layer 200) may be smaller than the Young’s modulus Yno of the second elastic and stretchable layer 110. In such a case, already a small pressure causes compression in the first elastic and stretchable layer, and such compression can be measured. As the pressure increases, at some point, the first elastic and stretchable layer becomes fully compressed, whereby a further increase in the pressure would not affect the deformation of the first elastic and stretchable layer. Flowever, since the Young’s modulus Y1 10 of the second elastic and stretchable layer 110 is larger, the second elastic and stretchable layer 110 is not fully compressed at that point. Thus, a further increase in the pressure affects the deformation of the second elastic and stretchable layer 110. Also these deformations are measurable by the sensor. In this way, the first elastic and stretchable layer may be responsible for deformations in the small pressure regime and the second elastic and stretchable layer 110 may be responsible for deformations in the large pressure regime. As is evident, it is immaterial, which one of the elastic layers is responsible for deformations in the small pressure regime. Thus, in an embodiment, wherein the sensor 900 comprises the first elastic and stretchable layer having a second Young’s modulus Y and the second elastic and stretchable layer 110 having a third Young’s modulus Yno_, wherein the third Young’s modulus Yno is different from the second Young’s modulus Y_. The ratio of the greater of the second and third Young’s moduli to the smaller of the second and third Young’s moduli, max(Y, Yno)/min(Y, Yno), may be e.g. more than 2, more than 5, or more than 10.

The Young’s moduli can be affected by selection of the material of the elastic and stretchable layer(s). In addition or alternatively, the Young’s moduli can be affected by arranging holes into the elastic and stretchable layer(s), as detailed in the international application PCT/FI2017/050462 corresponding to a Finnish patent application FI20165581 , both incorporated herein by reference.

Referring to Figs. 4a and 4b, in an embodiment, the sensor 900 comprises a first electrically conductive layer 510. As indicated above, the purpose of the first electrically conductive layer is to improve the accuracy of capacitive measurements. For example, the capacitance of the electrodes 300, 400 may be measured relative to the first electrically conductive layer 510. For such a purpose, the first electrically conductive layer 510 may be connected to a common potential. Flowever, also other methods are applicable for measurements of capacitance.

As indicated in Figs. 4a and 4b, the first electrically conductive layer 510 is left on a first side 101 of the second insulating layer 100; and the first primary electrode 301 and the first secondary electrode 401 , or all the electrodes 300, 400, is/are left on a second, opposite, side 102 of the second insulating layer 100. Correspondingly, a part of the second insulating layer 100 is left in between the first electrically conductive layer 510 and the first primary electrode 301 the direction Sz of the thickness of the sensor 900.

The first electrically conductive layer 510 may be uniformly conductive, e.g. made using conductive ink or paste on a uniform surface. In the alternative, the first electrically conductive layer 510 may be a mesh of conductive yarns, e.g. made using conductive ink or paste or filaments. It may also suffice that the first electrically conductive layer 510 consists of a meandering electrically conductive line. It may also suffice that the first electrically conductive layer 510 comprises multiple separate electrically conductive lines. In an embodiment, at least a part of the first electrically conductive layer 510 is made from a conductive ink. In an embodiment the first electrically conductive layer 510 comprises electrically conductive fabric. In an embodiment, the first electrically conductive layer 510 comprises electrically conductive polymer.

Any one of the sensor structures of Figs. 2a to 2g and 3a or 3b may be equipped with a first electrically conductive layer 510 to form an embodiment of a sensor 900. In addition, any one of the sensor structures of Figs. 2a to 2g may be equipped with a second elastic and stretchable layer 110 and further with a first electrically conductive layer 510 to form an embodiment of a sensor 900. In addition, any one of the sensor structures of Figs. 4a or 4b may be equipped with a second elastic and stretchable layer 110 to form an embodiment of a sensor 900.

Figures 5a to 5j and 10c show preferable embodiments. These embodiments comprise a second electrically conductive layer 520. For proper functionality, the second electrically conductive layer 520 overlaps in the direction of thickness of the sensor with [i] the whole area of the a first primary electrode 301 , [ii] the whole area of the a second primary electrode 302, [iii] the whole area of the a first secondary electrode 401 , and [iv] the whole area of the a second secondary electrode 402. When the sensor comprises further electrodes, preferably, the second electrically conductive layer 520 overlaps in the direction of thickness of the sensor with all the electrodes. What has been said above about the materials for the first electrically conductive layer 510 apply for the materials of the second electrically conductive layer 520. The first secondary electrode 401 is arranged in a direction of thickness Sz of the sensor 900 in between the second electrically conductive layer 520 and the first insulating layer 200. Moreover, a part of an insulating layer (110, 210) is arranged in between the first secondary electrode 401 and the second electrically conductive layer 520. More specifically, a part of an insulating layer (110, 210) is arranged [A] in between the first primary electrode 301 and the second electrically conductive layer 520 and [B] in between the first secondary electrode 401 and the second electrically conductive layer 520. Moreover, in an embodiment, the primary electrode(s) 300 and the secondary electrode(s) 400 are left in between the second electrically conductive layer 520 and the second insulating layer 100 in the direction Sz of the thickness of the sensor 900. Also the wirings 350, 450 are left in between the second electrically conductive layer 520 and the second insulating layer 100 in the direction Sz of the thickness of the sensor 900. In the embodiments of Figs. 5a to 5j, the second insulating layer 100 is a layer configured to be compressed and deform in use and under pressure. In the embodiments of Fig. 10c, only the first insulating layer 200 is a layer configured to be compressed and deform in use and under pressure. The material for such a layer may be selected e.g. from the material group B. When the sensor 900 comprises the first and second electrically conductive layers 510, 520, preferably, the controller 500 is configured to measure the capacitances from at least the whole area of the first primary electrode 301 , the whole area of the second primary electrode 302, the whole area of the first secondary electrode 401 , and the whole area of the second secondary electrode 402 relative to both the first and second electrically conductive layers 510, 520.

