Field of the Invention

The present invention relates to a sensor suitable for a smart shoe and/or smart clothing for complex monitoring of user data, in particular to a sensor suitable for the detection of pressure or tensile deformations, e.g. for monitoring of the foot-strike pressure field or deformations due to body functions such as breathing. The present invention further relates to a method of manufacture of said sensor and to its use, in particular for application into a shoe or fabric. Furthermore, the present invention relates to a smart shoe and a smart fabric or clothing which comprises said sensor of the present invention.

Background of the Invention

At present, there is an increased research and application interest in the area collectively called wearable electronics or wearables. This is due to the development in multi-disciplinary areas, such as electrical engineering, programming and software, development of mobile systems (Portable Systems, PA systems), as well as in material science in the field of development, design and testing of new materials. Wearable electronics includes integrated intelligent features that can be worn on the body like various electronic devices, sensors, control modules, devices for transmission and wireless signal transfer, battery power, and the like. It is a complex system containing additional features such as software and apps for mobile phones to evaluate and interpret data from monitoring. Development also includes the development of intelligent algorithms capable of analysing collected data using techniques of analytical methodology such as extracting data leading to retrieval of non-trivial hidden and potentially useful information, statistical classification where a category of phenomenon is identified using an embedded database of previously described observations (training set of data) and/or for example by creating so-called neural networks (Artificial neural networks, ANNs), when these computing systems are able to learn or increase their performance by performing tasks using examples, without the intervention of a programmer.

Wearable electronics then serves to monitor, for example, the physical activity of an individual, or to control and monitor the various body functions of an individual, for example in the area of so-called assisted living or care for the elderly. Here, for example, it is possible to collect biometric data from the human body, like the heart rate (ECG and HRV), brain activity (EEG) or muscle biological signals (EMG).

A widely used group of sensors that allow such monitoring and are suitable for wearable electronics are piezoresistive sensors, i.e. resistive sensors, based on a detection of electrical resistance of a member in its geometrical deformation. By applying an external mechanical force, the dipoles deform and a charge arises on the surface of the crystal (direct piezoelectric effect). Deformation in the direct piezoelectric effect is most often caused by push or pull within the limits of the Hooke ^' s law. The basic function of semiconductor strain gauges is therefore the transformation of a change of their dimensions in a determinable direction to a change of resistance. This electrical response describes the character and intensity of the deformation.

Sensors differ in their sensitivity; they are characterized by the so-called deformation sensitivity K (gauge factor GF).

Piezoresistive sensors - such as the metal foil strain gauges are made of metal alloys with factor K close to 2 and then are selected with respect to the minimum temperature coefficient of resistance. Other type is a sputtered metal strain gauge. These gauges are produced by sputtering in a vacuum where the dielectric layer is first formed on a carrier plate (e.g. silicone) and then the active layer. The same materials are used as for foil strain gauges (Cermet, Nichrome and others).

Mention can be made, for example, of copper-based materials with a gauge sensitivity factor (GF), indicating a change around 2.5 in the sensor resistance due to its deformation. A commonly used metal wire strain gauge (in the form of a bellows in an elastic film) has GF value between 2 and 5.

Also known is a pressure sensor of carbon nanotubes described in the Czech patent application PV 2010-506, which describes a pressure sensor comprising a thermoplastic polymer-based flat carrier with an anchored sensor layer comprising interleaved multi-walled carbon nanotubes (Multi -Walled Carbon Nanotubes - MWCNTs) with a diameter of 5 to 10 nm and a length of 1 to 20 μπι, with a porosity of 0.5 to 0.9 and a specific resistance 0.01 to 1 Ω/cm, wherein said sensor layer is connected to an electrical circuit equipped with a resistance sensor with pressure signalling. The sensitivity of these carbon nanotubes is GF ~ 10-20.

The extent of deformations caused by body functions, in particular breathing, is up to a maximum of 12 to 14 percent according to the disposition of an individual, and the extent of deformations caused by foot-strike in the shoe is even higher, up to 30 percent. Commonly known and used strain gauges are not capable of detecting deformations in this extent because their detection range is between deformations from 2 to 5 percent.To detect such deformations, a significantly more sensitive sensor is needed than sensors made from the above materials. Summary of the Invention

It is therefore an object of the present invention to provide a sensor with increased sensitivity, suitable for measuring deformations of higher extents. The solution is provided by the sensor as defined in claim 1.

