Flexible three-dimensional multidirectional force sensing detection array device and preparation method thereof

Abstract

The invention discloses a flexible three-dimensional multidirectional force sensing detection array device and a preparation method thereof. The device comprises a flexible substrate layer, an arrayed three-dimensional trapezoidal sensing unit, an upper-layer electrode structure, a lower-layer electrode structure, a through conductive hole, a liquid metal conductive layer and a packaging layer. The three-dimensional trapezoidal sensing unit is composed of four subunits distributed in the 90-degree direction, a 360-degree space sensing structure is formed, and multi-dimensional response to normal force and tangential force can be achieved. The upper and lower electrode layers are electrically connected through the through conductive holes to form a three-dimensional conductive path; the liquid metal layer is used for enhancing conductive continuity and flexibility; and the encapsulation layer adopts an Ecoflex elastomer to improve the stability. The device realizes three-dimensional directional force signal decoupling through opposite side difference and amplitude ratio inverse solution, has the characteristics of high sensitivity, multi-directional detection and excellent tensile property, and is suitable for the fields of bionic electronic skin, wearable equipment, tactile interaction systems and the like.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic device technology, specifically relating to a flexible three-dimensional multi-directional force sensing array device for multi-dimensional force detection and its fabrication method. This device can achieve independent measurement and decoupled detection of normal and tangential forces, and is suitable for flexible sensing applications such as wearable electronics, bionic electronic skin, intelligent robots, and human-computer interaction. Background Technology

[0002] With the rapid development of flexible electronics technology, traditional rigid sensors are limited in application under complex deformation environments due to their high material stiffness, fixed shape, and poor adaptability. Flexible sensors, with their excellent bendability, stretchability, and attachability, are gradually becoming an important component in fields such as next-generation smart wearable systems, medical monitoring equipment, and bionic electronic skin.

[0003] Among various types of flexible sensors, flexible pressure sensors, as key devices that convert external mechanical pressure or strain signals into electrical signals, have advantages such as high sensitivity, low power consumption, and good flexibility. However, most flexible pressure sensors can only detect forces in a single direction (such as normal force). In scenarios involving forces in multiple directions (including shear force, tensile force, torsional force, etc.), signal coupling and response aliasing often occur, leading to reduced measurement accuracy and making it difficult to achieve independent identification of the three-dimensional components of the force.

[0004] To address the aforementioned issues, exploring flexible sensing units based on three-dimensional structures is crucial. By using three-dimensional trapezoidal or multi-layered stacked structures, force responses in different directions can be distinguished in space, thereby achieving decoupled detection of multi-directional forces. Furthermore, combining algorithms based on multi-channel signal differential and calibration models can further improve the detection sensitivity and direction determination accuracy of normal and tangential forces.

[0005] However, existing flexible 3D sensors still have limitations in terms of structural integration, signal conduction path design, and array fabrication. For example, problems such as unstable interconnection between upper and lower electrodes, insufficient array stretchability, or complex multi-directional signal decoupling algorithms restrict their application in high-density arrays and complex stress environments.

[0006] Therefore, there is an urgent need for a flexible three-dimensional sensing array device with stable structure, clear conductive path, and the ability to achieve multi-directional force decoupling detection, so as to improve the overall performance of flexible electronic systems in spatial force sensing and interactive detection. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing flexible pressure sensors, such as only being able to detect unidirectional force, being prone to signal coupling under multidirectional force, having low array integration, and having unstable conductive paths, and to provide a flexible three-dimensional multidirectional force sensing and detection array device and its preparation method.

[0008] This device constructs a trapezoidal three-dimensional sensing unit, combined with upper and lower double-layer conductive electrodes and a through-hole structure, to achieve a high-density array arrangement on a flexible substrate. At the same time, it uses a three-dimensional force decoupling algorithm based on multi-channel signal differential to achieve independent identification of normal force, tangential force and tilt angle, thereby improving the sensor's detection accuracy and direction resolution capability, and meeting the multi-dimensional force sensing needs in complex force scenarios.

[0009] The technical solution adopted in this invention is as follows:

[0010] In one aspect, a flexible three-dimensional multi-directional force sensing and detection array device is provided, including a flexible substrate layer, a three-dimensional trapezoidal sensor array, an upper and lower double-layer electrode structure, a through conductive hole, a liquid metal conductive layer, and an encapsulation layer.

