A pressure monitoring-cushion protection integrated insole for diabetic foot and a preparation method thereof

Abstract

The present application relates to the technical field of flexible sensor, in particular to a pressure monitoring and buffer protection integrated insole for diabetic foot and a preparation method thereof.The insole has a three-layer structure: the surface layer is a skin-friendly fabric layer, the middle layer is a pressure sensing array layer with pressure resistance and pressure capacity dual-mode sensing function, and the bottom layer is a porous polyborosiloxane elastomer buffer layer.The middle pressure sensing array layer adopts a six-layer structure, and the upper and lower pressure sensitive materials are arranged oppositely.The number, size and distribution of the pressure sensing units can be customized through the silk screen printing process.The bottom layer utilizes the shear hardening effect of polyborosiloxane to realize dynamic buffering and immediate protection.The insole has both wide-range and high-sensitivity pressure monitoring capability and excellent impact buffering performance, can realize real-time monitoring and active early warning of plantar pressure, effectively absorb impact energy and reduce peak pressure, help diabetic patients prevent foot complications, and is easy to mass-produce and customize.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor technology, specifically to an integrated pressure monitoring and cushioning insole for diabetic foot and its preparation method. Background Technology

[0002] Diabetes has become a major global public health problem, characterized by high morbidity, high disability rate, and high mortality rate. Diabetic plantar ulcer (DFU) is the leading cause of non-traumatic lower limb amputation in diabetic patients. Studies have shown that abnormally elevated plantar pressure is an independent risk factor for DFU, and the two are highly correlated.

[0003] Diabetic patients often suffer from peripheral neuropathy and impaired blood circulation in the lower limbs, leading to decreased foot sensation and fragile tissues. Even minor, repetitive pressure and impact can easily trigger plantar ulcers, infections, and even amputation. Therefore, developing insoles that can monitor plantar pressure in real time and provide effective cushioning and protection is of great significance for the early warning and prevention of diabetic foot.

[0004] Existing technologies include several smart monitoring or cushioning insoles designed for diabetic patients. For example, patent CN120616501A proposes a foot pressure detection insole integrating multiple functional modules, and patent CN223142949U discloses an insole with shock absorption and cushioning functions. However, most of these existing solutions only possess single pressure monitoring or cushioning protection functions, and generally suffer from problems such as low sensor sensitivity, insufficient mechanical flexibility, poor protective capabilities, and inability to be customized, limiting their widespread application in the daily care of diabetic patients.

[0005] Therefore, developing an integrated insole that combines high-sensitivity pressure monitoring with excellent cushioning and protection performance, and allows for personalized customization, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention aims to provide an integrated pressure monitoring and cushioning protection insole for diabetic foot, overcoming the shortcomings of existing technologies, and its manufacturing method. This insole aims to simultaneously achieve high-precision, wide-range real-time monitoring of plantar pressure, and efficient, immediate dynamic impact cushioning protection, thereby solving the problems of existing products having limited functionality, poor sensing performance, and insufficient protective capabilities.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A pressure monitoring and cushioning insole for diabetic foot, featuring a three-layer composite structure, comprising: The outer fabric layer is made of skin-friendly and breathable fabric material, and is used for direct contact with the soles of the feet; The intermediate pressure sensing array layer is used to sense plantar pressure and has a dual-modal sensing function of piezoresistive / piezoresistive. The bottom buffer and damping layer is a porous polyborosiloxane elastomer layer that utilizes the shear hardening effect of the material to achieve dynamic buffering and immediate protection.

[0008] Preferably, the surface fabric layer is selected from polyester fiber fabric, polyurethane fiber fabric or pure cotton fabric.

