WO2026008760A1 - Insole for monitoring the temperature of a person's foot - Google Patents

Abstract

The present invention relates to an insole (100) comprising: a) a technical layer (10) incorporating an electronic circuit board (11) produced on a flexible substrate (12), the upper face (11a) of which is instrumented with a plurality of temperature sensors (13); and b) an intermediate layer (20) comprising a cellular foam (21) joined to the upper face (11a), the cellular foam (21) having a plurality of cells (22) each formed by a hole (23) passing through the intermediate layer (20), the cells (21) each being positioned facing one of the temperature sensors (13) so that each cell (22) receives a temperature sensor (13) in such a way that each temperature sensor (13) emerges on an upper face (20a) of the intermediate layer (20) while still being isolated from the other temperature sensors (13) in order to avoid any electromagnetic interference between the sensors (13).

Description

Description

Title: Insole for monitoring a person's foot temperature

technical field

The present invention relates to the field of monitoring the temperature of a person's foot.

The present invention relates more particularly to an insole for footwear, said insole comprising an electronic board equipped with temperature sensors, which consumes little energy and whose innovative design allows monitoring of the temperature of a person's foot without hindering foot movements, including during physical activity such as walking or running.

By insole for footwear, we mean here an insole, removable or not, intended to be placed inside a footwear item and comprising a plantar surface intended to be in direct or indirect contact with the sole of the foot.

Such an insole differs from an outsole whose underside is intended to be in direct contact with the ground.

For the purposes of this invention, "footwear" refers to any item that can be worn; this may include footwear such as dress shoes or athletic shoes. It may also include boots, slippers, or any other item into which a person can place their foot.

The present invention will find many advantageous applications, particularly in the field of health by offering, to people such as, for example, patients suffering from diabetes, arteriopathy or acute Charcot, a connected insole capable of taking measurements of foot temperature to determine early or even predictively the presence or absence of plantar lesions.

The present invention will find other advantageous applications, for example in the field of sport, by enabling the detection of abnormal heating of certain areas of the foot, in order to improve performance, recovery or even prevent injuries.

The present invention will find further advantageous applications in other fields by enabling the detection of poor load distribution, thereby reducing the occurrence of musculoskeletal disorders (MSDs). Previous art

One of the major problems encountered by patients suffering from diabetes is the appearance of plantar lesions, more commonly known as diabetic foot ulcers.

Nearly 25% of people with diabetes are affected by these foot conditions at some point in their lives.

These diabetic foot ulcers manifest as open sores resulting from a combination of pressure, friction, and poor healing.

These open wounds appear as a deep excavation in the skin exposing the dermis or even the hypodermis without any tendency to heal.

Such open wounds can quickly become infected without proper care, too often leading to severe complications such as osteomyelitis (bone infection) and/or gangrene, which may require amputation.

The detection of these ulcers in patients suffering from diabetes therefore represents a major challenge for healthcare professionals; the consequences of this ulceration can be extremely serious since diabetes remains the leading cause of amputation:

- 1 amputation every 30 seconds worldwide,

- 85% of amputations are secondary to a diabetic foot ulcer,

- The overall cost of an amputation is estimated to be between €15,000 and €50,000.

Diabetic foot is classified according to several risk categories ranging from very low risk grade 0 to high risk grade 3.

In Europe, there are nearly 6 million patients with grade 2 and grade 3 diabetes. Each year, 1.2 million patients develop a diabetic foot ulcer and 250,000 undergo a lower limb amputation following the onset of the ulcer.

It should also be noted that, even with adequate care, complete healing of an ulcer requires 1 year in 77% of cases;

The management of complications related to diabetic foot represents a significant cost amounting to nearly €28 billion per year in Europe and €700 million in France.

It seems important here to understand the origin of these plantar ulcers in diabetics.

These lesions occur due to several disease-related factors, including peripheral neuropathy and obliterative arteriopathy of the lower limbs.

Peripheral neuropathy is a common condition in diabetics that causes a loss of sensation in the feet, making patients less able to perceive minor trauma or areas of excessive pressure. It is understood here that the loss of sensation in the Foot neuropathy reduces the patient's ability to detect injuries, thus increasing the risk of infections and ulcerations.

Circulatory insufficiency, a consequence of arteriopathy, slows down the healing process, thus increasing the risk of ulceration.

For these reasons, diabetic patients are at-risk individuals who are particularly susceptible to developing ulcer-like lesions on their feet.

Prevention and early detection of these lesions are therefore crucial to reducing the risks of morbidity and improving the quality of life of these patients.

We know of medical devices and innovative technologies in the prior art aimed at improving the quality of life of diabetic patients by detecting, if possible early, the presence of these ulcers.

Unfortunately, to date, it has been observed that the prevention systems in place are not optimal; moreover, the associated medical follow-up is irregular and discontinuous.

