Electrodynamic three-dimensional force sensor with central reference electrode and signal correction method

Abstract

The application discloses a triboelectric three-dimensional force sensor with a central reference electrode and a signal correction method, and belongs to the technical field of flexible three-dimensional force sensors. The sensor comprises a lower electrode layer, a triboelectric sensitive layer, an upper electrode layer and a force guiding structure layer. The lower electrode layer comprises symmetrically arranged peripheral force receiving electrodes and a central reference electrode located in the enclosed area of the peripheral force receiving electrodes. The force guiding structure layer is provided with a central cavity and covers the central reference electrode in projection. The electrical signal response of the peripheral force receiving electrodes is modulated by external pressure and ambient temperature. A saturated contact ion film is formed on the surface of the central reference electrode, so that the electrical signal response of the central reference electrode is modulated by ambient temperature. The temperature reference channel is integrated in the sensor unit, in-situ temperature drift compensation is realized, external temperature sensing space deviation is eliminated, and the three-dimensional force decoupling accuracy and long-term stability under variable temperature conditions are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of flexible three-dimensional force sensor technology, specifically relating to an ionized three-dimensional force sensor with a central reference electrode and a signal correction method. Background Technology

[0002] Flexible three-dimensional force sensors, due to their high sensitivity, excellent conformability, and multi-dimensional force sensing capabilities, have wide applications in fields such as robotic electronic skin, wearable devices, and human-computer interaction. Currently, a common design approach for flexible three-dimensional force sensors involves placing a compressible ionized layer or pressure-sensitive layer between the upper and lower electrodes, combined with a geometrically asymmetrical structure to decouple normal and tangential forces. Among publicly available technologies, symmetrical four-electrode arrangements, hemispherical protruding contacts, and sandwich structures are all relatively mature three-dimensional force decoupling unit architectures. These structures induce microscopic deformation of the sensitive layer through external multi-dimensional forces, leading to differentiated changes in the contact area or interfacial spacing of different electrode regions, thereby achieving the separation and reconstruction of the three-dimensional force components.

[0003] However, in actual working conditions and array integration, the aforementioned existing technologies still have technical problems that urgently need to be improved: First, the inherent thermodynamic properties of ion-sensitive materials lead to severe temperature drift and coupling between the sensor and the mechanical / thermal signal. Key electrical / mechanical parameters such as ionic conductivity, interfacial double-layer capacitance, polymer matrix modulus, and contact resistance are all highly sensitive to temperature. Fluctuations in ambient temperature directly cause significant drift in the sensor's output baseline and sensitivity decay, and this temperature drift effect is highly coupled with the mechanical load response. In existing geometrically asymmetric electrode decoupling units, all force channels are simultaneously affected by temperature, resulting in calibration coefficient mismatch in different temperature zones and a significant decrease in the accuracy and long-term stability of three-dimensional force decoupling.

[0004] Secondly, traditional temperature compensation schemes struggle to achieve in-situ temperature and force matching at the unit level. To suppress temperature drift, existing technologies typically employ a patchwork or alternating arrangement of force sensing units and external independent temperature-sensitive units. This approach not only significantly increases device area, wiring complexity, and the integration difficulty of flexible arrays, but also fails to guarantee complete alignment between the temperature reference position and the three-dimensional force-sensitive area. In non-uniform temperature and force fields, such as wearable contact or robotic grasping scenarios, external temperature sensors struggle to accurately characterize local temperature drift, leading to distorted temperature mapping compensation.

[0005] Third, existing temperature drift suppression methods are costly to implement and have poor real-time performance. Relying on global temperature sensing, multi-temperature zone offline repeated calibration, or complex polynomial / neural network software temperature compensation is not only cumbersome in calibration process and consumes a lot of edge computing resources, but also difficult to meet the engineering requirements of flexible miniaturized devices for low power consumption, fast response and long-term maintenance-free operation.

[0006] Therefore, there is an urgent need in this field for a novel ionized three-dimensional force sensor and its signal correction method to solve the above problems.

[0007] It should be noted that this part of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or known technology. Summary of the Invention

[0008] This invention provides an ionized three-dimensional force sensor with a central reference electrode and a signal correction method, which at least solves the technical problems in the prior art, such as the inaccuracy of three-dimensional force decoupling caused by temperature drift and mechanical response coupling in ionized three-dimensional force sensors, the difficulty of achieving unit-level in-situ co-position reference by external independent temperature sensing units, and the cumbersome and difficult-to-adapt flexible array integration process of traditional software temperature compensation / repeated calibration.

