WO2015158952A1

WO2015158952A1 - An apparatus and method for sensing

Info

Publication number: WO2015158952A1
Application number: PCT/FI2015/050112
Authority: WO
Inventors: Chris Bower; Mark Allen
Original assignee: Nokia Technologies Oy
Priority date: 2014-04-14
Filing date: 2015-02-26
Publication date: 2015-10-22
Also published as: GB2525174A; EP3132335A1; GB201406615D0

Abstract

An apparatus and method wherein the apparatus comprises: a capacitive touch arrangement comprising a plurality of drive lines and a plurality of sense lines wherein the capacitive touch arrangement is provided in a first layer; and a sensor wherein the sensor is positioned in a second layer and configured to be capacitively coupled to at least one drive line and at least one sense line such that an output signal from the sensor can be measured using the at least one drive line and the at least one sense line.

Description

TITLE

An Apparatus and Method for Sensing TECHNOLOGICAL FIELD

Examples of the present disclosure relate to an apparatus and method for sensing. In particular, they relate to an apparatus and method for sensing a plurality of different parameters.

BACKGROUND

Apparatus which enable different parameters to be sensed are known. For example an apparatus may comprise different sensors which may be configured to sense different parameters. For instance a first sensor may be configured to detect a touch input and a second sensor may be configured to detect another parameter such as a bending or other deformation of the apparatus.

It is useful to provide a simple apparatus comprising such sensors.

BRIEF SUMMARY

According to various, but not necessarily all, examples of the disclosure there may be provided an apparatus comprising: a capacitive touch arrangement comprising a plurality of drive lines and a plurality of sense lines wherein the capacitive touch arrangement is provided in a first layer; and a sensor wherein the sensor is positioned in a second layer and configured to be capacitively coupled to at least one drive line and at least one sense line such that an output signal from the sensor can be measured using the at least one drive line and the at least one sense line. In some examples the apparatus may be configured such that the output signal from the sensor is measured by applying an alternating voltage to a pair of drive lines and measuring the output voltage between a pair of sense lines. In some examples the apparatus may be configured to alternately provide a first input signal to enable capacitive touch inputs to be detected from the capacitive touch arrangement and a second input signal to enable the output signal from the sensor to be measured. In some examples the apparatus may comprise a plurality of sensors.

In some examples the plurality of sensors may be arranged as an array and capacitively coupled to drive and sense lines at different points in the array. In some examples the sensor may comprise a strain gauge.

In some examples the sensor may comprise a Wheatstone bridge arrangement.

In some examples the plurality of sense lines may be arranged orthogonally to the plurality of drive lines.

In some examples the apparatus may comprise a plurality of layers. In some examples the sensor enables the position of the neutral axis of the plurality of layers to be determined.

According to various, but not necessarily all, examples of the disclosure there may be provided an electronic device comprising an apparatus as described above.

According to various, but not necessarily all, examples of the disclosure there may be provided a method comprising: providing a capacitive touch arrangement comprising a plurality of drive lines and a plurality of sense lines wherein the capacitive touch arrangement is provided in a first layer; and providing a sensor wherein the sensor is positioned in a second layer and configured to be capacitively coupled to at least one drive line and at least one sense line such that an output signal from the sensor can be measured using the at least one drive line and at least one sense line.

In some examples the apparatus may be configured such that the output signal from the sensor is measured by applying an alternating voltage to a pair of drive lines and measuring the output voltage between a pair of sense lines. In some examples the apparatus may be configured to alternately provide a first input signal to enable capacitive touch inputs to be detected from the capacitive touch arrangement and a second input signal to enable the output signal from the sensor to be measured. In some examples the apparatus may comprise a plurality of sensors.

In some examples the sensor may comprise a Wheatstone bridge arrangement.

In some examples the apparatus may comprise a plurality of layers. The sensor may enable the position of the neutral axis of the plurality of layers to be determined. According to various, but not necessarily all, examples of the disclosure there may be provided a method comprising: providing a laminar structure comprising a plurality of flexible layers, wherein at least one of the layers comprises an adhesive; providing a strain gauge mounted on at least one of the layers; using the strain gauge to determine the position of the neutral axis of the laminar structure as the liquid adhesive is cured; and controlling the modulus of the liquid adhesive to control the position of the neutral axis.

In some examples the adhesive may comprise at least one of a liquid adhesive, a low modulus solid adhesive.

In some examples the modulus of the adhesive may be controlled by controlling the pattern of curing within the adhesive.

In some examples the modulus of the adhesive may be controlled by controlling the duration of the curing of the adhesive. In some examples the method may further comprise using the strain gauge to detect delamination of the laminar structure. In some examples the strain gauge may be used to detect delamination after the apparatus is complete.

In some examples the laminar structure may comprise electronic components. In some examples the method may comprise comprising controlling the position of the neutral axis so that sensitive electronic components are provided on the neutral axis. The laminar structure may comprise display components. The adhesive may comprise an optically clear adhesive. According to various, but not necessarily all, examples of the disclosure there may be provided an apparatus comprising: a laminar structure comprising a plurality of flexible layers, wherein at least one of the layers comprises an adhesive; a strain gauge mounted on at least one of the layers; and wherein the strain gauge is configured to enable the position of the neutral axis of the laminar structure to be determined as the adhesive is cured so that the modulus of the adhesive can be controlled to control the position of the neutral axis. In some examples the adhesive may comprise at least one of a liquid adhesive, a low modulus solid adhesive.

In some examples the modulus of the liquid adhesive may be controlled by controlling the duration of the curing of the liquid adhesive. In some examples the strain gauge may be configured to detect delamination of the laminar structure. The strain gauge may be configured to detect delamination after the apparatus is complete. In some examples the laminar structure may comprise electronic components. In some examples the sensitive electronic components may be provided on the neutral axis. The laminar structure may comprise display components. The liquid adhesive may comprise an optically clear adhesive.