[0009] Preferably, the intermediate pressure sensing array layer is a six-layer structure comprising a lower encapsulation layer, a lower electrode layer, a lower pressure-sensitive layer, an upper pressure-sensitive layer, an upper electrode layer, and an upper encapsulation layer; wherein the upper pressure-sensitive layer and the lower pressure-sensitive layer are arranged opposite to each other with a tiny gap between them, and the sensing principle is that the contact area between the upper pressure-sensitive layer and the lower pressure-sensitive layer changes when pressure is applied, thereby causing a change in the electrical signal and realizing a piezoresistive and piezoresistive dual-mode response.

[0010] Preferably, the encapsulation material of the intermediate pressure sensing array layer is at least one of polyester (PET), polyimide (PI), polydimethylsiloxane (PDMS), or polyurethane (PU); the pressure-sensitive material is at least one of graphene slurry, graphene oxide slurry, carbon nanotube slurry, graphite slurry, or MXene slurry; and the electrode material is at least one of conductive carbon paste, conductive silver paste, or conductive copper paste.

[0011] Preferably, the intermediate pressure sensing array layer integrates 10-60 pressure sensing units.

[0012] Preferably, the size, number, and distribution of the pressure sensing units can be customized to achieve high monitoring accuracy and stability.

[0013] Preferably, the porous polyborosiloxane elastomer of the bottom buffer and shock-absorbing layer is prepared by template method, and the porous polyborosiloxane elastomer has a porous structure with a pore size of 0.5-3 mm and a pore spacing of 1-5 mm.

[0014] Preferably, the thickness of the bottom buffer and shock-absorbing layer can be customized as needed.

[0015] The present invention also provides a method for preparing an integrated pressure monitoring and cushioning insole for diabetic foot as described in any of the preceding claims, comprising the following steps: S1. Cut the surface fabric to the predetermined insole size to obtain the surface fabric layer; S2. Select a lower encapsulation layer and an upper encapsulation layer that conform to the predetermined insole size. Use screen printing to laminate the electrode material onto the surfaces of the lower encapsulation layer and the upper encapsulation layer respectively, forming a lower electrode layer on the lower encapsulation layer and an upper electrode layer on the upper encapsulation layer. S3. Pressure-sensitive materials are laminated onto the surfaces of the lower electrode layer and the upper electrode layer respectively by screen printing, forming a lower pressure-sensitive layer on the lower electrode layer and an upper pressure-sensitive layer on the upper electrode layer. S4. Use screen printing adhesive to bond the area on the lower electrode layer (excluding the lower pressure-sensitive layer) and the area on the upper electrode layer (excluding the upper pressure-sensitive layer) together to obtain the intermediate pressure sensing array layer. S5. Hydroxysilicone oil and boric acid are mixed in a mass ratio of 20-30:1, and after heat treatment, a catalyst is added and the mixture is reacted to obtain polyborosiloxane. S6. Mix polyborosiloxane with methyl vinyl silicone rubber to obtain a polyborosiloxane elastomer precursor; S7. Fill the polyborosiloxane elastomer precursor into a porous mold that conforms to the predetermined insole size, and then heat-cur it to obtain a porous polyborosiloxane elastomer. S8. The surface fabric, the intermediate pressure sensor array layer and the porous polyborosiloxane elastomer are bonded together to obtain the integrated pressure monitoring and cushioning protection insole for diabetic foot.

[0016] Preferably, in S2, the lower electrode layer and the upper electrode layer are distributed in a relative array with the same shape and size; in S3, each set of relative lower pressure sensitive layers and upper pressure sensitive layers constitutes a pressure sensing unit.

[0017] Preferably, in step S2, while forming the lower electrode layer on the lower encapsulation layer by screen printing, connecting lines are formed between the arrays of the lower electrode layers using electrode material; similarly, while forming the upper electrode layer on the upper encapsulation layer by screen printing, connecting lines are formed between the arrays of the upper electrode layers using electrode material; for example... Figure 1 As shown by the black connecting line in the image.

[0018] Preferably, the pressure sensing unit has a flexible flat cable interface for connecting to an external acquisition module, and the black connecting wire can be connected to the flexible flat cable.