[0011] The three-dimensional trapezoidal sensor consists of four sub-sensing units distributed along a 90° direction, forming a 360° spatial sensing structure to convert force signals from different directions into resistance change signals. The electrode structure includes an upper common electrode and a lower independent electrode, connected by through-holes to form a three-dimensional conductive path. The upper and lower electrode layers are laser-etched to form independent electrode areas and conductive paths, with holes drilled at overlapping locations. Conductive metal is deposited within the holes to form a vertical conductive structure, achieving reliable connection between the upper and lower signal layers. The electrode traces adopt a stretchable serpentine interconnect to ensure signal stability under 10%–30% stretching conditions. A liquid metal layer is brushed onto the electrode surface to enhance flexibility and conductive continuity. The encapsulation layer uses Ecoflex elastomer for overall protection and fatigue-resistant encapsulation.

[0012] The flexible substrate is formed by a composite of polydimethylsiloxane (PDMS) and antimony tin oxide (ATO); the sensing unit material is a PDMS / ATO / CNT composite conductive elastomer, with a two-layer partitioned design to avoid signal crosstalk.

[0013] Secondly, a method for fabricating a flexible three-dimensional multi-directional force sensing and detection array device is provided, including the following steps:

[0014] S1: Mold Preparation. A flexible mold for forming a three-dimensional trapezoidal structure is prepared using 3D printing technology; the mold includes four sub-cavities distributed along a 90° direction to correspond to the four directional structures of the trapezoidal three-dimensional sensing unit.

[0015] S2: Formulation of composite material. A mixed liquid of polydimethylsiloxane (PDMS), antimony tin oxide (ATO), and carbon nanotubes (CNT) was prepared at a mass ratio of 100:5:5. After thorough stirring and vacuum degassing of each component, a composite sol for forming a conductive sensitive layer was obtained.

[0016] S3: Three-dimensional structure molding. The prepared PDMS / ATO / CNT composite sol is injected into the mold prepared in S1. After curing at 60°C for 1 hour, a flexible sensing body with a three-dimensional trapezoidal structure is obtained. Then, a composite sol without CNT is poured into the bottom of the sensing body to form an isolation layer. After a second curing, the whole body is demolded to obtain a preliminary structure with an upper conductive layer and a lower flexible substrate layer.

[0017] S4: Electrode Formation and Through-hole Fabrication. A two-layer electrode interconnect structure is formed on the upper and lower surfaces of the sensor using laser etching; the etching paths correspond to independent electrode regions in four directions, with a depth of 0.1–0.3 mm; through-holes are formed at the overlapping positions of the upper and lower electrodes to facilitate the subsequent establishment of vertical conductive pathways.

[0018] S5: Construction of Conductive Metal Paths. The laser-etched sample was placed in a chemical copper plating solution for metal deposition. The copper plating solution was prepared by mixing deionized water, copper plating solution A, and copper plating solution B in a volume ratio of 75:5:10. The copper plating process consisted of two stages: the first stage involved reacting at 35°C for 1 hour to accelerate the initial deposition of copper ions in the etched gaps; the second stage involved reacting at 25°C for 3 hours to ensure sufficient deposition and complete coverage of copper ions at the etched areas. The plating thickness was controlled between 5 and 10 μm. The copper plating process was performed sequentially on the back and front sides to ensure complete deposition of copper ions at the laser-etched areas on both sides, thus forming conductive paths and ensuring continuous metal layer connectivity.

[0019] S6: Formation of liquid metal conductive layer. Gallium indium tin alloy liquid metal is uniformly brushed onto the metallized electrode surface, and the surface tension of the liquid metal is controlled at 35-40 mN / m; its surface is then subjected to plasma activation treatment to enhance adhesion.

[0020] S7: Encapsulation. An Ecoflex elastomer encapsulation layer is applied to the outer surface of the sensor. After curing, it forms an integral flexible encapsulation structure to protect the conductive layer and improve tensile and fatigue resistance, thereby obtaining a complete flexible three-dimensional multi-directional force sensing and detection array device.

[0021] Thirdly, the present invention also provides a three-dimensional directional force decoupling method based on a flexible three-dimensional multi-directional force sensing and detection array device. By analyzing and calculating the multi-channel signals of each sensing unit in the array, the normal force, tangential force and tilt angle are independently identified, so as to realize the real-time decoupling detection of multi-directional forces.