Several solutions have been developed so far to enable the detection of plantar lesions in diabetic patients:

Regular visual and manual inspections: Healthcare professionals recommend that patients perform daily self-examinations of their feet to detect any abnormalities. These inspections are often supplemented by regular consultations with podiatrists. However, this method relies on the patient's constant vigilance and may be ineffective in cases of advanced neuropathy.

Traditional orthotic insoles: Designed to redistribute pressure on the sole of the foot, these insoles aim to prevent the formation of ulcers. While they offer a degree of protection, they do not provide real-time data on the condition of the patient's feet.

Plantar pressure sensing technologies: These devices are equipped with pressure sensors integrated into the insoles or shoes, capable of measuring and analyzing areas of excessive pressure that could lead to ulcerations.

Smart insoles with multiple sensors: More recently, intelligent insoles equipped with several types of sensors (pressure, temperature, humidity) have been developed. These multi-sensors are capable of collecting several types of physiological data to detect abnormal changes which, combined, could indicate the development of an injury.

The company ORPYX® has thus developed a solution aimed at designing a connected insole including both pressure sensors and temperature sensors. We know, for example, of the document US2022/0395229.

From a scientific point of view, the combined measurement of these two types of measurement is relevant and allows for a good prediction of ulcers.

The Applicant notes, however, that the measurement of several data such as pressure and temperature is energy-intensive and does not allow the system to have autonomy of more than two weeks, thus making such a device ineligible for long-term remote monitoring.

Furthermore, the integration of temperature and pressure sensors makes the sole too complex to make and too thick, which makes it difficult to manufacture on the one hand and unattractive from a practical point of view because it cannot be integrated into just any footwear.

We also know of document GB2329022 which proposes the integration of a temperature sensor held in position in an epoxy resin (thermally insulating) so that the thermally sensitive surface of the thermistor protrudes from the upper surface of the insole for good contact of the sensor with the athlete's foot.

The thermal insulation of the base of the sensor by the epoxy resin prevents the temperature measurement from being disturbed by the heating of the components of the electronic board, the thermally sensitive surface of the thermistor (the upper part) being isolated from the rest of the sensor (the lower part).

However, such a configuration of the sensor protruding from the sole is likely to injure the foot of a user who suffers from a pathology such as diabetes, for example, which is not acceptable in the context of the applications targeted here by the present invention.

In conclusion, although significant progress has been made in the prevention and detection of diabetic foot ulcers, there is a continuing need to improve these technologies to provide more accurate monitoring, better adherence, and faster intervention.

Summary of the invention

The present invention aims to improve the situation described above.

The present invention aims to solve the various problems mentioned above by proposing a simple-to-design insole offering good autonomy and equipped with sophisticated sensors intended to accurately monitor the temperature of a person's foot while taking into account the anatomy of the foot without hindering the movements of the foot in a walking cycle. To this end, the object of the present invention relates, in a first aspect, to an insole for monitoring the temperature of a person's foot, such an insole being intended, for example, to:

- monitoring temperature variations between a patient's two feet to allow, for example, the (predictive or early) detection of a plantar lesion in a person such as a diabetic patient; or

- Monitor temperature variations between different areas of the foot: toes, metatarsals, midfoot or heel

By early or predictive, we mean here the detection of the lesion as early as possible in its formation process.

According to the present invention, the insole advantageously has a multilayer structure comprising at least one technical layer and one intermediate layer.

Advantageously, the technical layer includes the embedded electronics which will be used to measure the physiological data relevant to this monitoring.

In the example described here, this technical layer therefore integrates an electronic board made on a flexible substrate.

Advantageously, the upper surface of the electronic board is instrumented by a plurality of temperature sensors oriented towards the sole of the foot.

It is understood that the upper surface of the electronic board is the functional side of the board, on which the temperature sensors are located. The objective here is to position the temperature sensors as close as possible to the sole of the foot to obtain the most accurate temperature reading.

This upper face of the electronic board is therefore intended to be oriented towards the plantar surface of the user's foot when the user is wearing the insole.

It should be noted here that the present electronic board does not include pressure sensors, the measurements taken only relate to temperature measurement.

In the example described here, the intermediate layer comprises a convoluted foam assembled with the upper face of the technical layer.

It is understood here that the lower face of the inner layer is assembled to the upper face of the technical layer.

This foam is used in particular to provide the necessary comfort to users during walking or other pedestrian activity associated with foot movement. Advantageously, this open-cell foam comprises a plurality of cells, each formed by a hole passing through the intermediate layer. By "through hole," we mean a hole connecting the lower and upper surfaces of the foam.

Preferably, the through hole is straight. It can be elliptical, oblong, or have other shapes.

