Field of the Invention

The present invention relates to a smart shoe insole/midsole/outsole, including sensor system and hardware, which serves to collect, communicate and analyse data on the gait, footstep pressure or run of a person. The present invention thus belongs to the field of wearable electronics, and to the field of monitoring motoric activity of a person.

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.

Use of pressure sensors in shoes and shoe insoles is known from several patent documents, such as WO2019/034188, CN107772612, CN107232682, CN105520257, CN107361458, CN105956397, CN107028276, WO2017/197627, or WO2019/034188 (the last one being co invented by the applicant of the present invention).

However, in spite of existence of several types of smart shoes and sensors for monitoring the gait and/or run of a person, there is still a need for an improved system which would be able to provide and analyse more precise data at lower costs.

It is therefore an object of the present invention to provide a smart shoe part (insole/midsole/outsole), with an increased sensitivity, suitable for precise monitoring of motoric activity (gait or run) of a person.

Summary of the invention

The invention relates to a smart shoe insole/midsole/outsole comprising a layer comprising a flexible polyimide substrate upon which collecting electrodes are placed, the electrodes being connected by a structure of conductive paths with a common grounding cable, an active surface of conductive piezoresistive layer comprising a compact electrically conductive elastomer, having a thickness of 0.2 to 2 mm, a control module with wireless technology and a set of resistors between the electrodes and the control module. The term smart shoe means that the shoe is provided with technology enabling to collect, process and analyse data on the gait, footstep pressure or run of a person.

Generally speaking, the invention relates to a part of a shoe which is placed below the foot. The part may be an insole, a midsole or an outsole. The smart shoe insole/midsole/outsole according to the present invention is intended for use in any kind of shoes, sport shoes, running shoes, walking shoes, trekking shoes, medical shoes, etc. They may be used in shoes for adults, as well as in shoes for children of any age.

The purpose of the invention may be achieved by a smart shoe insole, midsole, or outsole. An insole is generally intended to be removable, whereas a midsole or an outsole usually form part of the shoe and are integrated into the shoe during the production.

The layer comprising a flexible polyimide substrate holds collecting electrodes which are placed on this layer. The electrodes are interconnected by a structure of conductive paths with a common grounding cable. Each electrode is connected by conductive paths with the neighbouring electrode or electrodes. The common grounding cable goes from the tip and from the heel and is put into one output before the processor. Possible layouts of conductive paths are visible from figures 1 and 2.

The collecting electrodes are preferably formed by means of the printed circuit technology.

The distance between the electrodes determines the resistance of the sensor at a specific pressure. The more electrodes, the lower the resistance.

The active surface of conductive piezoresistive layer comprises a compact electrically conductive elastomer, having a thickness of 0.2 to 2 mm. The conductive piezoresistive elastomer is commercially available, for example under the brand Wearic. This layer forms a piezoresistive pressure sensor layer.

The two layers - the layer comprising a flexible polyimide substrate with electrodes and the active surface of conductive piezoresistive layer - are in contact with each other and form the sensor system. It is not important whether the polyimide substrate is above the conductive piezoresistive layer surface, or vice versa, as long as the two layers are placed one next to the other. These two layers together are also referred to as the sensor system, or the sensor layers. The control module with wireless technology is intended for collecting, analysing and processing the data obtained from the sensors.

A set of resistors is placed between the electrodes and the control module.

In an embodiment of the invention, each collecting electrode is provided with its own resistor and the common grounding cable is provided with its own resistor. The number of resistors is thus higher by one compared to the number of collecting electrodes.

This arrangement of resistors and conductive paths and the grounding cable ensures that the resistance is stabilized, which in turn helps to obtain linear results when measuring the resistance.

The resistors can be set to a value, which helps to obtain linear results. Typically, they can be set to approximately 1000 to 1500 W, for example to 1200 W.

In a preferred embodiment of the invention, the flexible polyimide substrate comprises collecting electrodes in the following regions: at least one electrode in the phalanges bones region; at least one electrode in the metatarsal bones region; at least one electrode in the midfoot region; at least one electrode in the heel region.

In a yet more preferred embodiment of the invention, the flexible polyimide substrate comprises collecting electrodes in the following pattern: one electrode in the phalanges bones region; three electrodes in the metatarsal bones region; one electrode in the midfoot region; two electrodes in the heel region.

