Preparation method of flexible back array sensor

Abstract

The invention belongs to the technical field of flexible sensors, and discloses a preparation method of a flexible back array sensor, which comprises the following steps: uniformly mixing and stirring graphene conductive paste and 1, 2-propylene glycol according to a volume ratio of 1: 4 to obtain a sensing material; highlight photographic paper is used as a substrate, and a sensing material is printed on the substrate of the highlight photographic paper in a dispensing printing mode by using dispensing equipment according to the designed graphene sensing array arrangement mode, so that a graphene sensing array is formed; transferring the graphene sensing array onto a PDMS (Polydimethylsiloxane) precursor, so as to obtain a PDMS-graphene sensing array; and dispensing and printing a silver electrode on the PDMS-graphene sensing array to form a sensing unit, then covering the sensing unit with a protective layer PDMS, and finally obtaining the flexible back array sensor. Therefore, the sensor array prepared by the invention has good tensile property and long-term stability, and can be used for monitoring human body behaviors.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor technology, and in particular to a method for fabricating a flexible back array sensor. Background Technology

[0002] Flexible wearable sensors have significant applications in health monitoring, sports science, and human-computer interaction. Among these, back biomechanical monitoring is particularly crucial for spinal health assessment, posture correction, and rehabilitation training. Traditional flexible sensors typically use thin metal films, carbon nanotubes, or conductive polymers as sensing materials, fabricated through photolithography, screen printing, or inkjet printing processes.

[0003] Traditional linear silver electrodes have point-like or linear connections with sensitive materials (such as graphene), which are prone to interfacial delamination or crack propagation under repeated stretching, leading to a significant increase in contact resistance. Therefore, a square electrode printing method is used to stabilize the electrode contact area and control the difference in channel consistency between devices.

[0004] Currently, most devices are arranged in a regular grid (such as a 4×4 square array), without taking into account the distribution characteristics of back muscles. The human back muscles are distributed in an inverted triangle shape, resulting in many signal artifacts, low signal acquisition efficiency, and low signal-to-noise ratio. Spinal health monitoring requires simultaneous comparison of the activity of the left and right muscle groups. Summary of the Invention

[0005] To overcome the technical defects of the existing technology, the present invention provides a method for preparing a flexible back array sensor, which has good tensile properties and long-term stability and can be used for human behavior monitoring.

[0006] The technical solution adopted in this invention is: a method for fabricating a flexible back array sensor, comprising the following steps: Step 1: Prepare the raw materials by mixing graphene conductive paste and 1,2-propanediol in a volume ratio of 1:4 and stirring until homogeneous to obtain the sensing material. Step 2: Print the graphene sensor array. Using glossy photo paper as a substrate, use a dispensing device to print the sensing material onto the glossy photo paper substrate in the form of dispensing according to the designed graphene sensor array arrangement, thus forming a graphene sensor array. Step 3: Transfer the printed graphene sensor array. First, prepare a PDMS precursor, and then transfer the graphene sensor array onto the PDMS precursor to obtain a PDMS-graphene sensor array.

[0007] Step 4: Apply adhesive to print silver electrodes on the PDMS-graphene sensing array. The silver electrodes are located at both ends of each sensing unit in the graphene sensing array to form a sensing unit. Then, cover it with a protective PDMS layer to obtain a flexible back array sensor.

[0008] Preferably, the method of printing the sensing material onto the substrate of glossy photographic paper by dispensing is to use a 0.09mm dispensing needle, under a dispensing pressure adjustment of 5kPa, and at a printing speed of 4mm / s, to print the graphene sensing array onto the substrate of glossy photographic paper according to a set printing process.

[0009] Preferably, the method for preparing the PDMS precursor is as follows: the matrix and curing agent are mixed at a mass ratio of 10:1 to obtain the PDMS precursor; a glossy photographic paper substrate with a graphene sensor array printed on it is adhered to a glass plate with inorganic adhesive; the PDMS precursor is then placed on the glossy photographic paper with the graphene sensor array printed on it and cured at 70°C for about 2 hours; the cured PDMS precursor is then peeled off, thus transferring the graphene sensor array into the PDMS precursor, thereby obtaining a graphene sensor array transferred onto PDMS.

[0010] Preferably, multiple pins are printed on the PDMS-graphene sensing array, and then the silver electrodes at both ends of each sensitive unit in the graphene sensing array are connected to the multiple pins via printed conductive lines.

[0011] Preferably, the spacing between adjacent PINs is 2.54 mm.

[0012] Preferably, the flexible back array sensor has eight sensing units and an 8-channel design. In accordance with ergonomics, the human back muscle group is in the shape of an inverted triangle, so the eight sensing units are arranged in a 3-2-3 configuration.