In particular, when the sensor comprises at least one electrically conductive layer (510 or 520); the controller 500 may be configured to measure: the capacitance from the whole area of the first primary electrode 301 relative to the electrically conductive layer (or layers) at one instance of time; the capacitance from the whole area of the second primary electrode 302 relative to the electrically conductive layer (or layers) at one instance of time; the capacitance from the whole area of the first secondary electrode 401 relative to the electrically conductive layer (or layers) at one instance of time; and the capacitance from the whole area of the second secondary electrode 402 relative to the electrically conductive layer (or layers) at one instance of time. These instances of times may be the same or they may be different.

The embodiments of the Figs. 5a to 5j comprise also the second elastic and stretchable layer 110 as indicated above. Even if not shown in these figures, embodiments of a sensor 900 include also such sensors that do not include the second elastic and stretchable layer 110. For example the embodiments of Figs. 5c, 5e, 5f, 5h, and 5j without the second elastic and stretchable layer 110, such as the embodiment of Fig. 10c.

When the sensor comprises both the second elastic and stretchable layer 110 and the second electrically conductive layer 520, in addition to the second insulating layer 100 and the first electrically conductive layer 510, the second electrically conductive layer 520 is arranged on a first side 111 of the second elastic and stretchable layer 110 and the first secondary electrode 401 is arranged on a second, opposite, side 112 of the second elastic and stretchable layer 110. In an embodiment, the electrodes 300, 400 and at least a part of the wirings 350, 450 are arranged on the second, opposite, side 112 of the second elastic and stretchable layer 110. Correspondingly, a part of the second elastic and stretchable layer 110 is left in between the second electrically conductive layer 520 and the first secondary electrode 401 in the direction Sz of the thickness of the sensor 900. Both the two electrically conductive layers 510, 520 and the two elastic an stretchable layers improve the accuracy of capacitive measurements. In addition, the first insulating layer 200 in between the two elastic an stretchable layers simplifies the manufacturing process. Furthermore the mutual arrangement of electrodes and wiring improve measurement accuracy for force and without compromising reliability. Large electrodes (i.e. large coverage of electrodes) is needed when the force is measured, since the force is a surface integral of pressure. Thus, the pressure needs to be known at substantially all locations within the sensor to accurately determine the force. Some values for a large coverage have been disclosed above.

As indicated in Fig. 10c when the sensor comprises both the second electrically conductive layer 520 and the first electrically conductive layer 510, an insulating layer 210 is arranged in between the second electrically conductive layer 520 and electrodes 300, 400. The insulating layer 210 need not be elastic in the aforementioned meaning. Thus, the material for the layer 210 may be selected from material group A or C. Moreover, an insulating layer 100 is arranged in between the first electrically conductive layer 510 and electrodes 300, 400. The insulating layer 100 need not be elastic in the aforementioned meaning. Thus, the material for the layer 100 may be selected from material group A or C.

The embodiment of Fig. 5a corresponds to the embodiment of Fig. 1 a equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5b corresponds to the embodiment of Fig. 1 b equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5c corresponds to the embodiment of Fig. 2a equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5d corresponds to the embodiment of Fig. 2f equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5e corresponds to the embodiment of Fig. 2c equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5f corresponds to the embodiment of Fig. 5c; however, the electrode configuration is different. In the embodiment of Fig. 5f, some of the primary electrodes 300 overlap with some of the secondary electrodes 400. Such overlapping will be discussed in more detail below.

The embodiment of Fig. 5g corresponds to the embodiment of Fig. 2c. Flowever, the second insulating layer 210 of the embodiment of Fig. 2b is also elastic and stretchable, whereby that layer serves as the second elastic and stretchable layer 110. Moreover, the embodiment is equipped with the second electrically conductive layer 520. The properties of these layers have been discussed above.

The embodiment of Fig. 5h corresponds to the embodiment of Fig. 2c equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above. Moreover, in this embodiment, some of the primary electrodes 300 overlap with some of the secondary electrodes 400.

The embodiment of Fig. 5i corresponds to the embodiment of Fig. 2f. Flowever, in the embodiment of Fig. 5i, the first insulating layer 200 is reasonably thick, and moreover also elastic. Moreover, the sensor is equipped with the second elastic and stretchable layer 110 and the second electrically conductive layer 520. The properties of these layers have been discussed above. As indicated above, in the preferable embodiments of Figs. 5a to 5j, the sensor 900 comprises the parts discussed in connection with Fig. 1 a and, in addition, the second elastic and stretchable layer 110, the first electrically conductive layer 510, and the second electrically conductive layer 520. In the embodiments of Figs. 2a to 5j, [i] at least a part of the first insulating layer 200, [ii] the first primary electrode 301 , [iii] at least a part of the electrically conductive primary wiring 350, [iv] the first secondary electrode 401 , and [v] at least a part of the electrically conductive secondary wiring 450 are left in between the second elastic and stretchable layer 110 and the second insulating layer 100 in the direction Sz of the thickness of the sensor. Moreover, [i] at least a part of the second elastic and stretchable layer 110 and [ii] at least a part of the second insulating Iayer100 are left in between the first electrically conductive layer 510 and the second electrically conductive layer 520 in the direction Sz of the thickness of the sensor.

The second electrically conductive layer 520 may be uniformly conductive, e.g. made using conductive ink or paste on a uniform surface. In the alternative, the second electrically conductive layer 520 may be a mesh of conductive yarns, e.g. made using conductive ink or paste or filaments. It may also suffice that the second electrically conductive layer 520 consists of a meandering electrically conductive line. It may also suffice that the second electrically conductive layer 520 comprises multiple separate electrically conductive lines. In an embodiment, at least a part of the second electrically conductive layer 520 is made from a conductive ink. In an embodiment the second electrically conductive layer 520 comprises electrically conductive fabric. In an embodiment, the second electrically conductive layer 520 comprises electrically conductive polymer.