According to various, but not necessarily all, examples of the disclosure there may be provided examples as claimed in the appended claims. BRIEF DESCRIPTION

For a better understanding of various examples that are useful for understanding the brief description, reference will now be made by way of example only to the accompanying drawings in which:

Fig. 1 illustrates an apparatus;

Figs. 2A and 2B illustrate a sensor and an apparatus;

Figs. 3A and 3B illustrate a capacitive touch arrangement and a sensor;

Fig. 4 illustrates a sensor;

Fig. 5 illustrates a method;

Fig. 6 illustrates another apparatus;

Fig. 7 illustrates strain measured using an apparatus such as the apparatus of Fig. Fig. 8 illustrates a method;

Fig. 9 illustrates strain measured using an apparatus such as the apparatus of Fig. 6; and

Fig. 10 illustrates strain measured using an apparatus such as the apparatus of Fig. 6.

DETAILED DESCRIPTION

The Figures illustrate an apparatus 1 comprising: a capacitive touch arrangement 3 comprising a plurality of drive lines 7 and a plurality of sense lines 9 wherein the capacitive touch arrangement 3 is provided in a first layer 15; and a sensor 5 wherein the sensor 5 is positioned in a second layer 17 and configured to be capacitively coupled to at least one drive line 7 and at least one sense line 9 such that an output signal from the sensor 5 can be measured using the at least one drive line 7 and the at least one sense line 9 .

This provides the technical effect of providing a simple apparatus 1 which can be used to sense different parameters. The capacitive touch arrangement 3 may be configured to detect inputs made by a user touching or bringing their finger close to the capacitive touch arrangement 3. The sensor 5 may be configured to detect any other parameter such as a bending or other deformation of the apparatus 1 . The same circuitry may be used to read the output signal from both the capacitive touch arrangement 3 and one or more sensors 5 which are capacitively coupled to the drive lines 7 and sense lines 9. This keeps the circuitry and wiring within the apparatus 1 to a minimum.

The apparatus 1 may be for sensing. In some examples the apparatus 1 may be for wireless communication. The Figures also illustrate providing a laminar structure 60 comprising a plurality of flexible layers 63 and 65 wherein at least one of the layers comprises a liquid adhesive 67; providing a strain gauge 69 mounted on at least one of the layers 63, 65; using the strain gauge 69 to determine the position of the neutral axis of the laminar structure 60 as the liquid adhesive 67 is cured; and controlling the modulus of the liquid adhesive 67 to control the position of the neutral axis. This provides the technical effect of enabling the position of the neutral axis to be controlled. This may be useful to ensure that any components which are sensitive to strain are located on or close to the neutral axis. This can minimize the damage caused to such components. The laminar structure 60 may be provided in an apparatus 61 . The apparatus 61 may be for displaying information. The apparatus 61 may be an electronic apparatus.

Fig. 1 schematically illustrates an example apparatus 1 according to examples of the disclosure. The apparatus 1 comprises a capacitive touch arrangement 3 and a sensor 5. In the example of Fig. 1 the capacitive touch arrangement 3 is provided within a first layer 15 and the sensor 5 may be provided within a second different layer 17. The apparatus 1 may provide a touch pad or a touch sensitive display. The apparatus 1 may be provided within a device such as an electronic device. The electronic device could be a mobile telephone, a tablet computer, a lap top, a computer, a television, a display, a camera, a gaming device or any other device which may comprise a touchpad and/or touch sensitive display.

In some examples the apparatus 1 may be integrated within a flexible device. The flexible device may comprise any device which is intended to be deformed in response to a force applied by a user or a force applied in response to a user input. In some examples the flexible device may comprise a wearable device such as a watch or headset or any other suitable type of apparatus. The capacitive touch arrangement 3 may comprise any means which may be configured to enable a touch input to be detected. A touch input may comprise a user touching the surface of the apparatus 1 with an object such as their finger or a stylus. In some examples the touch input may comprise a user bringing an object close to the surface of the apparatus 1 .

In the example of Fig. 1 the capacitive touch arrangement 3 comprises a plurality of drive lines 7 and a plurality of sense lines 9. The plurality of drive lines 7 and plurality of sense lines 9 may enable touch inputs to be detected. In some examples a touch input may be detected by providing current through the drive lines 7. The sense line 9 can then detect changes in electric charge when a user touches the apparatus 1 .

The plurality of drive lines 7 may be arranged to be orthogonal or substantially orthogonal to the plurality of sense lines 9. A dielectric or other insulating material may be provided between the drive lines 7 and sense lines 9 to prevent a short circuit between the lines.

The drive lines 7 and sense line 9 may comprise a plurality of electrodes 13. In some examples the electrodes 13 may be transparent. For example, where the apparatus 1 forms part of a display the electrodes 13 may be transparent to enable content displayed on the display to be visible through the electrodes 13.

The sensor 5 may comprise any means which may enable a parameter to be sensed. The sensor 5 may be arranged to be capacitively coupled to at least one drive line 7 and at least one sense line 9. This may enable the drive lines 7 and the sense lines 9 of the capacitive touch arrangement 3 to be used to obtain an output signal from the sensor 5. This may enable the drive lines 7 and sense lines 9 from the capacitive touch arrangement 3 to be used obtain to an output signal from both the capacitive touch arrangement 3 and one or more sensors 5. In the example of Fig. 1 only one sensor 5 has been illustrated. In other examples a plurality of sensors 5 may be provided. The plurality of sensors 5 may be arranged as an array. Each of the plurality of sensors 5 may be arranged to capacitively couple to different drive lines 7 and different sense lines 9.

The one or more sensors 5 may be provided on a substrate 1 1 . The substrate 1 1 could be a flexible substrate. The flexible substrate may enable the apparatus 1 to be bent or otherwise deformed. The substrate 1 1 may be for example, a flexible circuit board or any other suitable supporting structure.

The sensor 5 may be configured to have a variable impedance that varies in response to a sensed parameter. The sensed parameter could comprise any suitable parameter. The sensed parameter may comprise strain, temperature, light, humidity, chemicals or any other suitable parameter.

In some examples the sensor 5 may comprise a strain gauge. In some examples the strain gauge may comprise a Wheatstone bridge arrangement. The strain gauge may comprise any means which may enable deformation of the apparatus 1 to be detected. The deformation of the apparatus 1 could be part of a user input. For example the deformation may be caused by a user pressing the surface of the apparatus 1 or otherwise bending the apparatus 1 . In some examples the deformation detected by the strain gauge may be used to detect delamination or other failure of the apparatus 1 . For example repeated bending of an apparatus 1 may cause one or more of the layers of a laminar structure to separate from the other layers. In some examples the strain gauge may be configured to enable the position of the neutral axis of a plurality of layers to be determined.