[0009] To achieve the above objectives, in a first aspect, the present invention provides an ionized three-dimensional force sensor with a central reference electrode, comprising a lower electrode layer, an ionized sensitive layer, an upper electrode layer, and a force-conducting structure layer; the lower electrode layer includes a plurality of peripheral force-receiving electrodes arranged symmetrically, and at least two central reference electrodes located in the area enclosed by the peripheral force-receiving electrodes; the ionized sensitive layer is disposed above the lower electrode layer, forming contact interfaces with the peripheral force-receiving electrodes and the central reference electrodes respectively; the upper electrode layer is disposed on the side of the ionized sensitive layer opposite to the lower electrode layer; the force-conducting structure layer is disposed on or above the upper electrode layer, and the force-conducting structure layer has a central cavity, the projection of which covers the central reference electrode; the electrical signal response of the peripheral force-receiving electrodes is configured to be modulated simultaneously with external pressure and ambient temperature; the ionized sensitive layer located on the surface of the central reference electrode is subjected to saturated contact treatment to form a saturated contact ion membrane, so that the electrical signal response of the central reference electrode is configured to be modulated only by the ambient temperature.

[0010] Preferably, the peripheral force-bearing electrodes are arranged in a 2×2 square array, a circular array, a fan-shaped array, an arc array, or using interdigitated electrodes; the central reference electrode is circular, square, cross-shaped, an annular island, or a split dual electrode.

[0011] Preferably, there are four peripheral force-bearing electrodes, each forming a quarter-circle, which are arranged at equal angular intervals along the same circumference to form an annular force-bearing area; the central reference electrode includes a first semi-circular electrode and a second semi-circular electrode arranged at intervals along the central axis of symmetry, which together form a circular central reference area; the outer ring diameter of the annular force-bearing area is 8mm~12mm, the inner ring diameter is 3mm~5mm, and the diameter of the central reference area is 0.5mm~1.5mm.

[0012] Preferably, the force-guiding structure layer is a hollow hemisphere, hollow truncated hemisphere, annular boss, or micro-dome array structure made of flexible elastomer material.

[0013] Preferably, the ratio of the diameter of the central cavity to the diameter of the bottom surface of the force-conducting structure layer is (1:4) to (1:6); the bottom edge of the force-conducting structure layer forms an annular contact area, and the force projection of the annular contact area covers the surrounding force-conducting electrodes.

[0014] Preferably, the thickness of the saturated contact ion membrane is 15 μm to 25 μm, and the thickness of the ion-sensitive layer above the peripheral force electrode is 50 μm to 70 μm.

[0015] Preferably, the saturated contact ion membrane is formed by in-situ curing of the ion gel mother liquor on the surface of the central reference electrode. After curing, there is no interface gap between the saturated contact ion membrane and the central reference electrode, so that the electrical signal response of the central reference electrode is configured to be modulated only by the ambient temperature.

[0016] Preferably, the material of the ionization sensitive layer includes a PVDF-HFP ion liquid system, a TPU ion liquid system, a PDMS-based ion gel system, a CNT composite ionization layer, or an MXene composite ionization layer.

[0017] Preferably, the upper electrode layer is a continuous conductive layer covering the area corresponding to the surrounding force-bearing electrodes, or it is a partitioned electrode that corresponds one-to-one with the lower electrode layer.

[0018] In a second aspect, the present invention provides a signal correction method based on the sensor of the first aspect, comprising: Simultaneously acquire the force signals output by the surrounding force electrodes and the temperature signals output by the central reference electrode; A temperature drift mapping relationship is established between temperature signals and force signals; The temperature drift mapping relationship is used to perform real-time temperature drift compensation on the force channel signal to generate a net force response signal; The three-dimensional force components are calculated and output based on the net force response signal.

