Area identification piezoresistive sensor, preparation method and application thereof

Abstract

The present application relates to the technical field of sensor, in particular to a region identification piezoresistive sensor and its preparation method and application. The present application provides a region identification piezoresistive sensor, which comprises a first electrode layer, a hydrogel layer and a second electrode layer which are stacked in sequence, the upper and lower surfaces of the hydrogel layer are both distributed with a plurality of strip-shaped microstructures, the strip-shaped microstructures in the same surface are parallel to each other, and the extension directions of the strip-shaped microstructures on the upper and lower surfaces form an included angle of 30-90°; the first electrode layer and the second electrode layer both comprise two independent electrodes, the two electrodes in the same layer are diagonally distributed along the surface of the hydrogel layer, and the electrodes of the first electrode layer and the second electrode layer do not overlap in the vertical projection direction. The region identification piezoresistive sensor of the present application not only has a simple structure, but also has position identification ability and excellent sensitivity at the same time, which breaks through the shortcomings of the existing non-array sensor.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a region identification piezoresistive sensor, its preparation method, and its application. Background Technology

[0002] Flexible piezoresistive sensors can be assembled into intelligent artificial electronic skin, which can be widely used in tactile signal detection and spatial pressure distribution recognition, showing important application prospects in human-computer interaction, robot perception and wearable medical devices.

[0003] Currently, flexible sensors for electronic skin applications mainly adopt array structures composed of a large number of sensing units. However, this type of sensor has obvious technical drawbacks: on the one hand, the complex array structure and small unit size lead to cumbersome manufacturing processes and high manufacturing costs; on the other hand, in order to transmit large-scale sensing data, a large number of wires need to be arranged inside the sensor, which not only easily introduces electromagnetic noise interference signals, but also significantly reduces the flexibility and tensile strength of the device, seriously restricting its practical application. Compared with array sensors, non-array sensors have a simpler structure, which is conducive to realizing large-area pressure detection and recognition. However, non-array sensors can only collect overall pressure signals and generally lack spatial resolution capabilities, making it difficult to accurately locate the tactile contact position and distinguish multiple simultaneous contact stimuli. They cannot meet the application requirements of intelligent sensing systems for multi-touch recognition and pressure spatial distribution information acquisition (Chen Haofeng. Research on Large-Area Non-Array Flexible Tactile Sensors Based on Electrical Impedance Imaging Technology [D]. University of Science and Technology of China, 2024.).

[0004] Therefore, there is an urgent need to develop a new type of piezoresistive sensor that is simple in structure and has both position recognition capability and excellent sensitivity, so as to overcome the limitations of existing flexible sensing technology in terms of integration, cost and functionality. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing non-array sensors that cannot combine position recognition capability and excellent sensitivity on the basis of simple structure, and to provide a region recognition piezoresistive sensor.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned region identification piezoresistive sensor.

[0007] Another object of the present invention is to provide the application of the above-mentioned area identification piezoresistive sensor in the fields of wearable monitoring, implantable medical devices or multi-parameter sensing.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: This invention protects a region identification piezoresistive sensor, comprising a first electrode layer, a hydrogel layer, and a second electrode layer stacked sequentially. Multiple strip-shaped microstructures are distributed on both the upper and lower surfaces of the hydrogel layer. The strip-shaped microstructures on the same surface are parallel to each other, and the extension directions of the strip-shaped microstructures on the upper and lower surfaces form an angle of 30 to 90°. The first electrode layer and the second electrode layer each contain two independent electrodes. The two electrodes in the same layer are diagonally staggered along the surface of the hydrogel layer. The electrodes of the first electrode layer and the second electrode layer do not overlap in the vertical projection direction.

