ES2554990B1 - Wireless controlled deactivation tag, manufacturing method and method and system for using said tag - Google Patents

Abstract

Wireless controlled deactivation tag, manufacturing method and method and system for the use of said tag. # The present invention proposes a deactivatable tag whose response can be annulled or modified by a certain external action thereon, a manufacturing method and a method and system for use. The tag would act as a normal passive tag under normal operating conditions and, when subjected to certain physical or chemical agents, its operation is reversibly or irreversibly impossible. It can be used in certain practical applications where it is important that the label is always active (for example, in order to check its correct operation) and can be deactivated at will.

Description

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DESCRIPTION

Wireless label of controlled deactivation, manufacturing method and method and system for the use of said label

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of wireless tags (for example RFID or NFC tags) and more specifically, to a wireless tag that allows its operation to be controlled, a manufacturing method thereof and a method and system for its use.

BACKGROUND OF THE INVENTION

Wireless tags are radio communication devices used primarily for the identification of objects to which they are incorporated (either because they are attached to the object by any means, attached, encapsulated within the object or in general, attached to the object by any means ). This use comes from its initial development as an "advanced" substitute for bar codes. These tags can be, for example, RFID tags (an acronym for Radio Frequency IDentification), NFC technology (an acronym for Near Field Communication , Near Field Communication) or any other class that is capable of establishing wireless communication.

With these labels it is intended to have a data storage and recovery system (for example, serial numbers and identification or any other useful information about the product that carries it) that works remotely, in adverse environments and without eye contact direct. A communication team (usually called a reader) can communicate with the label incorporated into a product and retrieve information about that product, for example some type of identification. The reading devices (or simply "readers") are specific devices that can communicate with the wireless tag allowing the reading (and sometimes writing) of the data stored in said tag. These readers can be general-purpose electronic devices (PCs, tablets, laptops, smartphones ...) in which a specific application has been downloaded that allows communication and reading / writing with the wireless label.

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As additional advantages, this type of labels allows identifying a unique product, not just a category such as bar codes. Generally, it can also be read and rewritten multiple times, which facilitates logistic work.

In recent years, these devices have been expanding their applications including new options such as indoor location (Real Time Location Systems, English, Real Time Location Systems, RTLS) or data collection through the incorporation of sensors. This trend has been limited by the variety of options available on different frequencies, as well as the existence of multiple proprietary protocols that make compatibility between labels and readers from different manufacturers difficult. The frequencies used by these RFID tag systems can be, for example, the following:

• Low frequencies (LF, between 125 and 134 kHz or between 140 and 148.5 kHz)

• High frequency (HF, around 13-14 MHz)

• Very high frequency (UHF, 860 and 960 MHz)

• Microwave (over 2.45 GHz)

These frequency classifications may change according to countries and laws, so they are included here only as an example.

Each frequency has different characteristics in terms of scope and interaction with its environment and is therefore suitable for different applications. As a general criterion, the elevation of the working frequency is associated with an increase both the reading distance and the amount of information transmitted. Low frequency labels require less power and are not suitable for working near obstacles such as metallic or liquid materials since the reading signal generally does not exceed 30-90 centimeters across the air (this is only an example since the distance achieved will depend on many factors, among others, the power used and the reading technology) and such objects can cause a strong absorption of it. High frequency labels work best with metal objects and can be read more than a meter away, but require more power. The devices at very high frequencies offer an even greater reading radius and allow a high speed of data transmission although the signal cannot easily pass through certain materials.

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Some examples of minimum range distances included in different technical standards are as follows:

• EM4100 at frequencies of 125KHz: from 1 to 100cm.

• Mifare (ISO 14443) or iCode (ISO 15693) in the range of 13.56 MHz (HF): from 1 to 15cm.

• ISO18000 using UHF signals (868 MHz): up to 10 meters.

All these values are minimum requirements that try to guarantee the correct operation in a real environment. However, numerous experiments have been carried out that have determined that it is possible to perform far greater readings and / or writes at a distance if the dimensions of the receiving antenna and / or the emission power are increased. In general, the signal strength received by an RFID tag must exceed 50 ^ iW to enable its activation and the sending of a response. These values are constantly being reviewed for the development of new very low consumption circuits that reduce this level.

A basic standard for defining the specifications of these labels is ISO / IEC 18000, "Information technology - Radio frequency". This standard is divided into several parts, among which 18000-2 stand out, which applies to small devices and short reading distances, using frequencies below 135 kHz (LF); 18000-3, referred to frequencies of 13.56 MHz and applies to products, bracelets, containers and, in general, the most general use frequency is considered; 18000-4, which details the use of the 2.45GHz (Microwave) frequency; 18000-6, which is used in long distance applications such as transport and logistics. Frequencies between 860 MHz and 960 MHz are used; 18000-7, also used in transport and logistics but with frequencies below 433 MHz.

There are other important standards that include the requirements in this field (such as ISO / IEC 15961 and 15962 dedicated to data management or ISO 17363, ISO 17364, ISO 17365, ISO 17366 and ISO 17367). And many companies that have made proprietary developments. Since the devices at each frequency have a different behavior, it is necessary to determine the application before choosing which RFID tag design is the most appropriate and at what frequency it should operate. For example, very high frequency (UHF) tags are not recommended for applications in humans, because they are very sensitive to the presence of water, also that included in a human being, since it can absorb a significant fraction of the emitted signal .

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According to their source in January, RFID tags can be classified into 3 types: passive, semi-active or active. Passive tags have no internal power supply and obtain the power necessary to activate their signal circuits sent by a reading device and that is received and transformed into an electrical current in the antenna. In accordance with ISO standards, low frequency (LF) and high frequency (HF) labels can only be passive while very high frequency (UHF) labels of English Ultra High Frequency) and microwaves can also be semi-active or active. Passive tags, which are those that will be used primarily in the present invention, are made up of very few elements. These would be: an integrated circuit (IC) containing certain stored information (serial number, product characteristics ...), the communications antenna and the protective housing. In a simplified version of this design (shown in Figure 1), called "inlay", the antenna (12) is printed (eg spiral) on a support and the integrated chip or circuit (11) is attached or attached to it.This variant allows a simpler manipulation.

