Patent Description:
Capacitive touch sensors embedded in a fabric are known. For example, <CIT> discloses a fabric implementing a capacitive touch sensing comprising a plurality of electrically conductive wires, electrically insulated from each other, and arranged to form a grid.

Document <CIT> discloses a stretchable touchpad of the capacitive type including a stretchable textile fabric having a plurality of conductive elements incorporated therein.

The conductive elements are resistive strain gauges which form electrodes to detect a change of capacitance caused by a touch. Such document also discloses a method for operating a stretchable touchpad comprising the steps of measuring continuously a capacitance analog signal provided by a resistive strain gauge of the stretchable touchpad and comparing the measured capacitance signal with a threshold value in order to determine whether or not a touch has taken place. In the method, the threshold value is continuously adjusted as a function of the actual measurement of capacitance and as a function of the resistance of said resistive strain gauges which form the capacitor electrodes of said touchpad.

Document <CIT> discloses a capacitive touch sensor of the "self-capacitance" type. In particular, this document is directed to resolve the technical problem of phantom touches or "ghosts" that negatively affects the multi-touch detection. The device operates as follows. In nominal mode, the rows and the columns of a pad are scanned permanently and successively by an input voltage VIN at a first working frequency FMIN and a second so-called discrimination frequency FMAX.

The voltage VIN is generated by an electronic assembly.

Upon a touch by a finger and depending on the position of this touch, a certain capacitance is created between the point of contact and the ground, this capacitance being mainly linked by the resistance of rows and columns to a multiplexer.

This resistive and capacitive component provokes a variation of the total impedance Z of the system, and act on the output signal VOUT.

The signal VOUT is then demodulated by an electronic subsystem. The frequencies FMIN and FMAX are modulated and demodulated separately by means of two synchronous demodulators, which makes it possible to obtain, in a single measurement, the values of the capacitance C and of the resistance R, representative of the position of the touch.

Document <CIT> describes a touch sensor that has a support layer of an insulating material and a resistive layer applied to the support layer.

A resistive material is shaped according to an elongated pattern forming a sequence of touch positions, and has a single terminal coupled to a sense input of a detecting device An open end of the sequence opposite to the terminal end remains unconnected.

The detecting device detects an active resistance Rp between the single terminal and one of said touch positions that is touched by a user via a return capacitance Cu constituted by the user and a mass element coupled to the detecting device.

Each wire is connected to a controller configured to evaluate the capacitance value of each wire. The controller detects the position of a touch event by detecting which horizontal wire and which vertical wire is touched, by detecting changes in capacitance of each respective wire of the capacitive grid. The controller uses the intersection of the crossing wires that are touched to determine the position of the touch event on the capacitive grid, so that the position of the touch is determined as X, Y coordinates on the capacitive grid.

The capacitive grid can be embedded in a fabric by using the electrically conductive wires as weft yarns and warp yarns. However, each electrically conductive wire of the capacitive grid (vertical and horizontal wires) have to be electrically connected to a correspondent input port of a sensing circuit.

When the capacitive grid has a great number of electrically conductive wires (for example if a wide sensing area of the touch sensor is desired), the number of input ports of the sensing circuit may be great and the routing of the electrical connections between the capacitive grid and the sensing circuit may be very complex.

Also in the case of a touch sensor having electrically conductive wires arranged parallel along only one direction (e.g. in case of a swipe sensor), the number of electrically conductive wires may be great, making the routing of the electrical connections complex and expensive during the design and production steps of the touch sensor.

Document <CIT> discloses a textile fabric implementing a capacitive grid. The textile fabric comprising a first set of electrically conductive and externally isolated yarns separated by isolating textile yarns; a second set of non-isolated conductive yarns; a plurality of textile yarns interlacing the first and the second set of yarns, wherein part of the interlacing textile yarns are non-isolated conductive yarns in order to form an electrical grounding grid with the non-isolated conductive yarns of the second set of yarns and part of the interlacing textile yarns are isolating textile yarns.

An object of the present invention is to overcome the drawbacks of the prior art cited above and to provide a capacitive touch sensor having a wide sensing area and a simple routing of electrical connections.

A further object of the present invention is to provide an assembly comprising a detection device and a capacitive touch sensor and a relating method for detecting a touch event that allow to reduce the number of input ports necessary for the detection of the touch event irrespective of the sensing area size of the capacitive touch sensor. These and other objects are achieved by the present invention by an assembly comprising a detection device and a capacitive touch sensor according to claim <NUM>, an article comprising such a capacitive touch sensor according to claim <NUM>, and a method for detecting a touch event according claim <NUM>. Preferred aspects of the invention are recited in dependent claims.

In particular, according to the present invention, the capacitive touch sensor comprises a support layer and a plurality of sensing elongated elements coupled to the support layer.

The term "elongated element" means an element having a shape similar to a thread (i.e. a thread-like element). An example of elongated element is a yarn. In general, in an elongated element, two of the three dimensions are much lower than and generally negligible with respect to the third dimension. For example, an elongated element may have the shape of a strip having width and thickness negligible with respect to the length. Preferably, elongated elements have two of the three dimensions comparable between them and negligible with respect to the third dimension (ideally a line). For example, elongated elements may be wires, yarns, filaments or traces of material arranged along a linear path. In an elongated element one of the three dimensions, i.e. the length, is at least ten times greater than the other two dimensions, preferably at least twenty times, more preferably at least fifty times.