Advantageously, each cell is positioned opposite one of the temperature sensors when the technical layer and the intermediate layer are assembled. It is therefore understood that a convoluted foam is designed so that each cell accommodates a temperature sensor.

This honeycomb foam is intended in particular to protect the temperature sensors from various mechanical stresses and any adjacent electronic circuitry.

Thus, the cells serve as housing for each of the sensors when the two layers are superimposed on each other.

When the two layers are glued together, each temperature sensor fits into a cavity and opens onto an upper face of the intermediate layer while being isolated from the other temperature sensors.

Thus, the presence of these alveoli suitable for receiving temperature sensors makes it possible to isolate the sensors from each other and to avoid any electromagnetic interference between the sensors or with other electronic devices.

Thus, thanks to the design of this multi-layered insole, composed of an electronic circuit board on a flexible substrate containing temperature sensors and a perforated foam with cells designed to house the sensors, we have a robust insole capable of deforming under the stresses exerted by the user during physical activity. Meanwhile, a network of sensors, protected within cells and positioned close to the underside of the foot, collects temperature data. This design allows for precise monitoring of foot temperature, enabling, for example, the early detection of lesions in diabetic foot. It also allows for monitoring the temperature of different areas of the foot to detect abnormal heating in certain areas, or to identify uneven weight distribution in order to reduce the occurrence of musculoskeletal disorders (MSDs).

Advantageously, the flexible substrate on which the electronic board is made is of the PCB type (for "Printed Circuit Board"). It is also referred to as a "flexible PCB" (flexible printed circuit board). This flexible PCB board is therefore capable of being bent and/or twisted without being damaged and thus aligns with the classic properties of a sole which must be flexible to offer comfort and adaptability to foot movements and also allow easy introduction into all types of shoes.

The use of flexible PCBs is also advantageous because they are lighter and thinner than rigid PCBs. This design further reduces the overall weight of the electronics integrated into the sole, which is essential for comfort and practicality.

The Applicant observes that, due to their flexibility, the flexible PCB can be more naturally integrated into the sole's structure. This technical layer can therefore conform to curved shapes and follow specific contours without compromising its functionality as an electronic component.

The Applicant further observes that PCB flex is a material that is highly resistant to shocks and vibrations, which is an important advantage for soles that are subjected to significant mechanical stresses during walking or other activities.

Finally, the Applicant notes that the chosen PCB Flex is resistant to water and other environmental elements. This represents a significant advantage for the shoes, which may be exposed to various weather conditions and moisture inside the shoe.

Advantageously, the temperature sensors are each positioned on the substrate at specific locations to measure temperatures in predetermined areas of the foot corresponding to zones of friction and/or contact. Such areas are often at risk for foot injuries.

Preferably, the temperature sensors are positioned according to a zone of the heel, a zone of the midfoot, a zone of the metatarsal heads, a zone of the toes.

Advantageously, each cell is sized to receive a temperature sensor without the sensor being in contact with the side walls of the cell.

It is understood here that it is preferable for the foam not to come into contact with the sensors in order to avoid influencing the measurements. Each cell therefore has dimensions larger than the dimensions of the temperature sensor. For example, the cell has a tubular shape with a base diameter greater than the width of the temperature sensor and a height slightly greater than or equal to the height of the temperature sensor. Preferably, the foam with a honeycomb structure has a thickness at each cell slightly greater than the height of the temperature sensor so that the sensor does not protrude from the surface of the hole opening from the cell.

This configuration allows the temperature sensors to be as close as possible to the plantar surface of the foot to acquire the best possible temperature measurement, without coming into contact with the foot to avoid any injury.

In a particular embodiment, the temperature sensors have a height of approximately 1 mm while the honeycomb foam has a thickness of approximately 3 mm at the level of the cells.

It is therefore clear here that with a ratio of 1/3, the sensors are set back in the cells compared to the upper surface of the foam.

It should also be noted that by measuring the temperature on the top, the measurement is taken as far away as possible from the pins of the integrated circuit to avoid parasitic heating and obtain a reliable and accurate measurement.

Advantageously, each temperature sensor is centered in its associated cavity. In one advantageous embodiment, the base also includes a protective layer.

This protective layer consists of a coating of the temperature sensors made of a thermally conductive and electrically insulating material. The coating at least partially fills the cells so as to encase the sensors.

The material used may be in the form of a silicone gel.

In one variant, the protective layer includes a coating of the sensors with a silicone gel that at least partially fills the cells. This is also known as "potting".

For example, a silicone in the form of a gel is applied to at least partially fill each of the alveoli and coat the sensors.

The principle here therefore lies in coating the sensors in a material (for example a silicone gel) acting as a thermal conductor and electrical insulator.

The use of such a material ensures: a) thermal conduction to obtain a good measurement of the user's foot temperature; and b) electrical insulation to avoid any interference with other sensors and with the electronic board.