The labels, and their antennas, can be constructed with very different shapes and dimensions depending on the intended destinations for it. It is possible to find flat round, rectangular (like the one in figure 1) labels or with fractal designs and flexible labels that can be applied on cylindrical tubes or containers, or folded on other objects. As a consequence, each tag will be different in its response to a given reader since the size of the tag, and its shape changes, affect the reception of the reader's signal. Therefore, the configuration of the tag / reader set may require some adjustments for each application. In passive tags, the antenna has to be designed so that it is capable of fulfilling two functions, capturing energy to power its integrated circuit and emitting a response signal to the reader. This limits both the scope and the capacity of the process and storage of the integrated circuit. Although there are multiple variants, the usual range of use of a passive tag in an industrial environment can reach up to 6 meters. Active type RFID tags have an internal source that is used to power their integrated circuit and generate the output signal. This allows them to have greater reach and greater capacity to store data than passive tags. At present, the smallest active tags are approximately the size of a coin and their range can reach up to 10 meters with a battery life of up to 10 years. In exchange, its cost is much higher than that of a passive label (between 30 and 100 times).

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The scheme presented above for RFID tags is the simplest, but there are many more advanced interesting technologies within the RFID field. Among them, it is worth mentioning the SAW type labels (acronym for Surface Acoustic Wave, Surface Acoustic Wave). Its operating mechanism is very simple. An antenna with a special design called IDT (acronym for Interdigital Transducer, Interdigital Transducer) converts the small electric current generated by receiving the signal from the reader, into a pressure wave that travels through a piezoelectric substrate until it reaches another antenna that reissues a signal modified This basic design can be modified using one or more reflectors to return the pressure wave to the original antenna that transmits the signal. Generally the antennas are made of aluminum while the piezoelectric material can be quartz, lithium niobate (LiNbO3) or lithium astalate (LiTaO3).

SAW tags have several interesting qualities. First, the response signal is delayed in time as the wave advances at the speed of sound in the piezoelectric material, speed much lower than the speed of any electromagnetic signal. This makes it possible to differentiate more simply the signal from the label against noises from rebounds of the original signal of the reader.

Secondly, it is possible to influence the propagation of the pressure wave in the material using various coating layers or by modifying its physical structure. This allows the development of a multitude of very precise and small-sized passive sensors. For example, devices of this type have been manufactured that allow simultaneous measurement of temperature, humidity and magnetic field with a single sensor of reduced dimensions (10mmx10mmx2mm) and that can operate without battery or by other energy sources other than the signal itself. reader interrogation. Finally, the simplicity and resistance of its design allow it to be used in strongly aggressive environments where the electronics of other more complex sensors would fail. SAW type temperature sensors have been developed with an operating range between 20 ° C and 200 ° C and an accuracy of 1% of the scale range. In exchange for these advantages, SAW tags do not usually include complex circuits, nor do they store data such as identification codes included in most RFID tags.

The main limitations of utilization of passive tags are given by their most significant characteristic, the absence of an internal power supply that allows their independent operation. Therefore, its correct feeding (and therefore its operation) depends entirely on the power of the signal source

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(reader) and the distance between them. In the current environment, the power of the signals that can be emitted is strongly regulated. This power depends on the legislation of each country and the specific frequency. This factor marks a first limit that has been included in the standards used to define RFID tags. As an example, the passive labels of greater scope that comply with the ISO 18,000 standard and emit the UHF band can be read and rewritten in distances of up to 10 meters that are reduced to 5-6 meters in environments with obstacles and / or electromagnetic noise.

But to define precisely this scope, it is necessary to go into detail in the operation of the labels. There are two important but different limits that must be considered. In the first place, the passive label must receive enough energy to guarantee the functioning of the electronics that it has incorporated. This limit depends on the characteristics of the electronic circuit used but is relatively high, especially when you want to overwrite some data. The second limit is the energy needed to send a response to the reading device. This limit is much lower and depends on the sensitivity of the receiver that is generally high, since since the number of readers is much lower than that of labels, high sensitivity devices and higher price are used. In a practical example, the range limit associated with the energy required for the operation of the circuit can be about 6 meters, much lower than the one defined by the sensitivity of the receiver that would be about 36 meters (this is just an example, to illustrate the difference between both limits, since the real scope in each case depends on many factors such as the technology used on the label and on the reading device); although new technologies are constantly reducing the energy requirements of the circuits used in passive RFID tags. While these more efficient solutions are generalized, other simpler ones to implement have been extended, such as the so-called semi-active tags in which a small battery is used to power the integrated circuit but not the antenna. This allows the scope to be increased very significantly but also raises the costs to bring them closer to the costs of the active tags. It is also possible to design labels that work passively when the signal is strong enough but use the battery when the power is not enough. Ultimately, it is possible to use a power harvesting system that allows the range of utilization of an RFID tag to be extended as long as its use is not very frequent. But these advances are not widely used due to their high price.

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Currently, another type of reader is being developed that resolves the limitations in distance (to supply enough Jan for the label) mentioned above, through the use of bistatic systems. That is, by separating the receiver circuit and the transmitter circuit responsible for activating (feeding) the tags into two different elements, it is possible to significantly increase the distance at which it can be detected. However, this solution is not simple since it implies the detection of weak signals, received through multiple paths and that must be clearly identified in environments that are usually highly noisy. In this area, the equipment produced by the American company Mojix, which is based on the use of local “exciters”, that is to say small emitters capable of providing enough energy to activate a label and one or several centralized detectors of very high sensitivity, stands out able to read the response signal at distances of up to 60 meters (reaching 182 meters in the most recent developments). These detectors use advanced signal processing algorithms to eliminate interference problems, multiple return paths or changes due to the movement of the source that could impair the reception of the signal.

The high cost of active type RFID tags has greatly slowed down their application, so the most commonly used today are passive ones. Precisely, trying to take advantage of the great advantages, for cost and simplicity, of the passive tags have developed several models of labels "value added" where you try to avoid the energy limitations of them by various means (as explained above with SAW type labels). Another work line is the testing of new geometries for “classic” RFID tags or the use of new installation techniques for them. In the first case, the use of labels divided into two parts as displacement sensors can be cited, in the second, the installation of two labels with different encapsulation whose comparison allows them to be used as passive humidity sensors within structures.

Another of the lines of work for new applications of passive tags are passive tags whose operation can be controlled by the user, for example, by pressing. For this purpose, a variable conductivity material located within the circuit of the tag is used, so that for the tag to work, the user must press it. However, this makes it impossible to know if a label is present or has been damaged since it would not issue any response until it is pressed.

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These designs are indicated for applications such as reading an RFID tag from a passport or payment card. Its mode of operation does not allow to distinguish between the absence of response because the user is not acting on it and the simple absence or damage of the device.

There are certain applications where this operating system is not the most appropriate. For example, applications within the hospital environment, in hazardous substance management environments or in many other fields, which do not fit well with the operating mechanism described above since in these areas it is very important to detect a device malfunction or an absence of the same of a certain area.

