PROTECTIVE COVER WITH ELECTROMAGNETIC RADIATION SHIELDING EFFECT AND NANOGENERATOR OF ELECTRICITY THROUGH TRIBOELECTRIC EFFECT

Abstract

A protective cover for electronic enclosures or similar items, comprising at least one low-electronegativity layer and at least one high-electronegativity layer, exhibiting high electromagnetic radiation shielding, capable of generating electricity via the triboelectric effect, and potentially flame-retardant. The cover may also incorporate elements such as metallic nanoparticles and metallic electrodes to further enhance shielding, as well as flame-retardant elements.

Description

PROTECTIVE COVER WITH ELECTROMAGNETIC RADIATION SHIELDING EFFECT AND NANOGENERATOR OF ELECTRICITY THROUGH TRIBOELECTRIC EFFECT Field of invention The invention relates to a protective cover capable of shielding electromagnetic radiation, which can generate electricity through the triboelectric effect and which may also be flame retardant. This cover can be used in various products such as electronic circuit protection enclosures, for use in space applications, as well as in environments where ionizing or non-ionizing radiation and electromagnetic radiation and / or particle jets may be present, where it is necessary to monitor the movement of objects or people, and in potentially explosive environments. State of the art The invention relates to a protective covering, which can be either rigid or soft, that serves as a shield against electromagnetic radiation, can generate electricity based on the triboelectric effect, and can also be flame retardant. Thanks to the triboelectric effect, the material can monitor the object's movement and the pressure it withstands, as well as its temperature and humidity, optionally emitting warning signals based on readings from various integrated sensors. It is considered a necessary and highly useful invention for applications in environments where ionizing or non-ionizing radiation, as well as electromagnetic radiation and / or particle jets, may be present, where it is necessary to monitor the movement of objects or people, and in environments that may be explosive or have a high risk of fire. The objective is to provide a protective covering that, at a minimum, achieves electromagnetic shielding and nanoelectric power generation through the triboelectric effect, and which may also include the optional additional effect of flame-extinguishing properties in the presence of fire. Thus, if the material is a fabric, it is possible to manufacture a soft covering that protects against electromagnetic radiation from cosmic rays and electromagnetic radiation in different regions of the radio frequency spectrum. Furthermore, for it to be triboelectric and generate electricity on its own, materials with a substantial difference in electronegativity between their layers must be used.On the other hand, the protective covering can form part of an electrical circuit housing located, for example, in a space station, a spacecraft, an astronaut's suit, or in the spaces occupied by a nuclear power plant. Furthermore, it can be advantageously flame-retardant, and therefore, flame-retardant elements are used in its manufacture, dispersed on the surface of the polymer material or fabric. Numerous examples of materials that shield electromagnetic radiation and are potentially usable in the housings of the invention can be found in the literature. In [1], a review of different radiation-shielding materials is presented: Mu-metal, a high-permeability alloy composed of 14% iron, 5% copper, 1.5% chromium, and 79.5% nickel; brass; aluminum; silver; nickel; stainless steel; metallized plastics; and conductive carbon / graphite composites. These latter materials present problems such as corrosion, high density, or brittleness. Also included are plastics, such as those with conductive coatings, others with internal conductive fillings, and still others that are intrinsically conductive polymers. All of these latter materials utilize an internal metallic foil as a radiation shield.Regarding polymers with metals or metallized materials, we have PPY or poly(3,4-ethylenedioxythiophene) PEDOT fabric compounds, with a shielding of 36 dB for the 300 MHz frequency range [2]; PPY based on intrinsically hot adhesives [3], with more than 30 dB and for an absorption frequency of 300 MHz; PPY / p-toluenesulfonate compounds with more than 40 dB, for an absorption band from 300 MHz to 2 GHz; PPY compounds impregnated with conductive polymers [4], with 26 dB in the 1 to 2 GHz frequency range; with PPY impregnated with microporous polyethylene [5], which in the 10 kHz to 1 GHz frequency range presents 40-50 dB. Regarding shielding, no materials have been found in the literature that function as sensors with shielding values ​​up to 140 dB within a measurement frequency range of 30 MHz to 1.5 GHz (and less so from 1 MHz to 3 GHz) according to the ASTM D4935 standard, along with free-space shielding measurements with minimum values ​​from 2.6 GHz to 40 GHz. Furthermore, no materials have been found that are triboelectric, such that by combining the layers they can generate electricity and thus monitor movement while shielding electromagnetic radiation. They also lack flame-retardant materials that would make them fireproof or highly fire-resistant. There are some similar materials in the literature that may have a flame-retardant component [6][7], however, none have been shown to possess both shielding properties and high electrical generation efficiency. Similarly, alarm sensor materials exist, but none have been found to have shielding properties [8][9]