It is to be appreciated that only features necessary for the understanding of the disclosure have been illustrated in Fig. 1 . Other examples of the disclosure may include other features. For instance a protective cover layer may be provided overlaying the capacitive touch arrangement 3 and a display may be provided underneath the capacitive touch arrangement 3. In the example of Fig. 1 the sensor 5 has been illustrated underneath the capacitive touch arrangement. In other examples the sensor 5 may be provided overlying the capacitive touch arrangement 3. In some examples the capacitive touch arrangement 3 may comprise a plurality of layers. In such examples the sensors 5 or a plurality of sensors may be provided between the plurality of layers of the capacitive touch arrangement 3. In such examples providing the sensors 5 between the plurality of layers of the capacitive touch arrangements 3 may enable the position of the neutral axis to be determined more accurately. Figs. 2A and 2B schematically illustrate a sensor 5 and an apparatus 1 which may be used in some examples of the disclosure.

Fig. 2A illustrates an example sensor 5 which may be used in some examples of the disclosure. The example sensor 5 of Fig. 2A comprises a Wheatstone bridge configuration. The Wheatstone bridge configuration comprises four impedance elements Zi , Z2, Z3 and Z₄. The voltage output V_out of the sensor 5 is zero when the bridge is balanced. The bridge is balanced when

One or more of the impedance elements Zi , Z2, Z3 and Z₄ within the sensor 5 may comprise a variable impedance. The variable impedance may be dependent upon a sensed parameter. For example, where the sensor 5 comprises a strain gauge the value of one or more of the impedances may be dependent upon the amount of strain caused by bending or other deformation within the apparatus 1 . In such examples the sensor 5 may comprise a length of wire which changes resistance as the apparatus 1 is deformed.

The value of the one or more variable impedance elements Zi , Z2, Z3 and Z₄ of the sensor may be obtained by applying an alternating voltage Vi_n as an input signal and measuring the output voltage V_out.

Fig. 2B schematically illustrates an example apparatus 1 in which the sensor 5 of Fig. 2A is capacitively coupled to a pair of drive lines 7A and 7B and a pair of sense lines 9A and 9B. In the example of Fig. 2A the two drive lines 7A and 7B are neighbouring drive lines 7 and the two sense lines 9A and 9B are neighbouring sense lines 9. In other examples there may be other drive lines 7 and sense lines 9 between the lines which are used to measure the sensors 5.

In the example of Fig. 2B the drive lines 7 are arranged to be orthogonal to the sense lines 9. The sensor 5 may be arranged so that the coupling capacitance C_s is the same between the sensor 5 and each of the drive lines 7 and sense lines 9. It is to be appreciated that in other examples the coupling capacitance C_s may be different for different parts of the sensor 5.

In the example of Fig. 2B the output signal from the sensor 5 may be obtained by applying an alternating voltage Vi_n between two drive lines 7A and 7B. This provides the input voltage to the Wheatstone bridge arrangement. The output of the sensor 5 may be obtained by measuring the alternating voltage V_out between the two sense lines 9A and 9B.

The frequency of the alternating input voltage Vin may be selected to enable precise measurements to be obtained. For instance, in some examples a high frequency may be used to reduce the value of the coupling reactance relative to the resistance of the sensor 5.

The drive lines 7 and sense lines 9 may also be used to detect touch inputs by measuring changes in the mutual capacitance between the drive lines 7 and sense lines 9. When a user touches the apparatus 1 , or brings an object close to the surface of the apparatus 1 , the object may absorb charge which produces a change in the capacitance between the drive lines 7 and the sense lines 9.

It is to be appreciated that the drive lines 7 and sense lines 9 from the capacitive touch arrangement 3 to be used obtain an output signal from both the capacitive touch arrangement 3 and one or more sensors 5. The drive lines 7 and sense lines 9 may be addressed differently depending upon whether they are being used to obtain an output signal from the capacitive touch arrangement 3 or the one or more sensors 5. In some examples the apparatus 1 may be configured to alternately provide a first input signal to enable capacitive touch inputs to be detected from the capacitive touch arrangement 3 and a second input signal to enable the output signal from the sensor 5 to be measured. In the example of Figs. 2A and 2B the first input signal may be a current provided to each of the drive lines 7 and the second input signal could be an alternating voltage provided between pairs of the drive lines 7. It is to be appreciated that other input signals could be used in other examples of the disclosure.

Figs. 3A and 3B schematically illustrate a capacitive touch arrangement 3 and sensor 5 according to examples of the disclosure. The capacitive touch arrangement 3 and sensor 5 may be provided in a laminar apparatus 1 such as a display. In some examples the sensor 5 may be provided underneath the capacitive touch arrangement 3. A display may be provided underneath the sensor 5. It is to be appreciated that the layers of the apparatus 1 may be arranged in a different order in other examples.

The capacitive touch arrangement 3 of Fig. 3A comprises a plurality of drive lines 7, a plurality of sense lines 9 and plurality of electrodes 13. The plurality of electrodes 13 may form at least part of the drive lines 7 and the sense lines 9. In the example of Fig. 3A the drive lines 7 extend horizontally and the sense lines 9 extend vertically. In the example of Fig. 3A the electrodes 13 which form the vertical sense lines 9 are galvanically connected to each other to form a continuous conductor for each sense line 9. The electrodes 13 may form a direct current path for the sense lines 9. The electrodes 13 which form the drive lines are connected to each other via interlinking bridges 33 to form a continuous conductor for each drive line 7. The electrodes 13 and interlinking bridges form a direct current path for the drive lines 7. Dielectric material 31 or any other suitable insulator may be provided to prevent short circuits between the drive lines 7 and the sense lines 9. The dielectric material 31 may be provided below the bridges 33. The drive lines 7 and sense lines 19 are arranged to enable a touch input to be detected by enabling a change in the mutual capacitance between drive lines 7 and sense lines 9 to be measured.

The plurality of electrodes 13 may comprise any conductive material. In some examples the electrodes 13 may comprise a transparent conductive material. In the example of Fig. 3A the electrodes 13 are arranged as interlocking diamonds. Other arrangements of the electrodes 13 may be used in other examples of the disclosure.