Therefore, there is a need for controllable wireless tags that solve the design, cost and operation problems discussed above in a simple and effective manner. These and other advantages of the invention will be apparent in light of the detailed description thereof.

SUMMARY OF THE INVENTION

The objective of the present invention is to develop a deactivatable label that is used in certain applications where controlled deactivation is essential. It is a label whose antenna is “short-circuited” when subjected to certain physical or chemical agents (for example, when applying pressure on it or when a temperature change occurs). In this way, the tag would act as a normal passive tag under normal operating conditions. However, by changing the physical or chemical conditions (by subjecting it to certain physical or chemical agents, for example applying pressure on it), the geometry of the electrical circuit of the antenna is substantially altered, making it impossible to operate reversibly or irreversibly. For example, as a result of this alteration of the antenna geometry, the tag would see the amount of energy received from the reader reduced or eliminated, which would cause the associated electronic circuit not to work since the received power would be less than necessary. to activate the tag circuit.

In a first aspect, the present invention proposes a wireless label comprising:

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- an antenna;

- at least one layer of variable electrical conductivity material in direct contact with the antenna and at least partially covering the antenna, said insulating material being in the absence of a determined external action on it and conductive when said determined external action occurs on the same;

where, in the absence of said determined external action, the antenna is capable of capturing radio frequency signals from a device at a certain first frequency and of emitting radio frequency signals to the device at said particular first frequency and where, when said action occurs externally determined, the antenna is not capable of capturing radio frequency signals from said device at said particular first frequency or sending radiofrequency signals to the device at said particular first frequency.

Said wireless tag is a radio frequency identification tag, RFID, or NFC near field communication type tag or any other type of wireless antenna.

The variable electrical conductivity material (also called variable resistance or variable electrical resistance) can be a piezoresistive material.

The variable electrical conductivity material may be a Quantum Tunnel Composite material, QTC.

Said variable electrical conductivity material may be covered by a layer of insulating material.

The material of variable electrical conductivity can be a matrix of a flexible polymer that contains metal microparticles within it.

Said external action may be the action of a physical or chemical agent on the label, such as a pressure on the label applied by a user, a sudden change in temperature, exceeding or lowering a certain temperature, the action of a certain chemical substance on the label...

For example, the external action may be a pressure applied to the device and said

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material can be a material of variable conductivity by pressure that in the absence of pressure is insulating and when undergoing pressure it becomes conductive by short-circuiting the part of the antenna with which it is in contact.

The layer of variable resistance material may be arranged in several ways, provided that when said determined external action is produced, the antenna is not capable of capturing radio frequency signals from said device at said particular first frequency or sending radiofrequency signals. to the device at said particular first frequency. Although depending on the disposition different effects can be achieved.

For example, the antenna can be formed by several turns of conductive material and the layer of variable conductivity material can be in contact with at least two of the turns and when said determined external action occurs, the at least one piece of material of Variable conductivity short-circuits the turns with which it is in contact, thus modifying the geometric characteristics of the antenna so it is not able to capture radio frequency signals or emit radio frequency signals to said device at said first frequency. That is, the label stops working as usual.

The layer of variable conductivity material may be in contact with all the turns of the antenna. In that case, when said determined external action occurs, all the turns of the antenna are short-circuited, so it is not capable of capturing radio frequency signals or emitting radio frequency signals at any frequency. That is, the tag stops working.

The layer of variable conductivity material may not be in contact with all the turns of the antenna and when said determined external action occurs, some of the turns of the antenna are short-circuited and others remain uncircuited. This changes the antenna geometry completely, normally changing the signal frequencies that the antenna can pick up and emit from the first frequency to a second frequency.

In one embodiment, when said determined external action occurs, the antenna is capable of capturing radio frequency signals at a second frequency and emitting radio frequency signals at said second frequency. This happens for example, when the antenna is

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divided into 2 parts (in 2 sub-antennas) and the layer of variable conductivity material is only in contact with one of the parts, so that when said external action occurs, said part that is in contact with the material layer it is short-circuited (that is, one of the 2 sub-antennas stops working correctly) and the antenna is capable of capturing and emitting radio frequency signals at the second frequency using the part of the antenna that is not in contact with the material layer of variable conductivity

These 2 sub-antennas can have their ends connected by a layer of variable resistance material so that, when said external action is produced, the path of electrons through said antennas is modified and, with it, the response frequency of the wireless label.

In one embodiment, the antenna from the signal received from the device generates energy that allows the wireless tag to function (that is, it is a passive tag).

The device that emits and receives signals from the tag can be a wireless tag reader device. When external action occurs, the material is able to significantly reduce its resistance (it becomes conductive), modifying the movement of electrons in the antenna and preventing the reading / writing of normal data when it is exposed to a physical agent or adequate chemical.

The layer of variable conductivity material may be continuous or divided into at least 2 different portions without contact between them covering different parts of the antenna, each of the portions in direct contact with said different parts of the antenna.

Depending on the material used, the effect may be irreversible or reversible. That is, it may be that after said determined external action occurs once, the antenna is not able to capture radio frequency signals from said device at said particular first frequency or send radio frequency signals to the device at said particular first frequency, even if said external action leaves to occur (irreversible effect) or to be able to capture and send signals to said first frequency once said external action ceases to occur.

In a second aspect the present invention proposes a method of manufacturing a

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wireless label, where said method comprises:

- provide on the label an antenna capable of capturing and emitting radio frequency signals;

- depositing at least one layer of variable electrical conductivity material in direct contact with the antenna and covering at least partially the antenna, said insulating material being in the absence of a determined external action on it and conductive when said determined external action occurs about it;

where, the layer of variable electrical conductivity material is deposited so that in the absence of said determined external action, the antenna is capable of capturing radio frequency signals from a device at a given first frequency and of emitting radio frequency signals to the device at said determined first frequency and, when said determined external action occurs, the antenna is not capable of capturing radio frequency signals from said device at said particular first frequency or sending radiofrequency signals to the device at said particular first frequency.

In a third aspect the present invention proposes a system for the activation of functions associated with wireless tags, said system comprises:

- any of the wireless tags described above, where the tag also comprises means for processing a radio frequency signal received through the antenna at said first frequency, and in response to said signal received, generate and transmit through the antenna, a response signal to a reading device at said first frequency;

- the wireless tag reader device comprising:

- means for periodically sending radio frequency signals at said first frequency to the wireless label,

- means for receiving response signals from said wireless label to said periodically issued signals and

- means for, when it does not receive a response signal from said wireless label to an emitted signal and after a certain interval of time, it receives again response from said wireless label to another emitted signal, activating a certain function associated with the wireless label.