[10] . Summary of the invention With regard to electromagnetic shielding, the material used in the cover of the invention is preferably, though not necessarily, based on graphene, and a large quantity of it can be incorporated. In particular, graphene oxide and reduced graphene oxide are preferably used, as these are conductive particles that increase the dielectric constant, thus shielding electromagnetic radiation. Similarly, an increase in porosity will also enhance this shielding. Furthermore, the inclusion of metallic nanoparticles along with sheets or electrodes of aluminum or copper will also increase it. To produce the triboelectric characteristic, materials such as PVA (polyvinyl alcohol), which is highly electropositive, and others such as PVDF (polyvinylidene fluoride), which is highly electronegative, or PDMS (polydimethylsiloxane), which is somewhat less electronegative but harder, are used. This hardness is also controllable. The invention's housing combines an electropositive face with an electronegative face. Materials are sought that meet the shielding requirements in the frequency range of the ASTM D4935 standard, i.e., from 30 MHz to 1.5 GHz, and, outside this standard, from 1 MHz to 3 GHz for coaxial waveguide measurements and from 2.6 GHz to 40 GHz for free-space measurements. Shielding is also required for gamma, X-ray, or neutron radiation. Different possibilities for the electropositive and electronegative layers of the material used in the covers of the invention would be summarized in the following table: Table 1: where the meaning of the acronyms is as follows: PVA: Polyvinyl alcohol PVDF: Polyvinylidene fluoride PANI: APS (8-Aminopyren-1,3,6-trisulfonic acid) + (3-aminopropyl)triethoxysilane + Aniline. The combination of aniline with APS and (3-aminopropyl)triethoxysilane results in a material called PANI with specific properties, including improved conductivity and controlled morphology due to the presence of the sulfonic dopant and the potential additional functionality of the silane. PDMS: Polydimethylsiloxane. Gmp: Graphene. GO: graphene oxide. The material used in the cover of the present invention therefore has a high electronegativity layer and a low electronegativity layer, also referred to as the electropositive face, such that friction between them produces voltage pulses whose amplitude and waveform depend on the frequency, speed, acceleration, force, and displacement of the layers. In the present invention, the low electronegativity layer has a charge density of less than 100 C / m² and the high electronegativity layer has an absolute charge density greater than 400 C / m², with a dynamically generated charge density at a pressure of 1.6 kPa between layers of less than 0.7 mC / m².Therefore, if a very soft bilayer material is made with the compounds indicated in Table 1, the contact between layers due to the inertia of the movement to which the casing is subjected will allow the speed, acceleration and force of the movement to be measured, both by induction and by impact. Finally, to achieve the optional flame retardant characteristic, these materials can optionally incorporate phosphorus compounds as flame retardants, should this function be necessary or recommended. The compounds used for this purpose are of the PO type, with phosphorus in its oxidized state. These materials do not change the shielding, but they do reduce the electrical generation efficiency by approximately 10%. One compound with these characteristics is ammonium polyphosphate (APP). The fact that these bilayer materials can be used as triboelectric nanogenerators (TENGs) allows them to be used for motion monitoring and as triggers to initiate the operation of an electronic circuit. This enables their use as long-range remote warning devices, utilizing LoRa-type communication protocols. These motion-generated signals can also be monitored locally or remotely. Because TENGs do not use batteries and the communication chips operating under the LoRA protocol have very low power consumption, the system is self-sufficient for years, operating in standby mode when inactive. Ideally, the energy generator, without batteries, could operate indefinitely. In the present invention, a "triboelectric nanogenerator" or TENG is understood to be a device that converts mechanical energy into electrical energy by exploiting the triboelectric effect, that is, by generating static electricity through friction between dissimilar materials. Therefore, in its simplest form, a triboelectric nanogenerator is composed of two layers of different materials in contact with each other, having a significant difference in electronegativity. In the present invention, the materials used to construct these triboelectric nanogenerators are selected from those listed in Table 1. Also, "cover" refers to a material that is placed on top of another to protect it. On the other hand, the material used in the casing of the invention can be manufactured from a hard polymer such as PLA, allowing for applications such as aircraft or helmet protection, or electronic encapsulation. The movement of the box or housing using it can be achieved through the triboelectric effect. Brief description of the figures To complete the description and provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate preferred embodiments of the invention. The drawings comprise the following