[0009] To address the issue that existing non-array sensors cannot simultaneously achieve both position recognition capability and excellent sensitivity, this invention overcomes these problems by controlling the angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer and the diagonally staggered electrode layout. Specifically: At the sensitivity control level, the strip-shaped microstructures on the hydrogel surface can dynamically change the effective contact area with the electrodes during pressure, causing a significant change in the interfacial contact resistance, which forms the basis of the pressure-sensitive response. At the same time, the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel are at an angle of 30° to 90°, causing the sensor to undergo differentiated deformations of opposing compression and oblique stretching in different areas under vertical pressure, inducing spatial heterogeneity reconstruction of the internal conductive network. Furthermore, the microstructures can generate a stress concentration effect, further amplifying the intrinsic deformation difference between the sensor's center and edge regions (the center region can extend freely in all directions, while the edge region is constrained by the boundary). Combined with the directional guidance effect of the specific angle on the deformation transmission direction, the two work together to improve the pressure-sensitive response sensitivity of the sensor. At the location recognition mechanism level, by combining independent electrodes arranged diagonally in the upper and lower layers, pressure will cause the corresponding electrodes to generate differentiated current response signals when applied to different areas. By coordinating and matching the current output values ​​of the two sets of electrodes, the location of the pressure can be accurately determined.

[0010] Furthermore, the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 30 to 60°.

[0011] Furthermore, the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form a 45° angle with each other.

[0012] In this invention, the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer do not need to have defined absolute extension directions. This is because the piezoresistive response mechanism of the sensor in this invention relies on the cross-coordination between the microstructures on the upper and lower surfaces. Its performance is determined by the relative angle between the extension directions of the two sets of microstructures, and is independent of the absolute orientation of either set of microstructures. In other words, regardless of whether the upper surface microstructures are arranged longitudinally, laterally, or obliquely along the sample, as long as the angle between the extension direction of the lower surface microstructure and the upper surface microstructure is adjusted to be within the range of 30° to 90°, the desired technical effect can be achieved; the roles of the upper and lower surfaces can be interchanged with the same effect.

[0013] Furthermore, the hydrogel layer is square or rectangular in shape. The regular contour facilitates electrode alignment, placement, and assembly.

[0014] Furthermore, the hydrogel layer is square in shape.

[0015] Preferably, the length of the hydrogel layer is 4-8 cm.

[0016] Preferably, the width of the hydrogel layer is 4 to 8 cm.

[0017] Preferably, the height of the hydrogel layer is 0.4~2 cm.

[0018] As an optional implementation, nine sensing points are evenly distributed on the surface of the hydrogel layer in a 3×3 arrangement.

[0019] This invention protects a method for preparing a piezoresistive sensor for identifying the above-mentioned region, comprising the following steps: S1. Using parallel needles as microstructure templates, the hydrogel precursor solution is poured into a closed reaction tank containing the microstructure template. After polymerization, it is demolded and cut to obtain a hydrogel film with parallel strip microstructures on one side and a smooth surface on the other side. S2. Take two hydrogel films obtained in step S1, and attach them together with their smooth surfaces facing each other to form a hydrogel layer with parallel strip-shaped microstructures on both the upper and lower surfaces. Make the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 30 to 90°. Then attach two independent electrodes to each of the two microstructure surfaces of the hydrogel layer, so that the two electrodes on the same surface are diagonally staggered and the electrodes on the two surfaces do not overlap in the vertical projection direction, thus forming the first electrode layer and the second electrode layer, respectively, to obtain the region identification piezoresistive sensor.

[0020] Furthermore, the diameter of the needle is 0.5~1 mm.

[0021] Furthermore, the hydrogel precursor solution is prepared by the following method: S1. Disperse the natural polysaccharide and conductive material thoroughly in the antifreeze to obtain a dispersion; S2. Mix the dispersion obtained in step S1 with the water-soluble polymer solution to obtain the hydrogel precursor solution.

[0022] Furthermore, the natural polysaccharide includes xanthan gum and / or sodium alginate.

[0023] Furthermore, the natural polysaccharide is xanthan gum.

[0024] Furthermore, the conductive material includes one or more of carbon nanotubes, graphene, and Mxene.

[0025] Furthermore, the conductive material is carbon nanotubes.

[0026] Furthermore, the mass ratio of the natural polysaccharide to the conductive material is 1:(0.6~0.9).

[0027] Furthermore, the antifreeze includes one or more of glycerin, ethylene glycol, and propylene glycol.

[0028] Furthermore, the antifreeze is glycerin.

[0029] Furthermore, the mass-to-volume ratio of the natural polysaccharide to the antifreeze is 1 g: (30~80) mL.

[0030] Furthermore, the water-soluble polymer includes one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polyacrylamide (PAM).

[0031] Furthermore, the water-soluble polymer is PVA.

[0032] As an optional implementation, the method for preparing the water-soluble polymer solution includes the following steps: Mix PVA with water until fully dissolved to obtain a PVA solution.