[0022] Furthermore, the three-dimensional directional force decoupling method includes the following steps:

[0023] S1: Signal Acquisition. Signals are acquired from the four directional sub-units of each flexible three-dimensional trapezoidal sensing unit in the array to obtain the four-channel output resistance change values. These correspond to the force responses in four directions, respectively.

[0024] S2: Tangential direction angle The determination is based on the differential relationship between the four-channel opposite signals, and the tangential direction angle is calculated. The calculation formula is as follows:

[0025] ;

[0026] in , , , These represent the resistance changes in the four channels. Using the side difference method, the direction and relative angular position of the tangential force can be accurately determined.

[0027] S3: Inverse calculation of tilt angle α. The tilt angle α under force is inversely calculated based on the single-channel relative gain or differential amplitude ratio combined with the calibration curve; by nonlinear fitting the single-channel output amplitude with the calibration curve, the angle between the external force and the normal can be determined, thus reflecting the tilt direction and tangential strength of the external force.

[0028] S4: Calculation of normal load Fz. The normal load Fz is characterized by the average output signal of the four directional channels, and its calculation formula is as follows:

[0029] ;

[0030] in These are the calibration coefficients obtained through standard loading experiments. This calculation effectively suppresses the interference of local noise and asymmetric strain on the results, ensuring the stability and repeatability of normal force measurements.

[0031] S5: Integrated Decoupling Output. By integrating the tangential angle ψ, tilt angle α, and normal force Fz obtained from steps S2 to S4, independent detection and real-time output of the three-dimensional force components of a single flexible three-dimensional trapezoidal sensing unit can be achieved. When multiple units form an array, a matrix-based signal differential and weighting algorithm can be used to further realize the visualization measurement of multi-point spatial force distribution.

[0032] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows:

[0033] The flexible three-dimensional multi-directional force sensing array device prepared by the above steps has the advantages of a three-dimensional trapezoidal structure, high-density array layout, interconnection of upper and lower double-layer electrodes and enhanced conductivity of liquid metal. It can achieve high-precision independent detection of normal force, tangential force and tilt angle, and has good flexibility, tensile strength and long-term stability. It is suitable for fields such as bionic electronic skin, wearable devices and multi-dimensional tactile interaction systems. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0035] Figure 1 This is a schematic diagram of the structure of a single flexible three-dimensional pressure sensor in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram showing the resistance response characteristics of the flexible three-dimensional multi-directional force sensing unit of the present invention under different pressure levels.

[0037] Figure 3 This is a dynamic response curve of a single flexible three-dimensional pressure sensor under low pressure conditions in an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram showing the change of the peak and valley differences of a single flexible three-dimensional pressure sensor under cyclic loading conditions with the number of cycles, according to an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram of the flexible three-dimensional multi-directional force sensor of the present invention under two circumferential angle test conditions, as well as a schematic diagram of multi-channel response and directional distribution.

[0040] Figure 6 This is a schematic diagram of the flexible three-dimensional multi-directional force sensor of the present invention under four normal angle test conditions, and a schematic diagram of the multi-channel response and the change of its variable resistance amplitude.

[0041] Figure 7 This is a schematic diagram of the structure and force of the flexible three-dimensional multi-directional force sensing unit of the present invention under different force directions.

[0042] Figure 8 This is a schematic diagram comparing the response characteristics and sensitivity of the flexible three-dimensional multi-directional force sensing unit of the present invention under different trapezoidal internal angle conditions.

[0043] Figure 9 This is a schematic diagram comparing the response characteristics and sensitivity of the flexible three-dimensional multi-directional force sensing unit of the present invention under different carbon doping concentrations.

[0044] Figure 10 This is a schematic diagram of the flexible three-dimensional pressure sensor array in an embodiment of the present invention.

[0045] Figure 11 This is a flowchart illustrating the fabrication process of the flexible three-dimensional pressure sensor array in an embodiment of the present invention.

[0046] Figure 12 This is a schematic diagram illustrating the device details, flexibility, and stretchability of the flexible three-dimensional pressure sensor array in an embodiment of the present invention.