[0019] The beneficial effects of this invention are as follows: This invention integrates a temperature reference channel directly into the three-dimensional force sensing unit. A saturated contact ion membrane is disposed on the surface of the central reference electrode, and the central cavity of the force-conducting structure layer projects onto the central reference electrode, placing it in a mechanically weakened region. This structure ensures that the electrical signal response of the central reference electrode is primarily modulated by ambient temperature and exhibits a weak response to mechanical pressure, while the electrical signal response of the surrounding force-bearing electrodes is modulated by both external pressure and ambient temperature. This achieves in-situ temperature reference within the sensing unit, eliminating the mismatch between the local thermal field and the environment of the force-bearing area caused by the spatial separation of an external independent temperature sensing unit, and improving the spatial co-location and thermodynamic consistency between the temperature reference signal and the force channel signal.

[0020] This invention retains the traditional peripheral electrode force-guiding decoupling structure, adding a reference electrode and corresponding force-guiding cavity only through functional reconstruction of the central region, without changing the arrangement of the peripheral force-bearing electrodes or the signal readout logic. This design achieves the integration of three-dimensional force sensing and in-situ temperature compensation functions with a smaller area cost, eliminating the need for a separate temperature sensing module and additional wiring. This reduces the device thickness, wiring complexity, and integration cost of flexible sensing arrays, making it suitable for large-scale array deployment in robotic electronic skin and wearable devices.

[0021] This invention establishes a temperature drift mapping relationship between the temperature reference signal output from the central reference electrode and the force channel signal output from the surrounding force-bearing electrodes by synchronously acquiring the latter. Real-time temperature drift compensation is then performed on the force channel signal. This compensation method eliminates common-mode signal drift caused by temperature variations in ionic conductivity, interfacial double-layer capacitance, and polymer modulus, restoring the net force response signal of the force channel. It can accurately reconstruct the normal and tangential force components under different ambient temperatures and non-uniform thermal field conditions, reducing zero-point drift and sensitivity attenuation, and improving the accuracy and long-term stability of three-dimensional force measurement. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a top view of the lower electrode layer of the ionized three-dimensional force sensor provided in an embodiment of the present invention. Figure 2 This is a side view cross-sectional structural diagram of an ionized three-dimensional force sensor provided in an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures: 10. Lower electrode layer; 11. Peripheral force-bearing electrodes; 12. Central reference electrode; 20. Ionization-sensitive layer; 21. Saturated contact ion membrane; 30. Upper electrode layer; 40. Force-guiding structural layer; 41. Central cavity; 42. Annular contact area. Detailed Implementation

[0025] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" are generally understood in conjunction with the accompanying drawings and the directions shown in actual applications.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0029] In a first aspect, the present invention provides an ionized three-dimensional force sensor with a central reference electrode, comprising a lower electrode layer, an ionized sensitive layer, an upper electrode layer, and a force-conducting structure layer; the lower electrode layer includes a plurality of peripheral force-receiving electrodes arranged symmetrically, and at least two central reference electrodes located in the area enclosed by the peripheral force-receiving electrodes; the ionized sensitive layer is disposed above the lower electrode layer, forming contact interfaces with the peripheral force-receiving electrodes and the central reference electrodes respectively; the upper electrode layer is disposed on the side of the ionized sensitive layer opposite to the lower electrode layer; the force-conducting structure layer is disposed on the side of the ionized sensitive layer opposite to the lower electrode layer, and the force-conducting structure layer has a central cavity, the projection of which covers the central reference electrode; the electrical signal response of the peripheral force-receiving electrodes is configured to be modulated simultaneously with external pressure and ambient temperature; the ionized sensitive layer located on the surface of the central reference electrode is subjected to saturated contact treatment to form a saturated contact ion membrane, so that the electrical signal response of the central reference electrode is configured to be modulated only by the ambient temperature.

[0030] Understandably, the main response mechanism of ion-conducting sensors lies in the double-layer capacitance formed at the interface between the electrode and the ion-conducting medium, and its capacitance value is positively correlated with the effective contact area. In existing electrode decoupling structures, ion mobility, dielectric constant, and polymer modulus change synchronously with ambient temperature fluctuations, leading to common-mode drift in all channels. Furthermore, the external temperature sensing element cannot characterize the local thermal field due to spatial separation. This invention, by placing a reference electrode in the central region and coordinating it with the central cavity of the force-conducting structure layer, places the central electrode in a mechanically weakened region, preventing the transmission of mechanical load to the reference channel. The design of the saturated contact ion membrane ensures that the initial contact area between the central electrode and the ion medium reaches its theoretical maximum value; under pressure, the change in contact area approaches zero, and the double-layer capacitance changes only with temperature-modulated ion conductivity and dielectric properties. This structure integrates the temperature and force parameters into the same sensitive layer and the same thermodynamic microenvironment, eliminating the spatial hysteresis error of external compensation. If the central cavity does not cover the reference electrode or does not use a saturated contact membrane, the reference channel will be mixed with a significant pressure component, causing the mapping model to be inaccurate. If a central weakening design is not used, in-situ temperature drift stripping cannot be achieved, and the three-dimensional force decoupling matrix will exhibit nonlinear mismatch with temperature, resulting in loss of long-term stability.