In one variant, the protective layer also incorporates metallic particles that promote thermal conductivity. Advantageously, the sole also includes a textile cover layer configured to cover the protective layer. This textile cover layer comprises a thermally conductive fabric designed to allow heat to pass through but not moisture, thus ensuring comfortable wear while allowing for accurate temperature measurement. This textile cover layer serves to guarantee comfortable wear of the insole with which the foot will be in contact.

Preferably, the protective layer further includes the addition of an adhesive silicone covering the upper face of the honeycomb foam and ensuring bonding of the covering textile layer with the intermediate layer.

In this variation, the surface of the open-cell foam is coated with an adhesive silicone. This is also referred to as silicone coating.

This first coating covering the top surface of the open-cell foam helps to homogenize the surface of the foam and in particular its hardness (called Shore), which improves user comfort.

Preferably, the underside of the textile cover layer is also coated with silicone. This second silicone coating works in conjunction with the first adhesive silicone coating to ensure bonding of the textile layer to the open-cell foam. Advantageously, the technical layer includes stiffening elements, also called stiffeners, on the inner face of the flexible substrate. These stiffeners are positioned under each of the temperature sensors and any other electronic components to reduce the various mechanical stresses applied to the sensors and other components, for example, during user movement.

The presence of these elements, which are placed under the electronic board (PCB flex) at the level of the sensors and other electronic components, makes it possible to stiffen these elements in order to protect them against the various mechanical stresses applied.

Advantageously, the sole according to the present invention comprises a mechanical layer placed beneath the technical layer, said mechanical layer being configured to provide an orthopedic function to the sole. Such a mechanical layer preferably has a shape configured to optimize the function and performance of the foot during a gait cycle.

Advantageously, the mechanical layer includes on its upper face a plurality of indentations serving as housings for the stiffening elements.

Advantageously, the electronic board is powered by a harvesting-type energy system including MFC sensors (for "Macro Fiber Composite" or composite of microfibres) employing piezoelectric elements which, by deforming, are capable of generating electricity, for example when subjected to mechanical stress, such as compression or bending during walking.

The presence of this power supply system gives the system good autonomy.

It should be noted here that simulations have shown that with 3800 steps, it is possible to obtain a battery life of 2 to 3 days.

Preferably, the electrical energy generated by the deformation of the piezoelectric elements is stored in a rechargeable solid-state Lithium-ion micro-battery.

This type of battery has several advantages:

Small footprint: Dimensions of 4.5x3x2 mm,

A good compromise between energy density and available peak current,

Constant voltage charging (simplicity of the charging circuit),

100 pAh to 500 pAh battery allowing current peaks of several tens of mA for 100 ms.

Possibility of connecting the micro-batteries in parallel

No explosion possible (because it is in a solid state), no toxic or rare materials. Advantageously, it is also possible to use a non-rechargeable lithium-manganese dioxide button cell with a capacity of approximately 230 mAh @3.0 V to power the entire system and achieve a minimum autonomy of 12 months.

Advantageously, the electronic board includes wireless communication means capable of communicating with a communication terminal to transmit periodically or continuously the measurement data taken by each of the temperature sensors.

Preferably, a BLE (Bluetooth Low Energy) antenna can be printed on the flexible PCB. This antenna allows the user's communication terminal to: detect the presence of the insole and pair with it (Advertising BLE); connect to the insole so that the measured data is transmitted to the communication terminal, which then acts as a gateway to transmit this information to the remote monitoring platform; update the device's firmware via OTA (Over The Air) BT using the application installed on the communication terminal; retrieve the insole's battery level; and configure certain insole parameters. In an advantageous embodiment, the temperature sensors are electrically connected to the electronic board by conductive tracks made of a flexible material and extending lengthwise to form a succession of open Q-shaped loops with cutouts in the flexible PCB.

The configuration of these tracks gives the card additional flexibility which allows it to withstand all the mechanical stresses related to walking: torsion, bending, traction, compression and shear.

Advantageously, the temperature sensors are clinical grade temperature sensors according to ASTM El 12 and ISO 80601-2-56 which are configured to perform temperature measurement with an accuracy of 0.1°C.

It should be noted that the selected temperature sensors offer, but are not limited to, the following advantages:

- low energy consumption during measurement (3.5-pA), and extremely low consumption when in standby mode (150-nA);

- an accuracy of 0.1°C over a temperature range of 5° to 50° Advantageously, the electronic board includes an accelerometer associated with an odometer configured to detect the user's movements and walking.

The accelerometer must allow the detection of the user's foot movements.

The odometer, for its part, must allow the detection of the position and orientation of the foot.

Those skilled in the art will understand that the configuration of these components and the motion detection tolerance depend on the chosen detection use case to ensure that temperature data is reported in a relevant and optimized manner. For example, it is unnecessary for the device to operate normally during the night. It can enter deep sleep mode and only wake up when, for instance, the accelerometer/odometer sends an interrupt following a confirmed motion detection.