As indicated above, the sensor 900 is configured to sense pressure and/or force acting in a direction having a component in the direction Sz of the thickness of sensor 900. Correspondingly, a thickness of at least an elastic and stretchable layer (e.g. 100 or 200) is configured to decrease under pressure. In such a case the material may be selected e.g. from the material group B. Preferably, the thickness of the elastic and stretchable layer layer is at least 0.5 mm. Therefore, in a preferable embodiment, the measurement area M301 comprising the first primary electrode 301 does not partially overlap with the measurement area M_4OI comprising the first secondary electrode 401 in the direction Sz of the thickness of sensor 900. There may be some overlap between the electrodes, but preferably, the amount of overlap with the measurement areas M301 , M₄OI is small. In the alternative, large one of the overlapping measurement areas may comprise the whole of the smaller measurement area. Then, when the capacitances are measured relative to at least one electrically conductive layer 510, 520, the capacitance of the non- overlapping part can be computed from the measurements. The capacitances of the smaller electrode and larger electrode may be measured e.g. subsequently, and the capacitance of the non-overlapping part can be computed by subtraction. Having the layer 200 sufficiently thick and elastic may help the computation such that the capacitances of the overlapping part and the non-overlapping part may be measurable also simultaneously. Thus, when the electrodes overlap, preferably the material of the first insulating layer 200 comprises material selected from the material group B (see above) and the thickness of the first insulating layer 200 is at least 0.5 mm.

Thus, in an embodiment, either

- (A) at most 10 % or at most 5 % or at most 2 % of an area (or effective area) of a primary or secondary electrode overlaps with a secondary or primary electrode respectively, or

- (B) at least 90 % or at least 95 % or at least 98 % of an area (or effective area) of a primary or secondary electrode overlaps with a secondary or primary electrode, respectively, and the primary or secondary electrode, respectively, is the smaller one of the overlapping electrodes.

In the above, the option (A) correspond to substantially no overlap; and the option (B) corresponds to substantially full overlap (full referring to the smaller one of the overlapping electrodes). In a preferable embodiment, the layout of the electrodes is designed such that this applies to each one of the electrodes. Thus, in an embodiment, for at least a quarter of the primary and secondary electrodes; preferably for at least a third or at least a half of the primary and secondary electrodes

- (A) at most 10 % or at most 5 % or at most 2 % of the area (or effective area) of the primary or secondary electrode overlaps with a secondary or primary electrode respectively, or - (B) at least 90 % or at least 95 % or at least 98 % of the area (or effective area) of the primary or secondary electrode overlaps with a secondary or primary electrode, respectively, provided that the primary or secondary electrode, respectively, is the smaller one of the overlapping electrodes.

This needs not to apply for each electrodes 300, 400, since the sensor may comprise dummy wires 352 and/or ground electrodes 313, as detailed below.

In the above, the ratios at least a quarter, at least a third and at least a half may be calculated as a ratio of the number of the electrodes or as a ratio of the area of the electrodes.

Embodiments, where the first primary electrode 301 does not overlap with the first secondary electrode 401 in the direction Sz of the thickness of sensor 900 are shown in Figs. 2a to 2i, 3a, 3b, 4a, 4b, 5a, 5b, 5c, 5d, 5e, 5g, 5i, and 5j. More precisely said, with reference to Fig. 5a, in an embodiment, the first primary electrode 301 and the first secondary electrode 401 are arranged relative to each other in such a way that none such third imaginary straight line S_en that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates the first primary electrode 301 penetrates the first secondary electrode 401. In an embodiment, none of the primary electrodes 300 overlaps with any one of the secondary electrodes 400 in the direction Sz of the thickness of sensor 900. More precisely said, in an embodiment, the primary electrodes 300 and the secondary electrodes 400 are arranged relative to each other in such a way that none such third imaginary straight line Sen that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates a primary electrode 300 penetrates a secondary electrode 400. Flowever, the electrodes may also overlap, as indicated above.

Fig. 5h shows an embodiment, where there is partial overlap. Flowever, as indicated above, such an embodiment is not preferred, because then the measurement accuracy is reduced.

Fig. 5j shows an embodiment, where there is a full overlap of a small electrode with a large electrode. In Fig. 5j, the first secondary electrode 401 overlaps with the first primary electrode 301. As indicated in the figure, the first secondary electrode 401 is smaller than the first primary electrode 301. Moreover, the whole of the first secondary electrode 401 overlaps with the first primary electrode 301. Correspondingly, the first primary electrode 301 has an overlapping part and a non-overlapping part. By measuring the capacitances of the first secondary electrode 401 and the first primary electrode 301 relative to a common potential, such as the layers 510, 520, the capacitance of the non-overlapping part of the first primary electrode 301 can be computed by subtracting, from the capacitance of the first primary electrode 301 the capacitance of the first secondary electrode 401. Thus, a measurement area M need not comprise the whole of an electrode. As indicated above, a capacitance of a non-overlapping part of the larger one of two overlapping electrodes can be computed, whereby such a non- overlapping part may serve as a measurement area. When the capacitance per area for the electrodes 301 and 401 is not the same, e.g. for reasons of material selections and/or geometry, a further correction may be needed.

Thus, in some embodiments (e.g. Fig. 5a and Fig. 5h) complying with the option (A), the first primary electrode 301 and the first secondary electrode 401 are arranged relative to each other in such a way that none such third imaginary straight line S_en that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates a major region of the first primary electrode 301 penetrates the first secondary electrode 401 , wherein the cross sectional area of the major region of the first primary electrode 301 is more than 90 %, more than 95 %, or more than 98 %, of the cross sectional area of the first primary electrode 301. In such a case at most 10 %, at most 5 %, or at most 2 % of the area of the first primary electrode 301 overlaps a secondary electrode. Preferably this applies to all electrodes subject to the substantially no overlap, as discussed above under“option A”.

Even if the first primary electrode 301 does not overlap the first secondary electrode 401 , it is possible that some other electrodes overlap a secondary electrode 400. Referring to Fig. 5h, in an embodiment the sensor 900 comprises a second primary electrode 302 arranged on the primary side 201 of the first insulating layer 200. Moreover, the first primary electrode 301 , the second primary electrode 302, and the first secondary electrode 401 are arranged relative to each other in such a way that [A] each third imaginary straight line S_en that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates the first primary electrode 301 does not penetrate the first secondary electrode 401 and [B] a fourth imaginary straight line S_ei2 that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates the second primary electrode 302 penetrates the first secondary electrode 401.