[0033] Furthermore, the mass-to-volume ratio of PVA to water is 1 g: (3~6) mL.

[0034] Furthermore, the mixing temperature is 95~105 ℃.

[0035] Furthermore, the mixing is agitation.

[0036] Preferably, the stirring and mixing conditions are 400~800 r / min for 0.5~3 h.

[0037] Furthermore, the polymerization time is 10~24 h.

[0038] Furthermore, the polymerization temperature is -50 to -35 °C.

[0039] Furthermore, the electrode material includes one or both of carbon cloth and copper electrodes.

[0040] This invention protects the application of the area identification piezoresistive sensor in wearable monitoring, implantable medical devices, or multi-parameter sensing.

[0041] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a region-identifying piezoresistive sensor, comprising a first electrode layer, a hydrogel layer, and a second electrode layer stacked sequentially. Both sides of the hydrogel layer have parallel strip-shaped microstructures, and the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 30-90°. Each of the first and second electrode layers contains two independent electrodes, which are diagonally staggered along the sensing area within the same layer. The electrodes of the first and second electrode layers do not overlap in the vertical projection direction. This region-identifying piezoresistive sensor not only has a simple structure but also possesses both position recognition capability and excellent sensitivity, overcoming the shortcomings of existing non-array sensors. Attached Figure Description

[0042] Figure 1 Schematic diagram of the angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer in Examples 1-4.

[0043] Figure 2 This is a schematic diagram of the region identification piezoresistive sensor in Example 1.

[0044] Figure 3 This is a point distribution diagram on the surface of the hydrogel layer in the region identification piezoresistive sensor in Example 1.

[0045] Figure 4 This is a schematic diagram showing the electrode placement in the first and second electrode layers of the region identification piezoresistive sensor in Comparative Example 4.

[0046] Figure 5 The graphs show the rate of change of current versus pressure for the region identification piezoresistive sensor in Example 1 and Comparative Examples 1-2 under a single electrode.

[0047] Figure 6 Figure 1 shows the curves of the rate of change of current at different points under a single electrode for the area identification piezoresistive sensor in Examples 1-4; (a) Figure 2 shows the curve of the rate of change of current at different points under a single electrode for the area identification piezoresistive sensor in Example 2; (b) Figure 1 shows the curve of the rate of change of current at different points under a single electrode for the area identification piezoresistive sensor in Example 1; (c) Figure 3 shows the curve of the rate of change of current at different points under a single electrode for the area identification piezoresistive sensor in Example 3; (d) Figure 4 shows the curve of the rate of change of current at different points under a single electrode for the area identification piezoresistive sensor in Example 4.

[0048] Figure 7 To illustrate the difference in current change rate with pressure at different points of the piezoresistive sensor in Example 3 under a single electrode, the graph shows the variation curves of the current change rate at different points.

[0049] Figure 8 This is a graph showing the rate of change of current at different points under dual electrodes in the area identification piezoresistive sensor of Example 1 as a function of pressure.

[0050] Figure 9 To compare the current change rate of the piezoresistive sensor at different points under different electrodes in Example 4 with pressure, the graph shows the change rate of current at different points under different electrodes.

[0051] Figure 10 This is a scatter plot showing the distribution of different points of the region identification piezoresistive sensor under dual electrodes in Example 1.

[0052] Figure 11 This is an accuracy graph of the region identification piezoresistive sensor in Example 1 with the assistance of machine learning algorithms. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0054] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0055] Example 1: A region-identifying piezoresistive sensor and its fabrication 1. A region-identifying piezoresistive sensor The region identification piezoresistive sensor includes a first electrode layer, a hydrogel layer, and a second electrode layer stacked sequentially. Multiple strip-shaped microstructures are distributed on both the upper and lower surfaces of the hydrogel layer. The strip-shaped microstructures on the same surface are parallel to each other, and the extending directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 45° with each other. Figure 1 ); The first electrode layer and the second electrode layer each contain two independent electrodes. The two electrodes in the same layer are diagonally staggered. The electrodes of the first electrode layer (denoted as electrode a) and the second electrode layer (denoted as electrode b) do not overlap in the vertical projection direction. Figure 2 The surface of the hydrogel layer is evenly divided into 9 sensing points arranged in a 3×3 pattern. Figure 3 ).