Advantageously, the electronic board includes a resin coating on all or part of the electronic components of which it is made.

Thus, the electronic components of the electronic board are resin-coated, which ensures their protection and integrity, but also prevents injuries to the user's foot in case of tearing of the textile covering and the honeycomb foam.

Correspondingly, the object of the present invention relates, according to a second aspect, to a footwear article incorporating a sole as described above. Thus, through its various structural and functional technical characteristics, the present invention proposes an innovative design integrating embedded electronics capable of reliably and accurately monitoring foot temperature (for example, to detect the presence of lesions such as ulcers) while taking into consideration the anatomy of the foot and the kinematics of its natural biomechanical deformations to improve the wearer's comfort.

Description of the attached figures

Other features and advantages of the present invention will become apparent from the description below, with reference to the attached Figures 1 to 7, which illustrate an example of an embodiment without being limiting in any way, and on which:

[Fig l]

Figure 1 represents an exploded perspective view of a sole according to an example of an embodiment of the present invention.

[Fig-2]

Figure 2 shows a top view of the upper face of the open-cell foam assembled to the technical layer and covered with the silicone coating.

[Fig.3]

Figure 3 represents a cross-section of a footing conforming to Figure 1.

[Fig.4]

Figure 4 shows a flat view of the top face of the technical layer comprising the electronic board with temperature sensors and made on a flexible PCB substrate.

[Fig. 5]

Figure 5 represents a flat view of the underside of the technical layer including stiffener-type stiffening elements.

[Fig.6]

Figure 6 shows a flat view of the top face of the mechanical layer including indentations for receiving the stiffening elements.

[Fig-7]

Figure 7 shows a flat view of another example of the implementation of the electronic board on a flexible PCB substrate. Detailed description

An insole according to an advantageous embodiment of the present invention will now be described in what follows with joint reference to figures 1 to 7.

In the embodiment described here, we take the example of an application aimed at monitoring the temperature between the two feet of a diabetic patient in order to detect the early appearance of lesions.

It is understood here that this is one example of application among others and that it is possible to consider using the sole according to the invention for other applications such as, for example, detecting the distribution of loads on the foot to reduce musculoskeletal disorders or detecting abnormal heating under the foot to, for example, reduce the risk of injury in an athlete.

As mentioned earlier, people with diabetes have an increased risk of foot lesions that can develop into ulcers. These complications can be caused by poor blood circulation in the arteries of the lower limbs and are also exacerbated by decreased sensation in the feet.

In the most serious cases, these complications may require prolonged hospitalization and sometimes lead to amputation.

It is therefore important to be able to detect the appearance of a lesion that is a precursor to an ulcer as early as possible in order to improve medical care and avoid amputation.

Previous solutions are not satisfactory: they are complex to manufacture, are not suitable for promoting walking, do not allow for continuous measurement, and offer little autonomy.

One of the objectives of the present invention is to design an insole incorporating embedded electronics specifically designed to facilitate temperature monitoring between a patient's two feet while respecting foot anatomy and reducing energy consumption.

This is made possible in the following example.

In the example described here, and as illustrated in particular in figures 1 and 3, an insole 100 is planned comprising a multi-layer structure.

Such a multilayered structure takes the form of a complex with several functional layers superimposed on one another.

The combination of these layers is characteristic of the present invention.

The first layer 10, known as the technical layer, integrates the embedded electronics of the sole. This layer 10, illustrated in particular in figures 4 and 5, constitutes the main layer in which the inventive concept of the invention resides.

Indeed, one of the technical challenges solved by this invention was to design a connected insole incorporating miniaturized electronics that does not compromise user comfort and offers good battery life. This differs from existing solutions that use energy-intensive, bulky, and complex electronics, making the insole heavy, thick, and uncomfortable for the patient.

In the example described here, this electronic board 11 is made on a flexible substrate, preferably here a flexible PCB (PCB for "Printed Circuit Board").

This flexible PCB serves as a mechanical and electronic support structure and improves the electrical and physical connections of the components while allowing efficient signal transmission and good power distribution.

This flexible PCB also offers an optimal solution for giving the sole the suppleness and flexibility necessary for its deformation during the user's movements. Finally, it should be noted that this flexible PCB provides good mechanical resistance.

The underlying concept of the present invention is the implementation of a solution that uses only temperature data. Indeed, previously known connected insoles primarily used data related to the pressure exerted under the foot. This pressure data was sometimes combined with temperature data.

The Applicant notes that under no circumstances has a sole solution exploiting only foot temperature been considered so far.

However, after numerous tests, it turned out that such an approach with temperature data only made it possible to accurately detect the appearance of lesions under the foot.