[0047] Figure 13 This is a schematic diagram of the upper and lower conductive structures and vertical interconnection of the flexible three-dimensional multi-directional force sensing array of the present invention.

[0048] Figure 14 This is a schematic diagram of the structure and spatial response distribution of the flexible three-dimensional multi-directional force sensing array of the present invention under local loading conditions at the fingertip.

[0049] Figure 15 This is a schematic diagram illustrating the experimental testing process and typical signal response of the flexible three-dimensional multi-directional force sensing array of the present invention under local loading conditions at the fingertip.

[0050] Figure 16 This is a schematic diagram of the structure and spatial response distribution of the flexible three-dimensional multi-directional force sensing array of the present invention under planar contact loading conditions.

[0051] Figure 17 This is a schematic diagram illustrating the experimental testing process and typical signal response of the flexible three-dimensional multi-directional force sensing array of the present invention under planar contact loading conditions.

[0052] Figure 18 This is a schematic diagram of the structure and spatial response distribution of the flexible three-dimensional multi-directional force sensing array of the present invention under curved surface contact loading conditions.

[0053] Figure 19 This is a schematic diagram illustrating the experimental testing process and typical signal response of the flexible three-dimensional multi-directional force sensing array of the present invention under curved surface contact loading conditions.

[0054] Figure 20 This is a schematic diagram illustrating the application of the flexible three-dimensional multi-directional force sensing array of the present invention integrated into a glove.

[0055] Figure 21 This is a schematic diagram of the typical signal response of the flexible three-dimensional multi-directional force sensing array of the present invention under the application conditions of container gripping and tipping.

[0056] Figure 22 This is a schematic diagram of the typical signal response of the flexible three-dimensional multi-directional force sensing array of the present invention in the application of grasping a rigid sphere. Detailed Implementation

[0057] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0058] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0059] Example 1:

[0060] This embodiment provides a basic sensing unit structure for a flexible three-dimensional multi-directional force sensing and detection device.

[0061] like Figure 1 and Figure 7 As shown, the flexible three-dimensional multi-directional force sensing unit adopts an integrated three-dimensional structure design, mainly including a flexible substrate layer, an arrayed three-dimensional trapezoidal sensing unit, and an encapsulation layer. The three-dimensional trapezoidal sensing unit consists of four identical trapezoidal sensing sub-units spaced 90° apart along the spatial circumference (respectively...). Figure 5 (The S1, S2, S3, and S4 channels). This orthogonally distributed structure forms a spatial perception architecture covering 360°.

[0062] To achieve excellent electromechanical response characteristics, the inner angle of the trapezoidal sensing subunit is designed to be 20°, 40°, 60°, or 80°, preferably 60° (e.g., ...). Figure 8 As shown in the figure, this angle design can effectively balance normal sensitivity and tangential resolution.

[0063] In terms of material composition, the flexible substrate layer is formed by a composite of polydimethylsiloxane (PDMS) and antimony tin oxide (ATO), serving as both support and insulation. The three-dimensional trapezoidal sensing unit employs a PDMS / ATO / CNT composite conductive elastomer material. Specifically, the upper three-dimensional sensing portion is doped with carbon nanotubes (CNTs) to construct a highly sensitive conductive network, while the lower substrate portion does not contain CNTs, acting as an isolation layer to prevent conductive crosstalk from the substrate and ensuring the independence of signals from each sensing subunit.

[0064] like Figure 7 As shown, when an external load is applied to this unit, if it is a vertical normal force (Fz), the four sub-units will produce balanced compressive deformation; if it is a tangential force (Fx / y) or tilting force, due to the geometric asymmetry of the trapezoidal structure, the sub-units on the windward and leeward sides will produce different resistance change signals. This structural design lays the foundation for multi-directional force decoupling at the physical level.

[0065] Example 2:

[0066] This embodiment focuses on illustrating the electrode interconnection structure of the sensing device and how its conductivity is achieved.

[0067] like Figure 13As shown, in order to achieve stable signal transmission in a flexible high-density array, this device adopts a three-dimensional interconnect architecture of "double-layer electrodes + vertical vias (Via)".