[0056] 2. Fabrication of a region-identifying piezoresistive sensor S1. Add 4 g of polyvinyl alcohol (PVA) to 20 mL of deionized water and heat and stir magnetically for 1 hour at 100 ℃ and 500 r / min to obtain a PVA solution; uniformly disperse 0.4 g of xanthan gum and 0.3 g of carbon nanotubes in 20 mL of glycerol to obtain a xanthan gum-carbon nanotube glycerol dispersion; mix the PVA solution and the xanthan gum-carbon nanotube glycerol dispersion evenly to obtain a hydrogel precursor solution; S2. Using parallel needles with a diameter of 0.7 mm as microstructure templates, the hydrogel precursor solution obtained in step S1 was poured into a closed reaction tank containing the microstructure templates. After polymerization at -40 ℃ for 12 h, the mixture was demolded and cut to obtain a hydrogel film with parallel strip-like microstructures on one side and a smooth surface on the other. The dimensions of the obtained hydrogel film were 6*6*0.5 cm. 3 ; S3. Take two hydrogel films obtained in step S2, and attach them together with their smooth surfaces facing each other to form a hydrogel layer with parallel strip-shaped microstructures on both the upper and lower surfaces. Make the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form a 45° angle. Then attach two independent carbon cloth electrodes to each of the two microstructure surfaces of the hydrogel layer, so that the two carbon cloth electrodes on the same surface are diagonally staggered and do not overlap in the vertical projection direction, thus forming the first electrode layer and the second electrode layer, respectively, to obtain the area recognition piezoresistive sensor.

[0057] Example 2: A region-identifying piezoresistive sensor and its fabrication The difference from Example 1 is that the included angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer is adjusted from 45° to 30°. Figure 1 ).

[0058] The other steps and conditions are the same as in Example 1.

[0059] Example 3: A region-identifying piezoresistive sensor and its fabrication The difference from Example 1 is that the included angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer is adjusted from 45° to 60°. Figure 1 ).

[0060] The other steps and conditions are the same as in Example 1.

[0061] Example 4: A region-identifying piezoresistive sensor and its fabrication The difference from Example 1 is that the included angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer is adjusted from 45° to 90°. Figure 1 ).

[0062] The other steps and conditions are the same as in Example 1.

[0063] Comparative Example 1: A piezoresistive sensor with a single-sided microstructure and its fabrication The difference from Example 1 is that the configuration of parallel strip-shaped microstructures on both the upper and lower surfaces of the hydrogel layer is adjusted to a hydrogel layer with parallel strip-shaped microstructures on only one side. The specific steps are as follows: S1. Add 4 g of polyvinyl alcohol (PVA) to 20 mL of deionized water and heat and magnetically stir at 100 ℃ and 500 r / min for 1 hour to obtain a PVA solution; uniformly disperse 0.4 g of xanthan gum and 0.3 g of carbon nanotubes in 20 mL of glycerol to obtain a xanthan gum-carbon nanotube glycerol dispersion; mix the PVA solution and the xanthan gum-carbon nanotube glycerol dispersion evenly to obtain a hydrogel precursor solution; S2. Using parallel needles with a diameter of 0.7 mm as microstructure templates, the hydrogel precursor solution obtained in step S1 was poured into a closed reaction tank containing the microstructure templates. After polymerization at -40 ℃ for 12 h, the mixture was demolded and cut to obtain a hydrogel film 1 with parallel strip-like microstructures on one side and a smooth surface on the other. The dimensions of the obtained hydrogel film 1 were 1*1*0.5 cm. 3 Simultaneously, an equal volume of hydrogel precursor solution was poured into a template-free, closed reaction tank. After reacting under the same polymerization conditions, the mixture was demolded and cut to obtain a hydrogel membrane 2 with smooth surfaces on both sides. The dimensions of the obtained hydrogel membrane 2 were 1*1*0.5 cm. 3 ; S3. Take the hydrogel membrane 1 and hydrogel membrane 2 obtained in step S2, and attach their smooth surfaces together to form a hydrogel layer with parallel strip microstructures on only one side. Then attach two independent carbon cloth electrodes to the microstructure surface and the smooth surface of the hydrogel layer, so that the two carbon cloth electrodes on the same surface are diagonally staggered and do not overlap in the vertical projection direction, thus forming the first electrode layer and the second electrode layer, respectively, to obtain the region identification piezoresistive sensor.