The sensing elongated elements comprise a first set of electrically resistive elongated elements electrically connected to a first common node configured to be electrically connected to a first input of a detection device.

The detection device is configured to provide an output signal comprising a first output value that is a function of the capacitance value of the first set of electrically resistive elongated elements.

For example, the support layer may be a flexible layer (for example a film or a non-woven fabric) having the sensing elongated elements coupled on its surface, or integrated therein. Other embodiments may provide that the support layer is a composite layer having the sensing elongated elements sandwiched between two layers of the composite layer. A preferred embodiment may provide that the support layer is a fabric (e.g. a non-woven fabric, or a fabric produced by weaving, knitting, crocheting, knotting, tatting, felting, or braiding).

According to an aspect of the present invention, the electrical resistance per unit of length of an electrically resistive elongated element is comprised between <NUM> kQ/m and <NUM> MΩ/m, preferably comprised between <NUM> kQ/m and <NUM> kQ/m.

Each electrically resistive elongated element has a capacitance value that changes when an object touches it (a parasitic capacitance of the object is coupled to the touched electrically resistive elongated element). The change in capacitance value of the electrically resistive elongated element is function of two main aspects: the parasitic capacitive coupling between the electrically resistive elongated element and the object touching it, and the location on which the touching event occurred along the length of the electrically resistive elongated element with respect to the read-out point (i.e. with respect to the point on which the electrically resistive elongated element is electrically connected to the detection device).

Basically, each electrically resistive elongated element can be represented with a lumped model of a capacitor in series with a resistor having a resistance value depending on the position of the touch event (i.e. the position on which the parasitic capacitance of the object is applied to the electrically resistive elongated element). Thanks to this aspect, a single common node can be used for evaluating the capacitance of a plurality of electrically resistive elongated elements arranged to define a sensing area within which a touch event can be detected. In other words, the electrically resistive elongated elements are arranged so that when a touch event occurred on the sensing area (e.g. an object or the finger of a user touches the sensing area), at least an electrically resistive elongated element is touched.

In particular, by connecting a plurality of electrically resistive elongated elements to a common node, an equivalent capacitance, substantially equal or proportional to the sum of the capacitance values of the electrically resistive elongated elements, may be evaluated. The capacitance value evaluated at the common node of the electrically resistive elongated elements provides an indication of the position of a touch event with respect to the position of the common node.

Some embodiments may provide that the detection device is configured to provide an output signal comprising a first output value that is the direct or indirect measurement of the capacitance of the first set of electrically resistive elongated elements. Thanks to this embodiment, the capacitive touch sensor can be for example employed as a swipe sensor for detecting the swipe direction of a touch event along the electrically resistive elongated elements with respect to the common node by means of a single input port of the detection device irrespectively of the sensing area size.

Some embodiments may provide that the plurality of sensing elongated elements comprises one or more electrically conductive elongated elements, electrically insulated from the electrically resistive elongated elements, and arranged at least partially within the sensing area defined by the electrically resistive elongated elements. The electrically conductive elongated elements are electrically connected to a reference common node configured to be electrically connected to a reference input of the detection device.

According to an aspect of the present invention, number and arrangement of the electrically conductive elongated elements is chosen so that when a touch event occurs on the sensing area defined by the electrically resistive elongated elements, at least one electrically conductive elongated element is touched.

The electrically conductive elongated elements are arranged to define an area overlapping the sensing area defined by the electrically resistive elongated elements. Each electrically conductive elongated element is coupled to a correspondent electrically resistive elongated element of the plurality of sensing elongated elements and vice versa.

According to an aspect of the present invention, the electrical resistance per unit of length of each electrically conductive elongated element is less than <NUM>Ω/m, preferably less than <NUM>Ω/m, more preferably less than or equal to about <NUM>Ω/m.

Preferably, the ratio between the values of electrical resistance per unit of length of the electrically resistive elongated elements and the electrically conductive elongated elements is in range of <NUM> to <NUM>, more preferably <NUM> to <NUM>.

For example, the electrical resistance per unit of length may be measured by following the standard AATCC Test Method <NUM>-<NUM> or AATCC Test Method <NUM>-<NUM>.

The output signal provided by the detection device comprises a reference output value that is the direct or indirect measurement of the capacitance of the electrically conductive elongated elements.

Each electrically conductive elongated element has a capacitance value that changes in response to a touch event; said change in value is substantially independent from the location on which the touching event occurred along its length.

When an object touches an electrically conductive elongated element, the change in capacitance value depends substantially only from the capacitive coupling between the electrically conductive elongated element and the object touching it.

Thanks to this aspect, the capacitance value of the electrically conductive elongated elements may be used, together with the capacitance value of the electrically resistive elongated elements, to obtain an indication of the position of a touch event on the sensing area substantially independent from the capacitive coupling between the electrically resistive elongated elements and the object touching them.

The reference output value can be used to calculate the ratio between the direct or indirect measurement of the capacitance of the first set of electrically resistive elongated elements and the direct or indirect measurement of the capacitance of the electrically conductive elongated elements.

The first output value of the output signal provided by the detection device is the ratio between the direct or indirect measurement of the capacitance of the first set of electrically resistive elongated elements and the direct or indirect measurement of the capacitance of the electrically conductive elongated elements.