The sensor of the present invention is made based on a polymer nanocomposite material containing electrically conductive multi-walled carbon nanotubes (Multi-Walled Carbon Nanotubes - MWCNTs), and comprise a polymeric matrix consisting of highly elastic thermoplastic polyurethane and a functional layer containing electrically conductive multi- walled carbon nanotubes MWCNTs.

The polymeric matrix of the highly elastic thermoplastic polyurethane serves as an elastic carrier for the functional MWCNT layer, said functional MWCNT layer being fixed in the polymeric matrix so that the deformation detected by the MWCNT layer is transferred to the polymeric matrix. Deformation results in a sensitive, reversible and lasting change, in many cycles, in the electrical resistance of the MWCNT layer. Additionally, the polymer matrix serves as an adhesive layer for melt bonding to the fabric.

The functional carbon layer is fixed by filtration on a polyurethane filter, wherein the carbon layer thickness is in the range of 15 to 45 μπι, preferably the layer thickness is approximately 30 μπι, wherein the polyurethane filter thickness is in the range of 15 to 50 μπι, preferably approximately 18 μπι.

The functional layer contains electrically conductive multi-walled carbon nanotubes MWCNTs, wherein the carbon nanotubes in the layer are randomly entangled and have a diameter of 10 to 30 nm, preferably 18 nm, and a length of 0.3 to 3 μπι; after formation of the functional carbon layer, the layer porosity is 0.6 to 0.75. Purity of carbon nanotubes ranges from 90 to 95 percent. To increase the sensitivity of the deformation detection, the surface of carbon nanotubes (MWCNTs) is adapted to increase/reduce the contact electrical resistance between the individual carbon nanotube crossings within the layer.

In a preferred embodiment, the carbon nanotubes comprise oxo-groups on their surface which are deposited therein by chemical treatment of carbon nanotubes, e.g. by oxidation with KMn0 ₄ /H ₂ S0 ₄ solution, oxidation with concentrated HNO ₃ , HNO ₃ /H ₂ SO ₄ nitrating mixture or 30% hydrogen peroxide, where the introduction of oxo-groups on the surface of MWCNTs increases the contact electrical resistance between the individual CNT network crossings and thus increases its sensitivity to the deformation stimulus. This treatment takes place before the sensor itself is manufactured. The sensor containing carbon nanotubes oxidized with KMn0 ₄ /H ₂ S0 ₄ solution has higher sensitivity compared with other solutions used; it has sensitivity of GF ~ 30-40.

In another preferred embodiment, the carbon nanotubes comprise silver (Ag) clusters which are deposited therein by chemical treatment of carbon nanotubes, e.g. by reduction from AgN0 ₃ solution. This treatment takes place before the sensor itself is manufactured. The sensor containing carbon nanotubes with silver clusters on the surface of the tubes has GF sensitivity ~ 15-25.

In another preferred embodiment, the sensitivity can be increased by the application of elastomeric spherical nano-spacers, which are the products of e.g. microemulsion polymerization techniques. The application of nano-spacers is particularly advantageous in combination with silver clusters for the pressure sensor, as will be described below.

In another preferred embodiment, the sensitivity of the sensor can be further increased by applying the pre-stress at a deformation level in the extent of 40 to 60 percent, preferably at 50 percent. In addition to the increase in sensitivity, this treatment also has a stabilizing function. For example, in an embodiment in which the sensor is applied as a tensile sensor onto clothing, e.g. T-shirt, for monitoring breathing, the sensor when taking T-shirt on and off is deformed at a higher extent than in the tested breathing. The pre-stress in the above-mentioned deformation extent is within the extent of deformations that occur when T-shirt is taken on or off. In these high deformations, partially irreversible deformations of the functional MWCNT layer occur as well as plastic deformation of the polymer matrix, whereby the sensor is stabilized for measured deformations when breathing when material changes to the sensor fixed on the T-shirt are no longer produced. Similarly, the tensile sensor can be stabilized prior to application to a smart shoe, where, for example, when taking on the shoes, the sensor can be subjected to deformation of a higher extent than when used for walking or running.

Sensor stabilization also occurs through use, with a partial irreversible change of resistance and deformation of several percent being recorded in the first cycles, which can be partly due to irreversible damage to the carbon layer and also due to plastic component of deformation of the polymer matrix. Sensor stabilization occurs when multiple cycles are applied, approximately 20 cycles.

The pre-stress is applied to the sensor after the sensor has been applied to the substrate, i.e. onto fabric or into the shoe insole, depending on the sensor application.

