Device for measuring mechanical stresses in a material with an array of elongate sensors that are intertwined in an elastic material, and sole for detecting blisters or ulcers

Abstract

The present invention relates to a device for measuring mechanical stresses in a material, comprising one or more sensor arrays, characterised in that the sensors are elongate in shape and a first portion of the sensors is arranged in one direction and the other portion of the sensors is arranged at an angle of between 1° and 90° with respect to the first portion. According to the invention, the sensors are flexible piezoelectric elements and the sensors are incorporated in an incompressible elastic material so that, when a stress is exerted, the material causes the sensors to stretch. The present invention also relates to a sole or a sock comprising a device of this kind.

Description

[0001] Description

[0002] Title of the invention: Device for measuring mechanical stresses in a material with a network of elongated sensors, interlaced in an elastic material and sole for detecting blisters or ulcers.

[0003] The present invention relates to a device for measuring mechanical stresses in a material comprising one or more sensor networks.

[0004] The field of the invention is the field of measuring mechanical stresses in a material comprising one or more networks of sensors, in particular in a sole or in a sock.

[0005] State of the art:

[0006] The feet are the most stressed parts of the body due to pressure, temperature, confined space, etc.

[0007] This is why foot ulcers are one of the most common complications among the 500 million diabetics worldwide, 15 to 25% of whom will have their feet partially amputated during their lifetime (Prevention of Diabetic Foot Ulcer, International Journal of Preventive Medicine, Vol 4, No 3, March, 2013). The article “Temperature and Pressure Regulating Insoles for Prevention of Diabetic Foot Ulcers” (J Foot Ankle Surg. 2020; 59(4): 685-688)” describes the importance of monitoring pressure and temperature conditions in the feet to prevent ulcers.

[0008] By detecting conditions that put people at risk for ulcers, patients could be warned of the risk of existing ulcers worsening, even before they occur. Patients would then be more inclined to leave their homes because ulcers, and especially the fear of developing them, are a barrier to activities like walking, which is essential for maintaining fitness and morale. In addition to the traumatic and disabling nature of ulcers, the cost of treatment and even amputations must also be taken into account, which range from €5,000 to €100,000 per operation.

[0009] A device for monitoring the conditions under which ulcer risks appear, such as a sole equipped with a multitude of pressure and temperature sensors, connected to a smartphone, would thus make it possible to slow down or even stabilize the state of health of patients' feet and thus have a significant impact on their quality of life.

[0010] A user-friendly interface on the smartphone would then continuously warn the patient with great precision. In addition, with a history of measurements of these risky conditions, on a secure cloud or to a health professional for analysis and advice on the type of sole, shoe, gait, etc. recommended: a dialogue could thus be established between the medical staff and the patient on their habits and activities, whether correct or not.

[0011] But for such devices to be widely used, it would be necessary that:

[0012] • The device is incorporated into a thin, soft and comfortable sole that is easy to forget,

[0013] • the number of measurement points is sufficient to detect ulcer risk conditions over very small areas and therefore with at least a hundred sensors per foot,

[0014] • the price is low (for example less than €200),

[0015] • that it does not use a battery (no need to be recharged) so that it is always operational.

[0016] If we look at what already exists, we see that the only devices on the market are very expensive, require batteries and that the number of sensors is often limited, as shown in the study "Concurrent Plantar Stress Sensing and Energy Harvesting Technique by Piezoelectric Insole Device and Rectifying Circuitry for Gait Monitoring in the Internet of Health Things" (https: / / www.researchgate.net / publication / 339992162) Similarly, the article in Electronics Review "A Comparative Review of Footwear-Based Wearable Systems" describes the following systems that do not meet the prerequisites for an efficient device:

[0017] • The device proposed by “Orpyx LogR”® can certainly have up to 99 sensors but needs to be powered by batteries and costs around $3,500 for the 8-sensor version.