[0013] Preferably, the plurality of said pins are connected to the nut via thickened silver wire, and said thickened silver wire is formed by twisting three strands of high-purity silver wire into one.

[0014] Preferably, the initial resistance of each of the sensing units is 300Ω±30Ω, and the resistance difference between different sensing units is controlled within 10%.

[0015] Preferably, the silver electrode is a square silver electrode.

[0016] The beneficial effects of this invention are as follows: This invention mixes graphene conductive paste and 1,2-propanediol in a volume ratio of 1:4 to obtain a sensing material. Using glossy photographic paper as a substrate, the sensing material is printed onto the substrate using a dispensing device according to a pre-designed graphene sensing array arrangement, forming a graphene sensing array. The graphene sensing array is then transferred onto a PDMS precursor to obtain a PDMS-graphene sensing array. Silver electrodes are then dispensed onto the PDMS-graphene sensing array, with the silver electrodes located at both ends of each sensing unit in the graphene sensing array, thus forming sensing units. A protective PDMS layer is then applied, resulting in a flexible back array sensor. This allows the sensor array prepared by this invention to possess excellent tensile properties and long-term stability, making it suitable for human behavior monitoring, such as posture monitoring, scoliosis detection, and movement behavior correction, with broad application prospects. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the transfer process during the fabrication of a flexible back array sensor according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the device electrode process of a flexible back array sensor provided in an embodiment of the present invention; Figure 4 This is a flexible back array sensor array diagram provided in an embodiment of the present invention; Figure 5 This is an initial resistance measurement diagram of a flexible back array sensor provided in an embodiment of the present invention; Figure 6 This is a welding diagram of the test electrodes for a flexible back array sensor provided in an embodiment of the present invention; Figure 7 This is a physical diagram of a single-channel sensing unit provided in an embodiment of the present invention; Figure 8 This is a tensile test diagram of a flexible back array sensor provided in an embodiment of the present invention; Figure 9 This is a time-resistance curve of a long-term tensile strain test for a flexible back array sensor provided in an embodiment of the present invention; Figure 10This is a device topography diagram of a flexible back array sensor provided in an embodiment of the present invention; Figure 11 This is a waveform of an arm being raised in an application of a flexible back array sensor provided in an embodiment of the present invention; Figure 12 This is a waveform diagram of a flexible back array sensor application in an orientation state with a leftward bend, provided by an embodiment of the present invention. Figure 13 This is a waveform diagram of a right-hand bend in a seated posture, provided by an embodiment of the present invention, for the application of a flexible back array sensor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0020] like Figure 1 As shown, this embodiment provides a method for fabricating a flexible back array sensor, including the following steps: Step 1: Prepare the raw materials by mixing graphene conductive paste with 1,2-propanediol at a volume ratio of 1:4 to obtain the sensing material. The low viscosity of propylene glycol can reduce the van der Waals forces between graphene sheets, promoting the exfoliation and dispersion of the two-dimensional material in the solvent. The 1:4 ratio may enable the graphene to form a three-dimensional permeable network, which maintains the conductive pathway while avoiding excessive aggregation, thus optimizing the conductive network.

[0021] The hydroxyl groups of propylene glycol can form hydrogen bonds with the oxygen-containing groups of graphene, improving the interfacial bonding strength. This ratio may balance wettability and conductivity, enhancing the material's adhesion to flexible substrates and improving interfacial performance.

[0022] The hygroscopic properties of propylene glycol can form a protective solvent film, reducing the interference of environmental humidity on the electrical properties of graphene. The viscosity of the mixed system is approximately in the range of 200-500 mPa·s, which is beneficial for the spin-coating of sensor devices.

[0023] The monolayer graphene exhibits high carrier mobility, and the three-dimensional conductive network formed in the slurry significantly reduces material resistance while providing ultra-high conductivity. Only 0.5-2% graphene content is required to construct a continuous conductive pathway (compared to over 20% for traditional carbon black), reducing the impact of fillers on the mechanical properties of the matrix. It is chemically inert, resistant to oxidation (temperature resistance >600℃), and suitable for acid / alkali sensing systems. The film formed after slurry coating can withstand >10% tensile deformation.

[0024] Step 2: Print the graphene sensor array. Using glossy photo paper as a substrate, use a dispensing device to print the sensing material onto the glossy photo paper substrate in the form of dispensing according to the designed graphene sensor array arrangement, thus forming a graphene sensor array. High-gloss photographic paper is used as the base material because its high-gloss coating can control the surface roughness to the 0.1-0.5μm level, which is beneficial for the uniform coating of functional materials (such as conductive pastes), reduces the generation of microcracks, and has low ink absorption. The resin coating keeps the ink / paste on the surface rather than penetrating, improving pattern resolution. This also facilitates the peeling off of the sensing unit.