In a fourth aspect the present invention proposes a method of activating a function associated with a wireless tag, said tag comprises an antenna and a layer of

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variable electrical conductivity material in direct contact with the antenna that at least partially covers the antenna, said insulating material being in the absence of a determined external action and conductor when said determined external action occurs and where the method comprises the following steps:

- a wireless tag reader device sends a first radio frequency signal to said first frequency;

- the wireless tag receives said radiofrequency signal from the antenna, processes the received signal and, in response to said received signal, transmits through the antenna, a response signal to the reading device at said first frequency;

- the reading device receives the label signal and marks the label as detected;

- performing the external action on the variable conductivity material and as a consequence, the antenna is not capable of capturing radio frequency signals from said device at said determined first frequency or sending radiofrequency signals at said determined first frequency;

- the wireless tag reader device sends a second radio frequency signal to said first frequency;

- when a period of time passes without the reader receiving a response signal from the tag to said second radio frequency signal, the reading device marks the tag as undetected;

- the external action on the variable conductivity material is stopped and as a consequence, the antenna is capable of capturing radio frequency signals of said device at said determined first frequency and sending radiofrequency signals at said determined first frequency;

- the wireless tag reader device sends a third radio frequency signal to said first frequency;

- the wireless label receives through said antenna said third radio frequency signal, processes the received signal and in response to said received signal, transmits through the antenna, a response signal to the reading device at said first frequency;

- the reading device receives the response signal from the tag to said third radio frequency signal, marks the tag as detected again and activates the function associated with said tag.

Said function associated with the tag can be, for example, an alarm signal, activate a certain device, perform a certain action in a system, send a signal of

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notice that a particular event has occurred ...

Finally, a computer program is presented that includes instructions executable by computer to implement the described method, when running on a computer, a digital signal processor, a specific integrated circuit of the application, a microprocessor, a microcontroller or any other form of programmable hardware. Said instructions may be stored in a digital data storage medium.

For a more complete understanding of these and other aspects of the invention, its objects and advantages, reference may be made to the following specification and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the features of the invention, in accordance with some preferred examples of practical embodiments thereof, a set of drawings is accompanied as an integral part of this description. where, with an illustrative and non-limiting nature, the following has been represented:

Figure 1 shows the basic design of a passive RFID tag according to a realization of the state of the art.

Figure 2 schematically shows the layer structure of a wireless tag according to an embodiment of the invention.

Figure 3 schematically shows the design of a label according to an embodiment of the present invention.

Figure 4 schematically shows the design of a label according to an embodiment of the present invention.

Figure 5 schematically shows the design of a label according to an embodiment of the present invention.

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Figure 6 schematically shows the design of a label according to an embodiment of the present invention.

Figure 7 schematically shows the layer structure of a wireless label according to an embodiment of the state of the art (specifically, an NXP NTAG 203_25R tag).

DETAILED DESCRIPTION OF THE INVENTION

The present invention proposes a deactivatable label whose response can be annulled or modified, for example, by applying a moderate pressure or other physical or chemical agents. The tag acts as usual when under normal conditions (for example, the user does not apply pressure on the tag). By altering the physical conditions (e. When applying pressure) the geometry of the electrical circuit of the antenna is substantially altered, making it impossible to function properly. For this, a thin layer of variable conductivity material is applied on the antenna. This layer is insulating, with a resistance of several mega-ohms [MQ], under normal conditions but it becomes conductive by reducing its resistance to a few ohms after applying a moderate pressure or if other materials are used, the resistance is it reduces when other alterations of the physical or chemical conditions of the same occur, for example, when the temperature decreases from a certain threshold or exceeds another certain temperature threshold or when it is exposed to a certain chemical agent.

It is a new design for a very low cost device that can be used as a switch, localization device, signal delivery or sensor for specific applications or many other uses.

The tag on which this layer of material is applied can be an RFID tag, NFC or any other type of wireless tag.

This variable conductivity material may be for example a material of type QTC (acronym for Quantum Tunnelling Composite, Quantum Tunnel Compound) or any other type of variable conductivity materials. QTC type materials are polymeric materials with very unusual electrical properties so, in the absence of pressure, this material behaves as an almost perfect insulator (with a resistivity close to 107

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ohms per cm) and when pressure is applied, this material begins to reduce this resistivity and with a moderate level of pressure a resistivity of a few ohms per cm can be achieved. Like other conductive polymeric materials, their characteristics are based on the incorporation of a conductive filler to the polymeric matrix, this filler can be from carbon in different forms (graphite, nanotubes, etc.) to metals such as ticket, copper, silver, aluminum or iron, for example.

In a particular embodiment, a material with nickel particles embedded within a polymer matrix, which is usually silicone, is used. The metal particles have dimensions that vary between 1 and 10 micrometers and are shaped including "sharp points" in their contour. They are incorporated into the matrix in a proportion ranging from 1 to 4 to 1 to 6 in weight. This material is described for example in the document "Metal-polymer composite with nanostructured filler particles and amplified physical properties" of Bloor D, Graham A, Williams EJ and Laughlin PJ, Lussey D; Appl Phys Lett. 2006; 88 (10): 102103

The mechanism of operation of the QTC material is based on both the composition and the shape of the particles. The sharp ridges that surround its contour act similarly to the sharp points used in the tunneling microscopes. The electric field in them is extremely high which favors the electric conduction by means of a tunnel effect of the Fowler-Nordheim type. It is important to note that the metal particles never come into direct contact since they remain coated with the polymer matrix at all times. This causes a high level of electrical resistance to recover as soon as the pressure decreases. The effect is highly reproducible. Samples of this material have been subjected to cycles of a million compressions maintaining their resistivity levels with and without pressure. The only requirement is to keep the current at a reduced level to avoid permanent damage to the material.

For example, in a typical sample of 20x20x1 mm3 of a material of this type (in this specific example, based on silicone and with 20% by weight of nickel microparticles), it is observed that the resistance of the uncompressed sample is similar to The theoretical resistance of the original composite material that is around 1012 ohms. By applying pressure, the resistance can decrease to only 1-10 ohms, which implies a reduction of 12 orders of magnitude. The resistance varies exponentially between a range of 10 to 21% compression and, as the deformation increases, the resistance begins to decrease from

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Slower way. This mechanism allows the material to be used as a pressure-operated «switch». It is important to emphasize that the resistance depends on the percentage of variation in volume of the material and not on the pressure exerted. Due to this, it is possible to adjust the force necessary to achieve good conductivity by modifying the thickness of the piece of QTC material used.