figures. Figure 1 shows various embodiments of the present invention, using different materials with varying electrical generation properties, their flame retardant characteristics (where applicable), and their electromagnetic shielding properties. These materials are as follows: PVA-GO7.5% (1), PVDF (2), PVA (3), PVA-GO7.5%PVA-GO50% (5), PDMS (6), PDMS-m (7), PVA-PANI (8), PET (9), Cu (10), PDMS+PVA+PANI (12), PDMS-GO7.5% (14), PVA+gmp (15%), and (15) PVA+gmp (15%)+PANI. The numbers in parentheses refer to the layer numbers shown in Figure 1. All may contain phosphor compounds as flame retardants, such as APP. All the proposed materials containing graphene (GO) shield non-ionizing radiation, especially gamma rays, X-rays, and neutrons. Furthermore, metallic nanoparticles can be added to all of them to further shield radio wave radiation from the spectra discussed in the manuscript. Furthermore, they may have a metallic electrode layer surrounding the polymer layers, which is a layer of Al or Cu. These shield gamma, X-ray, neutron, and non-ionizing radiation such as radio waves from the spoken spectrum. Figure 2 shows A) a hard protective case or cover made of a hard polymer with a double layer (one electropositive and one electronegative) manufactured from a graphene-coated material as shown in Figure 1, which protects the electronics inside from electromagnetic radiation and can act as a TENG (Transmitting Electromagnetic Enclosure). Figure B) shows a softer cover, usually made of nylon or cotton in the form of two layers, one electropositive and one electronegative, which protects it from electromagnetic radiation and acts as a TENG for monitoring. Figure 3 shows examples of triboelectric pulses for vibration frequencies of 0.2 Hz with the PDMS / PVA+PANI+GO1% bilayer and for forces of 100 (N) (28) and 1000 N (30) respectively. Figure 4 shows examples of calibration curves for PDMS / PVA-GO-0.15%, PDMS / PVA-GO-1%, PDMS / PVA-PANI. Figure 5 shows examples of electrical current and voltage calibration curves for stiffer materials of the PDMS (m) / PVA (m) type for different speeds and accelerations. Figure 6 illustrates the protection that soft or hard casings provide to chips or electrical components against electromagnetic radiation and how they can transmit signals via their protruding antennas to internet-connected devices. It also shows how they can function as alarm sensors for changes in temperature and humidity when movement is detected. Figure 7 shows the accuracies, losses, ROC curve, and confusion matrix for the results obtained with the classification and prediction algorithms performed with DL, for the amplitude and frequency classes of the pulses generated by the movement of the cover. Detailed description of the invention The covers of the invention can be made using different materials selected from those indicated in Table 1, the combination of which gives rise to different triboelectric nanogenerators with different electrical self-generation efficiencies, different shielding properties and flame retardancy. Therefore, in a first aspect, the protective cover of the invention comprises at least one low electronegativity layer having a charge density of less than 100 C / m2 and at least one high electronegativity layer having a charge density greater than 400 C / m2, with the charge density generated dynamically and for a pressure of 1.6 kPa between layers less than 0.7 mC / m2 and that, when used in the frequency range below 3 GHz, the cover has a shielding level greater than 18 dB, and when used in the frequency range between 3 GHz and 40 GHz, the cover has a shielding level greater than 55 dB. In a second aspect, the invention is directed to the use of the protective cover in the protection of boxes for electronic components. In a third aspect, the invention is directed to the use of the protective cover in the protection of aircraft or helmets. In a fourth aspect, the invention is directed to the use of the protective cover in electronic encapsulations. And in a fifth aspect, the invention is directed to any of the above uses in which the object to be protected is in high radiation environments such as outer space or nuclear power plants. The following materials have been manufactured that can act as triboelectric energy sensors with shielding properties. The list below indicates the materials that constitute, for each triboelectric generator, the electronegative layer material and the electropositive layer material respectively, separated by a slash (" / "). The number accompanying the acronym for graphene (gmp) or graphene oxide (GO) is the percentage of graphene or graphene oxide by weight over the weight of the corresponding layer: PVA-GO7.5% / PVDF, PVA / PVDF-GO7.5%, PVA-GO50% / PVDF, PVA-GO7.5% / PVDF-GO7.5%, PVA-PANI-GO7.5% / PVDF, PVA-GO7.5% / PDMS, PDMS(m)-PVA, PDMS / PVA-PANI, PDMS / PVA-GO50%, PVA+gmp(15%) / PDMS, PVA+gmp(15%)+PANI / PDMS. 1) PVA-GO7.5% / PVDF, 2) PVA-GO 50% / PVDF, 3) PVA-GO-7.5% / PDMS, 4) PDMS (m) / PVA, 5) PDMS / PVA-PANI, 6) PDMS / PVA-GO 50%, 7) PVA+gmp (15%) / PDMS, 8) PVA+gmp (15%) +PANI / PDMS, They all have shielding properties and high electrical efficiency. The order of electrical efficiency is inversely related to that of electrical shielding, as graphene reduces electrical efficiency. Shielding is primarily determined by the amount of graphene and graphene oxide present in