By combining the treatments, the sensitivity of the sensor will increase; with the combination of all the above treatments, the sensor's sensitivity will increase to GF ~ 50-60.

The above sensitivity values are given for the deformation extent of 12 to 14 percent and are measured for the sensor already applied to the fabric (GF increases with deformation).

Combining the functional layer of carbon nanotubes MWCNT containing any of the above treatments or their combination with highly elastic and flexible polymer matrix will provide a sensor that is sufficiently elastic and flexible, while sensitive enough and thus suitable for detecting deformations of the foot-strike pressure field in the footwear as well as deformations within the extent of deformations due to body functions, in particular breathing.

The present invention also provides a set of sensors forming a sensor array, for example for complex sensing of larger areas.

The present invention further provides a method of manufacturing a sensor of the present invention as defined in claim 2.

The sensor of the present invention is made on the basis of polymeric nanocomposite material containing electrically conductive multi-walled carbon nanotubes (MWCNTs).

The method of manufacturing the sensor of the present invention comprises preparing a filtration membrane of thermoplastic polyurethane nanofibres to make a functional layer of carbon nanotubes MWCNTs, wherein the filtration membrane is preferably prepared by electrostatic spinning from a polyurethane solution in dimethylformamide (DMF). The prepared membrane, provided as a nonwoven fabric of TPU fibres with sub-micron diameters, is subsequently used to filter the aqueous dispersion of MWCNT.

The aqueous dispersion is prepared from the multi-walled carbon nanotubes MWCNT and a surfactant system, preferably sodium dodecyl sulphate (SDS), and a co-surfactant (e.g. 1- pentanol), using intensive sonication with a sonication tip.

The aqueous dispersion is applied to the polyurethane filtration membrane. By means of a vacuum filtration, the functional carbon layer is fixed to a polyurethane filter formed by the polyurethane filtration membrane, wherein the carbon layer thickness is in the range of 15 to 45 μπι, preferably the layer thickness is approximately 30 μπι, and the polyurethane filter thickness is in the range of 15 to 50 μηι, preferably approximately 18 μιη. The layer of carbon multi- walled nanotubes fixed in the polyurethane filter is an intermediate product which is then melted onto the second layer of polyurethane, wherein the second layer of polyurethane is preferably a polyurethane film prepared by, for example, melt-pressing, wherein the layer thickness is in the range of 100 to 300 μπι, preferably approximately 100 μπι.

In order to increase sensitivity, MWCNTs may be treated prior to insertion into said aqueous dispersion by the following methods:

In a preferred embodiment, the oxo-groups are deposited on the surface of carbon nanotubes through chemical treatment of carbon nanotubes, preferably by oxidation with KMn0 ₄ /H ₂ S0 ₄ solution, oxidation with concentrated HN0 ₃ , HN0 ₃ /H ₂ S0 ₄ nitrating mixture or 30% hydrogen peroxide.

In another preferred embodiment, the silver (Ag) clusters are deposited on the surface of carbon nanotubes through chemical treatment of carbon nanotubes, preferably by reduction from AgN0 ₃ solution.

In another preferred embodiment, the pre-stress is applied on the sensor at a deformation level in the extent of 40 to 60 percent, preferably at 50 percent; the pre-stress is however applied only after the polymeric matrix and functional carbon layer have been applied to the substrate, i.e. onto fabric or into the shoe insole, depending on the sensor application.

In another preferred embodiment, elastomeric spherical nano-spacers being the products of e.g. microemulsion polymerization technique are applied on the sensor.

In an embodiment where the aforesaid treatments are combined, i.e. in which both the oxo- groups and Ag clusters are deposited on the surface of the carbon nanotubes (MWCNTs), and in which after application on the substrate, also mechanical pre-stress or nano-spacers are applied, the sensor containing such carbon nanotubes reaches a sensitivity in the range of GF 50 to 60.

Finally, the functional layer of MWCNTs is covered with a thin protective layer of thermoplastic polyurethane applied by a polymer solution coating, wherein it mainly serves to protect the MWCNT layer against moisture and mechanical damage as well as to avoid contact of MWCNTs with the environment. The thickness of the protective layer ranges from 80 to 120 μπι, preferably about 100 μπι. The sensor of the present invention may be a tensile or pressure sensor. The functional MWCNT layer, polymeric matrix, and treatments to increase the sensitivity of the sensor are the same for both types. The sensor becomes tensile or pressure based on the substrate to which the functional MWCNT layer and the polymeric matrix are applied. If the substrate is, for example, an elastic fabric which responds to the deformation by pulling, such an embodiment provides a tensile sensor. If the substrate is a material which responds to the pressure by deformation, such an embodiment provides a pressure sensor.