The characteristics of a QTC material allow it to be used in various designs for electrical or electronic circuits. There are applications where this material is incorporated into a circuit to open and close the flow of current. These designs have been proposed for various elements such as keyboards, fabrics or even RFID tags. However, using a normally insulating material as part of the circuit of a passive RFID tag would impede its operation under normal conditions. It would be impossible to know if a label is present or has been damaged since it would not issue any response until it is pressed. These designs are indicated for different applications such as reading an RFID tag from a passport or payment card. Its mode of operation does not allow to distinguish between the absence of response and the simple absence of the device, which is no problem for the security applications for which it is intended.

There are certain applications where this operating system is not the most appropriate. For example, the usual ones within the hospital environment that do not fit well with the operating mechanism described above. The label proposed in the present invention is based on a different design that allows better use of the characteristics of the material and allows its use in this type of applications.

In the present invention, instead of placing the material within the antenna circuit, it is proposed to place it on the antenna of the wireless label and in direct contact with it. By placing a layer of QTC material on said antenna, it is intended to modify its characteristics when the QTC material is pressed (and its resistance decreases drastically) causing it to be de-tuned (called "Tag detuning") and a reduction in profit that selectively blocks its operation.

For wireless tags of the RFID or NFC type, for example, which are commonly used, the antenna design usually consists of a flat spiral with a variable number of turns (see figure 1), for example, copper or aluminum (although other kind of

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materials is possible). In Figure 2, the layer structure of a wireless label according to an embodiment of the invention is shown schematically. In the lower part are the turns of conductive material (21) that forms the antenna of the tag. Between 2 turns of the conductive material of the antenna, a layer of the variable resistance material (for example, QTC material) (22) is located. Above the variable resistance material, an insulating layer (23) can be placed to protect the variable resistance material.

In an alternative embodiment, a layer of conductive material can be placed between the QTC material and the insulator. A conductive layer complicates the design but can add an advantage as it reduces the current path within the QTC material, the QTC material crosses the current, goes through the conductive part and crosses the QTC material back again. This "bridge" of conductive material reduces the overall resistance to the passage of current that only crosses the QTC material at the ends. .

It is important to note that the antenna on which the variable resistance (conductivity) material (for example, piezoresistive material) is placed is a normal antenna with a wireless label, that is, an antenna with which the wireless antenna operates in a normal way ( receiving a signal from a reading device from which it draws enough energy to operate and sending the same or another reader a signal with the required information). Therefore, when the physical or chemical agent that varies the conductivity of the material is not applied (in the case of the QTC material, in the absence of pressure), the antenna's operation is not modified by placing an insulating material on it. and the tag works as usual. However, when sufficient pressure is applied, the top layer becomes conductive providing an alternative path for the passage of electrons. These conditions substantially modify the geometry of the antenna and its response. The arrangement (for example, its position) of the variable conductivity material (for example, of the QTC type) on the antenna must be such that the modification of the antenna geometry produced by changing the conductivity of the material (for example, by pressing the material), modify the operation of the antenna by de-tuning it and / or reducing (or canceling) the power of the received signal so that the wireless label does not work properly.

In other words, these types of tags work like a radio receiver. For example, in RFID tags, signal captation depends on a resonant circuit at a

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determined frequency Said circuit in the antenna, only captures signals at a certain frequency that is fixed according to the characteristics of the antenna (shape and dimensions) since it is not tunable. With the material added to it in the present invention (for example, QTC) when said material functions as a conductor (for example, because pressure is applied to it) a short circuit is created that modifies these characteristics (shape and / or dimension) of the antenna so that the antenna (and therefore the tag) is not able to capture the signals (and therefore the energy) at the original frequency (that is why it is said that the tag is "untied). In other words , the tag does not "listen" to the frequency of the reading device.

Depending on how this material is arranged, the entire antenna can be canceled by not receiving signals at any frequency or, as we will explain later, it can only be partially canceled by not receiving signals at the original frequency but at another frequency.

In a realization, the practical operation would be the following:

1. A reader (for example, RFID) emits a signal at a certain distance from the tag and, in the absence of another action, the tag responds. In this way, its presence can be detected within the zone of influence of the reader.

2. By exposing the tag to a physical or chemical agent (for example, when pressure is applied to the tag), a layer of variable conductivity material that has been placed on the antenna becomes conductive. In this way, the geometry of said antenna is modified by reducing its gain and / or modifying its resonance frequency.

3. When the reader tries to make a reading, the label does not respond to said signal (or does not do it with enough energy to be captured at the distance that the reading device is) causing the label to stop being detected. The same effect would occur if the label leaves the reader's range, is shielded or damaged in any way.

4. If the effect is reversible, by ceasing to expose the label to the physical or chemical agent (when the pressure ceases), the layer of material placed on the antenna is conductive so that the antenna recovers its geometry and responds correctly

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In a system that uses these labels, a periodic sampling would be carried out to verify which are the present labels and verify their good condition. As the label proposed in the present invention, under the absence of pressure works in a normal way, if the label is damaged, removed or destroyed for any reason, the identification signal would disappear to not recover more and by means of periodic sampling said anomaly would be detected and I could report the loss or damage of said label. Unlike in state of the art labels with piezoelectric material, where in normal conditions (under the absence of pressure) the label does not work, so it is not possible to detect damaged labels with periodic sampling. This "always active" operation of the proposed label (with which damaged or lost labels can be easily detected), is considered more advisable in certain applications, especially those of a hospital type.

In a more advanced alternative design, an antenna divided into two parts (or rather in which the variable conductivity material only covers one part) would be used, which, when one of the parts was short-circuited, the rest would be able to emit a signal to a different frequency An appropriate RFID reader could detect the difference and deduce if the button is at rest or being pressed. That is, when the antenna is short-circuited, the characteristics (shape and / or dimension) of the antenna will be altered, so that it can no longer capture and emit signals at the original frequency but at another frequency. It could be seen as a very limited (bi-static) version of one of the applications of active tags, but because of the advantages explained above, it would be an interesting improvement over the on / off designs in the market.

That is, according to how the variable resistance material is arranged, the entire antenna can be annulled causing it to not receive signals at any frequency or it can be made to change the frequency at which it can receive and emit signals. These two possibilities will be explained below with the help of figures 3, 4, 5 and 6.