[0019] Furthermore, the pressure sensing unit also has a signal output terminal for communicating with an external Bluetooth module, which is connected to the acquisition module via a flexible flat cable, and can transmit the pressure signal to the smart device in real time via Bluetooth wireless transmission.

[0020] Preferably, in step S5, the catalyst is octanoic acid, the amount of catalyst added is 1.3%-3.3% of the mass of boric acid, the heat treatment temperature is 160-200℃, the heat treatment time is 30-40 min, the reaction temperature is 160-200℃, and the reaction time is 15-30 min.

[0021] Preferably, in step S6, the mass ratio of the polyborosiloxane to the methyl vinyl silicone rubber is 0.4-2.5:1.

[0022] Preferably, in step S7, the thermosetting conditions are: pressure 15-20 MPa, temperature 80-100℃, and time 10-20 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention designs a novel integrated pressure monitoring and cushioning protection insole for diabetic foot, integrating a conductive pressure sensor array layer and a cushioning and shock-absorbing layer, which can monitor high-pressure areas on the soles of diabetic patients in real time. Simultaneously, dynamic hardening cushioning is achieved through porous polyborosiloxane elastomers, enhancing protection in the event of high pressure, upgrading from "passive protection" to "active early warning + immediate protection"; 2. The sensing layer of this invention can realize dual-modal pressure sensing (piezoresistive + capacitive), resulting in more accurate and stable measurements. The piezoresistive mode is suitable for medium to high pressure and large deformation scenarios, while the capacitive mode is suitable for low pressure and weak pressure detection. The combination of the two can cover pressure changes in the entire plantar area, providing a wider measurement range. 3. This invention uses screen printing and flexible composite technology to integrate the sensor with the insole structure. There are no protruding hard components, and the thickness and cost are controllable. Compared with traditional monitoring equipment, it is lighter and more durable, making it suitable for long-term daily use by diabetic patients. Attached Figure Description

[0024] Figure 1 This is a structural diagram of the integrated pressure monitoring and cushioning protection insole for diabetic foot prepared according to the present invention; Figure 2 The front and side optical images are of the integrated pressure monitoring and cushioning protection insole for diabetic foot prepared according to the present invention. Figure 3 The SEM surface morphology of the surface fabric in Example 1; Figure 4 A schematic diagram of a cross-section of a single pressure sensing unit; Figure 5 The SEM cross-sectional morphology of a single pressure sensing unit; Figure 6 The surface optical morphology of the porous polyborosiloxane elastomer prepared in Example 1; Figure 7 The results of the piezoresistive sensing performance test of the integrated pressure monitoring and cushioning protective insole for diabetic foot prepared in Example 1 are as follows: Figure 8 The results are the pressure-capacity sensing performance test results of the integrated pressure monitoring and cushioning protective insole for diabetic foot prepared in Example 1; Figure 9Force-time curves of porous polyborosiloxane elastomers under different energy impacts; Figure 10 Comparison of peak forces of porous polyborosiloxane elastomers under different energy impacts; In the diagram: 1. Top fabric layer; 2. Middle pressure sensor array layer; 3. Single pressure sensor unit; 4. Bottom buffer and shock absorption layer. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] The specific information of the raw materials used in the following examples and comparative examples is as follows: (1) Hydroxy silicone oil was purchased from Jining Huakai Resin Co., Ltd., with a molecular weight of 4000; (2) Boric acid and octanoic acid were both purchased from Aladdin Chemical Co., Ltd., China; (3) Methyl vinyl silicone rubber was purchased from Shenzhen Muwei Technology Co., Ltd., with a molecular weight of 600,000-650,000 and a vinyl content of 0.16%-0.18%; (4) The conductive silver paste was purchased from Shenzhen Yingtai United Technology Co., Ltd., with a silver content of 75-80%.

[0027] (5) The graphene slurry was purchased from Ganzhou Selihui Technology Co., Ltd., with a graphene mass fraction of 3wt%-8wt% and a dispersion medium of polyurethane resin / butanone solution.