[0031] Preferably, the peripheral force-bearing electrodes are arranged in a 2×2 square array, a circular array, a fan-shaped array, an arc array, or using interdigitated electrodes; at least two central reference electrodes are arranged at intervals and together form a central reference area, which is circular, square, cross-shaped, or annular island; at least two central reference electrodes are split dual electrodes, interdigitated reference electrodes, or semi-circular opposing electrodes.

[0032] Understandably, the diversity of electrode geometry is designed to adapt to the force field distribution characteristics and array integration process constraints of different application scenarios. Among the various structural forms of peripheral force electrodes, the 2×2 square array facilitates photolithography and trace alignment on rectangular substrates, the circular array adapts to the axisymmetric force field of bionic fingertips, the fan-shaped or arc-shaped array can reduce edge stress concentration during tangential force detection, and the interdigitated electrode arrangement increases the capacitance change rate of small deformations by increasing the edge electric field gradient.

[0033] Understandably, various alternative structural designs for the central reference electrode can optimize the signal-to-noise ratio and array arrangement compatibility within a limited unit area. More preferably, the central reference electrode can adopt a split dual-electrode structure. By arranging the dual electrodes at intervals on both sides of the central axis of symmetry, a differential measurement loop can be constructed. In actual working conditions, the flexible substrate may still generate weak residual strain when subjected to tangential force or array bonding stress. The split arrangement makes the modulation of the residual stress on the two electrodes common-mode symmetry, and the differential output can effectively cancel mechanical crosstalk. At the same time, the dual-electrode loop can avoid the ground potential drift problem caused by the reliance on an external reference ground when using single-electrode measurement, ensuring that the reference signal only characterizes the intrinsic temperature drift characteristics of the ionic medium.

[0034] Preferably, the number of peripheral force-bearing electrodes is four, each forming a quarter-circle, and they are arranged at equal angular intervals along the same circumference to jointly form an annular force-bearing area; the central reference electrode includes a first semi-circular electrode and a second semi-circular electrode arranged at intervals along the central axis of symmetry, and the first semi-circular electrode and the second semi-circular electrode together form a circular central reference area.

[0035] Preferably, the outer ring diameter of the annular stress-bearing zone is 8mm to 12mm, specifically 8mm, 9mm, 10mm, 11mm, 12mm and any value between them; The inner ring diameter is 3mm to 5mm, specifically 3mm, 3.5mm, 4mm, 4.5mm, 5mm and any value between them; The diameter of the central reference area is 0.5mm to 1.5mm, specifically 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, and any value between them.

[0036] Understandably, the aforementioned geometric arrangement design is more conducive to optimizing the mechanical transmission path and improving signal acquisition consistency. The diameters of the outer and inner rings are mainly set to match the size requirements of the standard contact interface, ensuring that the force-conducting structure layer has sufficient load-bearing area to uniformly distribute the normal load, avoiding excessive local stress that could lead to plastic damage to the ionization sensitive layer, while also reserving space for the arrangement of the central cavity of the force-conducting structure layer. The diameter of the central reference area is much smaller than the effective sensing area of ​​a single peripheral force-bearing electrode. Since the temperature sensing unit does not need to consider the modulation effect of changes in the pressure area on the signal output, its design goal is to achieve high signal-to-noise ratio temperature reference signal acquisition with minimal space occupation. The smaller electrode area can reduce the absolute value of the double-layer capacitance, amplifying the temperature-induced changes in ionic conductivity and dielectric constant at the level of relative capacitance change rate, thereby improving the sensitivity of the temperature reference channel; at the same time, the small-sized central reference area can avoid encroaching on the effective sensing area of ​​the peripheral force-bearing electrodes, ensuring that the spatial resolution of three-dimensional force decoupling is not affected.