[0025] Step 3: Transfer the printed graphene sensor array. First, prepare a PDMS precursor, and then transfer the graphene sensor array onto the PDMS precursor to obtain a PDMS-graphene sensor array.

[0026] Step 4: Apply adhesive to print silver electrodes on the PDMS-graphene sensing array. The silver electrodes are located at both ends of each sensing unit in the graphene sensing array to form a sensing unit. Then, cover it with a protective PDMS layer to obtain a flexible back array sensor.

[0027] In this invention, the graphene sensor arrays are fabricated in the same batch, thus controlling the resistance difference between different sensors to within 10%, resulting in good channel consistency and consequently, better measurement accuracy. This invention utilizes dispensing printing technology to fabricate the graphene sensitive array and optimizes electrode design and connection methods, achieving a flexible sensor array with high precision, high consistency, and high stability. The sensor array of this invention exhibits good tensile properties and long-term stability, making it suitable for human behavior monitoring, such as posture monitoring, scoliosis detection, and movement behavior correction, with broad application prospects.

[0028] The method of printing the sensing material onto the substrate of glossy photographic paper by dispensing is as follows: using a 0.09mm dispensing needle, under a dispensing pressure adjustment of 5kPa, and a printing speed of 4mm / s, the graphene sensing array is printed onto the substrate of glossy photographic paper according to the set printing process.

[0029] The PDMS precursor is prepared by mixing a matrix and a curing agent at a mass ratio of 10:1. A glossy photographic paper substrate with a graphene sensor array printed on it is then adhered to a glass plate using inorganic adhesive. The PDMS precursor is then placed on top of the glossy photographic paper with the graphene sensor array printed on it and cured at 70°C for approximately 2 hours. The cured PDMS precursor is then peeled off, transferring the graphene sensor array to the PDMS precursor, thus obtaining a graphene sensor array transferred onto the PDMS. Multiple pins are printed on the PDMS-graphene sensor array. The silver electrodes at both ends of each sensitive unit in the graphene sensor array are then connected to these pins via printed conductive lines. The spacing between adjacent pins is 2.54 mm. This method solves the wiring problem while ensuring sensor accuracy.

[0030] The flexible back array sensor has eight sensing units with an 8-channel design. In accordance with ergonomics, the human back muscle group is inverted triangle, so the eight sensing units are arranged in a 3-2-3 configuration to monitor behavior and achieve the goal of symmetrical comparison of the units in the horizontal and vertical directions during testing.

[0031] Multiple pins are connected to the socket via thickened silver wires, which are formed by twisting three strands of high-purity silver wire into one. This increases the strength of the flexible connection before soldering it onto the socket, compensating for the insufficient strength of a single silver wire connection. After connecting to the socket, testing equipment can be connected. The initial resistance of each sensing unit is 300Ω±30Ω, and the resistance difference between different sensing units is controlled within 10%, thus achieving good channel consistency. The optimization of the design process compensates for insufficient dispensing and printing accuracy.

[0032] The silver electrode is a square silver electrode. The interface between the silver electrode and graphene is an important factor affecting the accuracy of the resistive sensor. In order to make the contact interface between the silver electrode and graphene more stable, the square electrode is printed by dispensing adhesive first. This method increases the contact area between the silver electrode and graphene and reduces the error of the previous method of only making single-line electrodes.

[0033] Figure 4 This is the sensor array invented in this paper. Figure 5 These are the resistance values ​​of each unit tested in this invention. As can be seen from the figure, the initial resistance of the sensor unit is 300Ω±30Ω. The resistance difference between different sensors is controlled within 10%, thus achieving good channel consistency. The insufficient dispensing and printing accuracy is compensated for by optimizing the design process.

[0034] Figure 6The part connecting the socket and the device uses three strands of high-purity silver wire twisted into one wire to increase the strength of the flexible connection wire before welding it onto the socket. This compensates for the insufficient strength of a single silver wire flexible connection. After connecting the socket, the test equipment can be connected through the socket.

[0035] Figure 8 This is the invention of Figure 7 The time-resistance curve of the tensile strain test of a single device is shown. We obtained the tensile performance of a single device by performing tensile strain tests on a single channel device in the array. The graph shows the resistance change from 4% to 28% stretching. The stretching degree here refers to the ratio of the deformation length of the strain sensor to the original length of the strain sensor (the original length and the deformation length are in the same direction). The vertical axis is the change in resistance after stretching relative to the initial resistance. It can be seen from the figure that the strain sensor made by this design pattern has a stable response from 4% to 28%.