[0028] It should be noted that the above raw materials are merely examples to make the technical solution of the present invention clearer, and do not mean that the present invention can only use the above raw materials. The specific scope is subject to the claims. Example 1

[0029] This embodiment provides an integrated pressure monitoring and cushioning insole for diabetic foot, the preparation method of which is as follows: S1. Cut the polyurethane fiber fabric to the predetermined insole size and use it as the surface fabric. Depend on Figure 3 It is known that the outer fabric is composed of fibers, which has good breathability and is beneficial for long-term wear; S2. Select PET polyester film (thickness of 0.1mm) that meets the predetermined insole size as the lower encapsulation layer and the upper encapsulation layer respectively. Apply conductive silver paste to the surface of the lower encapsulation layer and the upper encapsulation layer respectively by screen printing. Form a lower electrode layer on the lower encapsulation layer and an upper electrode layer on the upper encapsulation layer. The lower electrode layer and the upper electrode layer are distributed in a relative array of squares of the same size. The average thickness of the lower electrode layer and the upper electrode layer is 1.5μm. In this process, while forming the lower electrode layer on the lower encapsulation layer by screen printing, connecting lines are formed between the arrays of the lower electrode layers using electrode material; similarly, while forming the upper electrode layer on the upper encapsulation layer by screen printing, connecting lines are formed between the arrays of the upper electrode layers using electrode material. S3. Graphene paste is laminated onto the surfaces of the lower electrode layer and the upper electrode layer by screen printing, forming a lower pressure-sensitive layer on the lower electrode layer and an upper pressure-sensitive layer on the upper electrode layer. The average thickness of the lower pressure-sensitive layer and the upper pressure-sensitive layer is 8 μm. Each pair of opposing lower pressure-sensitive layers and upper pressure-sensitive layers constitutes a pressure sensing unit. According to the screen design, this embodiment has 48 pressure sensing units. S4. The area on the lower electrode layer (excluding the lower pressure-sensitive layer) and the area on the upper electrode layer (excluding the upper pressure-sensitive layer) are bonded together by screen printing acrylic adhesive (UV Acrylic Spacer Ink). The mixture is cured for 20 seconds under UV lamp (365nm / 50W) to form the intermediate pressure sensing array layer. like Figure 4 and Figure 5 As shown, the middle pressure sensing array layer has a six-layer structure. The lower pressure sensing layer and the upper pressure sensing layer are positioned opposite each other with a tiny gap. When pressure is applied, the contact area between the lower and upper pressure sensing layers increases, allowing pressure to be detected. Figure 5 Scanning electron microscopy revealed that there was a certain gap between the lower pressure-sensitive layer and the upper pressure-sensitive layer in the initial state, with less contact area. Under pressure, the contact area between the lower pressure-sensitive layer and the upper pressure-sensitive layer increased, thereby causing changes in the electrical signal and realizing a piezoresistive and piezoresistive dual-mode response. S5. Hydroxysilicone oil and boric acid are mixed evenly at a mass ratio of 20:1, and placed in an oven for heat treatment at 180°C for 30 min. Then, octanoic acid catalyst is added, and the mixture is stirred and reacted at 180°C for 15 min. The amount of catalyst added is 3% of the mass of boric acid, to obtain polyborosiloxane. S6. The polyborosiloxane obtained in S5 and methyl vinyl silicone rubber are mixed evenly in a 1:1 mass ratio using a rubber mixing mill to obtain a polyborosiloxane elastomer precursor. S7. Fill the precursor obtained in S6 into a porous mold and heat cure it at 19MPa and 90℃ for 15min to obtain a porous polyborosiloxane elastomer with a pore size of 0.8mm, a pore center-to-center distance of 2.5mm, and a thickness of 2mm. The porous polyborosiloxane elastomer serves as the bottom buffer and shock-absorbing layer. like Figure 6 As shown, the polyborosiloxane elastomer has a porous structure with smooth pore cuts and a uniform and orderly arrangement of pore cuts. S8. The surface fabric in S1, the intermediate pressure sensor array layer in S4, and the bottom cushioning and shock absorption layer in S7 are combined with 3M double-sided adhesive to obtain an integrated pressure monitoring and cushioning protection insole for diabetic foot. The structure of the integrated pressure monitoring and cushioning insole for diabetic foot is as follows: Figure 1-3 As shown. Example 2