From the point of view of the principle of deformation detection by changing the electrical resistance of the functional carbon layer, the tensile sensor is classified into the group of "crack based sensors". Deformation here creates micro cracks in the functional carbon layer. This leads to the disconnection of the electrically conductive paths and thereby to the increase of the electrical resistance of the layer. The resulting micro cracks in the carbon layer have a hierarchical character over the thickness of the layer so that the layer resistance increases continuously and there is no complete disconnection of the conductive paths. In addition, some micro cracks remain "bridged" by individual tubes, which further contributes to the smoothness of the change in electrical resistance with applied deformation. When releasing the deformation, the polyurethane elastic substrate, i.e. the polymeric matrix, returns the carbon layer back, micro cracks are sealed, and the electrical resistance of the layer decreases reversibly. This principle allows for higher sensitivity of the sensor.

From the point of view of the deformation detection principle, the pressure sensor can also be included in the group of "crack based sensors", but the opposite principle of detection is more often used, when instead of disconnecting, the electrically conductive paths approach each other.

Below, the preferred embodiment of the pressure sensor and its applications will be described. The smart shoe for monitoring the foot-strike pressure with a complex system for monitoring data of its user contributes to the smart shoe concept. The essence of the solution lies in the fact that a pressure sensor or a system of pressure sensors is deposited on the insole and/or the upper of the shoe, wherein the sensors are comprised of compact units for the two-point measurement of the change of resistance by introducing a pressure stimulus. Each of these units, with a thickness of 0.3 to 0.8 mm, consists of a pair of opposed collecting electrodes and a nanocomposite layer deposited between them, wherein the collecting electrodes of pressure sensors are made of polyurethane-saturated carbon fibre-based fabric. The collecting electrodes from the sensors are formed by the embroidery of an electrically conductive thread in the material of the insole and/or upper of the shoe.

As described above, the nanocomposite layer comprises a structure of randomly entangled carbon nanotubes fixed in the elastic polyurethane matrix which is the product of vacuum filtration of the aqueous dispersion of carbon nanotubes through the polyurethane nanofibre filtration membrane.

The carbon nanotubes in the nanocomposite layer may preferably contain Ag clusters on their surface which are the products of chemical functionalization.

To increase sensitivity to the introduced pressure stimulus, the nanocomposite layer of the pressure sensor may further preferably contain elastomeric spherical nano-spacers which are the products of the microemulsion polymerization technique.

For the pressure sensor, this combination is more advantageous (providing higher sensitivity), but any of the above sensitivity treatments can be used to increase the detection capability.

For pressure sensors of the present technical solution, a network of randomly entangled carbon nanotubes is used which is integrated into a polymeric nanocomposite. When deformed, it changes its electrical conductivity and this principle allows detecting and quantifying the introduced pressure stimulus. The nanocomposite material as applied in pressure sensors is sensitive, reversible and deformable in many cycles, capable of measuring even in areas of higher deformation extents.

This design provides a flat sensor, very compact and durable. It is designed, both in terms of the arrangement of the individual members and the specific material composition, precisely for the pressure range and character of foot-strike for integration into a human shoe.

The pressure sensor of the present invention is the basis for a system for complex monitoring of data by user that includes a control module with a microprocessor to which the pressure sensors and, preferably, the temperature sensors embedded in the insole and/or upper of the shoe, and preferably also a gyroscope and/or an accelerometer and/or a GPS module, preferably embedded in the lower part of the shoe, in particular the heel cavity, are connected. Here are also other modules of the system connected to the control module with microprocessor: communication modules, such as LTE and WiFi module, and a power battery.

The control module includes a memory part for temporarily storing the acquired data and information, and a communication and transmission part to secure the connection of smart shoe with a smart mobile phone or smart watches using wireless technology. It is also possible to connect smart shoes with a computer by means of a cable for transferring information and battery recharging.

The complex solution may include a mobile app that will ensure communication with the smart shoe via a mobile phone. The control unit may also provide for the initial evaluation of all the information thus obtained by means of a system of algorithms and for the first comprehensible visualization for the user. The application allows this information to be passed on to the server part, such as the cloud, and later to the web part.