[0064] The other steps and conditions are the same as in Example 1.

[0065] Comparative Example 2: A microstructure-free piezoresistive sensor and its fabrication The difference from Example 1 is that the configuration of parallel strip-shaped microstructures on both the upper and lower surfaces of the hydrogel layer is adjusted to a hydrogel layer with smooth upper and lower surfaces. The specific steps are as follows: S1. Add 4 g of polyvinyl alcohol (PVA) to 20 mL of deionized water and heat and magnetically stir at 100 ℃ and 500 r / min for 1 hour to obtain a PVA solution; uniformly disperse 0.4 g of xanthan gum and 0.3 g of carbon nanotubes in 20 mL of glycerol to obtain a xanthan gum-carbon nanotube glycerol dispersion; mix the PVA solution and the xanthan gum-carbon nanotube glycerol dispersion evenly to obtain a hydrogel precursor solution; S2. The hydrogel precursor solution was poured into a template-free, closed reaction tank and polymerized at -40 ℃ for 12 h. The mixture was then demolded and cut to obtain a hydrogel film with smooth surfaces on both sides. The dimensions of the obtained hydrogel film were 1*1*0.5 cm. 3 ; S3. Take two hydrogel films obtained in step S2, attach any smooth surface of the two films to each other, and then attach two independent carbon cloth electrodes to each of the remaining two smooth surfaces of the hydrogel layer, so that the two carbon cloth electrodes on the same surface are diagonally staggered and the carbon cloth electrodes on the two surfaces do not overlap in the vertical projection direction, thus forming the first electrode layer and the second electrode layer respectively, to obtain the region identification piezoresistive sensor.

[0066] The other steps and conditions are the same as in Example 1.

[0067] Comparative Example 3: A region-identifying piezoresistive sensor and its fabrication The difference from Example 1 is that the angle between the extension directions of the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer is adjusted from 45° to 0°.

[0068] The other steps and conditions are the same as in Example 1.

[0069] Comparative Example 4: A region-identifying piezoresistive sensor and its fabrication The difference from Embodiment 1 is that the electrode positions in the first and second electrode layers are changed. Both the first and second electrode layers contain two independent carbon cloth electrodes. The first group of electrodes consists of a carbon cloth electrode located at the upper left corner of the first electrode layer and a carbon cloth electrode located at the lower left corner of the second electrode layer; the second group of electrodes consists of a carbon cloth electrode located at the lower right corner of the first electrode layer and a carbon cloth electrode located at the upper right corner of the second electrode layer. The two carbon cloth electrodes within the same group are aligned with each other in the vertical projection direction, such as... Figure 4 As shown.

[0070] The other steps and conditions are the same as in Example 1.

[0071] Experiment Example 1: Performance Testing of a Region Identification Piezoresistive Sensor with a Single Electrode 1. Experimental Methods The first and second electrode layers of the piezoresistive sensors in Examples 1-4 and Comparative Examples 1-3 were replaced with a single electrode that completely covers the hydrogel layer, instead of the original two independent electrodes, and this was used as the experimental subject.

[0072] (1) Curve of current change rate versus pressure: The hydrogel layer of Example 1 was cut into 1*1*0.5 cm pieces. 3 Make it consistent with the magnitude of Comparative Example 1 and Comparative Example 2. Apply gradient pressure to the center point of the three sets of piezoresistive sensors, and record the current response value of the point at each pressure value using a source meter. Using the initial current (I0) when no pressure is applied as a reference, calculate the rate of change of current (ΔI / I0) at each pressure, and plot the "rate of change of current - pressure" response curve for each point; (2) Current change rate versus pressure curves at different points: Gradient pressure was applied to each point of the sensor in Examples 1-4 and Comparative Example 3, and the current response value at each point under each pressure value was recorded using a source table. The current change rate (ΔI / I0) under each pressure was calculated based on the initial current (I0) when no pressure was applied, and the "current change rate - pressure" response curves at each point were plotted.

[0073] 2 Experimental Results like Figure 5 As shown, the region identification piezoresistive sensor with a double-sided microstructure in Example 1 exhibits a significantly higher rate of current change than Comparative Example 1 (single-sided microstructure) and Comparative Example 2 (no microstructure). Specifically, the rate of current change in Example 1 is 54.5% higher than that in Comparative Example 1 and 9 times higher than that in Comparative Example 2, indicating that the double-sided microstructure can effectively enhance the piezoresistive response performance of the sensor.