[0030] This embodiment provides an integrated pressure monitoring and cushioning protection insole for diabetic foot, which differs from Embodiment 1 only in that: in S3, the number of pressure sensing units is 60. Example 3

[0031] This embodiment provides an integrated pressure monitoring and cushioning protection insole for diabetic foot, which differs from Embodiment 1 only in that: in S5, the mass ratio of hydroxyl silicone oil to boric acid is 25:1. Example 4

[0032] This embodiment provides an integrated pressure monitoring and cushioning protection insole for diabetic foot, which differs from Embodiment 1 only in that: in S6, the mass ratio of polyborosiloxane to methyl vinyl silicone rubber is 2.3:1. Example 5

[0033] This embodiment provides an integrated pressure monitoring and cushioning protection insole for diabetic foot, which differs from Embodiment 1 only in that: in S6, the mass ratio of polyborosiloxane to methyl vinyl silicone rubber is 1:2.3.

[0034] Performance testing The performance of the insole prepared in Example 1 was tested, and the results are as follows: Dual-modal sensing characteristics: The sensing layer was led out via wires, and pressure was applied using a DMA 3200 mechanical testing system. Resistance signals were recorded using a ModuLab XM MTS tester, and capacitance signals were recorded using a VC4092E digital bridge. Results are as follows: Figure 7 As shown, in piezoresistive mode, the sensor's monitoring range is 0.8-516.2 kPa, its sensitivity is 0.98 μA / kPa, and its linearity is good. Figure 8As shown, in pressure-capacity mode, the sensor's monitoring range is 0.2-513.9 kPa, with a linear operating range divided into two segments and sensitivities of 3.5 kPa. -1 and 0.58 kPa -1 This indicates that the insole has a wide range and high sensitivity dual-modal pressure monitoring capability, especially sensitive to subtle changes in plantar pressure.

[0035] Buffer protection characteristics: The sample was placed on a KD3005A force sensor, and impact tests were conducted using a ZCJ1302-A drop hammer impact tester, with a 0.53kg impact hammer head released from different heights. The signal was amplified by a MYE58531 charge amplifier and recorded by a Tektronix MDO4104C oscilloscope. Figure 9 and Figure 10 As shown, under gradient impact energies of 1 J, 1.6 J, and 2.1 J, compared to the unloaded control group without porous polyborosiloxane elastomer, the peak impact forces of the samples loaded with porous polyborosiloxane elastomer significantly decreased from 3.1 kN, 4.1 kN, and 4.8 kN to 1.4 kN, 1.7 kN, and 2.8 kN, respectively, and the impact duration was significantly prolonged. This is because the BO dynamic covalent bonds in the polyborosiloxane elastomer form a high-density instantaneous cross-linked network under impact, generating a shear hardening effect, thereby efficiently dissipating impact energy. This result demonstrates that the underlying buffer layer can provide excellent immediate protection for diabetic foot ulcers.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated insole for diabetic foot pressure monitoring and cushioning protection, characterized in that, The insole has a three-layer structure, from top to bottom as follows: Surface fabric layer; Intermediate pressure sensing array layer; The bottom layer is a cushioning and shock-absorbing layer; The intermediate pressure sensing array layer is a layered structure comprising a lower encapsulation layer, a lower electrode layer, a lower pressure-sensitive layer, an upper pressure-sensitive layer, an upper electrode layer, and an upper encapsulation layer, wherein the upper pressure-sensitive layer and the lower pressure-sensitive layer are disposed opposite to each other; the bottom buffer and shock-absorbing layer is a porous polyborosiloxane elastomer.