As a result, by means of only two input ports of the detection device, the capacitive touch sensor can be employed for detecting the location of a touch event along the electrically resistive elongated elements with respect to the common node independently from the capacitive coupling between the resistive elongated elements and the object touching them.

The plurality of electrically resistive elongated elements comprises a second set of electrically resistive elongated elements, electrically insulated from the first set of electrically resistive elongated elements, and electrically connected to a second common node configured to be electrically connected to a second input of the detection device.

In particular, the first set and the second set of electrically resistive elongated elements overlap to form a grid of electrically resistive elongated elements. According to this embodiment, the output signal comprises a second output value that is a function of the capacitance value of the second set of electrically resistive elongated elements. The second output value is the direct or indirect measurement of the capacitance of the second set of electrically resistive elongated elements.

Sensing elongated elements comprise one or more electrically conductive elongated elements and that the second output value is the ratio between the direct or indirect measurement of the capacitance of the second set of electrically resistive elongated elements and the direct or indirect measurement of the capacitance of the electrically conductive elongated elements.

According to an aspect of the present invention, the electrically resistive elongated elements of the first set are arranged parallel to each other along a first direction. Preferably, the electrically resistive elongated elements of the second set are arranged parallel to each other along a second direction substantially orthogonal to the first direction.

Some embodiments of the present invention may provide that the detection device is connected to a communication module configured to transmit the output signal to an external device (e.g. a smartphone, a smart TV, or other similar devices).

According to an aspect of the present invention, the elongated sensing elements are sensing yarns.

Some embodiments may provide that the electrically resistive elongated elements are electrically resistive yarns.

Some embodiments may provide that the electrically conductive elongated elements are electrically conductive yarns.

Preferably, the support layer is a fabric, more preferably a woven fabric.

According to an aspect of the present invention, the support layer is a woven fabric, and the sensing elongated elements form at least a part of the weft and/or of the warp of the woven fabric.

A further object of the present invention is an article comprising the capacitive touch sensor according to the present invention. The article may be for example a garment. Preferably, the article comprises the detection device for evaluating the capacitance values of the sensing yarns.

A further object of the present invention is a method for detecting a touch event on a support layer comprising the following steps:.

According to an aspect of the present invention, the support layer is a fabric and the sensing elongated elements are sensing yarns.

Some embodiments may provide that the method according to the present invention comprises a step of transmitting the output signal to an external device.

The invention will now be described in greater detail, by way of example, with reference to the accompanying non limiting drawings. It is emphasized that, according to common practice, the various features of the drawing are not necessarily to scale. Like numerals denote like features throughout the specification and the drawings in which:.

<FIG> show exemplary embodiments of a capacitive touch sensor <NUM> according to the present invention. The capacitive touch sensor <NUM> comprises a support layer <NUM> and a plurality of sensing elongated elements <NUM> coupled to the support layer <NUM>.

For the sake of simplicity, the following description of a touch sensor <NUM> according to the exemplary embodiments of the present invention shown in <FIG> refers to sensing yarns <NUM>, however the teaching of the description can be applied to a touch sensor having generic elongated elements in the place of yarns.

With respect to <FIG>, sensing yarns <NUM> comprise a first set 2rx of electrically resistive yarns 2r electrically connected to a first common node Nx (symbolically indicated as a dotted rectangle) configured to be electrically connected to a first input INx of a detection device <NUM>.

A common node may be constituted by connections having ideally zero resistance (for example a common node may be provided by an electrically conductive yarn).

The detection device <NUM> is configured to provide an output signal S_OUT comprising a first output value OUTx that is a function of the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r.

The electrically resistive yarns 2r have an electrical resistance per unit of length Rr comprised between <NUM> kΩ/m and <NUM> MS2/m, more preferably comprised between <NUM> kQ/m and <NUM> kQ/m, for example about <NUM> kQ/m. In other words, the cross section and the electrical resistivity of the electrically resistive yarns 2r are chosen to obtain a meter of electrically resistive yarn 2r having an electrical resistance comprised between <NUM> kS2 and <NUM> MS2, more preferably comprised between <NUM> kS2 and <NUM> kQ, for example about <NUM> kQ.

For example, the electrically resistive yarns 2r have electrical resistivity comprised between <NUM>-<NUM> S2m and <NUM><NUM> S2m, more preferably between <NUM>-<NUM> S2m and <NUM>-<NUM> S2m.

The electrically resistive yarns 2r are preferably plastic yarns (e.g. nylon) filled with electrically conductive elements (e.g. electrically conductive carbon). More preferably, the electrically resistive yarns 2r may comprise <NUM>-denier nylon <NUM>,<NUM> having electrically conductive carbon suffused into its surface.

For example, a suitable electrically resistive yarn 2r may be the electrically resistive yarn available with the commercial name RESISTAT© F901, MERGE R080 that is a <NUM>-denier nylon <NUM>,<NUM> monofilament which has electrically conductive carbon suffused into the surface. This particular resistive yarn has a round cross section with a coating thickness of about <NUM>, and a linear mass density of about <NUM> denier. The electrical resistance of this resistive yarn is about <NUM>×<NUM><NUM> S2 per centimeter (i.e. about <NUM> MS2/m). Even if the embodiment shown in <FIG> shows a first set 2rx of electrically resistive yarns 2r arranged parallel to each other, other embodiments may provide different arrangements of the electrically resistive yarns still remaining within the scope of protection of the present invention. For example, some embodiments may provide that the electrically resistive yarns 2r of the first set 2rx are arranged radially with respect to a central point. These embodiments may provide that the end facing to the central point of each electrically resistive yarn is electrically connected to the first common node Nx, or that the opposite end to the central point of each electrically resistive yarn is electrically connected to the first common node Nx.