In the case of the antenna of Figure 3 we would be in the first case. The variable resistance material (31) encompasses all the antenna spirals (32). When said material acts as a conductor (for example, when pressed) a short circuit is created in the antenna that completely cancels it so that the label is not able to capture the signals at any frequency (or at least not capture them with enough power) . But, if we limit the layer of variable resistance material (for example QTC) to one more area

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small, the antenna is not completely annulled when the material acts as a conductor but only a part of it. In this way, an antenna is still available but when its characteristics are modified due to the effect of said material, the resonant circuit is modified and becomes tuned to a different frequency. For example in Figure 4, when applying pressure on the variable resistance material (41), the antenna (42) would be divided into two antennas of smaller size with the central part annulled by the short circuit.

This basic idea allows great flexibility and multiple different antenna designs as the length or position of the layer of variable resistance material (for example, QTC) is modified. For example, in the case of Figure 5, the antenna (52) would remain one but its length would be reduced by a series of turns as the variable resistance material (51) became conductive. If the length of said material is changed (the number of turns it covers), the resonant circuit is modified and the frequency at which the circuit is sensitive. Finally, it is not necessary to limit yourself to a single fragment of material. Using two or more fragments (61) (as in Figure 6) it is possible to modify the structure and configuration of the antenna in more complex ways.

It should be noted at this point that although reference to an RFID type tag is often referred to in the present description, the present invention can also be applied to tags using NFC technology or any other type of wireless tags.

The NFC (Near Field Communication) technology is a radiofrequency technology designed to facilitate the interaction between two devices at close range allowing the exchange of information or the realization of secure payments. The technical specifications of the NFC technology are an extension of the ISO 14443 standard and the ECMA and ETSI standards. The NFC tags allow the reading and writing of information at a speed of 424Kbis / sg at a short distance (less than 4 cm). Although this distance limits the range of applications, this system guarantees secure communications avoiding the "phishing" of data.The great advantage of NFC tags over RFID tags is that their content can be read and rewritten by electronic devices such as mobile phones or tablets properly equipped.

Being based on similar protocols, NFC tags have physical characteristics similar to RFID tags. They usually communicate in the band of 13.56 MHz which is the

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same as high frequency RFID tags (HF, 13.56 MHz). The antenna design is similar to that of RFID tags (a flat spiral with a variable number of turns).

The results of the laboratory tests of an improved label according to the present invention will be explained below. The purpose of the tests was to demonstrate that it was possible to deactivate the operation of the label at will, reversibly and under moderate pressure. This made it necessary to access the metal part of the antenna and place the QTC material on it, as explained above. The labels used were acquired with an "in-lay" format intended to stick to any surface.

In figure 7, the layer structure of one of the wireless tags that can be found in the market is presented. As you can see, it first has a silicone paper (71) that protects the adhesive (it is removed when the label is to be glued), then the adhesive layer (72), then a substrate (73) that can be PET type (terephthalate of polyethylene), then the spiral of the antenna (74), with the integrated circuit on top (75) and then a layer of protective material on the label (called "face material") (76).

For the test of the complete solution, a fragment of QTC material was placed on the antenna and secured with the protective layer of the antenna that had previously been removed. After that, several reading and writing tests were carried out from a reading device (in this case a tablet with a program that allowed the reading and writing of NFC tags) in the absence of pressure that were successful so it was concluded that the presence of the material did not alter label behavior. However, when applying pressure, the QTC material became conductive, short-circuiting spirals of the antenna and making the attempts to read and write it negative. That is, the proper functioning of an RFID tag was prevented by altering the geometry of the antenna, by pressing the QTC material. Therefore, the tests of this configuration have been successful. It has been shown that it is possible to enable or disable RFID tags by applying moderate pressure on it. This pressure can be regulated by modifying the thickness of the layer of the QTC material since the passage from the condition of isolation to that of conduction depends on the variation in volume and not on the level of pressure applied. The process is completely reversible without the label or the QTC material suffering a loss in its properties.

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In the tests NFC tags were used but the results are totally extrapolated to RFID tags since, as indicated above, the physical characteristics of both types of tags are very similar. However, the present invention can be applied to all types of wireless tags. The objective of the QTC material is to modify the operation of the antenna of said tags, by de-tuning it (tag detuning) and / or reducing the power of the received signal. The incorporation of a conductive material that, when pressed, modifies the shape of the antenna, whatever it is, is an effective method to alter its characteristics. Since the power available by the labels is very limited any loss would have a significant effect and the utilization of sufficient QTC material should be able to reduce the energy received below the threshold necessary to allow the operation of the integrated circuit. That is, the proposed invention would be effective in any type of wireless label regardless of its specific characteristics.

The labels proposed in the present invention may have various applications. The following describes, by way of example, some applications of this type of labels, some of them focused on the hospital field or on the handling of dangerous substances, although of course, the labels proposed in the present invention can have many other uses in This or in different fields:

- Reconfigurable switch. This switch can be adapted, for example, as a sterile switch in high-risk infection environments (operating rooms, laboratories, etc.) or a switch for highly aggressive environments (explosive atmospheres, high humidity, etc.).

This application would consist of the use of the label as a remote switch in those situations in which a normal electrical switch presents a risk or is not recommended for various reasons. An example in this regard is the glove box, a very common element in numerous chemical, biological or radioactive laboratories and in a hospital environment. This equipment allows the safe or isolated manipulation of products of special risk for health personnel. It is common for these enclosures to contain aggressive chemicals and should be cleaned frequently to maintain adequate conditions of sterility or absence of contamination. In order to simplify its construction, and improve its efficiency, it makes sense to minimize the penetration points in the outer envelope thereof. In many cases, there is no type of drive inside which forces the arms to be removed to press a switch that turns on a light or activates an extractor, which slows down the work and facilitates

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The appearance of errors. If you choose to place these elements inside, it is necessary to replace the usual electrical switches with other ones prepared to operate without risks in explosive atmospheres or with other types of chemical risks. Under these conditions, the switches become substantially more expensive and it makes sense to look for alternatives. It is proposed to incorporate a button based on a wireless tag (for example, RFID) that can be deactivated inside a glove box. For this function it is proposed to use one or more passive RFID tags as a control device. In normal operation, these labels would respond to an external signal indicating that they are present and operational. An external device to the glove box could map the existing RFID tags by assigning a function to each of them.

After pressing the tag, there would be a short circuit in the antenna that would temporarily eliminate the response signal from the tag. When the pressure was reduced, the tag would work properly again and send its signal back to the outside reader. This loss and recovery of the signal can be interpreted as an order on or off depending on the initial state of the device to be activated. For example, a single reader device could simultaneously read multiple labels and assign, by software, a specific function to each of them. The labels would be much easier to install, clean and move than a classic switch. In especially aggressive environments, disposable labels could be used and the reader device software used to reassign the same function to the new labels as they are installed.