Thus, the electronic card 11 provided for in the context of the present invention incorporates temperature sensors 13. These sensors 13 are provided on the upper face 10a of the technical layer so as to be oriented with regard to the lower face of the foot and thus measure the temperature under the foot.

As illustrated in Figure 4, the temperature sensors 13 are positioned in predetermined locations to measure temperatures in specific predetermined areas of the foot corresponding to areas at risk for foot injuries, namely here for example the heel area 14a, the metatarsal head area 14b, the toe area 14c and the midfoot area 14d. Zones 14a, 14b, 14c, and 14d represent the most frequent areas of friction and pressure. Therefore, these are the areas where the risks of injury and ulceration are highest. In the example described here, there are nineteen such sensors.

Of course, it will be understood that this number can vary (increase or decrease) depending on the desired precision.

In the example described here, clinical grade temperature sensors 13 according to ASTM El 12 and/or ISO 80601-2-56 were selected to perform a temperature measurement with an accuracy of 0.1 °C; preferably the sensors are configured so that such accuracy is achieved over a range of 5 to 50°C.

This technical layer 10 is coupled to an intermediate layer 20 which includes a honeycomb foam 21.

This 21-cell foam is superimposed on the upper face l ia.

The function of the honeycomb foam 21 is to isolate the sensors 13 from each other to avoid any electrical and electromagnetic interference between the sensors 13.

It also serves to improve patient comfort.

In the example described here and as illustrated in figures 1, 2 and 3, the foam 21 has cells 22. It is understood here that each cell 22 is in the form of a hole 23 passing through the intermediate layer 20 on either side of the lower and upper face of the foam.

The location of the cells 22 follows the distribution of the location of the sensors 13. The cells 22 are therefore each positioned opposite one of the temperature sensors 13 when the technical layer 10 and the intermediate layer 20 are assembled together.

Thus, during the assembly of layers 10 and 20, the temperature sensors 13 each fit into the cavity 22 dedicated to it so that each temperature sensor 13 opens onto the upper face 20a of the intermediate layer 20 while being isolated from the other temperature sensors 13 in order to avoid any electromagnetic interference between the sensors 13.

In this example, the temperature sensors 13 are each approximately 1 mm high, while the convoluted foam 21 is approximately 3 mm thick at the level of the cells 22, so that the sensors 13 are slightly recessed within the cells 22 relative to the upper surface of the foam, thus preventing any direct contact with the foot. The combination of this electronic board 11 on a flexible PCB with the temperature sensors 13 and the convoluted foam 21 is characteristic of the present invention.

It is preferable that the sensors 13 not be in contact with the foam 21. It is therefore foreseen in the example described here that each temperature sensor 13 is centered in the cavity 22 and that each cavity 22 is dimensioned to receive a temperature sensor 13 without said sensor 13 being in contact with the lateral walls 22a of the cavity 22. t This electronic board 11 is instrumented by other electronic components.

For power, a non-rechargeable button cell battery with a capacity of approximately 230 mAh @3.0 V is planned.

To improve autonomy, a power supply is also planned by a 16-type harvesting energy system comprising MFC sensors implementing piezoelectric elements which, by deforming, are able to generate electricity for example when subjected to mechanical stress, such as compression or bending during walking.

In the example described here, wireless communication means 17, of the BLE antenna type (or equivalent), are also provided to communicate with a communication terminal in order to transmit the measurement data made by each of the temperature sensors 13.

In the example described here, this transmission occurs periodically (for example, every 15 or 30 minutes). Of course, this frequency can be adjusted according to the practitioner's preference.

In the example described here, the implementation on the electronic board 11 of an accelerometer/odometer is planned to detect the movements and orientation of the patient's foot; this makes it possible to determine the patient's activity (stationary or in motion).

The detection model used to exploit this data to weight the temperature, for example in the case of sustained activity.

Resin coating is also provided here on the electronic board and all of its electronic components; such resin coating ensures the protection and integrity of these components and also prevents injuries to the patient's foot in the event of, for example, tearing of the alveolar foam 21 (or of the textile coating layer 30 described below).

On the electronic board 11, it is also characteristic to have provided conductive tracks 18 which are made of a flexible material and which stretch lengthwise, forming a succession of open Q-shaped loops.

Such tracks 18 are illustrated in figures 4, 5 and 7.

This Q shape, as you will understand, allows for deformation of the tracks without risk of breakage, which improves the flexibility of the 11 card and its robustness.

The Applicant observes here that such Q-shaped tracks had never been used before in a sole for its on-board electronics. It should be noted here that, thanks to the use of "Ultra Low Power" components (temperature sensors, BLE module, accelerometer, processor), it is possible to achieve a battery life of twelve months; such battery life is greatly appreciated by patients who do not have to worry about frequently recharging their device as is currently the case with prior art solutions which offer a battery life of two weeks (only).