Placing the electrodes in these regions and in the preferred pattern (see also figures 1 and 2 ensures that all key parts of the foot sole are monitored, which enables to give the best idea of which zones of the foot are stressed more, and whether the gait or run of the person in question is correct, or not. In an embodiment of the invention, the control module and the resistors are placed in a casing situated in the foot arch region.

The casing situated in this region does not interfere with the collecting of the data and does not cause any discomfort to the user.

The casing is small and may be produced from any suitable material, preferably from polyamide material.

In an embodiment of the invention, the collecting electrodes are copper electrodes. They are preferably in the form of two interconnected combs. The two combs are put one against the other. Preferably, the distance between individual prongs is from 1 to 3 mm. The number of prongs is typically from 10 to 20 per comb, thus making it from 20 to 40 per electrode. Electrodes that are closer together typically have less prongs, electrodes that cover a bigger region typically have more prongs. Specifically, the electrodes in the metatarsal bones region can have 26 prongs (each comb having IS prongs), the other electrodes can have 32 prongs (each comb having 16 prongs).

Copper electrodes are cheap and have a very good conductivity. The system of two interconnected combs is the easiest from the construction point of view; the combs are close to each other, in order for the sensors to have a low resistance when pushed.

In an embodiment of the invention, the layer comprising a flexible polyimide substrate with collecting electrodes can be cut through the collecting electrodes in order to vary the insole/midsole/outsole size, without impairing the functionality of the collecting electrode. Typically, the electrodes in the phalanges bones region and/or in the heel region can be cut. The cut goes between prongs of the relevant electrode(s).

This means, in other words, that it is possible to produce only one size (or few several sizes) of this layer, whereas the size of this layer may be adapted to fit the size of the insole/midsole/outsole by cutting through the electrodes on the side of the layer, without the functionality of the collecting electrode (and thus the functionality of the smart shoe) being impaired. That might considerably reduce the costs associated with the production of smart shoe insoles/midsoles/outsoles of different sizes.

In an embodiment of the invention, the control module comprises a microprocessor, a battery, a Bluetooth communication module. The microprocessor is intended to collect and process the data obtained from the sensors. The battery provides energy for the microprocessor. The Bluetooth communication module is intended for communicating the obtained and processed data from the control module to the application in an external device.

In a yet more preferred embodiment, the control module comprises two microprocessors. One microprocessor is responsible for data collecting and operating the Bluetooth communication module, the other microprocessor is responsible for working as an energy saver for the battery, and switches the battery off when there is no pressure for a pre described period (for example 15 minutes). This arrangement allows less battery recharging, and generally saves more energy.

In an embodiment of the invention when the part of the smart shoe is an insole, the insole further comprises an outer layer comprising ethylene-vinyl acetate copolymer, the layer having a thickness of 0.2 to 5 mm.

The ethylene-vinyl acetate copolymer is in particular suitable for this purpose, since it is harmless for users, as it does not comprise any compounds defined by the List of substances of very high concern (SVHC) mentioned in Annex XVI I according to the REACH Regulation. This material does not contain any carcinogenic, mutagenic, persistent, bio accumulative or toxic substances.

The outer layer may be provided on the upper side of the insole only, or both on the upper and lower part, the basic sensor layers thus being inside the outer layer.

This outer layer may be further provided by a textile or leather cover. The textile or leather cover protects the layer comprising ethylene-vinyl acetate copolymer from damage, and it also feels better to users.

All layers, surfaces and the casing may be glued together by means of an adhesive commonly used in shoe industry. The adhesive may comprise a solution of polychloroprene in organic solvents and a hardener, or a polychloroprene rubber in organic solvents and additives (for example commercially available Chemopren glues).

In an embodiment of the invention when the part of the smart shoe is an insole, the insole is preferably removable from the shoe. It can be inserted into the shoe repeatedly, or it can be inserted into different shoes. In an embodiment of the invention when the part of the smart shoe is a midsole, or an outsole, the midsole or outsole is incorporated within the shoe during the production of the smart shoe.