Another simpler application is the adaptation of the home automation to the hospital environment, especially to the patients' rooms. Elderly patients or those with mobility problems can benefit from switches based on RFID tags that would allow simpler control systems for lights, blinds or help buttons that would replace the usual hodgepodge of electric switches with more ergonomic proposals. This alternative would be much simpler and cheaper than the installation of touch screens or other similar elements that are the main current tool to bring home automation to the hospital environment. Thanks to this, home development could be extended in the hospital environment by lowering its cost.

- Localization and alarm services. As already mentioned there are real-time localization systems (RTLS) for healthcare personnel (also applicable to any

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other personnel in a given installation) based on active RFID tags. However, its degree of implantation is limited due to their high cost. To address this obstacle, it would be interesting to study the use of the proposed passive deactivatable tags.

Each port center worker has a card with a passive label that can be deactivated. Under normal conditions, this label remains active and staff travel is controlled through a set of readers located throughout the facilities. In certain areas, such as bathrooms or rest areas, it would be possible to dispense with readers to ensure the privacy of employees. In case a person requires help, he would press his label that would stop working. A management software would detect this disappearance as well as the worker's last position and interpret it as a request for help. If pressure is no longer applied, the label can be located again which would allow the worker to be placed even if he is forced to move to another area. The installation of this system could be simplified using a technology similar to the Mojix system already mentioned that separates the activation functions of the labels and reading their position.

- Inventory control and alarm button on material. A more widespread application of localization systems is the inventory control of medical equipment present in a hospital. Systems that allow the location of objects with an accuracy of 5 to 12 centimeters have been tested, which is more than enough to allow the location of orthopedic aids such as crutches or wheelchairs. The use of these systems, or other simpler variants currently in use, allows a significant improvement in the logistics management of any mobile equipment that tends to be lost or stored in places not initially planned. An additional advantage is that, by accurately locating the position of orthopedic aids assigned to a patient, it can also keep the patient himself located and prevent him from unexpectedly leaving the area to which he is assigned. This is especially important in patients with mental problems such as Alzheimer's or other types of dementia that constitute a growing percentage of the patients admitted.

If we replace the normal passive RFID tags with deactivatable RFID tags we can incorporate an alarm button (which would work in the same way described in the previous application) to these orthopedic elements at very low cost and that would take advantage of

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existing infrastructure In this way, the patient could ask for help in case of getting lost or feeling disoriented.

This same application can be used in another type of material that is tracked and localized in other types of environments.

- Exercise meter performed. Performing a minimum of exercise is an essential part of recovery in a hospital. Quantify how much exercise has been done, during when, and at what rate, they can give very valuable information to the medical staff. Currently, this information is usually collected in a brief interview, so this collection is subjective, limited and prone to errors. In recent years, the use of quantifying devices has become popular among sports practitioners (for example, step meters), but its price (about 100 euros) makes its large-scale application unfeasible among hospital patients.

A much cheaper alternative would be to provide patients with templates that incorporate pressure-deactivatable RFID tags. Counting the number of times the label stops responding, it would be possible to count the steps taken, calculate the time spent walking and estimate the exercise performed by a patient or anyone whose activity you want to control.

In facilities equipped with RFID readers, such as a corridor, it would be possible to monitor multiple patients at a very low cost. Thanks to the high resistance of RFID tags it would be possible to reuse the templates after being washed and disinfected as is currently done with hospital clothes. If RFID readers have already been installed for another application, such as the one discussed in the previous section, the main cost would be the development of the control software

Although many of the embodiments and examples presented refer to the use of a material whose conductivity varies by pressure to change the geometry and therefore the characteristics of the antenna when said material is pressed, the present invention is not limited to this type of material. It can also be used any other type of material whose electrical resistance varies reversibly or irreversibly when subjected to a particular physical or chemical phenomenon. That is, a material that when subjected to a certain physical or chemical phenomenon goes from being insulating (with a high resistance) to

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be a conductor (with a very small resistance).

For example, a material that becomes irreversibly conductive can be used by exceeding a certain temperature threshold (for example, 0 ° C). This would allow to detect if a vaccine has broken the cold chain (and therefore must be discarded) since above 0 degrees the material would become conductive, changing the characteristics of the antenna and making it easily detectable that said temperature has been exceeded. Or a material that becomes reversibly conductive when the temperature leaves a certain range and becomes insulating again when the temperature is again within that range, so you can control how long the label has been outside the range of desired temperature. Or, for example, a material can be used which, before a certain chemical agent, becomes conductive, so it can be controlled when the label (and the product that has it attached) has been exposed to said agent.

Also, although many of the embodiments presented refer to a type of QTC type variable strength material, the present invention is not limited to this type of material but any other type of variable resistance material can also be used.

In summary, the main purpose of this proposal is the development of a deactivatable wireless tag that could replace, in certain applications, more expensive and complex systems (for example, based on the use of other technologies such as active RFID tags, Bluetooth, Zigbee , etc). The proposed wireless tags can be used in new functions, such as low-cost switches, pushbuttons or sensors, etc. Said labels proposed in the present invention have a series of significant differences with respect to the state of the art, such as:

• Variable resistance material (for example, piezoresistive material, of the QTC type ...) is not incorporated as a switch within the circuit but is used to modify the shape of the antenna.

• The wireless label (for example, RFID) is operative in the absence of the action of the physical or chemical agent (for example, the pressure on the part of the user), conversely as in the other examples presented. This means that under normal circumstances when the label is not being acted upon, it is possible at all times to check if the label works normally (or is in a certain area) or has been damaged (or is absent

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of the determined area). This cannot be done in other systems where the tag is only operational when the user acts on it (for example, presses it).

• It is a device based on the non-capture or reduction of the power of the received input signal and not on the frequency modulation, making the use of this type of labels much more economical (especially the reader devices thereof ). Although, as we have explained, it can also be done that in the presence of the appropriate physical or chemical agent the label does not work at a certain original frequency but at another second frequency.

• An important element in favor of this design is its low price. A passive RFID tag can be purchased for a few euro cents. The QFC material can be purchased in 3'5x3'5 mm square pieces at about 60 cents. The total cost of each handmade label is very low and could be reduced even more in a large-scale production.

In this text, the term "comprises" and its derivations (such as "understanding", etc.) should not be understood in an exclusive sense, that is, these terms should not be construed as excluding the possibility that what is described and defined can include more elements, stages, etc.

Some preferred embodiments of the invention are described in the dependent claims that are included below.