The sole proposed according to the present invention therefore significantly improves the user experience with an additional gain in terms of comfort.

This comfort is further enhanced by an additional protective layer 30 which includes a coating 32 of the temperature sensors 13 with a silicone gel.

This silicone coating 32 is illustrated in figure 3.

The sensors 13 are therefore embedded in this silicone coating 32, which protects them from deterioration while ensuring good thermal conductivity for measuring foot temperature and electrical insulation from the rest of the electronic board components.

The use of such a silicone gel differs from the prior art, and in particular from document GB2329022, which proposes embedding the lower part of the sensor in an epoxy resin. Epoxy resin is known for its thermal insulation and electrical conductivity properties, two physical properties that are precisely what is being avoided here through the use of silicone gel.

It should also be noted that, in this example, the silicone coating 32 incorporates metallic particles that enhance thermal conductivity. The presence of these particles therefore allows for an even more reliable and precise temperature measurement.

In the example described here, the use of an adhesive silicone is planned to allow the assembly by gluing of the open-cell foam 21 with a layer of covering textile 40.

It is therefore planned to coat the upper face of the honeycomb foam with an adhesive silicone.

This silicone coating 31 also helps to homogenize the surface of the foam and in particular its hardness, which improves patient comfort.

This layer of covering textile 40 which covers the protective layer 30 is made of a thermally conductive fabric 41 in order to allow the passage of heat but not moisture.

The presence of this additional layer 40 guarantees comfort when wearing the sole 100 while allowing for good temperature measurement. The use of Dermodry® fabric is planned here. Of course, a person skilled in the art may consider using another technical fabric with these properties (thermal conductivity and moisture barrier).

To promote the bonding of the textile layer 40 with the foam 20, a second silicone coating 42 is provided on the underside of the layer 40 to interact with the silicone coating 31 of the protective layer.

Finally, under the technical layer 10, a final layer called mechanical layer 50 is planned.

In the example described here, this mechanical layer 50 provides an orthopedic function to the insole 100.

We can therefore understand here that this mechanical layer 50 has a shape that respects the anatomy of the foot in order to improve its function during an activity.

To reinforce the strength of the electronic components, stiffening elements 15, also called stiffeners, are provided on the lower face 10b on the flexible substrate 12.

These elements 12 are positioned under each of the temperature sensors 13 in order to reduce the various mechanical stresses applied to the sensors 13 during the patient's walking, for example.

Here, the mechanical layer 50 includes on its upper face 50a a plurality of indentations 51, or notches, serving as housings for the stiffening elements 15.

By layering layers 10 and 50, the stiffeners 15 will therefore fit into these notches.

Thus, the present invention provides for the design of a sole that significantly improves existing solutions and whose main advantages are comfort, efficiency, robustness and autonomy:

Comfort is primarily achieved through optimized size and component placement. The sole components were chosen to make the sole as thin, flexible, and lightweight as possible.

Effectiveness is achieved through precise placement of temperature sensors, namely under the areas most prone to developing an ulcer.

Autonomy has also been significantly improved, increasing from approximately two weeks to a minimum of twelve months. The Applicant observes that increasing this autonomy greatly enhances patient adherence, thereby preventing complications related to diabetic foot.

This improved autonomy is achieved through:

- components such as the electronic board and sensors which consume very little energy and have perfectly optimized consumption modes. - The elimination of pressure sensors compared to competing solutions

- An energy harvesting system that converts the mechanical movement of the patient's foot into energy.

It should be noted that this detailed description relates to a particular embodiment of the present invention, but in no way does this description limit the scope of the invention; on the contrary, its purpose is to remove any possible inaccuracy or misinterpretation of the following claims.

It will be understood here that the present invention has been described in the example below for the monitoring and surveillance of the feet of a diabetic patient.

It will be understood, however, that the insole according to the invention is suitable for monitoring other people such as, for example, people suffering from neuropathies, arteriopathy or even acute Charcot.

Other applications could also be considered, such as:

- by enabling the detection of abnormal heating in certain areas of the foot to improve performance, recovery, or even prevent injuries; or

- by enabling the detection of poor load distribution, thereby reducing the occurrence of musculoskeletal disorders (MSDs).

It should also be noted that the reference symbols placed in parentheses in the following claims are in no way intended to be limiting; their sole purpose is to improve the intelligibility and understanding of the following claims and the scope of the protection sought.