2. The integrated pressure monitoring and cushioning insole for diabetic foot according to claim 1, characterized in that, The outer fabric layer is selected from one of polyester fiber fabric, polyurethane fiber fabric or pure cotton fabric.

3. The integrated pressure monitoring and cushioning insole for diabetic foot according to claim 1, characterized in that, The encapsulation material of the lower encapsulation layer and / or the upper encapsulation layer is selected from at least one of polyester, polyimide, polydimethylsiloxane, or polyurethane; the pressure-sensitive material of the lower pressure-sensitive layer and / or the upper pressure-sensitive layer is selected from at least one of graphene paste, graphene oxide paste, carbon nanotube paste, graphite paste, or MXene paste; the electrode material of the lower electrode layer and / or the upper electrode layer is selected from at least one of conductive carbon paste, conductive silver paste, or conductive copper paste.

4. The integrated pressure monitoring and cushioning insole for diabetic foot according to claim 1, characterized in that, The intermediate pressure sensing array layer integrates 10-60 pressure sensing units.

5. The integrated pressure monitoring and cushioning insole for diabetic foot according to claim 1, characterized in that, The porous polyborosiloxane elastomer has a porous structure with a pore size of 0.5-3 mm and a pore spacing of 1-5 mm.

6. A method for preparing an integrated pressure monitoring and cushioning insole for diabetic foot as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Cut the surface fabric to the predetermined insole size to obtain the surface fabric layer; S2. Select a lower encapsulation layer and an upper encapsulation layer that conform to the predetermined insole size. Use screen printing to laminate the electrode material onto the surfaces of the lower encapsulation layer and the upper encapsulation layer respectively, forming a lower electrode layer on the lower encapsulation layer and an upper electrode layer on the upper encapsulation layer. S3. Pressure-sensitive materials are laminated onto the surfaces of the lower electrode layer and the upper electrode layer respectively by screen printing, forming a lower pressure-sensitive layer on the lower electrode layer and an upper pressure-sensitive layer on the upper electrode layer. S4. Use screen printing adhesive to bond the area on the lower electrode layer (excluding the lower pressure-sensitive layer) and the area on the upper electrode layer (excluding the upper pressure-sensitive layer) together to obtain the intermediate pressure sensing array layer. S5. Hydroxysilicone oil and boric acid are mixed in a mass ratio of 20-30:1, and after heat treatment, a catalyst is added and the mixture is reacted to obtain polyborosiloxane. S6. Mix polyborosiloxane with methyl vinyl silicone rubber to obtain a polyborosiloxane elastomer precursor; S7. Fill the polyborosiloxane elastomer precursor into a porous mold that conforms to the predetermined insole size, and then heat-cur it to obtain a porous polyborosiloxane elastomer. S8. The surface fabric, the intermediate pressure sensor array layer and the porous polyborosiloxane elastomer are bonded together to obtain the integrated pressure monitoring and cushioning protection insole for diabetic foot.

7. The preparation method according to claim 6, characterized in that, In S2, the lower electrode layer and the upper electrode layer are distributed in a relative array with the same shape and size; in S3, each pair of relative lower pressure sensitive layers and upper pressure sensitive layers constitutes a pressure sensing unit.

8. The preparation method according to claim 6, characterized in that, In S5, the catalyst is octanoic acid, the amount of catalyst added is 1.3%-3.3% of the mass of boric acid, the heat treatment temperature is 160-200℃, the heat treatment time is 30-40 min, the reaction temperature is 160-200℃, and the reaction time is 15-30 min.

9. The preparation method according to claim 6, characterized in that, In S6, the mass ratio of the polyborosiloxane to the methyl vinyl silicone rubber is 0.4-2.5:

1.

10. The preparation method according to claim 6, characterized in that, In S7, the conditions for heat curing are: pressure 15-20 MPa, temperature 80-100℃, and time 10-20 min.

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