As indicated above, if some electrodes overlap, they preferably overlap in such a manner, that the smaller of the electrodes substantially fully overlap the larger electrode. Referring to Fig. 5j, in such a case, the first primary electrode 301 and the first secondary electrode 401 are arranged relative to each other in such a way that a fourth imaginary straight line S_ei2 that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates the smaller one of the first primary electrode 301 and the first secondary electrode 401 , also penetrates the larger one of the first primary electrode 301 and the first secondary electrode 401. As indicated above, the overlap needs not be full. Thus, in an embodiment, the first primary electrode 301 and the first secondary electrode 401 are arranged relative to each other in such a way that each such fourth imaginary straight line S_ei2 that is parallel to a thickness t2oo of the first insulating layer 200 and penetrates a major region of the smaller one of the first primary electrode 301 and the first secondary electrode 401 , also penetrates the larger one of the first primary electrode 301 and the first secondary electrode 401 , wherein the cross sectional area of the major region of the smaller one of the first primary electrode 301 and the first secondary electrode 401 is at least 90 %, at least 95 %, or at least 98 %, of the cross sectional area of the smaller one of the first primary electrode 301 and the first secondary electrode 401. Preferably this applies to all electrodes subject to the substantially full overlap, as discussed above under“option B”

Because of the material selections and a reasonably thin layered structure, the sensor 900 is easily deformable. Therefore, the sensor is particularly suitable for use in a wearable item, such as garment. In an embodiment, the sensor 900 has such a shape, as seen from a direction of the thickness of the sensor 900, that the sensor 900 is suitable for use as an insole for footwear. In an embodiment, the sensor 900 has such a thickness that the sensor 900 is suitable for use as an insole for footwear. An example of such a use is a wearable item, such as a garment, comprising a sensor 900 as discussed above. The wearable item may be e.g. a shoe, an insole, or a sock. The wearable item may be e.g. a glove or a mitt, such as a boxing glove. A particularly feasible application is an insole 910 (see Fig. 1d) suitable for footwear, wherein the shape of the insole 910 is adapted to the shape of the footwear and the insole 910 comprises a sensor 900 as discussed above.

Figure 8a shows, as a top view similar to Fig. 1 c, a sensor 900. As shown in the figure, the shape is the sensor 900 is such that the sensor is suitable for use as an insole. Only the primary side 201 of the first insulating layer 200 is shown with the primary electrodes 300 and the primary wiring 350. The primary wiring 350 comprises wires 351 that are electrically coupled to the primary electrodes. The wires 351 are also coupled to a controller 500.

Referring to Fig. 8a, in an embodiment the primary wiring 350 comprises parts that are not electrically connected to any of the primary electrodes 300, of which capacitance is configured to be measured by the controller 500. These parts may be referred to e.g. as dummy wires or ground electrodes. Such parts can be used in two ways: either as dummy wires for compensating the capacitance caused by the wires 351 or as supplemental common potential electrodes, relative to which the capacitance of other electrodes can be measured. The parts that may serve as dummy wires are generally denoted by the reference number 352, and three such parts 352a, 352b and 352c are identified in Fig. 8a.

The shape of a dummy wire 352 is substantially similar to a shape of a wire 351 adjacent thereto. Moreover, the area of a dummy wire 352 is substantially equal to an area of a wire 351 adjacent thereto. As an example, the area of a dummy wire 352 is may differ from the area of a wire 351 adjacent thereto by at most 25 %. This has the effect that the capacitance of the dummy wire 352 is substantially the same as the capacitance of the wire 351 adjacent thereto. Therefore, the capacitance of the wire 351 can be compensated for in the measurements.

Referring to Fig. 8a, as an example, when measuring the capacitance of the electrode 301 , inevitably the total capacitance of the electrode 301 and the wire 351 a becomes measured. However, because of the size and shape of the dummy wire 352a, the capacitance of the dummy wire 352a is substantially the same as the capacitance of only the wire 351 a would be. Thus, the capacitance of the dummy wire 352a can be subtracted from the total capacitance of the electrode 301 and the wire 351 a to obtain the capacitance of only the electrode 301. Same principles can be applied when measuring the capacitance of the electrode 305, which is connected to the controller 500 by a wire 351 b, the wire 351 b being adjacent to a dummy wire 352b of the wiring, the dummy wire 352b having size and shape substantially the same as the wire 351 b. Moreover, same principles can be applied when measuring the capacitance of the electrode 309, which is connected to the controller 500 by a wire 351 c, the wire 351 c being adjacent to a dummy wire 352c of the wiring, the dummy wire 352c having size and shape substantially the same as the wire 351 c.

The width of the wires 351 a, 351 b, and 351 c in Fig. 8a have been drawn reasonably large to emphasize the problem related to the capacitance of the wires. The wires 351 may be made as narrow as practically possible. However, the line width is limited by manufacturing techniques, in particular when the first insulating layer 200 is stretchable and flexible, and also by the reliability of the sensor 900, which deforms multiple times in use.

Therefore, in an embodiment, the primary wiring 350 comprises dummy wires 352 that are not electrically connected to any primary electrode. As indicated above, the primary wiring 350 further comprises wires 351 electrically coupled to the primary electrodes 300. In particular, the primary wiring 350 comprises a wire 351 a electrically coupled to the first primary electrode 301. In a similar manner, in an embodiment, the secondary wiring 450 comprises dummy wires that are not electrically connected to any secondary electrode (not shown). In an embodiment, the controller 500 is configured to compensate for the capacitance of the wires 351 as indicated above. Therefore, in an embodiment, the controller 500 is configured to [i] measure the capacitance of the dummy wire 352a of the electrically conductive primary wiring 350, [ii] measure the total capacitance of the combination of the wire 351 and the first primary electrode 301 , and [iii] determine the capacitance of the first primary electrode 301 using the capacitance of the dummy wire 352a of the electrically conductive primary wiring 350 and the total capacitance of the combination of the wire 351 and the first primary electrode 301. Such a procedure further improves the accuracy of the measurements by said compensation. Such a wiring makes it possible to compensate for the capacitance of the wires 351.