[0036] Figure 9 The time-resistance curve of the tensile strain test in the long-term stability test of this invention shows that after 500 cycles of 10% stretching, the device still maintains good stability after cyclic testing.

[0037] Figure 10 The device morphology designed for this invention is based on ergonomics. The human back muscle group forms an inverted triangle. The 8 channels of this invention are arranged in a 3-2-3 configuration for behavioral monitoring, achieving a symmetrical comparison in the test. When scoliosis or asymmetrical force occurs, by comparing symmetrical signal waveforms, it can identify behaviors such as improper posture and scoliosis. In other sports scenarios such as fitness, it can also correct asymmetrical force application when using the equipment. Figure 11 The waveform of a person raising their arm can reveal the characteristics of the waveform when a person is performing an action, thus achieving the purpose of behavioral monitoring. Figure 12 This is the waveform of a leftward bend in a seated position. Figure 13 This is a waveform showing the rightward bend in a seated position. Monitoring the waveform can detect the human body's seated posture.

[0038] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0039] The working principle involves mixing graphene conductive paste and 1,2-propanediol at a volume ratio of 1:4 to obtain a sensing material. Using glossy photographic paper as a substrate, the sensing material is printed onto the substrate using a dispensing device according to the designed graphene sensing array arrangement, forming a graphene sensing array. The graphene sensing array is then transferred onto a PDMS precursor to obtain a PDMS-graphene sensing array. Silver electrodes are then dispensed onto the PDMS-graphene sensing array, with the silver electrodes located at both ends of each sensing unit in the graphene sensing array, thus forming sensing units. Finally, a protective PDMS layer is applied, resulting in a flexible back array sensor. This method enables the sensor array prepared by this invention to possess excellent tensile properties and long-term stability, making it suitable for human behavior monitoring, such as posture monitoring, scoliosis detection, and movement behavior correction, with broad application prospects.

[0040] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for fabricating a flexible back array sensor, characterized in that, Includes the following steps: Step 1: Prepare the raw materials by mixing graphene conductive paste and 1,2-propanediol in a volume ratio of 1:4 and stirring until homogeneous to obtain the sensing material. Step 2: Print the graphene sensor array. Using glossy photo paper as a substrate, use a dispensing device to print the sensing material onto the glossy photo paper substrate in the form of dispensing according to the designed graphene sensor array arrangement, thus forming a graphene sensor array. Step 3: Transfer the printed graphene sensor array. First, prepare a PDMS precursor, then transfer the graphene sensor array onto the PDMS precursor to obtain a PDMS-graphene sensor array. Step 4: Apply adhesive to print silver electrodes on the PDMS-graphene sensing array. The silver electrodes are located at both ends of each sensing unit in the graphene sensing array to form a sensing unit. Then, cover it with a protective PDMS layer to obtain a flexible back array sensor.

2. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: The method of printing the sensing material onto the substrate of glossy photographic paper by dispensing is as follows: using a 0.09mm dispensing needle, under a dispensing pressure adjustment of 5kPa, and a printing speed of 4mm / s, the graphene sensing array is printed onto the substrate of glossy photographic paper according to the set printing process.

3. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: The method for preparing the PDMS precursor is as follows: a matrix and a curing agent are mixed at a mass ratio of 10:1 to obtain the PDMS precursor. A glossy photographic paper substrate with a graphene sensor array printed on it is adhered to a glass plate with inorganic adhesive. The PDMS precursor is then placed on the glossy photographic paper with the graphene sensor array printed on it and cured at 70°C for about 2 hours. The cured PDMS precursor is then peeled off, and the graphene sensor array is transferred to the PDMS precursor, thus obtaining the graphene sensor array transferred onto the PDMS.

4. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: Multiple pins are printed on the PDMS-graphene sensor array, and then the silver electrodes at both ends of each sensitive unit in the graphene sensor array are connected to the multiple pins via printed conductive lines.

5. The method for fabricating a flexible back array sensor according to claim 4, characterized in that: The spacing between adjacent pins is 2.54mm.

6. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: The flexible back array sensor has eight sensing units and an 8-channel design. In accordance with ergonomics, the eight sensing units are arranged in a 3-2-3 configuration.

7. The method for fabricating a flexible back array sensor according to claim 4, characterized in that: Multiple pins are connected to the female connector via thickened silver wire, and the thickened silver wire is formed by twisting three strands of high-purity silver wire into one.

8. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: The initial resistance of each of the aforementioned sensing units is 300Ω±30Ω, and the resistance difference between different sensing units is controlled within 10%.

9. The method for fabricating a flexible back array sensor according to claim 1, characterized in that: The silver electrode is a square silver electrode.

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