[0068] Layered wiring: The upper electrode layer is located on the surface of the 3D trapezoidal sensing unit and is responsible for acquiring the sensed signal; the lower electrode layer is located on the back of the flexible substrate layer and is responsible for signal collection and extraction. Both the upper and lower electrodes use a stretchable serpentine trace structure, such as... Figure 12 As shown, this geometric design ensures that the circuit can maintain signal transmission stability when the device is subjected to mechanical stretching of 10% to 30%.

[0069] Vertical interconnect: The upper and lower electrode layers are physically and electrically connected through conductive vias that penetrate the substrate. A copper layer is deposited within these vias, forming a vertical interconnect access, which effectively solves the problem of cross-interference in high-density arrays that is difficult to handle with traditional planar wiring.

[0070] Liquid metal reinforcement: To further improve conductivity reliability under extreme deformation, a liquid metal conductive layer (gallium indium tin alloy) is also coated on the surface of the conductive path formed by electroless copper plating. Liquid metal has fluid properties and can self-heal or bridge microcracks, significantly improving the fatigue resistance of the electrode.

[0071] Example 3:

[0072] This embodiment describes in detail the preparation process of the device, such as... Figure 11 As shown, the specific steps are as follows:

[0073] S1: Mold Preparation. A female mold is prepared using high-precision 3D printing technology. The mold cavity contains groove structures corresponding to four trapezoidal sub-units distributed at 90°.

[0074] S2: Functional material preparation. Prepare a sensor layer mixture according to the mass ratio of PDMS:ATO:CNT=100:5:5, stir thoroughly and degas under vacuum; at the same time, prepare a CNT-free PDMS:ATO mixture for the base layer.

[0075] S3: Step-by-step casting. First, the CNT-containing mixture is injected into the mold and cured at 60°C for 1 hour to form a three-dimensional trapezoidal sensing body with piezoresistive properties; then, a CNT-free mixture is poured into the back of the body, cured again, and demolded to obtain an integrated green body with an insulating substrate.

[0076] S4: Laser etching and drilling. Electrode grooves (depth 0.1–0.3 mm) are etched on the upper and lower surfaces of the device according to a preset path using a laser processing system, and laser drilling is performed at the intersection of the upper and lower electrodes to form through holes.

[0077] S5: Two-stage electroless copper plating. The sample is placed in a copper plating solution (deionized water: copper plating solution A: copper plating solution B = 75:5:10). An optimized two-stage process is employed: the first stage reacts at 35°C for 2 hours, utilizing the higher temperature to accelerate copper ion nucleation within the porous structure and etching tank; the second stage reacts at room temperature (25°C) for 4 hours, ensuring a dense and complete coating. This step must be performed on both the front and back sides separately to ensure a continuous copper layer forms on the inner walls of the holes.

[0078] S6: Liquid metal finishing. A gallium indium tin liquid metal with a surface tension controlled at 35–40 mN / m is brushed onto the copper-plated electrode surface and plasma-treated to enhance wettability.

[0079] S7: Overall Encapsulation. Finally, Ecoflex elastomer is used to encapsulate the entire device, and after curing, a protective layer is formed, completing the device fabrication.

[0080] Example 4:

[0081] This embodiment provides a three-dimensional force decoupling method based on the above hardware structure, which aims to extract normal force, tangential direction angle and tilt angle information from the resistance change signals of the four sub-channels.

[0082] like Figure 5 and Figure 6 As shown, the resistance values ​​of the four directional sub-units are defined as follows: The decoupling logic is as follows:

[0083] Tangential direction angle (θ) calculation: The direction of the force is determined using the signal differential characteristics of the relative position sensing unit (opposite side). Based on the principle of "opposite side difference", the formula for calculating the tangential angle θ is as follows: ;

[0084] like Figure 5 As shown, when forces with different circumferential angles are applied, the algorithm can accurately map the planar direction of the force.

[0085] Tilt angle (α) inverse solution: The tilt angle reflects the degree to which the force deviates from the normal. This is achieved by calculating the single-channel relative gain or the differential amplitude ratio in a specific direction, combined with a pre-calibrated R-α curve (such as...). Figure 8 (The nonlinear growth curve shown on the right) can be used to inversely calculate the current stress angle α.

[0086] Normal load ( Calculation: The normal force mainly causes compression of the overall structure. The normal force is characterized using the four-channel signal averaging method, with the following formula: ;

[0087] Where k is the calibration coefficient. For example... Figure 2 As shown, the calculation method exhibits good linearity and resolution at different pressure levels (50 kPa to 400 kPa) and can effectively suppress noise interference caused by unilateral force.