[0037] Preferably, the force-conducting structure layer is a hollow hemisphere, hollow truncated hemisphere, annular boss, or micro-dome array structure made of flexible elastomer material. The bottom edge of the force-conducting structure layer forms an annular contact area, and the force projection of the annular contact area covers the surrounding force-bearing electrodes.

[0038] Understandably, the force-conducting structure layer functions to transform external multidimensional forces into differentiated compression of the surrounding electrodes. Using flexible elastomer materials (such as PDMS, silicone rubber, or thermoplastic polyurethane) can endow the structure with excellent deformation recovery and surface conformability. The hollow design is a direct means of achieving mechanical isolation of the central reference electrode. When a normal force acts on the top of the force-conducting structure, the load is transmitted downwards along the elastomer's curved surface. Since there is no solid material supporting the central region, the deformation energy is mainly consumed by the bending of the sidewalls and the radial expansion of the bottom annular edge. Only a small axial displacement occurs in the central region, thus significantly attenuating the contact pressure transmitted to the central reference electrode. The hollow truncated hemisphere, while retaining its mechanical weakening properties, improves the top's puncture resistance, making it suitable for rough contact surfaces. The annular boss structure optimizes the tangential force transmission path through a concentrated bottom support ring, reducing normal and tangential coupling errors. The micro-dome array is suitable for large-area distributed tactile sensing, achieving localized stress concentration and rapid rebound through discrete dome units. If the force-conducting structure layer does not have a central cavity, the load will be uniformly distributed across the entire electrode area, and the central reference electrode will still be subject to pressure modulation, rendering temperature drift compensation ineffective. The force projection of the annular contact area covers the surrounding force-bearing electrodes, helping to ensure that external loads are converted into capacitive modulation of the effective sensing channel, preventing stress leakage to non-sensitive areas, and improving force-to-electricity conversion efficiency and signal consistency.

[0039] Understandably, the conductive structure layer is preferably made of polydimethylsiloxane (PDMS). PDMS, as an addition-type room temperature vulcanizing silicone rubber, has excellent elastic recovery, low Young's modulus, high elongation at break, and good biocompatibility. Its compressive modulus can be continuously adjusted by regulating the mass ratio of the prepolymer to the curing agent. In a preferred embodiment of the present invention, the mass ratio of PDMS prepolymer to curing agent is 10:1. The PDMS network formed under this ratio has a moderate crosslinking density, which ensures the structural stability of the conductive structure layer under cyclic loading, preventing plastic collapse or lateral buckling of the hollow hemisphere under normal pressure, while also providing sufficient flexibility to achieve deflection deformation under tangential force, ensuring differentiated compressive responses from the four peripheral force electrodes.

[0040] Besides PDMS, the force-conducting structural layer can also be made of other flexible elastomer materials, including but not limited to silicone rubber, thermoplastic polyurethane (TPU), styrene-ethylene-butene-styrene block copolymer (SEBS), ethylene-vinyl acetate copolymer (EVA), or natural rubber. These materials all possess low modulus and high elasticity, and can be molded into structures such as hollow hemispheres, truncated hemispheres, annular bosses, or micro-dome arrays through processes such as molding, injection molding, or 3D printing. The selection of different elastomer materials requires comprehensive consideration of their interfacial adhesion to the ionization sensitive layer, environmental resistance (such as temperature resistance and moisture resistance), and process compatibility. Regardless of the elastomer material used, the core function of the force-conducting structural layer is to directionally guide the mechanical transmission path through the geometric design of the central cavity, allowing external loads to be directionally transmitted to the surrounding force-bearing electrodes via the annular contact area, while simultaneously shielding the mechanical stress in the central reference electrode area. This function does not depend on the intrinsic properties of any specific material, but rather on the coordinated matching of the cavity projection coverage, the annular contact area layout, and the material modulus.

[0041] Preferably, the ratio of the diameter of the central cavity to the diameter of the bottom surface of the force-guiding structure layer is (1:4) to (1:6), specifically 1:4, 1:4.2, 1:4.5, 1:5, 1:5.5, 1:6 and any ratio between them.