Referring to Fig. 8b, in particular the reference numbers 313, 314, the sensor may further comprise primary supplemental common potential electrode (313 or 314) that overlaps with a secondary electrode 400. The primary supplemental common potential electrode (313 or 314) may fully overlap with a secondary electrode in the meaning discussed above.

Such primary supplemental common potential electrodes (313, 314) may be used as a part of common electrode during measurements. Therefore, such a primary supplemental common potential electrode (313, 314) be connected to a common potential G during measurements, in a manner similar to what has been discussed in connection with Figs. 7a and 7b. For example, a controller 500 may be configured to, at a first time t1 , connect the supplemental common potential electrode (313, 314) to a common potential G and measure the capacitance of at least a secondary electrode 400 relative to the common potential G, wherein the secondary electrode 400 overlaps with the supplemental common potential electrode (313, 314). At a second time t2, the controller 500 may be configured to disconnect the at least partially overlapping electrode (313, 314) from the common potential G. In the alternative, the supplemental common potential electrodes 313, 314 may be in electrical contact with the common potential at all times, at least when the first insulating layer 200 is also elastic (i.e. compressible). If the supplemental common potential electrodes 313, 314are in electrical contact with the common potential at all times, preferably the first insulating layer 200 comprises material from the material group B and the thickness of the first insulating layer 200 is at least 0.5 mm. This may apply also if the supplemental common potential electrodes 313, 314 are subsequently connected to and disconnected from the common potential.

In the Figures 1a, 1 b, 2a, 2b, 2c, 2f, 2g, 3a, 3b, 4a, 4b, and 5a to 5j, the second insulating layer 100 is drawn as a reasonably thick layer in order to indicate that in those figures, the second insulating layer 100 serves as an elastic and stretchable layer. Thus, in those figures, the second insulating layer 100 is configured to be compressed and deform under pressure in use.

However, it may be sufficient that only the first insulating layer 200 serves as an elastic and stretchable layer. Such embodiments are shown in Figs. 10a to 10c. Fig. 10a corresponds to the embodiment of Fig. 1 b, when the second insulating layer 100 is not compressed by at least 1 % in typical use. Thus, such layer may be referred to as a layer that is not elastic. Correspondingly, it may be made of a material of the material group A or C. For example, the second insulating layer 100 may be flexible without being elastic. Thus, the material of the second insulating layer 100 may be selected from material group A. The second insulating layer 100 may be rigid. Thus, the material of the second insulating layer 100 may be selected from material group C.

The embodiment of Fig. 10b is more preferable than the embodiment of Fig. 10a. The embodiment of Fig. 10b further comprises the first electrically conductive layer 510, as detailed above.

The embodiment of Fig. 10c is more preferable than the embodiment of Fig. 10c. The embodiment of Fig. 10c further comprises the second electrically conductive layer 520, as detailed above. The third insulating layer 210 may be elastic, as in the embodiment of Fig. 5b. Thus, the material of the third insulating layer 210 may be selected from material group B. The third insulating layer 210 may be flexible without being elastic, as in the embodiment of Fig. 4b when equipped with the second electrically conductive layer 520. Thus, the material of the third insulating layer 210 may be selected from material group A. The third insulating layer 210 may be rigid. Thus, the material of the third insulating layer 210 may be selected from material group C.

In particular, when the sensor is flexible, the flexibility allows for measurements of a pressure distribution with a high spatial accuracy, provided that a sufficient number of electrodes is used. The sensor is flexible, e.g. when each one of the insulating layer comprises material from the material group A or material group B. Conversely, if a rigid material from the material group C is used in at least one of the insulating layers, the rigidity of the material itself decreases the need for use of a large amount of electrodes. Thus, the solutions of the presented embodiments are particularly suitable for flexible and/or conformable sensors. The high number of individual electrodes may also improve the temporal accuracy, as indicated above.

Examples:

1. A sensor (900) suitable for use as a pressure and/or a force sensor, the sensor (900) comprising

- a first insulating layer (200) having a primary side (201 ) and a secondary side (202),

- on the primary side (201 ) of the first insulating layer (200)

• at least a first primary electrode (300, 301 ) and

• electrically conductive primary wiring (350) coupled to the first primary electrode (300, 301 ) with a first primary wire (351 a) comprised by the electrically conductive primary wiring (350),

- on the secondary side (202) of the first insulating layer (200)

• at least a first secondary electrode (400, 401 ) and

• electrically conductive secondary wiring (450) coupled to the first secondary electrode (400, 401 ) with a first secondary wire (451 a) electrically conductive secondary wiring (450), and

- a second insulating layer (100), wherein

- at least one of the first insulating layer (200) and the second insulating layer (100) is configured to be compressed under pressure.

2. The sensor (900) of the example 1 , comprising

- a second primary electrode (300, 302) arranged on the primary side (201 ) of the first insulating layer (200) and a distance apart from the first primary electrode (300, 301 ), and

- a second secondary electrode (400, 402) arranged on the secondary side (202) of the first insulating layer (200) and a distance apart from the first secondary electrode (400, 401 ), wherein

- the electrically conductive primary wiring (350) is coupled also to the second primary electrode (300, 302) with a second primary wire (351 b) comprised by the electrically conductive primary wiring (350), and - the electrically conductive secondary wiring (450) is coupled also to the second secondary electrode (400, 402) with a second secondary wire (451 a) electrically conductive secondary wiring (450).

3. The sensor (900) of example 1 or 2, wherein

- a total effective cross-sectional area (åA_ei,i) or the a cross-sectional area (åA_ei,i) of the primary electrode or primary electrodes (300, 301 , 302) and the secondary electrode or secondary electrodes (400, 401 , 402) is at least 75 % of the total cross-sectional area (A200) of the first insulating layer (200).

4. The sensor (900) of any of the examples 1 to 3, comprising

- at least one controller (500)

• attached to the first primary wire (351 a), the second primary wire (351 b), the first secondary wire (451 a), and the second secondary wire (451 b) and

• configured to measure capacitances from

o the whole area of the first primary electrode (301 ),

o the whole area of the second primary electrode (302), o the whole area of the first secondary electrode (401 ), o the whole area of the second secondary electrode (402).