From the web and presentation part, which is able to further process the information of complex analysis of walking, running as well as kicking techniques in football or pedalling a bicycle, and visualize them using a 3D human anatomy model so that it is clear and evident to the professional consultants or users themselves how to make physical activities more efficient, how to improve the technical performance, what muscles to use and how to avoid movements that cause painful musculoskeletal syndromes such as enthesopathy and the like.

The main advantage of the smart shoe comprising the pressure sensor of the present invention is that, through a complex analysis of data related to the movement of the human body, it is technically possible to evaluate the accuracy of the physical activity. The pressure sensors used consist of composite collecting electrodes with a composite, highly elastic functional piezoresistive core. The core is made of an elastomeric matrix containing carbon nanotubes, further subsidized by silver clusters, and its intrinsic sensitivity to the introduced pressure stimulus is further enhanced by the addition of elastomeric spherical nano-spacers.

The sensor is sensitive and reversible, and resistant to load in many cycles. A great advantage of this solution is that, in addition to pressure sensors, the footwear itself is equipped with a complex solution of related segments that are interconnected and transmit information to the control circuit (microprocessor) and subsequently wirelessly to the software application installed in the mobile phone.

Below, the preferred embodiment of the tensile sensor and its applications will be described. The sensor of the present invention can be ironed on to a fabric, preferably an elastic fabric; in case of breathing, the fabric may be clothing items for upper body, such as a T-shirt. The composite layer made of the composite of elastic thermoplastic polyurethane and the said carbon nanotubes of the functional layer is fixed to a second layer of polyurethane, the second layer of polyurethane being preferably a polyurethane film prepared by, for example, melt- pressing, wherein the thickness of the layer is in the range 100 to 300 μπι, preferably approximately 100 μπι. After melting, the functional carbon layer is fixed in a polymeric matrix containing the composite layer, which comprises a polyurethane filter and carbon nanotubes fixed therein, and serves as the functional layer carrier, and a second layer of polyurethane that is used as an adhesive layer for sticking onto the fabric.

The method of fixing to the substrate is as follows: the second polyurethane layer is melted onto the fabric, preferably an elastic fabric, at a temperature in the range of about 160 to 180 °C, preferably about 170 °C, for example by ironing, thereby resulting in melt bonding with the fabric (adhesion is achieved by melting the polyurethane which acts as a hot melt adhesive). Subsequently, the functional carbon layer on the polyurethane filter is melted in the same way, for example by ironing.

After fixing the sensor onto the fabric, the sensor is further provided with two electrodes for the two-point electrical resistance measurement, preferably by means of two metal rivets.

Since both the fabric and the polymeric matrix are highly elastic, they are able to accurately copy the movement of muscles or, in terms of breathing, the movement of the chest and abdomen when breathing. The deformation of the fabric occurs from which this deformation is transmitted to the sensor and the electrical resistance response that describes the nature and intensity of the deformation, e.g. the deformation of the chest and abdomen due to breathing, is transmitted by the collecting electrode system further to the processing, the said collecting electrodes being formed by two metal rivets and a set of embroidered electrical connections. The response is recorded in real time of the deformation.

The sensor of the present invention is reversible upon the deformation stimulus, e.g. the deformation induced by muscle movement or when breathing. The sensor of the present invention thus permits detection of repeated deformation stimuli without significant changes in its material properties. The fabric, such as the upper body clothing item, comprising the sensor or set of sensors of the present invention, may be freely and without limitations taken off and on again. It is possible to wash it at 40 °C, ideally without spin-drying, and dry by free hanging on the dryer. Washability is also provided, for example, by the top protective layer by which the MWCNT layer is covered

Since the sensor of the present invention is reversible after deformation, the fabric under strain, for example in normal wearing, is free of substantial material changes of sensors. However, it is better not to expose the fabric containing the said sensors to unnatural deformations beyond the normal fabric handling (e.g. wearing and handling of the T-shirt), temperatures above 50 °C and aggressive chemical environments.

The present invention also provides a set of sensors forming a sensor array, for example for complex scanning of a larger area. The set of sensors of the present invention can be applied to the fabric in the same manner as one single sensor so that they create a sensor array advantageous, for example, for complex trunk-vertical breath analysis.

In another aspect, the present invention further relates to a fabric comprising at least one sensor of the present invention. The fabric may preferably include a set of sensors, preferably a set of at least two sensors, preferably a set of 4 to 10 sensors, e.g. 5, 6, or 8 sensors.