With respect to <FIG>, the electrically resistive yarns 2r of the first set 2rx are preferably arranged parallel to each other along a first direction X. This embodiment provides that the capacitive touch sensor <NUM> implements a one-dimensional swipe sensor (i.e. a capacitive touch sensor able to detect the swipe direction of a touch event along at the first direction X).

According to this embodiment, the first output value OUTx of the output signal is the direct or indirect measurement of the capacitance CRx of the first set 2rx of electrically resistive yarns 2r.

The capacitance value CRx may be evaluated for example by measuring the charging time, or the oscillation frequency of an oscillator, or by other measuring techniques known in the art.

Some embodiments may provide that the detection device <NUM> comprises a front-end circuit 5a and that the first input INx is the input of the front-end circuit 5a. For example, the front-end circuit 5a may comprise at least one oscillator (e.g. a Colpitts oscillator). The first common node Nx of the electrically resistive yarns 2rx is connected to the oscillator that has (in absence of a touch event) a predetermined oscillation frequency.

A change of the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r is detected as a change of the oscillation frequency of the oscillator. In other words, by evaluating the oscillation frequency of the oscillator, the capacitance value CRx of the electrically resistive yarns 2rx can be evaluated.

Preferably, the detection device <NUM> comprises a microcontroller 5b connected to the front-end circuit 5a, and configured to calculate the capacitance values CRx of the first set 2rx of electrically resistive yarns 2r on the basis of the oscillation frequency of the oscillator.

Some embodiments may provide that the detection device <NUM> comprises a front-end circuit 5a and a microcontroller 5b that sends a forward signal (e.g. a Boolean signal) to a forward terminal of the front-end circuit 5a. The front-end circuit 5a comprises a returning terminal that provide a return signal with a delay with respect to the forward signal. The delay between the forward signal and the return signal is a function of the charging time of the electrically resistive yarns 2rx that is in turn a function of the capacitance value CRx of the electrically resistive yarns.

As explained above, a change in the capacitance value CRx of the electrically resistive yarns 2rx is indicative of a touch event occurred on one or more electrically resistive yarns 2rx. Assuming that the touch area size of a touch event is substantially constant (i.e. the number of touched electrically resistive yarns 2rx remain constant during a touch event), the first output value OUTx is indicative of the swipe direction of a touch event along the first direction X.

In particular, the detection device <NUM> is configured to provide an output signal S_OUT comprising a first output value OUTx that is the measurement of the capacitance value CRx of the electrically resistive yarns 2rx preferably updated with a predetermined cadency having a refresh period (e.g. some milliseconds) during which the capacitance value CRx is reevaluated for updating the output value OUTx.

When the first output value OUTx overcome a determined threshold value means that a touch event occurred. In particular, as long as the first output value is greater than the threshold value, an increase over time of the first output value OUTx means that a touch event occurred with a swipe direction towards the common node Nx. Analogously, the decrease of the first output value OUTx means that the swipe direction of a touch event occurred toward the opposite direction, i.e. away from the common node Nx.

Thanks to the capacitive touch sensor <NUM> according to the present invention, only a single input INx is necessary for implementing a unidimensional swipe sensor. The sensing area <NUM> defined by the electrically resistive yarns 2rx can be increased (increasing the number and/or the length of the electrically resistive yarns) without the need of increasing the number of input ports of the detection device <NUM>.

<FIG> shows a further embodiment of a capacitive touch sensor <NUM> according to the present invention. The capacitive touch sensor <NUM> shown in <FIG> comprises the same first set 2rx of electrically resistive yarns 2r of the embodiment shown in <FIG>. The sensing area <NUM> defined by the electrically resistive yarns 2r is symbolically indicated as a dotted rectangle.

With respect to <FIG>, sensing yarns <NUM> further comprise a plurality of electrically conductive yarns 2c arranged at least partially within the sensing area <NUM> and electrically insulated from the electrically resistive yarns 2r.

The electrically conductive yarns 2c are electrically connected to a reference common node Nc configured to be electrically connected to a reference input INc of the detection device <NUM> for evaluating the capacitance value Cc of the electrically conductive yarns 2c.

The detection device <NUM> is configured to evaluate the capacitance value Cc of the electrically conductive yarns 2c by means of the same techniques above discussed for the evaluation of the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r.

Even if the embodiment of <FIG> shows a capacitive touch sensor <NUM> having a plurality of electrically conductive yarns 2c, further embodiment may provide that sensing yarns <NUM> comprise only one electrically conductive yarn 2c arranged at least partially within the sensing area <NUM> and electrically connected to the reference common node Nc. Preferably, the electrically conductive yarn 2c is arranged to define an area overlapping the sensing area <NUM> defined by the electrically resistive yarns 2r. For example a single electrically conductive yarn 2c may be arranged along a snake-shaped path so that the area defined by the electrically conductive yarn overlaps the sensing area <NUM>.