5. The sensor (900) of the example 4, wherein the controller (500) is configured to

- at a first time (t1 ),

• connect the first primary electrode (300, 301 ) to a common potential (G) and

• measure the capacitance of at least the first secondary electrode (401 ) relative to the common potential (G), and

- at a second time (t2),

• connect the first secondary electrode (400, 401 ) to a common potential (G) and

• measure the capacitance of at least the first primary electrode (301 ) relative to the common potential (G).

6. The sensor (900) of any of the examples 1 to 5, wherein - the primary wiring (350) and/or the secondary wiring (450) comprises wires (351 , 451 ) of which width is at most 700 mΐti, at most 500 mΐti, or at most 200 mhh.

7. The sensor (900) of any of the examples 4 to 6, wherein

- the primary wiring (350) comprises a wire (351 , 351 a) coupled to the first primary electrode (300, 301 ),

- the electrically conductive primary wiring (350) comprises a part (352, 352a) that is not connected to any of the primary electrodes (300),

- the part (352, 352a) of the electrically conductive primary wiring (350) is located such and has such a shaped and size, that it can be used to compensate for the capacitance of the wire (351 , 351 a), and

- the controller (500) is configured to

• measure the capacitance of the part (352, 352a) of the electrically conductive primary wiring (350),

• measure the capacitance of the combination of the wire (350, 351 ) and the first primary electrode (300, 301 ), and

• determine the capacitance of the first primary electrode (300, 301 ) using the capacitance of the part (352, 352a) of the electrically conductive primary wiring (350) and the capacitance of the combination of the wire (351 , 351 a) and the first primary electrode (300, 301 );

in an embodiment,

- the primary wiring (350) and/or the secondary wiring (450) comprises wires (351 , 451 ) of which width is more than 200 mΐti or more than 500 mΐti;

8. The sensor (900) of any of the examples 1 to 6, wherein

- the primary and secondary wiring (350, 450) comprise only such wires (351 , 451 ), of which width is at most 700 mΐti, at most 500 mΐti, or at most 200 mΐti.

9. The sensor (900) of any of the examples 1 to 8, wherein

- the first insulating layer (200) is stretchable and/or

- the first insulating layer (200) is elastic.

10. The sensor (900) of any of the examples 1 to 9, wherein

- the first primary electrode (300, 301 ) is made of such material that is stretchable by at least 5 % without breaking and - the first secondary electrode (400, 401 ) is made of such material that is stretchable by at least 5 % without breaking.

11. The sensor (900) of any of the examples 1 to 10, wherein

- at least one of

• the first primary electrode (300, 301 ),

• the first secondary electrode (400, 401 ),

• the electrically conductive primary wiring (350), and

• the electrically conductive secondary wiring (450), and, if present also

• the second primary electrode (300, 302),

• the second secondary electrode (400, 402),

comprises electrically conductive particles, such as flakes or nanoparticles, attached to each other in an electrically conductive manner;

preferably

- the electrically conductive particles comprise at least one of carbon, copper, silver, and gold;

more preferably,

- the electrically conductive particles comprise carbon.

12. The sensor (900) of any of the examples 1 to 11 , wherein

- the first insulating layer (200) comprises at least one of polyester, polyimide, polyethylene naphthalate, polyethylene terephthalate, polyetheretherketone, polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel.

13. The sensor (900) of any of the examples 1 to 12, wherein

- the electrically conductive primary wiring (350) comprises parts (352, 352a, 352b), i.e. dummy wires (352, 352a, 352b), that are not connected to any of the primary electrodes (300).

14. The sensor (900) of the example 13, wherein

- at least one of the parts (352a) of the electrically conductive primary wiring (350) is located and shaped in such a way that is can be used to compensate for the capacitance of a wire (351 ) of the electrically conductive primary wiring (350).

15. The sensor (900) of any of the examples 1 to 14, comprising

- a third insulating layer (205, 210), wherein

[A]

- the first secondary electrode (400, 401 ) is arranged in between the first insulating layer (200) and the third insulating layer (210), OR

[B]

- a part of the third insulating layer (205) is left in between the first secondary electrode (400, 401 ) and the second insulating layer (100); for example

- at least a part of the third insulating layer (205) is left in between the first insulating layer (200) and the second insulating layer (100).

16. The sensor (900) of the example 15, wherein

- the third insulating layer (205, 210) comprises at least one of polyester, polyimide, polyethylene naphthalate, polyethylene terephthalate, poly- etheretherketone, polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile- butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel.

17. The sensor (900) of any of the examples 1 to 16, wherein

- the second insulating layer (100) is stretchable and/or elastic, whereby the second insulating layer (100) is configured to be compressed under pressure, and

- the first primary electrode (300, 301 ) is arranged in between the second insulating layer (100) and the first insulating layer (200).

18. The sensor (900) of any of the examples 1 to 17, wherein

- the first primary electrode (300, 301 ) and the first secondary electrode (400, 401 ) are arranged relative to each other in such a way that

- each third imaginary straight line (S_en ) that is parallel to a thickness (t2oo) of the first insulating layer (200) and penetrates the first primary electrode (300, 301 ) does not penetrate the first secondary electrode (400, 401 ). 19. The sensor (900) of any of the examples 1 to 18, wherein

- the electrically conductive primary wiring (350) and the first secondary electrode (400, 401 ) are arranged relative to each other in such a way that

[A]

- a first imaginary straight line (S_wi) that is parallel to a thickness (t2oo) of the first insulating layer (200) and penetrates the electrically conductive primary wiring (350) penetrates also the first secondary electrode (400, 401 ) and/or

[B]

- a second imaginary straight line (S_W2) that is parallel to a thickness (t2oo) of the first insulating layer (200) and penetrates the electrically conductive secondary wiring (450) penetrates also the first primary electrode (300, 301 ); whereby

- at least some of the electrically conductive primary wiring (350) or the electrically conductive secondary wiring (450) overlaps, in a direction of a thickness (t2oo) of the first insulating layer (200), the first secondary electrode (400, 401 ) or the first primary electrode (300, 301 ), respectively.