In Fig. 3A only two drive lines 7A and 7B and two sense lines 9A and 9B are illustrated. It is to be appreciated that any number of drive lines 7 and sense lines 9 may be used in implementations of the disclosure.

Fig. 3B illustrates an example sensor 5 which may be capacitively coupled to the capacitive touch arrangement 3 of Fig. 3A.

The sensor 5 comprises a Wheatstone bridge arrangement as described above in relation to Figs 2A and 2B. The example sensor 5 of Fig. 3B may be used to measure strain in an apparatus 1 . It is to be appreciated that other types of sensors 5 may be used to measure other parameters.

The Wheatstone bridge configuration comprises four impedance elements Zi , Z2, Z3 and Z₄. In the example of Fig. 3B two of the impedance elements Zi and Z2 are fixed. The two fixed impedance elements Zi and Z2 may have the same value Z₀. One of the impedance elements Z3 provides a reference strain gauge. The reference strain gauge may be arranged in a direction orthogonal to the applied strain. The final impedance element Z₄ may comprise an active strain gauge. The active strain gauge may be arranged in the same direction as the applied strain.

The sensor 5 also comprises a plurality of coupling electrodes 35. The plurality of coupling electrodes 35 may comprise any means which may be arranged to capacitively couple with the electrodes 13 of the capacitive touch arrangement 3. The impedance elements Zi , Z2, Z3 and Z₄ may be galvanically coupled to the coupling electrodes 35. In the example of Fig. 3B four coupling electrodes 35 are provided. It is to be appreciated that other numbers and arrangements of coupling electrodes 35 may be provided in other examples of the disclosure.

The coupling electrodes 35 may be positioned relative to the electrodes 13 of the capacitive touch arrangement 3 so as to provide a maximum overlap of the electrodes 13, 35. The drive lines 7 and sense lines 9 are indicated in Fig. 3B to indicate the relative position of drive lines 7and sense lines 9. It is to be appreciated that the drive lines 7 and sense lines 9 would be provided in a different layer. It can be seen that the coupling electrodes 35 may be positioned so that they are aligned or substantially aligned with the electrodes 13 of the capacitive touch arrangement 3. In the examples of Figs. 3A and 3B the coupling electrodes 35 have substantially the same shape as the electrodes 13 of the capacitive touch arrangement 3. This may optimize the overlap of the electrodes 13, 35 and provide for efficient capacitive coupling. The coupling electrodes 35 enable the sensor 5 to be capacitively coupled to the drive lines 7 and sense lines 9. In the example of Figs. 3A and 3B there might be no galvanic connection between the sensor 5 and the drive lines and sense lines 9. There might be no direct current path between the sensor 5 and the drive lines and sense lines 9.

The capacitive coupling between the electrodes 35, 13 may enable an input signal to be provided to the sensor 5 using the drive lines 7 and an output signal to be obtained from the sensor 5 using the sense lines 9. Fig. 4 illustrates a circuit which represents the sensor 5 and capacitive touch arrangement 3 of Figs. 3A and 3B. Corresponding references have been used for corresponding components. In the example of Fig. 4 the impedance elements Zs and Z₄ which comprise strain gauges comprise both resistive and inductive components. The resistive component of the reference strain gauge is given by RG. The resistive component of the active strain gauge is given by RG+ARG where ARG is the additional resistance caused by the strain applied to the apparatus 1 .

The coupling electrodes 35 and the electrodes 13 of the capacitive touch sensor arrangement form capacitors with capacitance C_S. In the example of Fig. 4 the coupling capacitance C_S is the same for each of the capacitors. It is to be appreciated that in other examples the coupling capacitance C_S may be different.

Fig. 5 illustrates a method. The method may be used to provide an apparatus 1 such as the apparatus 1 as described above with reference to Figs. 1 to 4.

At block 51 the method comprises providing a capacitive touch arrangement 3 comprising a plurality of drive lines 7 and a plurality of sense lines 9 wherein the capacitive touch arrangement 3 is provided in a first layer 15. At block 53 the method comprises providing a sensor 5 wherein the sensor 5 is positioned in a second layer 17. The sensor 5 may be configured to be capacitively coupled to at least one drive line 7 and at least one sense line 9 such that an output signal from the sensor 5 can be measured using the at least one drive line 7 and at least one sense line 9. The apparatus 1 described above may enable the drive lines 7 and sense lines 9 of a capacitive touch arrangement 3 to be used to enable an input signal to be provided to a sensor 5 and an output signal to be obtained from the sensor 5. This may enable one or more sensors 5 to be integrated into an apparatus such as a touch pad or touch display without requiring any additional circuitry.

In some examples the sensor may be arranged in an array. Each sensor within the array of sensors 5 could be arranged to be capacitively coupled to drive and sense lines at different points in the array. In some examples the array may comprise a plurality of sensors 5 coupled to each drive line 7 or drive line pair. The input signal maybe provided to each drive line 7 or drive line pair. The sensors 5 can be individually addressed by measuring each sense line 9 or sense line pair at a line. Once all of the sensors 5 coupled to a given drive line 7 or drive line pair have been addressed the input signal may be provided to the next drive line 7 or drive line pair. Again each pair of sense lines 9 is sequentially read-out to obtain the information from each sensor 5. The sensors 5 may enable a plurality of different parameters to be detected. For instance they may enable strain of the apparatus to be detected. This may be used to detect other type of user input such as a user pressing or deforming an apparatus. This may also be used to detect failure of an apparatus such as delamination of layers within a stack such as a display stack.

Fig. 6 schematically illustrates an example apparatus 61 according to another example of the disclosure.

The apparatus 61 of Fig. 6 may be any apparatus 61 which comprises a laminar structure 60. The laminar structure 60 comprises a plurality of layers 63, 65, 67. In the particular example of Fig. 6 three layers 63, 65, 67 are provided. It is to be appreciated that any number of layers may be provided in other examples of the disclosure. The example apparatus 61 may comprise any apparatus 61 which comprises a plurality of layers. One or more of the plurality of layers may comprise electronic components. In some examples the apparatus 61 may comprise a display. In such examples the plurality of layers within the apparatus 61 may comprise a display layer, a polarizer layer, colour filter array layer, a capacitive touch arrangement layer and a cover layer and any other suitable layers. In some examples the apparatus 61 may be flexible. In order for the apparatus 61 to be flexible the plurality of layers 63, 65, 67 may comprise flexible layers. The apparatus 61 may be flexible so that it can be bent or otherwise deformed by a force applied to a user. In some examples the apparatus may be flexible so that it can be bent, folded or otherwise deformed in response to a user input.