In general, sensing yarns <NUM> comprise at least one electrically conductive yarn 2c. In particular, some embodiments may provide that the number of electrically conductive yarns 2c is different from the number of the electrically resistive yarns 2r. According to an aspect of the present invention, number and arrangement of the electrically conductive yarns 2c is chosen so that when a touch event occurs on the sensing area <NUM> defined by the electrically resistive yarns 2r, at least one electrically conductive yarn 2c is touched.

With respect to <FIG>, each electrically conductive yarn 2c is associated to a correspondent electrically resistive yarn 2r and vice versa. In other words, the embodiment shown in <FIG> provides that the number of electrically conductive yarns 2c is equal to the number of electrically resistive yarns 2r and that for each electrically resistive yarn 2r an electrically conductive yarn 2c is associated thereto. The electrically conductive yarns 2c are electrically insulated from the electrically resistive yarns 2r, for example by an electrically insulating coating provided on the surface of the electrically conductive yarns 2c.

The electrically conductive yarns 2c are preferably insulated metal wires, for example magnet wires. A magnet wire, also called "enameled wire" is a metal wire (for example made of copper or aluminum) coated with a very thin layer of insulation. Magnet wires are commercially available and are typically used in the construction of transformers, inductors, motors, speakers, hard disk head actuators, electromagnets, and other applications that require tight coils of insulated wire.

The electrically conductive yarns 2c has an electrical resistance per unit of length Rc less than <NUM>Ω/m, more preferably less than <NUM>Ω/m, for example about <NUM>Ω/m. In other words, the cross section and the electrical resistivity of the electrically conductive yarns 2c are chosen to obtain a meter of electrically conductive yarn 2c having an electrical resistance less than <NUM>Ω, more preferably less than <NUM>Ω, for example about <NUM>Ω.

For example, the electrically conductive yarns 2c may be made of a material having electrical resistivity less than <NUM>-<NUM> Ωm, more preferably less than <NUM>-<NUM> Ωm (e.g. silver, copper, gold, aluminum, platinum, iron may be suitable materials for the electrically conductive yarns 2c).

According to an aspect of the present invention, the electrical resistance per unit of length of the electrically conductive yarns 2c is at least two order of magnitude less than the electrical resistance per unit of length of the electrically resistive yarns 2r.

Preferably, the ratio Rr/Rc between the values of electrical resistance per unit of length of the electrically resistive yarns 2r and the electrically conductive yarns 2c is in range of <NUM> to <NUM>, more preferably <NUM> to <NUM>.

With respect to <FIG>, some embodiments may provide that the output signal S_OUT comprises a reference output value OUTc that is the direct or indirect measurement of the capacitance value Cc of the electrically conductive yarns 2c. In other words, these embodiments may provide that the output signal S_OUT comprises a couple of output values (the first output value OUTx and the reference output value OUTc) that are the measurement of the capacitance value CRx and Cc of the electrically resistive yarns 2rx and of the electrically conductive yarns 2c, preferably updated with a predetermined cadency having a refresh period (e.g. some milliseconds) during which the capacitance values CRx and Cc are reevaluated for updating the output values OUTx and OUTc.

The reference output value OUTc can be used to calculate the ratio CRx/Cc between the direct or indirect measurement of the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r and the direct or indirect measurement of the capacitance value Cc of the electrically conductive yarns 2c.

Some embodiments may provide that the detection device <NUM> is configured to calculate (for example by means of the microcontroller 5b) the ratio CRx/Cc between the direct or indirect measurement of the capacitance CRx of the first set 2rx of electrically resistive yarns 2r and the direct or indirect measurement of the capacitance Cc of the electrically conductive yarn 2c. In these embodiments, the first output value OUTx may be preferably the ratio CRx/Cc. More preferably, the detection device <NUM> may be configured to provide an output signal S_OUT comprising only the first output value OUTx.

In these embodiments, the detection device <NUM> is preferably configured to provide an output signal S_OUT comprising a first output value OUTx that is the ratio CRx/Cc between the measurements of the capacitance value CRx of the electrically resistive yarns 2rx and the capacitance value Cc of the electrically conductive yarns 2c, preferably updated with a predetermined cadency having a refresh period (e.g. some milliseconds) during which the capacitance values CRx and Cc is reevaluated to recalculate the ratio CRx/Cc for updating the output value OUTx.

As a result, the capacitive touch sensor <NUM> may be employed for detecting the location (in addition to the swipe direction) of a touch event along the first direction X with respect to the first common node Nx.

As explained above, the change in the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r is function of two main aspects: the parasitic capacitive coupling between the electrically resistive yarn 2rx and the object touching it, and the location on which the touching event occurred along the length of the electrically resistive yarns with respect to the common node Nx. Moreover, the change in the capacitance value Cc depends substantially only from the capacitive coupling between the electrically conductive yarns and the object touching them, i.e. the change in value of Cc is substantially independent from the location on which the touching event occurred along the length of the electrically conductive yarns 2c.

As a result, when an object touches the sensing area <NUM>, a change in value of capacitance CRx and Cc occurs. The value of the ratio CRx/Cc is indicative of the location of a touch event along the first direction X with a negligible dependency of the capacitive coupling between the electrically resistive yarns 2rx and the object touching them. In other words, the value of the ratio CRx/Cc is indicative of the location of a touch event along the first direction X with respect to the position of the common node Nx irrespectively of how strong is the capacitive coupling between the electrically resistive yarns and the object touching them.