[0074] like Figure 6 (a) ~ Figure 6 As shown in (d), the region identification piezoresistive sensors in Examples 1-4 all exhibit obvious current response grouping characteristics under different pressures. In the pressure-current change rate curves, points marked with the same color correspond to similar slope values, indicating that they are located in the same spatial position. Therefore, each example presents more than three groups of color groups with different response slopes, indicating that these sensors can effectively identify at least three different spatial positions; among them, Example 1 has the best region identification capability, and can distinguish four different positions ( Figure 6 (b)). In contrast, the area identification piezoresistive sensor in Comparative Example 3 cannot effectively identify each point because the angle between the microstructures on the upper and lower surfaces of the hydrogel layer is 0°. Figure 7 ).

[0075] Experiment Example 2: Performance Testing of a Region Identification Piezoresistive Sensor with Two Electrodes To overcome the ambiguity of "the same rate of change of current corresponds to multiple positions" in single-electrode testing, a second set of electrodes is introduced. By jointly judging the response values ​​of the two sets, more accurate position identification can be achieved.

[0076] 1. Experimental Methods (1) Current change rate versus pressure curves at different points: Using the piezoresistive sensors in Example 1 and Comparative Example 4 as experimental objects, gradient pressure was applied to each point of the sensors, and the current response values ​​of the upper electrode a and the lower electrode b at each point were recorded using a source meter. Based on the initial current (I0) when no pressure was applied, the current change rate (ΔI / I0) under each pressure was calculated, and the "current change rate - pressure" response curves of electrode a and electrode b at each point were plotted.

[0077] (2) Scatter plot of the distribution of different points of the piezoresistive sensor for area identification: Read the current change rate values ​​of the two electrodes in the data set, take the current of the upper electrode (a) as the X-axis and the current of the lower electrode (b) as the Y-axis, and mark the position number (label_position) of each test point with different colors. If all data points at the same position show a clustered distribution on the two-dimensional plane, and the 9 positions are separated into independent clusters, it indicates that the current response combination of the double-layer electrodes can effectively distinguish different spatial positions; (3) Accuracy of the region identification piezoresistive sensor with the assistance of machine learning algorithm: To evaluate the recognition performance of the RandomForestClassifier model for 9 test locations, the dataset was divided into training and validation sets in a 7:3 ratio. The model was trained using the current change rate (a and b) of the double-layer electrode as input features and the location number as the output label. Subsequently, the trained model was used to predict the validation set samples (x_val), and the prediction results (y_pred) were compared with the true labels (y_val) to construct a confusion matrix. The diagonal elements in the matrix represent the proportion of each location that is correctly identified (i.e., accuracy), and the off-diagonal elements reflect the misjudgment situation. The closer the diagonal value is to 100%, the better the recognition effect of that location.

[0078] 2. Experimental Results like Figure 8 As shown, the area identification piezoresistive sensor of Example 1 was tested using a dual-electrode scheme. Both groups of electrodes, a and b, exhibited distinct current response grouping characteristics. When observed individually, electrode a ( Figure 8 (a) and electrode b Figure 8 The response curves of (b) can only distinguish two positions, but the distinguishing dimensions of the two sets of electrodes do not overlap. After cross-comparing the response results of electrodes a and b, at least three positions can be identified in the 45° microstructure. Under the condition of relying solely on threshold classification, although the number of identification categories of the dual-electrode scheme does not increase significantly, the two-dimensional feature space it provides lays the foundation for subsequent algorithmic processing.

[0079] In contrast, comparative example 4 ( Figure 9 Because electrodes a and b overlap in the vertical direction, the response signals of the two electrodes are coupled, and the same current change rate corresponds to multiple spatial positions, making it difficult to achieve effective position identification based on this two-electrode scheme.

[0080] The above results demonstrate that, regardless of whether it is a single-electrode or a vertically overlapping dual-electrode scheme, it is difficult to achieve accurate identification of all nine positions by simply relying on the slope range of the response curve. To overcome this limitation, this application introduces a machine learning algorithm to train a model to learn the complex mapping relationship between the current change rate signal of the dual-electrode system and the spatial position, thereby achieving accurate prediction of the position of unknown samples.