[0088] Through the above processing, the multi-channel resistance change signal generated by the sensing unit under the action of external forces can be decoupled into parameters such as normal load magnitude, tangential action direction, and tilt angle, thereby realizing decoupled detection of external three-dimensional forces.

[0089] Example 5:

[0090] This embodiment demonstrates the test results of a 5×5 flexible sensor array composed of multiple sensing units under different operating conditions.

[0091] like Figure 10 and Figure 12 As shown, the prepared 5×5 array has good flexibility and stretchability, and can be rolled up at will.

[0092] Fingertip local loading test: such as Figure 14 and Figure 15 As shown, when two fingers press on a specific position of the array, the heat map clearly shows two independent force peak regions, and there is no obvious crosstalk in the surrounding units, which proves that the array has excellent spatial resolution and anti-crosstalk capability.

[0093] Planar contact loading test: such as Figure 16 and Figure 17 As shown, when a rigid plane is used to apply pressure to the array, the output signals of each unit of the array are uniform and consistent. The heat map shows the force distribution over a large area, which verifies the uniformity of the array in large-area tactile perception.

[0094] Surface contact loading test: such as Figure 18 and Figure 19 As shown, when a curved object (such as a sphere) is loaded, the central element of the array has the strongest response, while the edge element responses decrease with curvature. The heat map accurately reproduces the geometric features of the contact surface (concentric circle distribution), indicating that the array has the potential to recognize complex surface morphology.

[0095] Under the aforementioned loading conditions, typical sensing units can be selected from the array, and their output signals from multiple directional sensing channels can be analyzed. As shown in the figure, the typical sensing unit can output stable multi-channel resistance change signals during loading, indicating that the flexible three-dimensional multi-directional force sensing array has good response capability under different loading conditions.

[0096] Example 6:

[0097] This embodiment demonstrates the practical application of this flexible three-dimensional multi-directional force sensing array in the field of smart wearables.

[0098] like Figure 20 As shown, the sensor array is integrated into the palm and fingertips of the smart glove. Through a flexible substrate and flexible packaging structure, the sensor array can conform to the hand surface and maintain stable operation during hand movement and deformation.

[0099] Beaker grasping and pouring experiment: such as Figure 21 As shown, the wearer performs a continuous motion of "grabbing-lifting-pouring-putting down" a beaker. The sensor records the mechanical changes throughout the process in real time: during the grasping phase, the normal force signal (corresponding to gripping force) increases sharply; during the pouring phase, the tangential force signal fluctuates significantly due to changes in the gravitational component. The sensor can clearly distinguish the dynamic process of the gesture.

[0100] Sphere grasping experiment: such as Figure 22 As shown, when grasping a smooth, rigid sphere, the array not only detects the contact pressure, but also reflects the curvature distribution and sliding trend of the contact surface between the sphere and the palm through the signal differences of each unit.

[0101] In summary, the flexible three-dimensional multi-directional force sensing and detection array device proposed in this embodiment of the invention, with its unique three-dimensional trapezoidal structure and decoupling algorithm, has successfully achieved accurate capture and analysis of three-dimensional force information, and has broad application prospects in fields such as bionic robot skin, human-computer interaction interfaces, and medical rehabilitation monitoring.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A flexible three-dimensional multi-directional force sensing and detection array device, characterized in that, The system includes a flexible substrate, a three-dimensional sensor array, a double-layer electrode structure, conductive holes, a liquid metal conductive layer, and an encapsulation layer. The flexible substrate is formed by a composite of polydimethylsiloxane (PDMS) and antimony tin oxide (ATO). The three-dimensional sensor array is arranged on the flexible substrate, and the three-dimensional sensor array is composed of three-dimensional sensor units. Each three-dimensional sensor unit is made of a composite of polydimethylsiloxane (PDMS), antimony tin oxide (ATO), and carbon nanotubes (CNTs). The structure consists of four trapezoidal sensing sub-units distributed along a 90° direction. The four units together form a 360° spatial force sensing structure, converting mechanical strain into a resistance change signal. The double-layer electrode structure includes an upper electrode located on the upper surface of the flexible substrate, a lower electrode located on the lower surface of the flexible substrate, and metal wires. The upper and lower electrodes have the same structure and correspond to each other, both including: a central electrode and four distributed electrodes along a 90° direction; The center electrode of the upper electrode is connected to the center-facing end of four trapezoidal sensing sub-units, and the four distributed electrodes of the upper electrode are respectively connected to the far ends of the four trapezoidal sensing sub-units; the center electrode and four distributed electrodes of the lower electrode are connected to the center electrode and four distributed electrodes of the upper electrode through conductive holes; the center electrode of the upper electrode in each row is connected by a metal wire, and the distributed electrodes in the same direction in each column of the lower electrode are connected by a metal wire; the liquid metal conductive layer covers the surface of the upper and lower double-layer electrode structure to improve the overall conductivity continuity, stretchability and fatigue resistance; the encapsulation layer is Ecoflex elastomer, used to seal and protect the sensing structure.