The apparatus 61 may also comprise means for coupling the respective layers together. The means for coupling the layers 63, 65 together may comprise an adhesive 67 such as a liquid adhesive 67 or low modulus solid adhesive 67.

In the example of Fig. 6 the apparatus 61 comprises a first layer 63 and a second layer 65. The first layer 63 and the second layer 65 are coupled together by an adhesive layer 67. In the example of Fig. 6 the first layer 63 and the second layer 65 may provide flexible substrates. One or more electronic components may be mounted on and/or integrated within the flexible substrates. The flexible substrates may comprise circuit boards and/or other electronic components. In some examples sensitive components may be mounted on the flexible substrates. The sensitive components may comprise any components which are likely to be damaged if exposed to stresses or strains. The sensitive components may comprise transistors, integrated circuits, microprocessors, custom application-specific integrated circuitry (ASICS) display components such as polarisers, colour filter arrays, liquid crystal layers or any other suitable components.

The first layer 63 and the second layer 65 may comprise any suitable material. Examples of materials which may be used to provide flexible substrates in example apparatus 61 comprise Polyethylene 2, 6-naphthalate (PEN), Polyethylene Terephthalate (PET), Polyimide (PI), Polycarbonate (PC), Polyethylene (PE), Polyurethane (PU), Polymethylmethacrylate ( PMMA), Polystyrene (PS), natural rubbers or synthetic rubbers such as, Polyisoprenes, Polybutadienes, Polychloraprenes, Polyisobutylenes, Nitrile Butadienes and Styrene Butadienes, saturated elastomeric materials such as, Polydimethylsiloxane (PDMS), Silicone rubbers, Fluorosilicone rubbers, Fluoroelastomers, Perfluoroelastomers, Ethylene Vinyl Acetate (EVA) Thermoplastic Elastomers such as Styrene Block copolymers, Thermoplastic polyolefins, Thermoplastic vulcanisates, Thermoplastic Polyurethane (TPU) Thermoplastic Copolyesters, Melt processable rubbers or any other suitable material. In some examples the flexible substrate may comprise a metal foil. The metal foil may comprise planarised metal foils on which components such as thin film transistors (TFTs), displays or other component can be created. In some examples one or more of the layers 63, 65 within the apparatus 61 may comprise flexible display layers. The flexible display layers may comprise any means which may be configured to display information or other content. The flexible display layers may comprise any suitable flexible displays such as Organic Light Emitting Diodes (OLED), Liquid Crystal (LCD), Polymer Dispersed Liquid Crystal (PDLC) or other reflective LCD displays, ElectroPhoretic (EP), Electroluminescent (EL), Electrowetting (EW) Electrochromic (EC), or other optical modulation effects such as Interference based on frustrated internal reflection or Fabry Perot cavities or any other suitable display. In some examples one or more the layers 63, 65 within the apparatus 61 may comprise a touch sensitive arrangement. The touch sensitive arrangement may comprise any means which may enable a touch input to be detected. A touch input may comprise a user touching the surface of the apparatus 61 with an object such as their finger. In other examples the touch input may comprise a user bringing an object close to the surface of the apparatus 61 .

The touch sensitive arrangement may use any suitable means to detect the user input. In some examples the touch sensitive arrangement may be comprised within a display layer. In other examples the touch sensitive arrangement may be provided as a separate layer to the display layer. The touch sensitive arrangement may use any suitable means such as resistive, optical or capacitive sensing to detect the user input. In examples where the touch sensitive arrangement uses resistive or capacitive sensing to detect the user input the touch sensitive arrangement may comprise conductive patterns created from transparent conducting metal oxides such as Indium Tin Oxide (ITO), Fluorine doped tin oxide (FTO), Aluminium doped zinc oxide (AlZnO), Poly(2,3- dihydrothieno-1 ,4-dioxin)-poly(styrenesulfonate )(PEDOT:PSS), Polypyrrole (Ppy), Silver nanowires, Carbon Nanotubes and Graphene based materials including composites thereof Graphene or any other suitable material.

The adhesive layer 67 may comprise any means which may be arranged between the first layer 63 and the second layer 65 to enable the two layers 63, 65 to be coupled together. In some examples the adhesive may comprise a liquid adhesive. In some examples the liquid adhesive may comprise a liquid optically clear adhesive (LOCA).

Examples of adhesives which may be suitable for use in implementations of the disclosure comprise acrylic, polyurethane, methyl methacrylate or silicone-based adhesives.

The adhesives may be cured using any suitable means such as ultraviolet radiation, thermal curing, chemical curing or any other suitable means. The curing of an adhesive may control the modulus of the adhesive. The curing may control the amount of cross linking between molecules within the adhesive.

Some adhesives may be cured by exposure to moisture. Such adhesives may comprise silicone-based LOCAs and may require exposure to a combination of moisture and ultraviolet radiation. Some adhesives may be cured using chemical curing. The chemical curing may comprise the addition of a chemical cross-linker. In some examples the chemical cross linker may be catalyzed by a metal. In other examples the chemical cross linker might not require the metal catalyst. The example apparatus 61 of Fig. 6 also comprises a strain gauge 69. The strain gauge 69 may comprise any means which enables a strain applied to the apparatus 61 to be measured. The strain gauge 69 may be integrated into a Wheatstone bridge arrangement as described above with respect to Figs. 1 to 5.

The strain gauge 69 may comprise any suitable strain gauge. In some examples the strain gauge may comprise an evaporated gold strain gauge, an inkjet printed strain gauge, a patterned ITO strain gauge or any other suitable type of strain gauge. In the example of Fig. 6 the strain gauge 69 is provided on the underside of the first layer 63. In other examples the strain gauge 69 may be provided at any other point within the laminar structure 60.

The strain gauge 69 may be configured to enable the position of the neutral axis of the apparatus 61 to be determined. The strain gauge 69 may be configured to enable the position of the neutral axis of the apparatus 61 to be determined as the adhesive is being cured. The modulus of the adhesive 67 may be controlled in response to measurements of the position of the neutral axis. This may enable the position of the neutral axis of the laminar structure 60 to be controlled.