[0018] • The “Moticon”® device only has around ten sensors, which is insufficient to detect risks in small areas, costs almost €2,000 and needs to be powered by batteries.

[0019] • Certainly, the “Novel Pedar”® device offers up to 256 measurement points but it needs to be powered by batteries and is prohibitively expensive (more than $3,500).

[0020] • Finally, the “TekScan F-Scan”® device offers up to 960 measurement points but needs to be powered by batteries and at a cost that is also exorbitant ($50 to $100 per sensor!).

[0021] If we also look at the patent databases, we certainly find interesting patents but which still do not meet the requirements for such devices to be widely used:

[0022] US2010037709A1

[0023] The invention relates to a network-type pressure sensing apparatus suitable for detection and quantification, said network certainly comprising a plurality of first axes, a plurality of second axes ... which can be arranged in a cross and a plurality of piezoresistive units. . ., but it is not the sensors which are arranged along the various axes. Indeed, the piezoresistive units are arranged on the cross between a first axis and a second axis and the said sensors therefore do not intersect at all and for each sensor it is necessary to have a measurement input on a microprocessor.

[0024] It is thus claimed a network type pressure detection apparatus adapted to pressure detection with a plurality of first axes, a plurality of second axes, arranged in a cross with the first axes but it is not the sensors which are thus arranged in a cross.

[0025] WO03087737A1

[0026] A sensor unit for detecting mechanical vibrations is described, comprising at least one strip of piezoelectric foil (piezo strip) as a sensor element, but in no case is a network of intersecting sensors mentioned or claimed, even if several sensor units can be mounted together in a plastic material, they are never intersecting and even less mounted in an elastic material which is essential to increase the stresses on a piezo.

[0027] Thus a sensor unit for sensing mechanical vibrations is claimed with at least one strip of piezoelectric foil being claimed but never an array of intersecting sensors.

[0028] US2017146493A1

[0029] A network of piezoelectric sensors embedded in a fabric is described, which may comprise multiple laminar layers, such as sensor layers...

[0030] It is therefore a piezoelectric sensor network fabric comprising one or more laminar layers which is claimed and not a network of intersecting sensors.

[0031] Description of the invention:

[0032] The present invention relates to a device for measuring mechanical stresses in a material comprising one or more networks of elongated sensors in an elastic material.

[0033] The device according to the invention as described below can be included in a sole or in a sock. In particular, the elastic material comprising one or more sensor networks can have a sole shape. These embodiments aim to allow the detection of pressure and temperature conditions leading to risks of blisters appearing for athletes, construction workers, etc. or ulcers for diabetics.

[0034] The sensors of the device according to the invention are incorporated in an elastic material. Said material is therefore flexible.

[0035] Embedding means that the sensors are embedded in the elastic material so that there is a strong cohesion between the material and the sensors. Thus, when the material deforms, the sensors will follow this deformation, especially when the sensors used are also flexible. Elongated sensors can, for example, be thin strips of metallized PVDF piezoelectrics.

[0036] In addition, the sensors are arranged for a first part in one direction and the other part with an angle between 1° and 90° relative to the first part. In other words, the sensors of the device according to the invention form a network of intersecting sensors. According to a preferred embodiment, the sensors are arranged for a first part in one direction and the other part with an angle equal to 90°.

[0037] Preferably, particularly when the device is included in a sole or sock, the device may include enough intersecting piezoelectric sensors to allow for more than one hundred pressure and temperature measurement points. In other words, the number of intersecting points between the different sensors is greater than one hundred.

[0038] In the device according to the invention, the sensors are incorporated in an incompressible elastic material so that when a stress is exerted, said material induces a greater stretching of said sensors. Thus the signals coming from the sensors are amplified.

[0039] By way of non-limiting examples, the incompressible elastic material may be an elastomer such as Silicone, rubber, TPU (Thermoplastic Polyurethane) etc.