[0042] Understandably, controlling the above ratio helps control the mechanical isolation effect and structural load-bearing stability. When the ratio is less than 1:4, the diameter of the central cavity is relatively too small, the width of the solid ring at the bottom of the force-guiding structure is too large, the support stiffness of the central region under normal load is significantly increased, the cavity's ability to release deformation energy is weakened, and some mechanical stress may still be transmitted to the central reference electrode, causing the saturated contact ion membrane to be subjected to additional compression, and the temperature reference signal to be mixed with pressure components. When the ratio is greater than 1:6, the diameter of the central cavity is relatively too large, the bottom annular support wall is too narrow, the structural bending section modulus decreases sharply, and local buckling or lateral instability is prone to occur under normal operating load or tangential shear force, causing nonlinear jumps in the contact state between the annular contact area and the surrounding force-bearing electrodes, inaccurate three-dimensional force decoupling matrix, and fatigue cracking after long-term cyclic use. Maintaining the ratio within the range of 1:4 to 1:6 helps the force-guiding structure to maintain elastic buckling-dominated deformation during normal compression. The bottom annular contact area uniformly bears the load and directionally transfers stress to the four surrounding force-bearing electrodes, while the central region maintains a low strain state.

[0043] Preferably, the thickness of the saturated contact ion membrane is 15 μm to 25 μm, specifically 15 μm, 18 μm, 20 μm, 22 μm, 25 μm and any value between them, and the thickness of the ion-sensitive layer above the peripheral force electrode is 50 μm to 70 μm, specifically 50 μm, 55 μm, 60 μm, 65 μm, 70 μm and any value between them.

[0044] Understandably, the differentiated design of the thickness parameters between the saturated contact ion membrane and the ion-sensitive layer above the peripheral force-bearing electrode facilitates the configuration where the electrical signal response of the peripheral force-bearing electrode is modulated simultaneously by external pressure and ambient temperature, while the electrical signal response of the central reference electrode is modulated only by ambient temperature. The capacitance modulation mechanism of the ion-sensitive sensor relies on the dynamic change of the effective contact area of ​​the electrode-ion interface double layer and the drift of the intrinsic physical parameters of the dielectric layer with temperature. In the peripheral force-bearing electrode region, the thickness of the ion-sensitive layer is limited to 50 μm–70 μm. This thickness range provides sufficient elastic compression stroke for the microstructure interface. When external pressure is applied to the conductive structure layer, the peripheral sensitive layer undergoes macroscopic deformation, and the micro-protrusions or pore structures on its surface are gradually flattened. The effective contact area between the electrode and the ion medium expands nonlinearly, thereby generating a highly sensitive pressure response signal.

[0045] In the central reference electrode region, the thickness of the saturated contact ion exchange membrane is limited to 15 μm to 25 μm. The thinner membrane thickness directly increases the macroscopic compressive modulus of the ion medium in this region. Combined with the mechanical weakening effect of the central cavity in the conductive structure layer, the residual mechanical stress transmitted to the central region can hardly cause thickness compression, failing to break through the initial saturated contact state between the ion exchange membrane and the electrode interface. Under this condition, the geometric area component of the double-layer capacitance remains constant, and the change in capacitance is entirely dominated by the viscosity of the ionic liquid, the mobility of polymer chain segments, and the intrinsic drift of the dielectric constant with temperature, thus achieving signal output characteristics modulated only by ambient temperature.

[0046] Preferably, the saturated contact ion membrane is formed by in-situ curing of the ion gel mother liquor on the surface of the central reference electrode. After curing, there is no interface gap between the saturated contact ion membrane and the central reference electrode, so that the electrical signal response of the central reference electrode is configured to be modulated only by the ambient temperature.

[0047] Understandably, this invention provides a preferred method for preparing a saturated contact ion exchange membrane. The saturated contact ion exchange membrane is formed by in-situ curing of an ion gel mother liquor on the surface of a central reference electrode, resulting in a seamless interface after curing. This process path and microstructure control further help ensure that the electrical signal response of the central reference electrode is configured to be modulated only by ambient temperature. Traditional ionization sensitive layers often employ a pre-fabricated thin film hot-pressing process, inevitably leaving air gaps or microscopic roughness between the bottom surface of the film and the electrode surface. Under pressure, the expulsion of the air layer and the reconstruction of the contact area of ​​the rough peaks introduce a significant nonlinear capacitance step, leading to the unavoidable coupling of mechanical pressure components into the reference channel. This invention deposits the prepared ion gel mother liquor onto the surface of the central reference electrode, utilizing solvent evaporation kinetics and the polymer chain crosslinking contraction effect to allow the gel precursor to completely wet the microstructure and oxide layer of the electrode surface under capillary force. As the solvent system escapes in a gradient, the polymer network densely stacks at the electrode interface. After curing, the initial physical gap between the ion exchange membrane and the electrode is eliminated, allowing the initial contact area at the electrode-ion interface to reach the theoretical saturation limit of the electrode's geometric projection area. Under this saturation state, even if the conductive structure layer transmits a small amount of residual stress to the central region under overload or tangential off-center loading conditions, there is no additional microscopic space at the ion exchange membrane and electrode interface for contact area expansion, and the change in double-layer capacitance caused by pressure approaches zero.