[0081] Figure 10 The distribution of nine test locations in a two-dimensional feature space (with the rate of change of electrode current (a) on the horizontal axis and the rate of change of electrode current (b) on the vertical axis) is shown, with different colors representing different locations. As can be seen from the figure, the data points at each location cluster into independent clusters, with only a small overlap between locations 6 and 9. This distribution characteristic indicates that the response signal of the double-layer electrode has good discriminative power across different locations, providing a data foundation for accurate identification by subsequent machine learning models. From a qualitative analysis perspective, Figure 9 It intuitively reflects the separability of the original data in the feature space.

[0082] Figure 11 This is the confusion matrix obtained by identifying nine positions based on RandomForestClassifier. The results show that the overall recognition accuracy for all positions reaches 99.3%, except for position 9, which has a 5.6% probability of being misclassified as position 6 (corresponding to...). Figure 10 Except for the overlapping area of ​​the two clusters, all other locations achieved 100% correct identification. This result quantitatively verifies that the region identification piezoresistive sensor provided in this application possesses excellent position identification accuracy and reliability.

[0083] In summary, by introducing a dual-electrode acquisition scheme and combining it with machine learning, the recognition accuracy was successfully improved from a maximum of four coarse categories under the threshold division to accurate differentiation of nine independent locations, fully demonstrating the synergistic advantages of this scheme in sensor design and data processing strategies.

[0084] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A region identification piezoresistive sensor, characterized in that, It includes a first electrode layer, a hydrogel layer, and a second electrode layer stacked sequentially. Multiple strip-shaped microstructures are distributed on both the upper and lower surfaces of the hydrogel layer. The strip-shaped microstructures on the same surface are parallel to each other, and the extension directions of the strip-shaped microstructures on the upper and lower surfaces form an angle of 30 to 90°. The first electrode layer and the second electrode layer each contain two independent electrodes. The two electrodes in the same layer are diagonally staggered along the surface of the hydrogel layer. The electrodes of the first electrode layer and the second electrode layer do not overlap in the vertical projection direction.

2. The region identification piezoresistive sensor according to claim 1, characterized in that, The strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 30 to 60°.

3. The region identification piezoresistive sensor according to claim 1, characterized in that, The strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form a 45° angle between them.

4. The region identification piezoresistive sensor according to claim 1, characterized in that, The hydrogel layer is square or rectangular in shape.

5. The region identification piezoresistive sensor according to claim 4, characterized in that, The size of the hydrogel layer includes at least one of the following (1) to (3): (1) Length 4~8 cm; (2) Width 4~8 cm; (3) Height 0.4~2 cm.

6. A method for preparing the region identification piezoresistive sensor according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Using parallel needles as microstructure templates, the hydrogel precursor solution is poured into a closed reaction tank containing the microstructure template. After polymerization, it is demolded and cut to obtain a hydrogel film with parallel strip microstructures on one side and a smooth surface on the other side. S2. Take two hydrogel films obtained in step S1, and attach them together with their smooth surfaces facing each other to form a hydrogel layer with parallel strip-shaped microstructures on both the upper and lower surfaces. Make the strip-shaped microstructures on the upper and lower surfaces of the hydrogel layer form an angle of 30 to 90°. Then attach two independent electrodes to each of the two microstructure surfaces of the hydrogel layer, so that the two electrodes on the same surface are diagonally staggered and the electrodes on the two surfaces do not overlap in the vertical projection direction, thus forming the first electrode layer and the second electrode layer, respectively, to obtain the region identification piezoresistive sensor.

7. The preparation method according to claim 6, characterized in that, The hydrogel precursor solution was prepared by the following method: S1. Disperse the natural polysaccharide and conductive material thoroughly in the antifreeze to obtain a dispersion; S2. Mix the dispersion obtained in step S1 with the water-soluble polymer solution to obtain the hydrogel precursor solution.

8. The preparation method according to claim 6, characterized in that, The polymerization time is 10~24 h.

9. The preparation method according to claim 6, characterized in that, The polymerization temperature is -50 to -35 ℃.

10. The application of the region identification piezoresistive sensor according to any one of claims 1 to 5 in the fields of wearable monitoring, implantable medical devices, or multi-parameter sensing.

Images