Claims

Demands 1. Insole (100) for monitoring the temperature of a user's foot, said insole (100) having a multilayer structure comprising: - a technical layer (10) integrating an electronic board (11) made on a flexible substrate (12) whose upper face (l ia) is instrumented by a plurality of temperature sensors (13) oriented towards the lower face of the foot; - an intermediate layer (20) comprising a convoluted foam (21) assembled with the upper face (l ia), said convoluted foam (21) having a plurality of cells (22) each formed by a hole (23) through the intermediate layer (20), said cells (21) each being positioned opposite one of the temperature sensors (13) when the technical layer (10) and the intermediate layer (20) are assembled together so that each cell (22) receives a temperature sensor (13) in such a way that each temperature sensor (13) opens onto an upper face (20a) of the intermediate layer (20) while being isolated from the other temperature sensors (13) in order to avoid any electromagnetic interference between the sensors (13). 2. Base (100) according to claim 1, in which the flexible substrate (12) on which the electronic board (11) is made is a flexible PCB board. 3. Sole (100) according to claim 1 or 2, wherein the temperature sensors (13) are each positioned on the substrate (12) according to determined locations (14a, 14b, 14c) to measure temperatures in specific predetermined areas of the foot corresponding to areas of friction and/or contact. 4. Insole (100) according to claim 3, in which the temperature sensors (13) are positioned according to a zone of the heel (14a), a zone of the metatarsal heads (14b), a zone of the toes (14c), a midfoot zone (14d). 5. Insole (100) according to any one of the preceding claims, wherein the open-cell foam (21) has at each cell (22) a thickness slightly greater than or equal to the height of the temperature sensor so that the sensor (13) does not protrude from the surface of the hole (23) opening from the cell. 6. Insole according to claim (5), in which the temperature sensors (13) have a height of 1 mm and the open-cell foam (21) has a thickness of 3 mm at the level of the cells (22). 7. Base (100) according to any one of the preceding claims, wherein each cavity (22) is dimensioned to receive a temperature sensor (13) without said sensor (13) being in contact with the lateral walls (22a) of the cavity (22). 8. Base (100) according to claim 7, in which each temperature sensor (13) is centered in the associated cavity (22). 9. Base (100) according to any one of the preceding claims, which includes a protective layer (30) comprising a coating (32) of the temperature sensors (13) by a thermally conductive and electrically insulating material, said coating (32) at least partially filling the cells (22). 10. Sole according to claim 9, wherein the material used for the coating (32) comprises a gel such as, for example, a silicone gel. 11. Sole (100) according to claim 9 or 10, wherein the protective layer (30) comprises metallic particles promoting thermal conductivity. 12. Insole (100) according to any one of claims 9 to 11, which includes a textile cover layer (40) configured to cover the protective layer (30), said textile cover layer (40) comprising a thermally conductive fabric (41) configured to allow the passage of temperature but not moisture in order to ensure comfortable wearing of the insole (100) while allowing good temperature measurement. 13. Sole (100) according to claim 12, in which the protective layer (30) comprises a first silicone coating (31) covering the upper face (21a) of the open-cell foam (21) and made of an adhesive silicone ensuring bonding of the covering textile layer (40) with the intermediate layer (20). 14. A sole (100) according to any one of the preceding claims, wherein the technical layer (10) comprises on the inner face (10b) on the flexible substrate (12) stiffening elements (15) positioned under each of the temperature sensors (13) in order to reduce the various mechanical stresses applied to said sensors (13) during the user's walking, for example. 15. Insole (100) according to any one of the preceding claims, which includes a mechanical layer (50) placed under the technical layer (10) to provide an orthopedic function to said insole (100). 16. Sole (100) according to claim 15 related to claim 14, in which the mechanical layer (50) comprises on its upper face (50a) a plurality of indentations (51) serving as housings for the stiffening elements (15). 17. Sole (100) according to any one of the preceding claims, wherein the electronic board (11) is powered by a harvesting-type energy system (16) comprising MFC sensors implementing piezoelectric elements which, by deforming, are capable of generating electricity, for example, when subjected to mechanical stress, such as, for example, compression or bending during walking. 18. Base (100) according to any one of the preceding claims, wherein said electronic card (11) includes wireless communication means (17) capable of communicating with a communication terminal to transmit periodically or continuously the measurement data obtained by each of the temperature sensors (13). 19. A sole (100) according to any one of the preceding claims, wherein the temperature sensors (13) are electrically connected to the electronic board (11) by conductive tracks (18) made of a flexible material and stretching lengthwise to form a succession of open loops in the shape of . 20. Insole (100) according to any one of the preceding claims, wherein the temperature sensors (13) are clinical grade temperature sensors according to ASTM El 12 and/or ISO 80601-2-56 which are configured to perform temperature measurement with an accuracy of 0.1°C. 21. Sole (100) according to any one of the preceding claims, wherein the electronic card (11) includes an accelerometer associated with an odometer. 22. Base (100) according to any one of the preceding claims, wherein the electronic board (11) includes a resin coating on all or part of the electronic components of which it is made. 23. Footwear article incorporating a sole (100) according to any one of the preceding claims.