the sample. Graphene generally reduces triboelectric efficiency slightly. Thus, the order from highest to lowest shielding efficiency would be as follows: PDMS / PVA+gmp (15%) +PANI > PDMS / PVA+gmp (15%) > PDMS / PVA-GO-50%>PDMS / PVA-GO-7.5% > PVA-GO50% / PVDF > PVAGO7.5% / PVDF > PDMS (m) / PVA > PDMS / PVA-PANI In the context of the present invention, for the described compounds, for frequencies below 3 GHz, a high electromagnetic shielding level is considered to be a value greater than 20 dB and a low electromagnetic shielding level is considered to be a value less than 12 dB. For frequencies between 3 GHz and 40 GHz, a high electromagnetic shielding level is considered to be a value greater than 55 dB and a low electromagnetic shielding level is considered to be a value less than 40 dB. Thus, PDMS / PVA+gmp (15%) will have a high shielding level, while PVA-PANI-GO 7.5% / PVDF will have a low shielding level. When metallic foils are used, the shielding is superior and can reach more than 50 dB for all triboelectric generators across the entire frequency range (1 MHz - 40 GHz). However, the more graphene / GO there is in the layers, especially with PVDF, the lower their electrical efficiency will be compared to those with only PDMS or PVDF. Thus, the electrical efficiency, characterized by the difference in electronegativity between layers, will be as follows: PVA-GO7.5% / PVDF > PVA-GO50% / PVDF > PDMS / PVA+gmp (15%) > PDMS / PVA+gmp (15%) +PANI > PDMS / PVA-GO-50% > PDMS / PVA-PANI > PDMS (m) / PVA. With these compounds, the following bilayer materials have been produced according to the invention, using the electropositive and electronegative layers indicated, where the numbers in parentheses correspond to the numbering of the layers in Figure 1: • The TENG A has an electropositive layer of PVA-GO7.5% (1) and an electronegative layer of PVDF (2). • The TENG C has an electropositive layer of PVA-GO7.5%PVA-GO50% (5) and an electronegative layer of PVDF (2). • TENG D has an electropositive layer of PVA-GO7.5% (1) and an electronegative layer of PDMS (6). • The TENG G has an electropositive layer of PVA (7) and an electronegative layer of PDMS-m (3) (modified with nanohorns). • The TENG H has an electropositive layer of PVA-PANI (12) and an electronegative layer of PDMS (6). • The TENG I has an electropositive layer of PVA-GO7.5%PVA-GO50% (5) and an electronegative layer of PDMS (6). • The TENG J has an electropositive layer of PVA+gmp15% (15) and an electronegative layer of PDMS (6). • TENG K has an electropositive layer of PVA+gmp (15%) +PANI (16) and an electronegative layer of PDMS (6). When PVDF is used, it can be replaced by PDMS. All these materials have shielding properties and high electrical efficiency. Protective copper or aluminum sheets and PET can be optionally added to all these bilayer materials. In a preferred embodiment of the invention, the low electronegativity layer comprises at least one fabric selected from nylon, cotton, PDMS, PLA or PVA, either modified with nanohorns or unmodified, fabric that is impregnated in a compound selected from polyvinyl alcohol (PVA), graphene (gmp), graphene oxide (GO) and PANI (8-aminopyren-1,3,6-trisulfonic acid (APS) + (3-aminopropyl) triethoxysilane) + aniline) and mixtures thereof. In another preferred embodiment, the high electronegativity layer comprises at least one fabric selected from nylon, cotton, PDMS, PLA or PVA, either modified with nanohorns or unmodified, fabric that is impregnated in a material selected from polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), graphene oxide (GO) and mixtures thereof. In another embodiment, in the protective cover the low electronegativity layer fabric is impregnated in a compound or combination of compounds selected from the list consisting of PVA, PVA-GO 7.5%, PVA-GO 50%, PVA-Gmp 50% and PVA-PANI. In another embodiment, the high electronegativity layer fabric is impregnated in a compound or combination of compounds selected from the list consisting of PVDF, PDMS and PDMS-GO 7.5%. In another embodiment, the protective coating is composed of the following compounds or combinations of compounds that impregnate the high and low electronegativity layers respectively: PVA-GO7.5% / PVDF PVA / PVDF-GO 7.5% PVA-GO 50% / PVDF PVA-GO-7.5% / PDMS PDMS (m) / PVA PDMS / PVA-PANI PDMS / PVA-GO 50% PVA+gmp (15%) / PDMS PVA+gmp (15%) +PANI / PDMS. In another embodiment of the protective covering, the fabric also comprises magnetic nanoparticles. In another embodiment, the protective cover also comprises metal sheets that enclose the triboelectric nanogenerator. In another embodiment, the metal sheets are made of Al or Cu, and with them the cover shows a shielding of up to 50 dB for all triboelectric generators across the entire frequency range from 1 MHz to 40 GHz. In another embodiment, the protective cover further comprises at least one flame-retardant material. In another embodiment, the protective covering in which the flame retardant material is a phosphorus compound such as ammonium polyphosphate. In another embodiment, when used in the lower frequency range of 3 GHz, the cover has a high shielding level greater than 18 dB, with the low shielding level being considered to be a value less than 10 dB for frequencies below 3 GHz. In another embodiment, when used in the frequency range between 3 GHz and 40 GHz, the protective cover has