20. The sensor (900) of any of the examples 1 to 19, wherein

- the second insulating layer (100) comprises at least one of polyimide, poly- ethylene naphthalate, polyethylene terephthalate, polyetheretherketone, poly- urethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, poly- borodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene- butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, thermoplastic elastomeric gel, epoxy, and phenolic resin.

21. The sensor (900) of any of the examples 1 to 20, wherein

- a thickness (t) of the layer or layers (100, 200) that is/are configured to be compressed under pressure is at least 0.5 mm.

22. The sensor (900) of any of the examples 1 to 21 , wherein

- the layer or layers (100, 200) that is/are configured to be compressed under pressure comprise or comprises at least one of polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel. 23. The sensor (900) of any of the examples 1 to 22 comprising

- a first electrically conductive layer (510) such that

- the first electrically conductive layer (510) is left on a first side (101 ) of the first elastic and stretchable layer (100) and

- the first primary electrode (300, 301 ) and the first secondary electrode (400, 401 ) are left on a second, opposite, side (102) of the second insulating layer (100).

24. The sensor (900) of any of the examples 1 to 23 comprising

- a second elastic and stretchable layer (110), wherein

- the first secondary electrode (400, 401 ) is left in between the second elastic and stretchable layer (110) and the first insulating layer (200);

preferably

- at least a part of the first insulating layer (200), the first primary electrode (300, 301 ), at least a part of the electrically conductive primary wiring (350), the first secondary electrode (400, 401 ), and at least a part of the electrically conductive secondary wiring (450) are left in between the second elastic and stretchable layer (110) and the second insulating layer (100).

25. The sensor (900) of the example 23, wherein

- the layer or layers (100, 200) that is/are configured to be compressed under pressure has a second Young’s modulus (Y) that is less than 1 GPa and

- the second elastic and stretchable layer (110) has a third Young’s modulus (Y1 10) that is less than 1 GPa;

in an embodiment,

- the third Young’s modulus (Yno) is different from the second Young’s modulus (Y100);

preferably

- a ratio of the greater of the second and third Young’s moduli to the smaller of the second and third Young’s moduli, max(Y, Yno)/min(Y, Yno), is more than 2.

26. The sensor (900) of any of the examples 23 to 25 comprising

- a second electrically conductive layer (520) and a third insulating layer (110, 210) such that

- the second electrically conductive layer (520) is arranged on a first side (111 ) of the third insulating layer (110, 210) and - the first primary electrode (300, 301 ) and the first secondary electrode (400, 401 ) are arranged on a second, opposite, side (112) of the third insulating layer (110, 210);

optionally

- the third insulating layer (110, 210) forms the second elastic and stretchable layer (110).

27. The sensor (900) of any of the examples 1 to 25 comprising

- a second electrically conductive layer (520) such that

- the first secondary electrode (400, 401 ) is arranged in a direction of thickness of the first insulating layer (200) in between the second electrically conductive layer (520) and the first insulating layer (200).

28. The sensor of any of the examples 1 to 27, comprising

- a third insulating layer (210, 110), which optionally forms a second elastic and stretchable layer (110),

- a first electrically conductive layer (510), and

- a second electrically conductive layer (520) such that

- at least a part of the first insulating layer (200), the first primary electrode (300, 301 ), at least a part of the electrically conductive primary wiring (350), the first secondary electrode (400, 401 ), and at least a part of the electrically conductive secondary wiring (450) are left in between the third insulating layer (210, 110) and the second insulating layer (100), and

- at least a part of the third insulating layer (110) and at least a part of the second insulating layer (100) are left in between the first electrically conductive layer (510) and the second electrically conductive layer (520).

29. The sensor (900) of any of the examples 1 to 28, wherein

- the layer or the layers (100, 200) that is/are configured to be compressed under pressure comprise or comprises material of which yield strain is at least 10 per cent.

30. The sensor (900) of any of the examples 1 to 29, wherein

- a Young’s modulus (Y) of the layer or the layers (100, 200) that is/are configured to be compressed under pressure is at most 15 MPa or at most 5 MPa;

preferably, - the Young’s modulus (Y) of the layer or the layers (100, 200) that is/are configured to be compressed under pressure is from 0.05 MPa to 15 MPa; more preferably,

- the Young’s modulus (Y) of the layer or the layers (100, 200) that is/are configured to be compressed under pressure is from 0.2 MPa to 5 MPa.

31. The sensor (900) of any of the examples 1 to 30, wherein

- the sensor (900) has such a shape, as seen from a direction of the thickness of the sensor (900), that the sensor (900) is suitable for use as an insole for footwear.

32. A wearable item, such as a garment, comprising a sensor (900) of any of the examples 1 to 31. 33. The wearable item of example 32, the item being one of

- a shoe, an insole, or a sock, or

- a glove or a mitt, such as a boxing glove.

34. An insole (910) suitable for footwear, wherein

- the shape of the insole (910) is adapted to the shape of the footwear and

- the insole (910) comprises a sensor (900) of any of the examples 1 to 33.

Claims

- a second insulating layer (100),

- on the primary side (201 ) of the first insulating layer (200)

• a first primary electrode (300, 301 ),

• a second primary electrode (300, 302), and

• electrically conductive primary wiring (350) comprising a first primary wire (351 a) coupled to the first primary electrode (300, 301 ) and a second primary wire (351 b) coupled to the second primary electrode (300, 302), and

- on the secondary side (202) of the first insulating layer (200)

• a first secondary electrode (400, 401 ),

• a second secondary electrode (400, 402), and

• electrically conductive secondary wiring (450) comprising a first secondary wire (451 a) coupled to the first secondary electrode (400, 401 ) and a second secondary wire (451 b) coupled to the second secondary electrode (400, 402), the sensor (900) comprising

- at least one controller (500) that is

• configured to measure capacitances from

o the whole area of the first primary electrode (301 ),

o the whole area of the second primary electrode (302), o the whole area of the first secondary electrode (401 ), o the whole area of the second secondary electrode (402), wherein

- at least one of the first insulating layer (200) and the second insulating layer (100) is configured to be compressed and deform under pressure, and

- at least some of the electrically conductive primary wiring (350) or the electrically conductive secondary wiring (450) overlaps, in a direction of a thickness (t2oo) of the first insulating layer (200), the first secondary electrode (400, 401 ) or the first primary electrode (300, 301 ), respectively, wherein - a wire (351 a, 351 b, 451a, 451 b) connects only one electrode (300, 301 , 302, 400, 401 , 402) to the controller (500).