Usually, the sensor layers are placed upon the internal part of the midsole or outsole, which is typically made by rubber. The internal part of the midsole or outsole is further covered by a suitable material, such as ethylene-vinyl acetate copolymer (EVA) to protect the sensor system. The sensor system may be further covered by other materials to protect it from the upper side, such as ethylene-vinyl acetate copolymer (EVA), possibly in combination with other suitable material commonly used in the shoe industry, such as leather, foil, or textile.

As the person wearing the smart shoe makes a step, the part of the shoe (insole/midsole/outsole) equipped with the electrodes and sensors is reversibly deformed. This deformation is transmitted to the sensor system and the electrical resistance response that describes the nature and intensity of the deformation, is transmitted by the collecting electrode system further to the control module.

The insole/midsole/outsole of the present invention is reversible after deformation. No substantial material changes of the insole/midsole/outsole occur at normal strain and normal conditions.

The electrical resistance response is recorded in real time of the deformation by the microprocessor, which processes the response into data and sends the processed data via the Bluetooth module for assessment into an application.

The application may be downloaded into a mobile phone or a similar device, and it is adjusted to show the stress applied on different regions of the insole, to evaluate average values of every step and its correctness, and compare the actual pressure with that of an optimal gait or run. The application may be also adjusted to provide data on the number of steps, on the frequency of steps, or any other required set of information.

Explanation of the Drawings

Fig. 1 shows one possible pattern of electrodes and conductive paths layout according to claim 4. Fig. 2 shows another possible pattern of electrodes and conductive paths layout according to claim 4.

Fig. 3 shows a diagram of connection between electrodes, resistors and the control module.

Examples

Example 1

A smart shoe outsole

The smart shoe outsole is prepared in the following way:

A layer comprising a flexible polyimide substrate is placed upon the internal rubber part of the outsole that is further covered by ethylene-vinyl acetate copolymer (EVA) to protect the sensor system. The layer comprises four copper electrodes, one in each of the following regions: phalanges bones region, metatarsal bones region, midfoot region and heel region. Each electrode consists of two interconnected comb electrodes, having 17 prongs each, thus each electrode has 34 prongs. All electrodes are connected by a structure of conductive paths with a common grounding cable.

An active surface of conductive piezoresistive layer is placed upon the layer comprising the flexible polyimide substrate and electrodes. The active surface of conductive piezoresistive layer is formed by a compact electrically conductive elastomer and has a thickness of 0.8 mm.

In the foot arch region, a polyamide casing is provided. Inside the casing, the control module consisting of a microprocessor, a battery, and a Bluetooth communication module, and five resistors (set at 1100 W) are placed. Each electrode is provided with its own resistor and the grounding cable is provided with its own resistor. The conductive paths lead from the electrodes to the control module trough an opening in the polyamide casing.

The layer with electrodes, the surface of conductive piezoresistive layer and the polyamide casing are glued together by Chemopren. Subsequently, they are covered by ethylene-vinyl acetate copolymer (EVA) and leather. Example 2

A smart shoe midsole

The smart shoe midsole is prepared in the following way:

A layer comprising a flexible polyimide substrate is placed upon the internal rubber part of the midsole that is further covered by ethylene-vinyl acetate copolymer (EVA) to protect the sensor system. The layer comprises seven copper electrodes, in the pattern shown in Figure 1. Each electrode consists of two interconnected comb electrodes, having 17 prongs each, thus electrode having 34 prongs. All electrodes are connected by a structure of conductive paths with a common grounding cable.

An active surface of conductive piezoresistive layer is placed upon the layer comprising the flexible polyimide substrate and electrodes. The active surface of conductive piezoresistive layer is formed by a compact electrically conductive elastomer and has a thickness of 0.5 mm.

In the foot arch region, a polyamide casing is provided. Inside the casing, the control module consisting of a microprocessor, a battery, and a Bluetooth communication module, and eight resistors (set at 1300 W) are placed. Each electrode is provided with its own resistor and the grounding cable is provided with its own resistor. The conductive paths lead from the electrodes to the control module trough an opening in the polyamide casing.

The layer with electrodes, the surface of conductive piezoresistive layer and the polyamide casing are glued together by Chemopren. Subsequently, they are covered by ethylene-vinyl acetate copolymer (EVA) and textile.