a high shielding level that is greater than 55 dB, with the low shielding level being considered to be a value less than 40 dB for frequencies between 3 and 40 GHz. In another embodiment, the protective coating is composed of the following compounds or combinations of compounds that impregnate the high and low electronegativity layers respectively PDMS / PVA+gmp and that have the following order of preference according to the degree of shielding: PDMS / PVA+gmp (15%) > PDMS / PVA+gmp (15%) +PANI > PDMS / PVA-GO-50% > PDMS / PVA-GO-7.5% > PVA-GO50% / PVDF > PVAG7.5% / PVDF> PDMS (m) / PVA > PDMS / PVA-PANI. In another embodiment, the protective cover is configured to act as a temperature sensor by measuring the mechanical amplitude of the signal generated by friction between the high and low electronegativity layers compared to the signal generated by another sensor that serves as a reference. The housing of the present invention may additionally include various types of sensors, should this function be necessary or convenient. In preferred embodiments of the invention, these sensors are sheets of copper or aluminum, or even heavier metals, which can be placed in the polymer areas of the TENG. Electrodes or thin wires extend from these to connect to the various acquisition systems or signal processing and communication chips. The covers of the invention can have different uses, for example: A) Robust protective layers for electronics (19) and radiation shielding. To act as a radiation shield, they must contain graphene and are preferably porous. They can be made of PVA+gmp (15%) +PANI (16) as an electropositive layer and have another electronegative layer (17) which can be any of those mentioned previously. In this way, the protective casing (18) inside, where chips may be located, should advantageously be at least partially flexible and can monitor the vibration state of the environment or the impact it suffers, as well as protect it from heat or flame in case of fire. B) The cover of the invention may also take the form of a preferably flexible fabric or textile material so that it can be folded like a blanket, with an electropositive layer (17) and an electronegative layer (18), and which can act as a protective covering for the chip (19) it encloses. The cover may have a flame-retardant coating to protect it from potential fires. Preferred embodiment of the invention: First, the following materials with shielding and triboelectric generation properties are produced: PVA-GO 15% / PVDF, PVA / PVDF-GO 15%, PVA-GO 50% / PVDF, PVA-GO-7.5% / PDMS, PDMS (m)-PVA, PDMS / PVA-PANI, PDMS / PVA-GO 50%, PVA+gmp (15%) / PDMS, PVA+gmp (15%)+PANI / PDMS. The higher the graphene content, the greater the electromagnetic shielding of the material. Depending on the movement of the box, we will see different pulse generation due to the triboelectric effect. In the case of PDMS / PVA+GO (50%) (TENG C) (6) and (3), with slow movement (frequencies of 0.2 Hz), we can observe fast, more impactful pulses with higher amplitudes (20) and with materials that generate a large amount of pulse, such as TENG F (layers (6) and (11)), due to the greater efficiency of electrical generation when its layers come into friction or contact, and also depending on the tensile / compressive force exerted (100 N). Similarly, other types of pulses appear for the same TENG F (21) with layers (6) and (11) but with a greater force (1000 N) and with the same speed (70 mm / min) and frequency, where an impact pulse is observed. All these measurements allow us to obtain calibration curves, making the cover, for example for electronic protective enclosures, a sensor of motion, speed, acceleration, force, or pressure. The Force vs. Voltage calibration curves vary depending on the material: thus, we have different calibration curves for different types of materials such as: PDMS / PVA-GO-7.5% (22), PDMS / PVA-GO-7.5% (23), and PDMS / PVA-PANI (24). It is observed that the PANI material has a higher electrical generation efficiency compared to the soft materials and that the forces are high because the materials are soft. The tests were performed with a tensile-compression machine that has a 2 kN load cell. A 50 Hz low-pass filter was used. In addition, all the TENGs with graphene have the property of electromagnetic shielding, and the calibration curves show linear behavior, but for two different slopes. For more rigid structures such as PDMS (m) (7) / PVA (m) (3), we can also obtain sensors for velocity, acceleration, force, displacement, etc. To do this, we performed calibration curves, although this time the measurements were taken with a sphere placed inside a prismatic box fixed to a vibration table, on whose walls the TENGs rested. A sphere impacted these TENGs and generated different voltage pulses. The vibration table varied at different frequencies (1, 2, 3, 4, and 5 Hz), and the impacts generated different voltage (25) and current (26) values. The calibration curves are shown for the magnitude of Force (F) versus the magnitudes of voltage (V) (27), current (I) (28), velocity (29), and acceleration (40). In these cases, since the material is harder and has high efficiency, the pulses have a greater amplitude in voltage, and the behavior is linear with a single slope. The material of the invention could also function as an alarm sensor in the event of a temperature rise or fire. In