Fig. 7 illustrates of plot of strain against time. To obtain the data in Fig. 7 an apparatus as illustrated in Fig. 6 was used.

In the example of Fig. 7 the first layer 63 and the second layer 65 comprised a layer of Polyethylene naphthalate (PEN). Both the first layer 63 and the second layer 65 were 125 μιτι thick.

A layer of liquid adhesive 67 was provided between the first and second layers 63, 65. In the example used to obtain the data for Fig. 7 the layer of liquid adhesive 67 comprises LOCA which was 100 μιτι thick. The laminar structure 60 was masked using a rectangular piece of adhesive Aluminium foil so that the LOCA was only cured using ultraviolet radiation at the edges of the sample. The majority of the LOCA which was positioned beneath the Aluminium foil remained uncured. The strain in the sample was measured whilst it was subjected to repeated 3 point bend testing with the strain gauge 69 positioned on the underside of the first layer 63 as illustrated in Fig. 6. The three points 71 were arranged as illustrated in Fig. 6. A force was applied as indicated by the arrow 70. A series of four bend/relax cycles separated by approximately 2 minutes was applied to the apparatus 61 . The results are shown in Fig. 7.

At t=0 the adhesive layer 67 is not cured. Before the adhesive 67 is cured the adhesive layer 67 is liquid and the first layer 63 and the second layer 65 are not bonded together. This allows the first layer 63 and the second layer 65 to move relative to each other. As the first layer 63 and the second layer 65 can move relative to each other each of them has their own neutral axis 73, 75. The neutral axis 73, 75 is the axis within the apparatus 61 which has no stresses or strains when the apparatus 61 is bent.

The neutral axis 73, 75 at time t=0 is indicated by the dotted lines in Fig. 6. At t=0 the strain gauge is subjected to positive (tensile) strain because the strain gauge 69 is positioned beneath the neutral axis of the first layer 63.

As time t increases the amount of curing of the adhesive 67 increases. This increases the amount of cross linking within the adhesive 67. This increases the modulus of the adhesive 67 which increases the coupling between the first layer 63 and the second layer 65.

As the adhesive is cured the first layer 63 and the second layer 65 gradually become bonded together and the neutral axis of the laminar structure 60 moves towards the centre of the laminar structure 60. As can be seen in Fig. 7, at t=2 min the strain gauge is still subjected to positive strain however the magnitude of the strain has decreased. At t=4min the strain gauge 69 is aligned with the neutral axis and experiences minimal strain. The axis then moves below the strain gauge 69 so that from t=6min to t=16min the strain become compressive (negative).

At t=16mins the adhesive layer 67 may be cured so that the neutral axis 77 is provided in the centre of the apparatus 61 as indicated by the dashed line 77.

Fig. 8 illustrates a method. The method may be used to control the position of a neutral axis in an apparatus such as the apparatus of Fig. 6. The method comprises, at block 81 , providing a laminar structure 60 comprising a plurality of flexible layers 63, 65, 67. At least one of the layers comprises an adhesive 67. The method also comprises, at block 83, providing a strain gauge 69 mounted on at least one of the layers 63, 65, 67. At block 85 the method comprises using the strain gauge 69 to determine the position of the neutral axis of the laminar structure 60 as the adhesive 67 is cured and at block 87 the method comprises controlling the modulus of the adhesive 67 to control the position of the neutral axis. The laminar structure 60 which is provided at block 81 may be provided within an apparatus 61 as described above.

The strain gauge 69 which is provided at block 83 may be provided so that it causes minimal displacement to other layers and components within the apparatus 61 . Any suitable method may be used to provide the strain gauge 69. For example an evaporated gold strain gauge may be fabricated using a shadow mask, photolithography or laser patterning steps or any other suitable means. The evaporated gold strain gauge may be provided as a serpentine trace or in any other suitable configuration. In examples where a shadow mask method is used the shadow mask may comprise a steel mask which may be placed over a layer 63, 65 of an apparatus 61 prior to evaporation of the gold. In some examples the thickness of the gold may be approximately 100nm. In other examples other thicknesses of gold may be used.

In examples where the strain gauge 69 comprises an inkjet printed strain gauge the strain gauges 69 may be directly patterned onto the layers 63, 65 of the apparatus 61 . The inkjet printed strain gauges 69 may comprise any suitable material such as silver nanoparticle ink, carbon based ink, conductive polymer ink, grapheme or carbon nano-tube based ink or any other suitable material. In other examples an ultra thin film strain gauge 69 may be transferred onto a display or other flexible layer 63, 65. In such examples the strain gauges 69 may also prefabricated on ultra thin substrates and transferred onto the display or other flexible layer 63, 65 using any suitable method. This may allow the strain gauges 69 to be made very small. In some examples this may allow the strain gauges 69 to be small enough so that they are not visible to the user of the apparatus 61 . Such examples may use using conventional photolithographic methods. In such examples the thickness of strain gauge may be kept below 10 μιτι.

The methods described above in relation to Figs. 6 and 7 may be used to enable the strain gauge 69 to be used to determine the position of the neutral axis of the laminar structure as the liquid adhesive is cured. If the strain gauge 69 measures minimal strain then it can be determined that the neutral axis is in line with, or substantially in line with, the strain gauge 69. If the strain gauge 69 measures a positive strain then it can be determined that the strain gauge 69 is positioned below the neutral axis. If the strain gauge 69 measures a negative strain then it can be determined that the strain gauge 69 is positioned above the neutral axis.

Any suitable methods may be used to control the modulus of stiffness of the liquid adhesive 67. By controlling the modulus of the liquid adhesive 67 this controls the coupling between the first layer 63 and the second layer 65. This enables the position of the neutral axis to be controlled. In some examples the modulus of the adhesive 67 may be controlled by creating different regions of different modulus of stiffness within the adhesive 67. The pattern of the different regions of different modulus of stiffness may be designed to enable the neutral axis of the laminar structure 60 to be located at a particular point within the laminar structure 60. In some examples it may enable the neutral axis of the laminar structure 60 to be aligned with sensitive components within the apparatus 61 .

In such examples an adhesive such as a LOCA is first spread to form a wet film of uniform thickness by using a thin film coating technique such as slot-die coating, bar-coating, rod-coating, knife coating or similar. The first layers 63 and the second layer 65 which are to be coupled together by the adhesive are then laminated together. The layers 63, 65 may be laminated together under vacuum to remove any unwanted air bubbles.