2. The apparatus according to claim 1, characterized in that, The inner angle of the trapezoidal sensing subunit is 20°, 40°, 60° or 80°.

3. The apparatus according to any one of claims 1 to 2, characterized in that, The array is a 5×5 or higher density matrix structure with a spacing of 2.5 mm between adjacent units; the electrode interconnection lines of each unit adopt a stretchable serpentine routing structure to ensure that the array maintains signal stability under a stretching state of 10% to 30%.

4. The apparatus according to any one of claims 1 to 2, characterized in that, The upper and lower double-layer electrode structure is formed on a flexible substrate by laser etching; the etching path corresponds to independent electrode areas in four directions, and the etching depth is 0.1–0.3 mm; the upper electrode and the lower electrode are drilled to form a through hole after laser etching.

5. The apparatus according to claim 4, characterized in that, The upper and lower double-layer electrode structure forms a conductive path through a two-stage electroless copper plating process. The first stage involves reacting at 35°C for 2 hours to accelerate the initial deposition of copper ions in the etched gaps. The second stage involves continuous electroless copper plating at room temperature (25°C) for 4 hours to achieve full deposition and complete coverage. The electroless copper plating process is first performed on the back side, and then the front side is flipped over to ensure that the copper layer is completely continuous.

6. The apparatus according to claim 5, characterized in that, The liquid metal conductive layer is formed by brush coating; the liquid metal is a gallium indium tin alloy, and the surface tension is controlled at 35–40 mN / m. Its surface is plasma treated to enhance adhesion to the Ecoflex encapsulation layer.

7. The method for preparing the flexible three-dimensional multi-directional force sensing and detection device according to any one of claims 1 to 2, characterized in that, Includes the following steps: 1) 3D printing technology is used to prepare molds for flexible devices; 2) Inject a PDMS:ATO:CNT mixture of 100:5:5 into the mold and solidify to form a three-dimensional sensing structure; 3) Pour PDMS without CNTs into the bottom of the upper structure to form an isolation layer, and then solidify and demold; 4) Use laser etching technology to form electrodes and conductive paths on the upper and lower surfaces; 5) Drill holes at predetermined positions after laser etching; 6) Perform two-step chemical copper plating: the first step is accelerated deposition at 35°C for 2 hours, and the second step is complete deposition at 25°C for 4 hours; 7) Flip the sample to the front and back, and plate copper sequentially at the laser-etched electrodes and conductive paths; 8) Brush a liquid metal conductive layer onto the conductive paths on the back; 9) Encapsulate the top and bottom layers using Ecoflex.

8. A three-dimensional directional force decoupling method based on the flexible three-dimensional multi-directional force sensing and detection device according to any one of claims 1 to 2, characterized in that, The calculation is performed using a four-channel unit signal: the tangential direction angle ψ is determined by the "side difference"; the tilt angle α is obtained by combining the single-channel relative gain or differential amplitude ratio with the calibration curve; and the normal load Fz is characterized by the four-channel mean; thus realizing the three-dimensional directional decoupling detection of a single pressure sensor.

9. The decoupling method according to claim 8, characterized in that, The orientation angle θ is calculated from the differential signal of the opposite channel: ,in These are the resistance values ​​for the four channels, respectively; The tilt angle α is obtained by inversely calculating the single-channel differential amplitude ratio and the calibration curve; the normal load Fz is the arithmetic mean of the four-channel output. , where k is the calibration coefficient.

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