[0040] The sensors of the device according to the invention are flexible piezoelectrics. According to one embodiment of the invention, the sensors can be connected to tracks or cables, connecting them to signal processing electronics, using magnets or pressure contact systems (with springs for example). This embodiment is particularly advantageous when the device according to the invention is included in a sole. Indeed, in use a sole is subjected to multiple deformations, the electrical contacts will be just as much and pressurizing them by magnet or spring will allow micro-displacements without breakage.

[0041] According to a preferred embodiment, the sensors arranged for a first part in one direction, called longitudinal sensors, can be separated from the other part of the sensors arranged at an angle, called transverse sensors, by an insulating layer so as not to short-circuit the signals generated by the different sensors. Indeed, the longitudinal and transverse sensors can be metallized on each face to conduct the electrical charges generated when they are stressed.

[0042] To obtain an insulating layer, it is, for example, possible to first cast an incompressible elastic material such as silicone onto the longitudinal sensors and then place the transverse sensors, which will then also be covered with an incompressible elastic material such as silicone. The energy generated by the sensors can be stored in a battery or a supercapacitor. Alternatively or in addition, this generated energy can be used to power the signal processing electronics. Thus, the signal processing electronics do not require charging from outside the device to operate.

[0043] The sensors of a device according to the invention can be connected to tracks or cables connecting them to the signal processing electronics, for example using magnets.

[0044] The processing electronics can be designed to be connected wirelessly to a smartphone.

[0045] An AI on the smartphone can then compare the sensor signals with each other and over time and precisely calculate risk situations.

[0046] A sole comprising a device according to the invention may comprise a matrix of sensors. The sensors may for example be thin piezoelectric strips of 5 to 200 pm and preferably 25 pm, intersecting and which make it possible to grid the entire surface of the sole (and similarly it is possible to grid an entire sock) by managing only a few inputs at the microprocessor level.

[0047] For example, with only 10 sensors along the entire length of the sole and 15 sensors arranged orthogonally across the width, this will represent only 25 inputs at the microprocessor level but 150 measurement points.

[0048] In addition, the energy generated by the sensors can be recovered in a supercapacitor or a battery to power signal processing electronics, for example a low-power microprocessor. The generated energy can also power a low-power communication module, for example Bluetooth, allowing connection to a smartphone.

[0049] Artificial intelligence on a smartphone can then compare the signals from the various sensors over time and calculate the pressure at each intersection.

[0050] Furthermore, the use of an application on the smartphone which analyses the signals transmitted by the device can make it possible to limit the electrical consumption of the elements of the device so that it can be powered solely by the energy generated by the sensors.

[0051] Such an application can, for example, make it possible to analyze the signals transmitted by the device to convert them into pressure at each intersection of transverse and longitudinal sensors by analyzing the time shifts of said signals.

[0052] Indeed, when a constraint, such as a support or impact, is exerted on the sole in a superposition / intersection of sensors, the signal measured on each of these impacted orthogonal bands will give a similar value but above all at the same time. The signals of the adjacent bands, before or after these impacted bands, will give weaker signals but above all out of phase in time (positive or negative) compared to the impacted bands which will make it possible to geolocate exactly the precise area of ​​the impact.

[0053] It is thus possible to precisely map the pressure on a device according to the invention. In particular, it is possible when the device is included in a sole or in a sock to precisely map the pressure exerted by the sole or sock on a user's foot.

[0054] On the other hand, the incorporation of the sensors into an incompressible elastic material such as silicone is of great importance.

[0055] Indeed, a flexible piezoelectric sensor, for example of the PVDF type, generates a relatively weak signal when subjected to mechanical stress, such as compression, while it is on a surface.

[0056] Indeed, this type of sensor generates a larger signal when it is stretched rather than compressed. Therefore, incorporating this type of piezo sensor into an incompressible elastic material, such as by pouring silicone (or rubber, TPU, etc.) around the said sensors so that there is good adhesion between the sensor and the material, the compression of the material / sensor assembly will lead to a significant stretching of the sensor leading to a much larger signal. In our tests, surprisingly, the use of an incompressible elastic material increased the signal by a factor of 10.