If the LOCA is cured by ultra violet exposure then the ultra violet exposure is performed through a shadow mask having the desired pattern. This causes some regions of the LOCA to receive a higher ultra violet exposure than other regions. The regions of the LOCA which receive higher ultra violet exposure are cross-linked to a greater degree than other regions. The regions of the LOCA which are more highly cross-linked have a higher stiffness modulus than regions which have lower cross-link density.

In other examples the LOCA may comprise a heat curing positive photoresist LOCA with a photo inhibitor within it. In such examples the regions of LOCA exposed to UV and heat cured will be photo softened, with respect to the unexposed regions. In such examples the crosslinker and base monomer may be combined with a photoinhibitor which may make them resistant to further curing. In some examples a shadow mask may be used to create different regions of different modulus of stiffness. The shadow mask may allow for a rapid, selective exposure of the entire sample. In other examples an ultra violet point source such as a ultra violet light emitting diode or laser may be used to selectively write to small regions of the LOCA. This method may control of the UV exposure in all regions of the adhesive. In other examples selective heat curing can be used in a similar way as ultra violet radiation curing to create regions of different stiffness. For instance silicone materials such as polydimethylsioxane (PDMS) can be cross-linked to different degrees depending upon the curing temperature. After lamination of the two substrates heat may be applied to selected areas of the adhesive 67. Heat may be applied to selected areas of the adhesive 67 using any suitable means such as an infra red heater and shadow mask, an infrared spot curing system, or a patterned heat transfer plate or any other suitable means. The patterned heat transfer plate may be particularly useful when the first layer 63 and the second layer 65 are not transparent to UV radiation.

In the case of moisture-curable silicone LOCAs, the substrate/substrates can be selectively patterned by printing water on the first layer 63 and/or the second layer 65 prior to coating the LOCA. Once laminated, ultraviolet curing will only cure the LOCA areas in contact with water. The water-patterning and LOCA coating steps can be sequentially repeated to obtain better water contact throughout the desired regions.

In some examples, transparent conducting routing may be patterned onto the substrate/substrates prior to coating the thermally curable LOCA. After lamination, electric current is driven through the conductors to generate local heating and hence localized curing of the LOCA.

Chemically cured LOCAs can also be selectively cured by patterned deposition of the cross-linking agent onto a uniform coating of the monomer material. For instance the monomer can be slot coated, or bar coated or applied by any other suitable means. The cross-linker can then be applied only in the desired locations by using a non-contact patterned deposition technique such as inkjet printing, spraying, stencil printing or any other suitable method. In this way the LOCA is selectively cured in certain regions which have a high cross-link density whilst other regions retain little or no cross-linking, creating regions of high and low modulus. In some instances this may create regions of solid material and regions of liquid material.

The example apparatus 61 and methods of Figs. 6 to 8 provide for a method of controlling the position of a neutral axis within a laminar structure 60. Such methods may be used during manufacture of an apparatus 61 such as a display to ensure that sensitive components which may be damaged by stresses and strains are located on or close to the neutral axis.

In some examples the apparatus 61 may also be used to detect delamination or other failures within a laminar structure 60 after the apparatus 61 has been manufactured. Fig. 9 illustrates of plot of strain against time for such an apparatus 61 . The strain may be measured using an apparatus such as the apparatus of Fig. 6 and a three point bending test as illustrated in Fig. 6.

To obtain the data of Fig. 9 a display stack using a flexible OLED (organic light emitting diode) display with a nano steel backing layer and a dummy touch screen was used. A gold strain gauge 69 was laminated directly on top of the display and used to measure strain as the apparatus 61 was repeatedly 3-point bend tested.

The data in Fig. 9 shows that the tensile strain in the layer immediately above the display increases over time for the three successive measurements. Each new measurement causes the initial strain value to return to zero. However the initial strain value is still seen to increase with time as the apparatus 61 is flexed during the 3-point bend test. The increase in the initial strain value may be caused by delamination of the nano steel backing layer. The delamination of the nano steel backing layer may cause a shift in the position of the neutral axis to a higher position in the stack. This causes the tensile strain above the display to increase. This may be due to incomplete curing of the adhesive in the shadow region on the back of the display.

Fig. 10 illustrates of plot of strain against time for another apparatus 61 . The apparatus 61 used to obtain the data for Fig. 10 may have the same structure as the apparatus 61 used to obtain the data for Fig. 9.

The strain data for Fig. 10 was obtained by attaching the apparatus to a fold tester with an adhesive tape. The measured strain is approximately an order of magnitude higher during the fold testing compared to the 3 point bend test data shown above. The data in Fig. 10 shows a similar pattern to the data in Fig. 9. The strain is seen to increase over time and clear evidence of delamination could be seen in the apparatus 61 over this timescale. Fig. 10 shows an initial decrease in the value of the strain over the first 100. The decrease in the value of the strain data over the first 100s may be due to delamination of the protective window above the dummy touch screen layer with the strain gauges. This may cause the neutral axis to move downwards through the apparatus 61 .

Fig. 10 then shows an increase in the strain over the next 200. The increase in the strain may be due to the delamination of the nano steel backing layer. The delamination of the nano steel backing layer may cause the neutral axis moving upwards in the stack.

This shows that the example apparatus 61 may also be used to detect movement of the neutral axis of the apparatus 61 during use of the apparatus 61 . The change in the strain measured by the strain gauge may provide an indication that the neutral axis has moved. The movement of the central axis may be due to delamination or other decoupling of layers within the laminar structure 60. In some examples it may be possible to use measurements from the strain gauge 69 to determine which of the layers 63, 65 have become decoupled. For example if the strain increases (becomes more positive) then this may indicate that layers 63, 65 above the strain gauge 69 have become decoupled. Conversely if the strain decreases (becomes more negative) then this may indicate that layers 63, 65 below the strain gauge 69 have become decoupled.

In this description the term coupled means operationally coupled and any number or combination of intervening elements can exist (including no intervening elements).

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

The term "comprise" is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use "comprise" with an exclusive meaning then it will be made clear in the context by referring to "comprising only one.." or by using "consisting".