The fabric comprising at least one sensor of the present invention further comprises electrically conductive electrodes for the two-point electrical resistance measurement, preferably in the form of metal rivets, preferably two metal rivets. The electrodes further comprise flexible electrically conductive threads formed by embroidering. Changes in the electrical resistance of the sensor are sensed over time with a two-point method. The electrodes connect the said sensor with an electronic module for data acquisition and processing. The electronic module can be placed in any position with respect to the T-shirt, preferably on the lower side. The data bus and the electronic data processing module may be provided as two separate modules, but the arrangement with one single module is more advantageous. Data may be available via a USB interface, the electronic module can, for example, contain directly the connector for connection. The wireless transmission of data to the user's mobile device is also possible either via an electronic module adapted for wireless data transmission or by a transmitter also applied to the said fabric, such as the Bluetooth interface. As already mentioned for the pressure sensor, the complex solution includes a mobile app that will ensure communication via mobile phone and/or evaluation of all the information thus obtained by means of a system of algorithms for a given analysis of the type, frequency, and intensity of breathing or other body functions, as well as their visualization for the user. The app can also ensure that this information is passed on to the server part, such as the "cloud" and then to the web part.

In another aspect, the invention relates to clothing which is made of an elastic fabric of the present invention, wherein the clothing is preferably the clothing item for upper part of the body or the T-shirt.

In another aspect, the invention relates to the use of the sensor of the present invention for detection of deformations caused by body functions, preferably deformations caused by breathing.

In another aspect, the invention relates to the use of the sensor of the present invention for application onto clothing, wherein the clothing is preferably the clothing item for upper part of the body or the T-shirt.

In another aspect, the invention relates to the use of the sensor of the present invention for application into a sleeping mattress, especially the sleeping mattress cover, for a complex analysis of breathing and sleep anatomy which allows monitoring the position and body movements of a sleeping person during sleep (frequency and type of movements), wherein it is possible from the analysis to evaluate the quality of sleep or use the analysis to design a custom made mattress.

In another aspect, the invention relates to the use of the sensor of the present invention for application into a chair or chair cover for a complex analysis of the user's anatomy while sitting which allows analysing the type of sitting position, movements, and activity of a sitting person, recording the presence of a sitting person and possible analysis of his/her activity, correctness of the sitting position, etc.

The system can be configured to invite a sitting person to take a break and relax body according to the measured data or, as far as detecting the presence of a sitting person is concerned, the system can be configured so that if there is no sitting person, the lighting or heating of the room can be controlled by evaluating that no person is in the room.

In another aspect, the invention relates to the use of the sensor of the present invention for application into a car or aircraft seat for a complex analysis of forces relative to the person sitting in the seat. From the analysis, it is possible to evaluate the sitting position of the person or possible increased fatigue or sleep as well as forces caused by, for example, braking, accelerating, impact, or climbing and descending for aircraft, and consequences of these forces for a person in the seat.

Explanation of the Drawings

Fig. 1 a) - URTEM analyses of the MWCNT nanotube structure

Fig. 1 b) and c) - TEM analysis of the MWCNT nanotube with deposited Ag clusters

Fig. 2 - Schematic overall layout of sensors and modules in an exemplary smart shoe solution

Fig. 3 - Detail of pressure sensor solutions

Fig. 4 - Diagram of instep kick evaluation

Fig. 5 - Example of the walking waveform

Fig. 6 - Visualization of the foot-strike sensing results

Fig. 7 a) and b) - Schematic layout of sensors and control module in the embodiment where the sensors of the present invention are applied onto a T-shirt

Fig. 8 - Schematic layout of sensors in the embodiment where the sensors of the present invention are applied into the sleeping mattress cover

Fig. 9 - Schematic layout of sensors in the embodiment where the sensors of the present invention are applied into the chair cover

Examples

Example 1

The sensor of the present invention comprises a polymeric matrix consisting of highly elastic thermoplastic polyurethane and a functional layer containing electrically conductive multi- walled carbon nanotubes (MWCNT s).

The functional layer contains electrically conductive multi-walled carbon nanotubes (MWCNTs), wherein the carbon nanotubes in the layer are randomly entangled and have a diameter of 10 to 30 nm, preferably 18 nm, and a length of 0.3 to 3 μιη; after formation of the functional carbon layer, the layer porosity is 0.6 to 0.75. Purity of carbon nanotubes ranges from 90 to 95 percent. The functional carbon layer is fixed by filtration on a polyurethane filter, wherein the carbon layer thickness is approximately 30 μπι and the polyurethane filter thickness is approximately 18 μπι.