Example 3 A smart shoe insole

The smart shoe insole is prepared in the following way:

The layer comprising a flexible polyimide substrate with conductive material comprises seven copper electrodes, each electrode in the form of two interconnected combs, in the pattern shown in Figure 2. Each electrode consists of two interconnected comb electrodes, the three electrodes in the metatarsal bones region have 26 prongs (each comb having 13 prongs), and the other electrodes have 32 electrodes (each comb having 16 prongs). All electrodes are interconnected by a structure of conductive paths with a common grounding cable.

An active surface of conductive piezoresistive layer is placed upon the layer comprising the flexible polyimide substrate and electrodes. The active surface of conductive piezoresistive layer is formed by a compact electrically conductive elastomer (Wearic) and has a thickness of 1.25 mm.

In the foot arch region, a polyamide casing is provided. Inside the casing, the control module consisting of two microprocessors, a battery, and a Bluetooth communication module, and eight resistors (set at 1200 W) are placed. Each electrode is provided with its own resistor and the grounding cable is provided with its own resistor. The conductive paths lead from the electrodes to the control module trough an opening in the polyamide casing.

The layer with electrodes, the surface of conductive piezoresistive layer and the polyamide casing are covered from all sides by an outer layer comprising ethylene-vinyl acetate copolymer, the layer having a thickness of 2 mm at each side, and glued by Chemopren. The outer layer is further covered by textile cover.

The smart shoe insole can be inserted into any shoe of a suitable size and it can be removed from the shoe and re-inserted into the same shoe, or newly inserted into another shoe.

Example 4

Collecting and processing data

As the user makes a step, or starts running, the outsole according to example 1, the midsole according to example 2, or the insole according to example 3 starts deforming by pressure made by user's foot.

The sensor layers equipped with the electrodes and piezoresistive layer are reversibly deformed. This deformation in the form of the electrical resistance response that describes the nature and intensity of the deformation is transmitted by the collecting electrode system to the control module.

Once the pressure from the step is over, the layers return to their original state. No substantial material changes of the insole/midsole/outsole occur at normal strain and normal conditions.

The electrical resistance response is recorded in real time of the deformation by the microprocessor, which processes the response into data and sends the processed data via the Bluetooth module for assessment into an application into cloud solution for data collecting.

In the embodiment of example 3, one microprocessor collects and processes the data and operates the Bluetooth communication module, whereas the other microprocessor is responsible for working as an energy saver for the battery and switches the battery off, whenever there is no pressure for a period longer than 15 minutes. After reloading the sensor system, the second microprocessor wakes up the battery to start powering.

Example 5 Application

The data collected by the microprocessor, as shown in example 4, is further processed by the Bluetooth module into a device, for example a mobile phone, where the corresponding application has been downloaded.

The application analyses and assesses the data provided by the microprocessor, compares the data and shows one or more of the following: the number of steps made by the user; the average step; the pressure applied by each foot of the user, highlighting the regions of the foot which are stressed more - the applications shows the level of stress by a colour scale - blue colour showing no pressure, green colour showing low pressure, yellow colour showing average pressure and red colour showing maximum pressure in the particular region; the course of the centre of gravity movement; the differences between the actual pressure applied by the user, and the pressure applied on in optimal gait or run; average value of first contact with the ground area during running or walking (front foot, mid foot, heel) most stressed/loaded area by time.

The application enables analysing of each individual step, as well as the analysis of the whole gait or run (by means of analysing average step).

The application further stores the collected data in user's mobile phone and cloud and makes it available for further analyses by the user, by a podiatric physician, by a running coach, or any other interested person.

Industrial applicability

The insole/midsole/outsole according to the present invention will find wide application in the fields of sports and training, medicine, or rehabilitation. The smart shoe provided with the insole/midsole/outsole and the connected application will enable users to correct the gait or run, without the necessity of being diagnosed by a medical expert (a podiatry expert), or checked by a coach. It will also substitute costly medical apparatuses. The main advantage is that the shoe provided with the insole/midsole/outsole according to the present invention and the connected application may be used in any circumstances, and on different terrains, without any necessity of changes.

The insole/midsole/outsole according to the present invention combines a small thickness with a very good flexibility. The insole/midsole/outsole according to the present invention is very resilient and will last for a long period, with only recharging the battery needed to keep it working.