In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term "example" or "for example" or "may" in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus "example", "for example" or "may" refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a subclass of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a features described with reference to one example but not with reference to another example, can where possible be used in that other example but does not necessarily have to be used in that other example.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

I/we claim:

Claims

1. An apparatus comprising:

a capacitive touch arrangement comprising a plurality of drive lines and a plurality of sense lines wherein the capacitive touch arrangement is provided in a first layer; and

a sensor wherein the sensor is positioned in a second layer and configured to be capacitively coupled to at least one drive line and at least one sense line such that an output signal from the sensor can be measured using the at least one drive line and the at least one sense line.

2. An apparatus as claimed in any preceding claim wherein the apparatus is configured such that the output signal from the sensor is measured by applying an alternating voltage to a pair of drive lines and measuring the output voltage between a pair of sense lines.

3. An apparatus as claimed in any preceding claim wherein the apparatus is configured to alternately provide a first input signal to enable capacitive touch inputs to be detected from the capacitive touch arrangement and a second input signal to enable the output signal from the sensor to be measured.

4. An apparatus as claimed in any preceding claim wherein the apparatus comprises a plurality of sensors.

5. An apparatus as claimed in claim 4 wherein the plurality of sensors are arranged as an array and capacitively coupled to drive and sense lines at different points in the array.

6. An apparatus as claimed in any preceding claim wherein the sensor comprises a strain gauge.

7. An apparatus as claimed in any preceding claim wherein the sensor comprises a Wheatstone bridge arrangement.

8. An apparatus as claimed in any preceding claim wherein the plurality of sense lines are arranged orthogonally to the plurality of drive lines.

9. An apparatus as claimed in any preceding claim wherein the apparatus comprises a plurality of layers.

10. An apparatus as claimed in claim 9 wherein the sensor enables the position of the neutral axis of the plurality of layers to be determined.

1 1 . An electronic device comprising an apparatus as claimed in any of claims 1 to 10.

12. A method comprising:

providing a capacitive touch arrangement comprising a plurality of drive lines and a plurality of sense lines wherein the capacitive touch arrangement is provided in a first layer; and

providing a sensor wherein the sensor is positioned in a second layer and configured to be capacitively coupled to at least one drive line and at least one sense line such that an output signal from the sensor can be measured using the at least one drive line and at least one sense line.

13. A method as claimed in claim 12 wherein the apparatus is configured such that the output signal from the sensor is measured by applying an alternating voltage to a pair of drive lines and measuring the output voltage between a pair of sense lines.

14. A method as claimed in any of claims 12 to 13 wherein the apparatus is configured to alternately provide a first input signal to enable capacitive touch inputs to be detected from the capacitive touch arrangement and a second input signal to enable the output signal from the sensor to be measured.

15. A method as claimed in any of claims 12 to 14 wherein the apparatus comprises a plurality of sensors.

16. A method as claimed in claim 15 wherein the plurality of sensors are arranged as an array and capacitively coupled to drive and sense lines at different points in the array.

17. A method as claimed in any of claims 12 to 16 wherein the sensor comprises a strain gauge.

18. A method as claimed in any of claims 12 to 17 wherein the sensor comprises a Wheatstone bridge arrangement.

19. A method as claimed in any of claims 12 to 18 wherein the plurality of sense lines are arranged orthogonally to the plurality of drive lines.

20. A method as claimed in any of claims 12 to 19 wherein the apparatus comprises a plurality of layers.

21 . A method as claimed in claim 20 wherein the sensor enables the position of the neutral axis of the plurality of layers to be determined.

22. A method comprising:

providing a laminar structure comprising a plurality of flexible layers, wherein at least one of the layers comprises an adhesive;

providing a strain gauge mounted on at least one of the layers;

using the strain gauge to determine the position of the neutral axis of the laminar structure as the liquid adhesive is cured; and controlling the modulus of the liquid adhesive to control the position of the neutral axis.

23. A method as claimed in claim 22 wherein the adhesive comprises at least one of a liquid adhesive, a low modulus solid adhesive.

24. A method as claimed in any of claims 22 to 23 wherein the modulus of the adhesive is controlled by controlling the pattern of curing within the adhesive.

25. A method as claimed in any of claims 22 to 24 wherein the modulus of the adhesive is controlled by controlling the duration of the curing of the adhesive.

26. A method as claimed in any of claims 22 to 25 further comprising using the strain gauge to detect delamination of the laminar structure.

27. A method as claimed in claim 26 wherein the strain gauge is used to detect delamination after the apparatus is complete.

28. A method as claimed in any of claims 22 to 27 wherein the laminar structure comprises electronic components.

29. A method as claimed in claim 28 comprising controlling the position of the neutral axis so that sensitive electronic components are provided on the neutral axis.

30. A method as claimed in any of claims 28 to 29 wherein the laminar structure comprises display components.

31 . A method as claimed in claim 30 wherein the adhesive comprises an optically clear adhesive.

32. An apparatus comprising: a laminar structure comprising a plurality of flexible layers, wherein at least one of the layers comprises an adhesive;

a strain gauge mounted on at least one of the layers; and

wherein the strain gauge is configured to enable the position of the neutral axis of the laminar structure to be determined as the adhesive is cured so that the modulus of the adhesive can be controlled to control the position of the neutral axis.

33. An apparatus as claimed in claim 32 wherein the adhesive comprises at least one of a liquid adhesive, a low modulus solid adhesive.

34. An apparatus as claimed in any of claims 32 to 33 wherein the modulus of the adhesive is controlled by controlling the pattern of curing within the adhesive.

35. An apparatus as claimed in any of claims 32 to 34 wherein the modulus of the liquid adhesive is controlled by controlling the duration of the curing of the liquid adhesive.

36. An apparatus as claimed in any of claims 32 to 35 wherein the strain gauge is configured to detect delamination of the laminar structure.

37. An apparatus as claimed in claim 36 wherein the strain gauge is configured to detect delamination after the apparatus is complete.

38. An apparatus as claimed in any of claims 32 to 33 wherein the laminar structure comprises electronic components.

39. An apparatus as claimed in claim 38 wherein sensitive electronic components are provided on the neutral axis.

40. An apparatus as claimed in any of claims 38 to 39 wherein the laminar structure comprises display components.

41 . An apparatus as claimed in claim 40 wherein the liquid adhesive comprises an optically clear adhesive.