[0057] Thus, it is possible to obtain more energy to power electronics present in the device such as a super capacitor and a microprocessor as well as a Bluetooth wireless communication module,

[0058] In addition, the signal being stronger, it is therefore more easily measurable and allows for better precision.

[0059] It is also possible to simultaneously power the electronics present in the device and precisely measure the signals generated by the sensors.

[0060] Description of the figures:

[0061] Other advantages and characteristics will appear on examining the detailed description of a non-limiting embodiment, and the attached drawings in which:

[0062] - Figure 1 is a schematic and sectional representation of a non-limiting example of a device according to the invention;

[0063] - Figure 2 is a schematic representation seen from above of a non-limiting example of a device according to the invention;

[0064] - Figure 3 is a schematic and sectional representation of a non-limiting example of a device according to the invention.

[0065] It is understood that the embodiments which will be described below are in no way limiting. In particular, it is possible to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one characteristic, preferably functional, without structural details, or with only a part of the structural details if this part is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0066] In the FIGURES, the elements common to several FIGURES retain the same reference.

[0067] Figure 1 illustrates in a sectional view an example of a device (A) according to the invention. In Figure 1 the device has the shape of a sole. This cross-sectional view of the sole illustrates transverse piezoelectric sensor strips (1), longitudinal piezoelectric sensor strips (2), corresponding in this example to the length direction of the sole, all incorporated in the incompressible elastic material (3) constituting the sole.

[0068] Figure 2 illustrates in top view an example of a device (B) according to the invention having a sole shape: the incompressible elastic material

[0069] (3), for example silicone, is illustrated transparently, which allows a glimpse of the transverse (1), longitudinal (2) sensors, an electronic card

[0070] (4), all incorporated in the incompressible elastic material (3). The electronic card may, for example, comprise electronics for processing the signal generated by the transverse (1) and longitudinal (2) sensors. The electronic card may further comprise a wireless communication module, for example Bluetooth.

[0071] Figure 3 illustrates in sectional view the device (B) described above in relation to Figure 2. Figure 3 illustrates a foot (5) pressing in the direction of the arrow (6) on the device (B) made of the incompressible elastic material (3). The elastic material is said to be incompressible because the force of the foot pressing on the device does not induce compression of the material (3) but induces a lateral displacement along the arrows (7) and (8) but also in the direction orthogonal to these arrows (not shown). This displacement creates a greater extension of the transverse and longitudinal sensors which results in a stronger generated signal. It is therefore possible to determine the pressures exerted on the sole by the foot as follows:

[0072] Piezo sensors produce energy when they are mechanically stressed. This signal can be conditioned with the least possible loss to be then recovered by an energy harvesting circuit to charge a battery or a supercapacitor. When the energy level is sufficient for a signal measurement, the piezo sensors can be switched to analog conditioning for pressure measurement, the latter can then be converted to digital by a converter and then this data can be formatted and transmitted via Bluetooth to be subsequently analyzed by an external system (mobile application, software, etc.).

[0073] The energy required for measurement and Bluetooth transmission will discharge the energy source and the cycle can then be repeated to recharge this energy reservoir again.

[0074] To optimize this system it is therefore possible to play on 2 elements:

[0075] - optimize energy recovery by playing on the previous points,

[0076] - minimize energy consumption during measurement and transfer, for example via Bluetooth.