Thus, when a touch event occurs on the sensing area <NUM> the ratio CRx/Cc overcomes a determined threshold value and assumes a value within a determined range comprised between a lower and a upper values. Such lower value and upper value can be considered as two points in a one-dimensional space arranged parallel to the first direction X. For example, the lower value can be considered as the origin of the one-dimensional space.

If the ratio CRx/Cc assumes the upper value means that the touch event occurred at the end of the electrically resistive yarns 2rx electrically connected to the common node Nx. Analogously, the lower value of the ratio CRx/Cc indicates that the touch event occurred at the opposite end of the electrically resistive yarns 2rx.

The value of the ratio CRx/Cc can be used to obtain the swipe direction of a touch event occurred on the sensing area <NUM> along the first X direction, without giving information about what electrically resistive yarn 2rx was touched. In other words, the value of the ratio CRx/Cc does not change if a touch event swipes along a second direction Y orthogonal to the first direction X.

Some embodiments may provide that a plurality of sub-ranges comprised between the lower and the upper values of the ratio CRx/Cc can be defined, so that different regions of the sensing area <NUM> can be used for detecting the swipe direction of a touch event. <FIG> shows a further embodiment of a capacitive touch sensor <NUM> according to the present invention. The capacitive touch sensor <NUM> shown in <FIG> comprises the same first set 2rx of electrically resistive yarns 2r of the embodiment shown in <FIG>, and a second set 2ry of electrically resistive yarns 2r, electrically insulated from the first set 2rx of electrically resistive yarns 2r.

The electrically resistive yarns of the second set 2ry are electrically connected to a second common node Ny configured to be electrically connected to a second input INy of the detection device <NUM>.

The first set 2rx and said second set 2ry of electrically resistive yarns 2r overlap to form a grid of electrically resistive yarns 2r. Preferably, the electrically resistive yarns of said second set 2ry are arranged parallel to each other along a second direction Y substantially orthogonal to the first direction X.

The detection device <NUM> is configured to provide an output signal S_OUT comprising a first output value OUTx and a second output value OUTy that are a function of the capacitance value CRx and CRy of the first set 2rx and of the second set 2ry of electrically resistive yarns 2r respectively.

The detection device <NUM> is preferably configured to evaluate the capacitance values CRx and CRy of the first and second set 2rx, 2ry of electrically resistive yarns by means of the same techniques discussed above.

In particular, the output values OUTx and OUTy are the direct or indirect measurements of the capacitance CRx and CRy of the first set 2rx and of the second set 2ry of electrically resistive yarns 2r.

This embodiment provides that the capacitive touch sensor <NUM> implements a two-dimensional swipe sensor (i.e. a capacitive touch sensor able to detect the swipe direction of a touch event on a orthogonal plane X-Y).

In other words, the output values OUTx and OUTy can be considered as the components of a vector on a Cartesian plane that indicates the swipe direction of a touch event. Thanks to this embodiment the capacitive touch sensor <NUM> needs of only two inputs INx, INy for the detection of the swipe direction of a touch event also in case of a wide sensing area and/or a great number of sensing yarns.

<FIG> shows a further embodiment of a capacitive touch sensor <NUM> according to the present invention. The capacitive touch sensor <NUM> shown in <FIG> comprises the same first set 2rx and second set 2ry of electrically resistive yarns 2r of the embodiment shown in <FIG>. The sensing area <NUM> defined by the electrically resistive yarns 2r is symbolically indicated as a dotted rectangle.

Preferably, each electrically conductive yarn 2c is associated to a correspondent electrically resistive yarn 2r and vice versa. In other words, the embodiment shown in <FIG> provides that the number of electrically conductive yarns 2c is equal to the number of electrically resistive yarns 2r and that for each electrically resistive yarn 2r an electrically conductive yarn 2c is associated thereto. However, as explained above, further embodiments may provide a different number and/or a different arrangements of electrically conductive yarns 2c with respect to the embodiment shown in <FIG> still remaining within the scope of protection of the present invention.

According to an aspect of the present invention, number and arrangement of the electrically conductive yarns 2c is chosen so that when a touch event occurs on the sensing area <NUM> defined by the electrically resistive yarns 2r, at least one electrically conductive yarn 2c is touched.

In other words, the skilled person, knowing the average size of the sensing area portion touched by the objects intended to be used (e.g. a finger of a user, a tip of a touch pen), is able to choose the number and the arrangement of electrically resistive yarns and/or electrically conductive yarns so that when an object touches the sensing area <NUM> at least one electrically resistive yarn and at least one electrically conductive yarn (if present) is touched.

Preferably, with respect to the embodiment shown in <FIG>, sensing yarns <NUM> are arranged so that when a touch event occurs on the sensing area <NUM> at least one electrically resistive yarn 2r of the first set 2rx, at least one electrically resistive yarn 2r of the second set 2ry and at least one electrically conductive yarn 2c are touched together.