this case, the electrically generated signal would have a different mechanical amplitude than if there were no high temperature, thus warning of an emerging fire or temperature rise due to a programmed voltage vs. temperature threshold known from a prior T vs. V calibration. Furthermore, the conductivity of the graphene-containing material (oxidized and reduced) would increase with temperature and humidity. On the other hand, the physical quantities of frequency, velocity, acceleration, and displacement can be analyzed using Deep Learning (DL) programs with multiple processing layers. In this way, through controlled environments of pulse amplitude and frequency, it is possible to classify and predict these quantities based on noise, baseline values, and pulses produced by the triboelectric layers. As mentioned, the purpose of the enclosure is to protect electronic and communications systems from radiation damage. Because of this protection, polymer enclosures can also be manufactured to shield the electronics inside. If cables need to extend from the enclosure, they will preferably be surrounded by the polymer and embedded in the matrix during the manufacturing process, as will any external antenna required for communication. This antenna will preferably be sealed to prevent gaps. For more rigid protective enclosures, materials such as unmodified or carbon nanohorn-modified PDMS and PVA can be used. Optionally, fabrics and covers can be coated with a phosphorus-containing component coating (e.g., ammonium phosphate or APP) that acts as a flame retardant. On the other hand, the covers can be used to manufacture enclosures to protect the communications and electronic systems housed within them. A sealed antenna can protrude from this enclosure to transmit information. Both rigid and soft covers will generate voltage pulses in vibration situations, and in the case of excess temperature, these signals will be different in amplitude and waveform, thus constituting a temperature sensor. The covers, due to their protection with phosphorescent elements (i.e., APP), can be subjected to fire or high temperatures, thus allowing a warning of the critical situation to be sent. These covers can also be used to manufacture early warning systems (EDAS) and long-range warning systems (LDAS) that can send warning signals hundreds of kilometers away when using the LoRA protocol, and even into space. The same can be applied to temperature and humidity, allowing for the creation of a temperature sensor that will send alerts wirelessly. For each fabric cover or box manufactured, calibration curves can be generated with the selected materials. These curves will allow us to determine the calibrated physical magnitudes as a function of the generated pulse. Deep Learning (DL) algorithms can then be used with the pulses generated by the movement of the fabrics or the walls of the boxes, utilizing the same generated data. The majority of the initial data will be used to train the model, enabling the subsequent use of classification and prediction algorithms. The speed, acceleration, force, displacement, and frequency of the moving and monitored user can be determined from the waveform of the pulses generated by algorithms programmed using Machine Learning and Deep Learning. Similarly, vibrations experienced by more rigid covers or boxes housing electronic and communication systems can also be analyzed. The entire protective enclosure can be shielded, thus protecting electronic or communications devices (19) located inside a building, a radioactive installation, exposed to flames (32), etc. A double-walled radiation shield (16), one wall made of electronegative material (17) and the other of much less so (18), can be flexible and, due to the inertia of movement, generate a signal by induction (34) or contact (35). The double-walled enclosure is manufactured with the layers described above, depending on the application. Sometimes an inertial mass may be inside the enclosure. The electronics (19) are protected from electromagnetic radiation and act as a shield, since they are transformed into a TENG (Transformer Electronegative Element) with graphene.Movement in different directions (35), (36) in space will generate pulses of varying amplitude and width. Depending on the calibration curves obtained, we can determine the velocity, force, acceleration, and displacement of the box relative to a stationary reference frame. An antenna, tightly sealed to the box, extends from it (37) and emits the movement signal or the pre-programmed warning message, depending on the threshold reached. As mentioned in the case of the suit, the box can be made of any of the materials cited above (TENG AK), although if greater rigidity is desired, it can typically be constructed from PDMS (m) (3) - PVA (m) (6) layers with a rigid but not overly rigid plastic cover, such as PET (9). Recall that all data can be sent to the cloud (33).The materials can be fire-resistant (32) due to the coating of the enclosure with phosphorus-based composite materials (flame retardant, such as HPO). Recall also that the chemical elements (1) - (16) could be distributed in fabrics such as cotton, forming two layers of different electronegativity (17) and (18) that will protect the electronics (19) with its protruding antenna (38). These electrical pulses depend on the direction (39) of the system's movement