[0077] A device according to the invention may for example be included in soles or in a sock to detect pressure and temperature conditions conducive to the formation of ulcers or blisters and according to examples not illustrated may include:

[0078] Piezoelectric or flexible piezoelectric sensors of elongated shapes and arranged for a first part in the direction of the length of said soles or of the sock and the other part with an angle of between 1° and 90° relative to the first part,

[0079] An incompressible elastic material that incorporates said sensors, Electronics for processing the sensor signals, to calculate the values ​​of the pressures exerted by the feet, and for communicating said values, wirelessly and at low consumption to a smartphone, Contact pressure connections, by magnets or springs, between said sensors and the cables or tracks connected to said electronics, A battery or a supercapacitor to store the energy of said sensors, An application on the smartphone that analyzes the signals transmitted by the soles to convert them into pressure at each intersection of transverse and longitudinal sensors by analyzing the time shifts of said signals

[0080] The smartphone application displays audible and / or visual alerts and stores a history of values ​​for future analysis.

[0081] Of the 460 million diabetics worldwide, about 50 million will require foot surgery and sometimes foot amputation due to ulcers.

[0082] By knowing the pressure and temperature of the feet all day long, while walking... our solution will help avoid many ulcers and therefore surgical intervention:

[0083] • Practitioners (podiatrists, etc.) will be able to understand when ulcers appear and treat them more quickly.

[0084] • Customers can adapt their activities or modify their footwear...

[0085] Of course, the invention is not limited to the examples detailed above.

Claims

Claims

1. Device (A; B) for measuring mechanical stresses in a material comprising one or more networks of sensors (1, 2), characterized in that said sensors (1, 2) are of elongated shape and arranged for a first part in one direction and the other part with an angle of between 1° and 90° relative to the first part, in which said sensors (1, 2) are flexible piezoelectrics and in which said sensors are incorporated in an incompressible elastic material (3) so that when a stress is exerted, said material (3) induces a stretching of said sensors (1, 2).

2. Device (A;B) according to claim 1, characterized in that said sensors (1,2) are arranged for a first part in one direction and the other part with an angle equal to 90° relative to the first part.

3. Device (A;B) according to any one of the preceding claims, characterized in that said sensors (1,2) are connected to tracks or cables, connecting them to signal processing electronics, using magnets.

4. Device (A;B) according to any one of the preceding claims, characterized in that the energy generated by said sensors (1,2) is stored in a battery or a super-capacitor.

5. Sole (A;B) comprising a device according to any one of the preceding claims.

6. Sole (A;B) according to the preceding claim characterized in that the sole is formed by said incompressible elastic material (3).

7. Sole (A;B) according to claim 5 or 6, provided for detecting pressure and temperature conditions conducive to the formation of ulcers or blisters, in which the flexible piezoelectric sensors (1,2) of the first part are arranged in the length direction of said sole, said sole further comprising: • • Electronics for processing sensor signals, to calculate the values ​​of the pressures exerted by the feet, and to communicate these said values, wirelessly and with low consumption to a smartphone, • Contact pressure connections, by magnets, between said sensors and the cables or tracks connected to said electronics, • A battery or supercapacitor to store the energy of said sensors, • A smartphone application that analyzes the signals transmitted by the soles to convert them into pressure at each intersection of the transverse and longitudinal sensors by analyzing the time shifts of said signals, • application on the smartphone that displays audible and / or visual alerts and stores a history of values ​​for future analyses.

8. A sock comprising a device according to any one of claims 1 to 4.

9. Sock according to the preceding claim characterized in that the sock is formed by said incompressible elastic material.

10. A sock according to claim 8 or 9, provided for detecting pressure and temperature conditions conducive to the formation of ulcers or blisters, wherein the flexible piezoelectric sensors of the first part are arranged in the lengthwise direction of said sock, said sole further comprising: • Electronics for processing sensor signals, to calculate the values ​​of the pressures exerted by a user's foot, and to communicate said values ​​wirelessly and with low consumption to a smartphone, • Contact pressure connections, by magnets, between said sensors and the cables or tracks connected to said electronics, • A battery or supercapacitor to store the energy of said sensors, • A smartphone application that analyzes the signals transmitted by the soles to convert them into pressure at each intersection of transverse and longitudinal sensors by analyzing the time shifts of said signals, • Smartphone application that displays audible and / or visual alerts and stores a history of values ​​for future analysis.

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