With respect to <FIG>, the electrically conductive yarns 2c are electrically connected to a reference common node Nc configured to be electrically connected to a reference input INc of the detection device <NUM> for evaluating the capacitance value Cc of the electrically conductive yarns 2c. The electrically resistive yarns 2rx are electrically connected to a first common node Nx configured to be electrically connected to a first input INx of the detection device <NUM> for evaluating the capacitance value CRx of the first set 2rx of electrically resistive yarns 2r. The electrically resistive yarns 2ry are electrically connected to a second common node Ny configured to be electrically connected to a second input INy of the detection device <NUM> for evaluating the capacitance value CRy of the second set 2ry of electrically resistive yarns 2r.

The detection device <NUM> is configured to evaluate the capacitance values CRx, CRy and Cc of the first and second set 2rx, 2ry of electrically resistive yarns 2r and of the electrically conductive yarns 2c by means of the same techniques discussed above. Some embodiments may provide that the output signal S_OUT comprises three output values: a first output value OUTx that is the direct or indirect measurement of the capacitance CRx of the first set 2rx of electrically resistive yarns 2r, a second output value OUTy that is the direct or indirect measurement of the capacitance CRy of the second set 2ry of electrically resistive yarns 2r, and a reference output value OUTc that is the direct or indirect measurement of the capacitance Cc of the electrically conductive yarns 2c.

Some embodiments may provide that the detection device <NUM> is configured to calculate (for example by means of the microcontroller 5b) the ratio values CRx/Cc and CRy/Cc. In particular, CRx/Cc is the ratio between the direct or indirect measurement of the capacitance CRx of the first set 2rx of electrically resistive yarns 2r and the direct or indirect measurement of the capacitance Cc of the electrically conductive yarn 2c. CRy/Cc is the ratio between the direct or indirect measurement of the capacitance CRy of the second set 2ry of electrically resistive yarns 2r and the direct or indirect measurement of the capacitance Cc of the electrically conductive yarn 2c.

In these embodiments, the first output value OUTx and the second output value OUTy may be the ratio CRx/Cc and the ratio CRy/Cc, respectively. The detection device <NUM> may be configured to provide an output signal S_OUT comprising only the first output value OUTx and the second output value OUTy.

As explained above, the value of the ratio CRx/Cc is indicative of the location of a touch event along the first direction X with a negligible dependency of the capacitive coupling between the electrically resistive yarns 2rx and the object touching them. Analogously, the ratio CRy/Cc is indicative of the location of a touch event along the second direction Y with a negligible dependency of the capacitive coupling between the electrically resistive yarns 2ry and the object touching them.

In other words, the values of the ratio CRx/Cc and CRy/Cc are indicative of the location of a touch event along the first direction X and the second direction Y with respect to the position of the common node Nx and Ny irrespectively of how strong is the capacitive coupling between the electrically resistive yarns 2rx, 2ry and the object touching them.

The values of ratio CRx/Cc and CRy/Cc can be considered as coordinates of a Cartesian plane X-Y having abscissa parallel to the first direction X and ordinate parallel to the second direction Y.

Thus, when a touch event occurs on the sensing area <NUM>, the ratio values CRx/Cc and CRy/Cc overcome a correspondent threshold value and assume two values that are indicative of the position of the touch event on the sensing area <NUM>.

In particular, CRx/Cc assumes a value within a range of values comprised between a first lower value and a first upper value. CRy/Cc assumes a value within a range of values comprised between a second lower value and a second upper value. For example, the first lower value and the second lower value can be considered the origin of the Cartesian plane X-Y.

Thanks to this embodiment the capacitive touch sensor <NUM> needs of only three inputs INx, INy and INc for the detection of the location of a touch event on the sensing area <NUM> also in case of a wide sensing area <NUM> and/or a great number of sensing yarns <NUM>. Sensing yarns <NUM> (or in general sensing elongated elements <NUM>) may be coupled to the support layer <NUM> by various coupling technics known per se in the art.

For example, some embodiments may provide that the sensing elongated elements <NUM> comprise traces of electrically resistive material (as electrically resistive elongated elements 2r) and/or traces of electrically conductive material (as electrically conductive elongated elements 2c) arranged along a substantially linear paths.

Such traces may be produced for example including a biopolymer (such as microbial cellulose, microbial collagen, cellulose/chitin copolymer, microbial silk, or a mixture thereof) with electrically conductive material (such as carbonaceous material, preferably selected from the group consisting of activated carbon, high surface area carbon, graphene, graphite, activated charcoal, carbon nanotubes, carbon nanofibers, activated carbon fibers, graphite fibers, graphite nanofibers, carbon black and mixtures thereof). A preferred embodiment provides that the biopolymer is microbial cellulose. For example, electrically conductive material may be provided to the biopolymer (e.g., to a biopolymer layer or trace) by printing (e.g., screen printing and/or digital printing), or by localized impregnation.

According to an embodiment, a culture containing biopolymer-producing microorganisms comprises electrically conductive material. For example, the support layer may be contacted with a culture including biopolymer-producing microorganisms and an electrically conductive material. The microorganisms may be cultured to produce a biopolymer including electrically conductive material, so that the support layer is provided with a trace of electrically resistive material made of biopolymer comprising electrically conductive material.

According to an aspect of the present invention, the support <NUM> layer may be a fabric. Sensing yarns <NUM> may be coupled to a fabric <NUM> by sewing, by knitting, by weaving, or by any other coupling technique known in the art.