and the speed and acceleration to which the (semi-)rigid layers-electronics assembly is subjected. Again, the information will be sent to the cloud (33) via LoRa or another communication protocol. The fabrics or layers of material of the enclosure can be fire-resistant and flame-extinguishing (32). Deep Learning can be used to classify physical quantities using different neural layers. This involves using datasets related to different frequencies, as well as datasets related to different amplitudes. Considering the different frequencies or classes: The accuracy results (40) in the classification are high (almost 100%), both for the training and validation populations. Data loss (41) is relatively low, around 1% for the training data and an average of around 5% for the validation. The ROC curve (true positives vs. false positives) (42) achieves 100% for all classes. For data classification / prediction, the last string of data in each file is selected, and the different frequencies are predicted.To study the accuracy of the prediction (44), we use the confusion matrix, obtaining a very high value on the diagonal, thus demonstrating the model's high efficiency. This shows that, in a controlled frequency environment, we are able to predict frequencies based on the pulse shape and the baseline with virtually 100% accuracy. Therefore, in the case of an astronaut's suit or a typical user, we will be able to determine the velocities, frequencies, forces, accelerations, and displacements that occur when they move. Regarding amplitude classification, very similar results are obtained for accuracy (61), data loss (45), ROC cure (46), and confusion matrix (47). The cover of the invention does not require batteries to operate due to the triboelectric effect as its operating principle. Its monitoring or warning electronics can be powered by the movement of the cover itself, which generates electrical energy and simultaneously detects the movement. The communications system will send pulses to a remote server or locally obtained information to that server. It can also be sent to a clock or display worn by an operator monitoring the facility. Depending on the temperature of the box walls and the mechanical impulse received, this temperature will be known based on the variation of the amplitude of the generated pulses and the pulses obtained from another sensor (piezoelectric, for example) that serves as a reference and that responds differently to the temperature. On the server or on an embedded card such as Raspberr and Pi 5, Deep Learning techniques will be used that will allow us to know, based on the frequency and amplitude of the pulses, along with their bandwidth, the physical magnitudes of speed, acceleration, displacement and force exerted. The more movement there is, the better trained the system will be with the different pulses recorded to predict and classify. The communication technologies to be used will be LoRa, for long-distance transmission and reception, and above all, low power consumption. For shorter distances and higher bandwidth, Wi-Fi, Zigbee, or Bluetooth, among others, will be used. We can perform triangulation with LoRA transmitters and thus know the position of the objects protected by the cover, although the error in the measurement will have to be taken into account. Literature [1] D. D. L. Chung, "Materials for electromagnetic interference shielding, " Mater. Chem. Phys., vol. 255, no. April, p. 123587, 2020, doi: 10.1016 / j.matchemphys.2020.123587. [2] P. Chandrasekhar and K. Naishadham, "Broadband microwave absorption and shielding properties of a poly (aniline) , " Synth. Met., vol.105, no.2, pp.115-120, 1999, doi: 10.1016 / S0379-6779 (99) 00085-5. [3] S. K. Dhawan and D. C. Trivedi, "Thin conducting polypyrrole film on insulating surface and its applications, " Bull. Mater. Sci., vol.16, no.5, pp.371-380, 1993, doi: 10.1007 / BF02759550. [4] Y. K. Hong et al., "Electromagnetic interference shielding characteristics of fabric complexes coated with conductive polypyrrole and thermally evaporated Ag, " Curr. Appl. Phys., vol. 1, no. 6, pp. 439-442, 2001, doi: 10.1016 / S1567-1739 (01) 00054-2. [5] K. S. Kim et al., "Large-scale pattern growth of graphene films for stretchable transparent electrodes, " Nature, vol. 457, no. 7230, pp. 706-710, 2009, doi: 10.1038 / nature07719. [6] A. Yusuf, J. S. del Río, X. Ao, I. A. Olaizola, and D. Y. Wang, "Potential energyassisted coupling of phase change materials with triboelectric nanogenerator enabling a thermally triggered, smart, and self-powered IoT thermal and fire hazard sensor: Design, fabrication, and applications, " Nano Energy, vol. 103, 2022, doi: 10.1016 / j.nanoen.2022.107790. [7] J. S. del Río et al., "High-resolution TENGS for earthquakes ground motion detection, " Nano Energy, vol.102, 2022, doi: 10.1016 / j.nanoen.2022.107666. [8] X. Li, J. S. del Río Saez, X. Ao, A. Yusuf, and D. Y. Wang, "Highly-sensitive fire alarm system based on cellulose paper with low-temperature response and wireless signal conversion, " Chem. Eng. J., vol. 431, 2022, doi: 10.1016 / j.cej.2021.134108. [9] X. Li, J. S. del Río Saez, X. Ao, B. Xu, and D. Y. Wang, "Tailored P / Si-decorated graphene oxide-based fire sensor for sensitive detection at low-temperature via local and remote wireless transmission, " Constr. Build. Mater., vol.349, 2022, doi: 10.1016 / j.conbuildmat.2022.128600.