2. The sensor (900) of claim 1 comprising

- a first electrically conductive layer (510) such that

- the first electrically conductive layer (510) is left on a first side (101 ) of the second insulating layer (100) and

- the first primary electrode (300, 301 ) is left on a second, opposite, side (102) of the second insulating layer (100).

3. The sensor (900) of claim 1 or 2, wherein

- the material of the layer or layer (100, 200) that is/are configured to be compressed and deform under pressure has a Young’s modulus of at most 1 GPa;

preferably, the sensor (900) comprises

- an second elastic and stretchable layer (110) having a Young’s modulus of at most 1 GPa, wherein

- the first secondary electrode (400, 401 ) is left in between the second elastic and stretchable layer (110) and the first insulating layer (200).

4. The sensor (900) of the claims 2 or 3, comprising

- a second electrically conductive layer (520) such that

- the second electrically conductive layer (520) is arranged on a first side (111 ) of a third insulating layer (210, 110) and

- the first secondary electrode (400, 401 ) is arranged on a second, opposite, side (112) of the third insulating layer (210, 110);

optionally,

- the third insulating layer (210, 110) is configured to be compressed and deform under pressure.

5. The sensor of any of the claims 1 to 5, wherein

- the first primary wire (351a) and the second primary wire (351 b) overlap, in the direction of a thickness (t2oo) of the first insulating layer (200), with the first secondary electrode (401 ) and/or

- the first secondary wire (451a) and the second secondary wire (451 b) overlap, in the direction of a thickness (t2oo) of the first insulating layer (200), with the first primary electrode (301 ).

6. The sensor (900) of any of the claims 1 to 5, wherein

7. The sensor (900) of any of the claims 1 to 6, comprising

- a third insulating layer (205, 210), wherein

[A]

- the first secondary electrode (400, 401 ) is arranged in between the first insulating layer (200) and the third insulating layer (210) or

[B]

- a part of the third insulating layer (205) is left in between the first secondary electrode (400, 401 ) and the second insulating layer (100).

8. The sensor (900) of any of the claims 1 to 7, wherein

- a thickness (t, tioo_, t2oo) of the layer that is configured to be compressed and deform under pressure is at least 0.5 mm.

9. The sensor (900) of any of the claims 1 to 8, wherein

- the Young’s modulus (Y, Y100_, Y2oo) of the layer (100, 200) that is configured to be compressed and deform under pressure is at most 15 MPa or at most 5 MPa;

preferably,

- the Young’s modulus (Y, Y100_, Y200) of the layer that is configured to be compressed and deform under pressure is from 0.05 MPa to 15 MPa;

more preferably,

- the Young’s modulus (Y, Y100_, Y200) of the layer that is configured to be compressed and deform under pressure is from 0.2 MPa to 5 MPa.

10. The sensor (900) of any of the claims 1 to 9, wherein

- the layer (100, 200) that is configured to be compressed and deform under pressure comprises at least one of polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, and thermoplastic elastomeric gel;

optionally

- another insulating layer (200, 100, 110, 205, 210) comprises at least one of polyester, polyimide, polyethylene naphthalate, polyethylene terephthalate, polyetheretherketone, polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone, thermoplastic elastomeric gel, epoxy, and phenolic resin.

11. The sensor of any of the claims 1 to 10, wherein

- the primary electrodes (300) and the secondary electrodes (400) define such measurement areas (M,) that

- the cross sections of the measurement areas (M,) and the cross-section of the controller (500), in combination, cover at least 80 %, such as at least 90 %, of a cross-sectional area of the sensor (900).

12. The sensor of (900) of any of the claims 1 to 11 , further comprising

- on the primary side (201 ) of the first insulating layer (200), multiple other primary electrodes (300) and

- on the secondary side (202) of the first insulating layer (200), multiple other secondary electrodes (400), wherein

- the primary wiring (350) comprises multiple primary wires (351 ) separate from each other, each one of the multiple primary wires (351 ) connected to one of the multiple other primary electrodes (300) such that each one of the multiple other primary electrodes (300) is connected, by one of the primary wires (351 ) to the at least one controller (500), and

- the secondary wiring (450) comprises multiple secondary wires (451) separate from each other, each one of the multiple secondary wires (451 ) connected to one of the multiple other secondary electrodes (400) such that each one of the multiple other secondary electrodes (400) is connected, by one of the primary wires (451 ) to the at least one controller (500), wherein

- each one of the first primary electrode (300, 301 ), the second primary electrode (300, 302), the multiple other primary electrodes (300), the first secondary electrode (400, 401 ), the second secondary electrode (400, 402), the multiple other secondary electrodes (400) defines a measurement area (Mi), and

- the at least one controller (500) is configured to measure a capacitance from each measurement area (M,).

13. The sensor (900) of any of the claims 1 to 12, wherein the at least one controller (500) is configured to

- at a first time (t1 ),

• connect at least a part of the electrically conductive secondary wiring (450) to a common potential (G) and

• measure the capacitance of at least the first primary electrode (301 ) relative to the common potential (G) and

- at a second time (t2),

• connect at least a part of the electrically conductive primary wiring (350) to a common potential (G) and

• measure the capacitance of at least the first secondary electrode (401 ) relative to the common potential (G).

14. The sensor (900) of the claim 12 or 13, wherein

- the electrically conductive primary wiring (350) comprises a dummy wire (352, 352a) that is not connected to any of the primary electrodes (300), and

- the controller (500) is configured to

• measure the capacitance of the dummy wire (352, 352a) of the electrically conductive primary wiring (350),

• determine the capacitance of the first primary electrode (300, 301 ) using the capacitance of the dummy wire (352, 352a) of the electrically conductive primary wiring (350) and the capacitance of the combination of the wire (351 , 351 a) and the first primary electrode (300, 301 ).

15. A wearable item, such as a garment, such as an insole, comprising a sensor (900) of any of the claims 1 to 14.