Describing sufficiently the nature of the invention, as well as the way in which it is carried out in practice, it is necessary to state the possibility that its different parts can be manufactured in a variety of materials, sizes and shapes, and can also be introduced into its constitution or procedure, those variations that the practice advises, as long as they do not alter the fundamental principle of the present invention.

The description and drawings simply illustrate the principles of the invention. Therefore, it should be appreciated that those skilled in the art may devise several provisions which, although not explicitly described or shown herein, represent the principles of the invention and are included within its scope. In addition, all the examples described in this document are provided primarily for pedagogical reasons to help the reader understand the principles of the invention and the concepts contributed by the inventor (s) to improve the technique, and should be considered as not

limiting with respect to such examples and conditions described specifically. In addition, everything stated in this document related to the principles, aspects and embodiments of the invention, as well as the specific examples thereof, cover their equivalences.

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Although the present invention has been described with reference to specific embodiments, those skilled in the art should understand that the foregoing and various other changes, omissions and additions in the form and detail thereof can be made without departing from the spirit and scope of the invention as defined by the following claims 10.

Claims (15)

5 10 fifteen twenty 25 30 35 1. Wireless label comprising: - an antenna; - at least one layer of material of variable electrical conductivity, in direct contact with the antenna and at least partially covering the antenna, said insulating material being in the absence of a determined external action on it and conductive when said determined external action occurs about it; where, in the absence of said determined external action, the antenna is capable of capturing radio frequency signals from a device at a certain first frequency and of emitting radio frequency signals to the device at said particular first frequency and where, when said action occurs externally determined, the antenna is not capable of capturing radio frequency signals from said device at said particular first frequency or sending radiofrequency signals to the device at said particular first frequency. 2. Wireless tag according to any of the preceding claims wherein said wireless tag is a radio frequency identification, RFID, or NFC near field communication type tag. 3. Wireless label according to any of the preceding claims wherein said variable conductivity material is a piezoresistive material. 4. Wireless label according to any of the preceding claims wherein said variable conductivity material is a Quantum Tunnel Composite type material, QTC. 5. Wireless label according to any of the preceding claims wherein said external action is a pressure on the label. 6. Wireless label according to any of the preceding claims wherein said antenna is formed by several turns of conductive material and the layer of material of 5 10 fifteen twenty 25 30 35 Variable conductivity is in contact with at least two of the turns and when said determined external action occurs, the at least one piece of material of variable conductivity short-circuits the turns with which it is in contact modifying the geometric characteristics of the antenna so It is not capable of capturing radio frequency signals from or emitting radio frequency signals to said device at said first frequency. 7. Wireless label according to claim 6 wherein the layer of variable conductivity material is in contact with all the turns of the antenna and when said determined external action occurs, all the turns of the antenna are short-circuited so it is not capable of capturing radiofrequency signals of or emitting radio frequency signals to said device at any frequency. 8. Wireless label according to any of the preceding claims 1-6, when said determined external action occurs, the antenna is capable of capturing radio frequency signals at a second frequency and emitting radio frequency signals at said second frequency. 9. Wireless label according to claim 8 where the antenna is divided into 2 parts and where the layer of variable conductivity material is only in contact with one of the parts, so that when said external action occurs said part that it is in contact with the material layer is short-circuited and where the antenna is capable of capturing and emitting radio frequency signals at the second frequency using the part of the antenna that is not in contact with the material layer of variable conductivity. 10. Wireless tag according to any of the preceding claims wherein the antenna from the signal received from the device at said first frequency generates energy that allows the wireless tag to operate. 11. Wireless tag according to any of the preceding claims wherein the device is a wireless tag reader device. 12. Wireless label according to any of the preceding claims wherein the layer of variable conductivity material is divided into at least 2 distinct portions without contact between them covering different parts of the antenna, each portion being in 5 10 fifteen twenty 25 30 35 direct contact with said different parts of the antenna. 13. Method of manufacturing a wireless label, where said method comprises: - provide on the label an antenna capable of capturing and emitting radio frequency signals; - depositing at least one layer of variable electrical conductivity material in direct contact with the antenna and at least partially covering the antenna, said insulating material being in the absence of a determined external action on it and conductive when said determined external action occurs about it; where, the layer of variable electrical conductivity material is deposited so that in the absence of said determined external action, the antenna is capable of capturing radio frequency signals from a device at a given first frequency and of emitting radio frequency signals to the device at said determined first frequency and, when said determined external action occurs, the antenna is not capable of capturing radio frequency signals from said device at said particular first frequency or sending radiofrequency signals to the device at said particular first frequency. 14. A system for the activation of functions associated with wireless tags, said system comprises: - a wireless tag according to any of claims 1-12, wherein the tag also comprises means for processing a radio frequency signal received through the antenna at said first frequency, and in response to said signal received, generate and transmit through the antenna, a response signal to a reading device at said first frequency; - the wireless tag reader device comprising: - means for periodically sending radio frequency signals at said first frequency to the wireless label, - means for receiving response signals from said wireless label to said periodically issued signals and - means for, when it receives no response signal from said wireless label to a signal emitted at said first frequency and after a certain time interval, it receives again 5 10 fifteen twenty 25 30 35 response of said wireless tag to another signal emitted at said first frequency, to activate a certain function associated with the wireless tag. 15. A method of activating a function associated with a wireless tag, said tag comprises an antenna and a layer of variable electrical conductivity material in direct contact with the antenna covering at least partially the antenna, said insulating material being in the absence of a determined external action and driver when said determined external action occurs and where the method comprises the following steps: - a wireless tag reader device sends a first radio frequency signal to said first frequency; - the wireless tag receives said radiofrequency signal from the antenna, processes the received signal and, in response to said received signal, transmits through the antenna, a response signal to the reading device at said first frequency; - the reading device receives the label signal and marks the label as detected; - performing the external action on the variable conductivity material and as a consequence, the antenna is not capable of capturing radio frequency signals from said device at said determined first frequency or sending radiofrequency signals at said determined first frequency; - the wireless tag reader device sends a second radio frequency signal to said first frequency; - when a period of time passes without the reader receiving a response signal from the tag to said second radio frequency signal, the reading device marks the tag as undetected; - the external action on the variable conductivity material is stopped and as a consequence, the antenna is capable of capturing radio frequency signals of said device at said determined first frequency and sending radiofrequency signals at said determined first frequency; - the wireless tag reader device sends a third radio frequency signal to said first frequency; - the wireless label receives through said antenna said third radio frequency signal, processes the received signal and in response to said received signal, transmits through the antenna, a response signal to the reading device at said first frequency; - the reading device receives the response signal from the label to said third signal of radio frequency, marks the tag as detected again and activates the function associated with that tag.