<FIG> shows a preferred embodiment of a capacitive touch sensor <NUM> according to the present invention. The embodiment shown in <FIG> has the same sensing yarns <NUM>, or in general the same sensing elongated element <NUM>, of the embodiment shown in <FIG>, wherein the support layer <NUM> is a woven fabric and wherein sensing yarns <NUM> form at least part of the weft <NUM> and of the warp <NUM> of the woven fabric <NUM>.

Further embodiments may provide that sensing yarns <NUM> form at least part of the weft or of the warp of a woven fabric <NUM>, for example in the case of a capacitive touch sensor <NUM> implementing a one-dimensional swipe sensor as shown in <FIG> and <FIG>, still remaining within the scope of protection of the present invention. In general, sensing yarns <NUM> preferably form at least part of the weft and/or of the warp of a woven fabric <NUM>.

Preferably, sensing yarns <NUM> can be used as a sensing core of a composite yarn having a sheath formed for example by an electrically non-conductive yarn having an electrical resistance per unit of length Rn greater than <NUM> MS2/m, more preferably greater than <NUM> GΩ/m. According to an aspect of the present invention, the sheath of the composite yarn comprises staple fibers made of an electrically non-conductive material, preferably having electrical resistivity greater than <NUM><NUM> S2m, more preferably greater than <NUM><NUM> S2m.

The sensing yarns <NUM> may be preferably core-spun with the staple fibers of the sheath. Some embodiments may provide that the sensing yarns <NUM> are embroidered around with the staple fibers of the sheath, or covered by other sheathing processes known in the art. The staple fibers are preferably natural fibers such as cotton, wool, silk and the like. Some embodiments may provide that the sheath of the composite yarn is provided with a dyeing, for example an indigo dye.

Some embodiments may provide that each electrically conductive yarn 2c is coupled to a correspondent electrically resistive yarn 2r and vice versa, forming a composite yarn. A suitable composite yarn may be preferably the one as described in <CIT> in the name of the same Applicant and having the following title: "COMPOSITE YARN FOR THE POSITION SENSITIVE CAPACITIVE TOUCH SENSING". The priority date of <CIT> and, consequently, falls under Article <NUM>(<NUM>) EPC.

With respect to <FIG>, the detection device <NUM> is preferably connected to a communication module <NUM> configured to transmit the output signal S_OUT to an external device <NUM>.

The capacitive touch sensor <NUM> of the present invention may be used for controlling or sending a control command to an external device <NUM>. Preferably, the communication module <NUM> is a wireless communication module (e.g. Bluetooth module, WiFi module, Infrared module, and the like).

The capacitive touch sensor <NUM> may be coupled to the fabric <NUM> of an article for providing a sensing region that allows the user to control an external device <NUM> in a simple and reliable way.

Some embodiments may provide that the that the touch sensor <NUM> is coupled to a fabric <NUM> of a garment, preferably a shirt, a j acket or a pair of pants, on a sensing region (for example the cuff of a shirt, a sleeve of a j acket, or a pant leg) for allowing the wearer to control an external device <NUM> (e.g. a smartphone, a music player, or the like) easily. Some embodiments may provide that the touch sensor <NUM> is coupled to a fabric <NUM> for lining a seating furniture (preferably a sofa or an armchair) on a sensing region (e.g. on the arms of the seating furniture) for allowing the sitting user to control an external device <NUM> (e.g. a smart TV, a stereo or the like) easily.

Summarizing, a method for detecting a touch event on a support layer <NUM> comprises the following steps:.

Claim 1:
An assembly comprising a detection device (<NUM>) and a capacitive touch sensor (<NUM>), the capacitive touch sensor (<NUM>) comprising a support layer (<NUM>) and a plurality of sensing elongated elements (<NUM>) coupled to said support layer (<NUM>), wherein said sensing elongated elements (<NUM>) have one of their three dimensions which is at least ten times greater than the other two dimensions, said plurality of sensing elongated elements (<NUM>) comprising a plurality of electrically resistive elongated elements (2r) having an electrical resistance per unit of length comprised between <NUM> kΩ/m and <NUM> MΩ/m, said plurality of electrically resistive elongated elements (2r) comprising a first set (2rx) of electrically resistive elongated elements (2r) electrically connected to a first common node (Nx) configured to be electrically connected to a first input (INx) of the detection device (<NUM>), said detection device (<NUM>) being configured to provide an output signal (S_OUT) comprising a first output value (OUTx) that is a function of the capacitance value (CRx) of said first set (2rx) of electrically resistive elongated elements (2r) that is indicative of a touch event occurred on one or more electrically resistive elongated elements (2rx), said plurality of electrically resistive elongated elements (2r) defining a sensing area (<NUM>), said plurality of sensing elongated elements (<NUM>) comprises at least one electrically conductive elongated element (2c) having an electrical resistance per unit of length that is less than <NUM>Ω/m, the electrically conductive elongated element (2c) being arranged within said sensing area (<NUM>) and electrically insulated from said electrically resistive elongated elements (2r), said at least one electrically conductive elongated element (2c) being electrically connected to a reference common node (Ne) configured to be electrically connected to a reference input (INc) of said detection device (<NUM>) for evaluating the capacitance (Cc) of said at least one electrically conductive elongated element (2c) that is indicative of a touch event occurred on one or more electrically conductive elongated elements (2c).