The composite layer, which comprises a polyurethane filter and carbon nanotubes fixed therein, is prepared by filtration of the aqueous dispersion, wherein the said dispersion is prepared from the multi-walled carbon nanotubes (MWCNTs) and a surfactant system of sodium dodecyl sulphate (SDS) and 1-pentanol as the co-surfactant, using intensive sonication with a sonication tip. The filtration is carried out through a filtration membrane of thermoplastic polyurethane nanofibres, which then forms the polyurethane filter of the composite layer. The filtration membrane or filter is prepared by electrostatic spinning from the polyurethane solution in dimethylformamide (DMF). The thus prepared membrane is provided as a nonwoven fabric of TPU fibres with sub-micron diameters.

The said aqueous dispersion is applied to the said polyurethane filtration membrane. By means of a vacuum filtration, the functional carbon layer is fixed to the polyurethane filter formed by the polyurethane filtration membrane.

Finally, the functional layer of MWCNTs is covered with a thin protective layer of thermoplastic polyurethane applied by a polymer solution coating, wherein it mainly serves to protect the MWCNT layer against moisture and mechanical damage as well as to avoid contact of MWCNTs with the environment. The thickness of the protective layer is approximately 100 μπι.

To increase the sensitivity, the carbon nanotubes comprise oxo-groups on their surface which are deposited therein by oxidation with solution, where the introduction of oxo- groups on the surface of MWCNTs increases the contact electrical resistance between the individual CNT network crossings and thus increases its sensitivity to the deformation stimulus. This treatment takes place before the sensor itself is manufactured.

The sensitivity of the sensor is further increased by applying the pre-stress at a deformation level of 50 percent, wherein the pre-stress is applied to the sensor after it has been applied to the substrate, i.e. onto fabric or into the shoe insole, depending on the sensor application, and wherein the pre-stress is applied in cycles. The sensor stabilization occurs after approximately 20 cycles are applied.

Example 2

The sensor of Example 2 differs from the sensor of Example 1 in that the carbon nanotubes further contain silver Ag clusters on their surface deposited by reduction from AgN0 ₃ solution. This treatment takes place before the sensor itself is manufactured

The cluster deposition is preceded by oxidation of MWCNTs, e.g. by KMn0 ₄ /H ₂ S0 ₄ solution, which leads to higher concentration of Ag clusters and thereby higher sensitivity of the sensor.

Example 3

The complex system for monitoring data of the smart shoe user in the exemplary embodiment (see the scheme of the bottom part of footwear in Fig. 2) includes the control module with a microprocessor 4 to which the pressure sensors 5 and temperature sensors 6 embedded in the insole I are connected. In addition, it includes a gyroscope 7, an accelerometer 8, a GPS module 9, communication modules 10, such as LTE and WiFi module, and a power battery 11, embedded in the heel 3a cavity of the lower part 3 of the shoe. The collecting electrodes from the sensors 5, 6 are formed by the embroidery of an electrically conductive thread in the material of the insole I and/or upper 2 of the shoe.

The complex monitoring system is further complemented by an interface for cable connection of the smart shoe with an external computer to transfer information and recharge the battery JJ _. .

Individual pressure sensors 5 deposited on the insole I and/or the upper 2 of the shoe are comprised of compact units for the two-point measurement of the change of resistance by introducing a pressure stimulus (see Fig. 3). Each of these units, with a thickness of 0.3 to 0.8 mm, consists of a pair of opposed collecting electrodes 5a and a nanocomposite layer 5b deposited between them. The composition of individual layers of the pressure sensor are shown in Fig. 3a, while the overall sensor layout is shown in Figure 3b) and visualization 3c).

The nanocomposite layer 5b comprises a structure of randomly entangled carbon nanotubes fixed in the elastic polyurethane matrix which is the product of vacuum filtration of the aqueous dispersion of carbon nanotubes through the polyurethane nanofibre filtration membrane.

The collecting electrodes 5a are made up of a carbon fibre-based fabric. The control module with microprocessor 4 manages the activities of individual sensors and modules. It provides communication with individual sensors that are necessary for obtaining information from the activity carried out (walking, running, cycling, etc.) and wireless transmission of all data and information from these sensors using communication modules 10 (LTE and WiFi).

The complex solution includes a mobile app to ensure communication with the smart shoe via a mobile phone. The control unit also provide for the initial evaluation of all the information thus obtained by means of a system of algorithms and for the first comprehensible visualization for the user. The application allows this information to be passed on to the server part, such as the cloud, and later to the web part.