[10] X. Li, J. Sánchez del Río Sáez, S. Du, R. Sánchez Díaz, X. Ao, and D. Y. Wang, "Bio-based chitosan-based film as a bifunctional fire-warning and humidity sensor, " Int. J. Biol. Macromol., vol. 253, no. May, 2023, doi: 10.1016 / j.ijbiomac.2023.126466.

Claims

1. A protective cover comprising at least one low electronegativity layer having a charge density of less than 100 C / m² and at least one high electronegativity layer having a charge density greater than 400 C / m², with the dynamically generated charge density for a pressure of 1.6 kPa between layers being less than 0.7 mC / m², and wherein, in the frequency range below 3 GHz, the cover has a shielding level greater than 18 dB, and in the frequency range between 3 GHz and 40 GHz, the cover has a shielding level greater than 55 dB. 2.A protective cover according to claim 1, wherein the low electronegativity layer comprises at least one fabric selected from nylon, cotton, PDMS, PLA, or PVA, either modified with nanohorns or unmodified, the fabric being impregnated with a compound selected from polyvinyl alcohol (PVA), graphene (gmp), graphene oxide (GO), and PANI (8-aminopyren-1,3,6-trisulfonic acid (APS) + (3-aminopropyl)triethoxysilane) + aniline) and mixtures thereof.

3. A protective cover according to claim 1 or 2, wherein the high electronegativity layer comprises at least one fabric selected from nylon, cotton, PDMS, PLA, or PVA, either modified with nanohorns or unmodified, the fabric being impregnated with a material selected from polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), graphene oxide (GO), and mixtures thereof. 4.Protective cover according to any one of claims 1 to 3, wherein the fabric of the low electronegativity layer is impregnated with a compound or combination of compounds selected from the list consisting of PVA, PVA-GO 7.5%, PVA-GO 50%, PVA-Gmp 50%, and PVA-PANI.

5. Cover according to any one of claims 1 to 4, wherein the fabric of the high electronegativity layer is impregnated with a compound or combination of compounds selected from the list consisting of PVDF, PDMS, and PDMS-GO 7.5%.

6. Protective coating according to any of claims 1 to 5, comprising the following combinations of compounds impregnating the high and low electronegativity layers respectively: • PVA-GO7.5% / PVDF • PVA / PVDF-GO 7.5% • PVA-GO 50% / PVDF • PVA-GO-7.5% / PDMS • PDMS (m) / PVA • PDMS / PVA-PANI • PDMS / PVA-GO 50% • PVA+gmp (15%) / PDMS • PVA+gmp (15%) +PANI / PDMS 7.Protective cover according to any one of claims 1 to 6, wherein the fabric further comprises magnetic nanoparticles.

8. Protective cover according to any one of claims 1 to 7, further comprising metallic sheets enclosing the triboelectric nanogenerator.

9. Protective cover according to claim 8, wherein the metallic sheets are made of Al or Cu, and with them the cover provides shielding of up to 50 dB for all triboelectric generators across the entire frequency range from 1 MHz to 40 GHz.

10. Protective cover according to any one of the preceding claims, further comprising at least one flame-retardant material.

11. Protective cover according to claim 10, wherein the flame-retardant material is a phosphorus compound such as ammonium polyphosphate. 12.A protective cover according to any of claims 1 to 11, comprising the following combinations of compounds impregnating the high and low electronegativity layers respectively, and having the following order of preference according to the degree of shielding: PDMS / PVA+gmp (15%) > PDMS / PVA+gmp (15%) +PANI > PDMS / PVA-GO-50% > PDMS / PVA-GO-7.5% > PVA-GO50% / PVDF > PVA-GO7.5% / PVDF > PDMS (m) / PVA > PDMS / PVA-PANI.

13. A protective cover according to any of the preceding claims, configured to act as a temperature sensor by measuring the mechanical amplitude of the signal generated by friction between the high and low electronegativity layers compared to the signal generated by another sensor serving as a reference.

14. Use of the protective cover of any of claims 1 to 13 in the protection of enclosures for electronic components. 15.Use of the protective cover of any of claims 1 to 13 for protection in aircraft or helmets.

16. Use of the protective cover of any of claims 1 to 13 for the protection of electronic encapsulations.

17. Use of any of claims 14 to 16, wherein the object to be protected is in high-radiation environments such as outer space or nuclear power plants.

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