From the web and presentation part, which is able to further process the information of complex analysis of walking, running or pedalling a bicycle (see, for example, the waveform of walking recorded as a relative change in electrical resistance over time from one pressure sensor integrated in the smart shoe in Fig. 5) and visualize them using a 3D human anatomy model (see, for example, the visualization of results gathered during the smart shoe activity via the app installed on the mobile phone in Fig. 6) so that it is clear and evident to the professional consultants or users themselves how to make physical activities more efficient, what muscles to use and how to avoid movements that cause painful musculoskeletal syndromes such as enthesopathy and the like.

Example 4

The complex system for monitoring the smart shoe user data is solved similarly as in Example 3. But in this case the pressure sensors 5 are deposited also in the upper 2 of the footwear, a football boot (see Fig. 4) and are mainly used to evaluate a young football player's kicking technique.

Example 5

The complex system for monitoring the smart shoe user data is solved similarly as in Examples 3 or 4.

However, here the carbon nanotubes of the nanocomposite layer 5b of pressure sensors 5 contain the silver Ag clusters on their surface as products of chemical functionalization to increase the detection capability.

In addition, the nanocomposite layer 5b contains elastomeric spherical nano-spacers which are the products of the microemulsion polymerization technique to optimize the sensitivity to the introduced pressure stimulus.

Example 6

In a preferred embodiment, where the sensor of the present invention is applied to a sports T- shirt for complex trunk-vertical breath analysis, the said T-shirt contains sensors ID1 to ID9 for breath analysis and sensors ID20 to ID27 for a more precise breath analysis. The T-shirt further comprises sensors ID30 and ID31 for movement analysis and the control module or sensors marked a - e.

The intermediate in the form of a composite layer of multi-walled carbon nanotubes fixed in a polyurethane filter is melted through ironing and therefore fixed to the second polyurethane layer in the form of a film prepared by melt-pressing, wherein the thickness of this layer is approximately 100 μπι, and which is already ironed (and fixed) onto the fabric being a T-shirt in this case.

In both cases, melting and fixation is achieved at a temperature of about 170 °C, thereby melt- bonding with the fabric takes place (adhesion is achieved by melting the polyurethane which acts as a hot melt adhesive).

Individual sensors of the set are strategically positioned to cover the entire chest to obtain the most accurate data for making the complex breath analysis of the user. This embodiment is shown in Figures 7a and 7b.

The T-shirt further comprises electrically conductive electrodes for the two-point electrical resistance measurement, in the form of two metal rivets. The electrodes further comprise flexible electrically conductive threads formed by embroidering. Changes in their electrical resistance are sensed in real time. The electrodes connect the said sensor with an electronic module for data acquisition and processing.

The electronic module can be placed in any position, preferably on the lower side. The data bus and the electronic data processing module are one single module that also includes a USB connector so data are backwards available also in this manner. The wireless transmission of data to the user's mobile device is also possible either via an electronic module adapted for wireless data transmission or by a transmitter also applied to the said fabric, such as the Bluetooth interface.

Also in this embodiment the complex solution includes a mobile app that will ensure communication via mobile phone and/or evaluation of all the information thus obtained by means of a system of algorithms for a given analysis of the type, frequency, and intensity of breathing or other body functions, as well as their visualization for the user. The app can also ensure that this information is passed on to the server part, such as the "cloud" and then to the web part.

Example 7

In Example 7 we refer to Figures 8 and 9 which illustrate possible applications of the sensor of the present invention. These are in particular the application into a sleep mattress, especially the sleep mattress cover (sensors a - k, Fig. 8), which allows to monitor the position of a sleeping person and physical activity during sleep (frequency and type of movements), wherein it is possible from the analysis to evaluate the quality of sleep or use the analysis to design a custom made mattress, and the application into the chair cover (sensors a - f, Fig. 9), which allows to analyse the type of sitting position, and movements and activities of the sitting person, and record the presence of the sitting person and possible analysis of their activity, correctness of the sitting position, etc. The system can be configured to invite a sitting person to take a break and relax body according to the measured data.

As far as the presence of a sitting person is concerned, the system can be configured so that if there is no sitting person, the lighting or heating of the room can be controlled by evaluating that no person is in the room.

Industrial applicability

The use of the tensile sensor of the present invention, and the fabric or clothing items that contain such tensile sensor, finds wide application in the fields of sports and training, medicine, or rehabilitation.