[0048] Preferably, the material of the ionization sensitive layer includes a PVDF-HFP ion liquid system, a TPU ion liquid system, a PDMS-based ion gel system, a CNT composite ionization layer, or an MXene composite ionization layer.

[0049] Understandably, taking the PVDF-HFP ionic liquid system as an example, this system can be formed by cross-linking a first PVDF polymer, a second PVDF polymer, an ionic liquid, a wetting agent, a solvent, and fillers in a certain proportion. The first PVDF polymer has high crystallinity and high content, spontaneously precipitating spherical or near-spherical microcrystalline frameworks during solvent evaporation and phase separation, forming a three-dimensional porous network and surface microstructure of the ionizing sensitive layer. The second PVDF polymer has low crystallinity and low content, mainly distributed in the intercrystalline gaps during film formation, playing a bonding and toughening role, forming a stable polymer ionic gel particle layer. The preferred anions of the ionic liquid are hexafluorophosphate and bis(trifluoromethanesulfonyl)imide, while the preferred cations are imidazole derivatives. Their high ionic conductivity and wide electrochemical window ensure the rapid establishment and stable maintenance of the double-layer capacitance. The introduction of nanoscale fillers such as fumed silica or nano-alumina can promote the homogenization of phase separation nucleation, improve the spatial distribution consistency of the microstructure array, and avoid signal nonlinearity caused by local strength or resilience differences. In the surrounding area of ​​the stressed electrodes, the inherent microphase separation characteristics and microstructure morphology of the material system cause a significant change in the contact area under pressure, thus achieving a highly sensitive pressure response.

[0050] As an example, the specific preparation method of the ionization sensitive layer material can be found in the previous patents CN119060476B and CN119060387B. However, it should be noted that the ionization sensitive layer material in this application can also be prepared from other components, and this application does not impose any restrictions on this.

[0051] Furthermore, the ionization-sensitive layer in the surrounding force-bearing electrode region possesses microstructures, which can be in the form of nanopores, microchannels, microprotrusions, etc. These microstructures can increase the surface area of ​​the ionization-sensitive layer, improve ion conduction efficiency, and help improve the capacitance effect. The shape of the microstructure can be referred to in the descriptions in patents CN119060476B and CN119060387B, and will not be repeated here.

[0052] In the central reference electrode region, although a homogeneous ion-sensitive material system is used, its interfacial mechanical behavior and capacitance modulation mechanism are altered through saturated contact treatment. The use of homogeneous materials ensures that the central reference region and the surrounding stress-bearing region maintain consistency in thermodynamic intrinsic parameters such as thermal expansion coefficient, ion migration activation energy, dielectric relaxation time, and solvation effect. When the ambient temperature fluctuates, the ionic conductivity drift, thermal expansion and contraction of the double-layer thickness, and polymer modulus decay of the two sensitive layers exhibit completely synchronized common-mode changes. Due to the physical constraints of saturated contact and a seamless interface, the capacitance change in the central region is modulated only by the external temperature; the surrounding stress-bearing electrode region experiences pressure modulation under the same temperature field. The synergistic design of homogeneous materials and heterogeneous interfaces eliminates the temperature parameter signal lag and mapping distortion caused by differences in heat capacity, thermal conductivity, or material aging rates in heterogeneous temperature sensing elements.

[0053] Preferably, the upper electrode layer is a continuous conductive layer covering the area corresponding to the surrounding force-bearing electrodes, or it is a partitioned electrode that corresponds one-to-one with the lower electrode layer.

[0054] Understandably, the topology design of the top electrode layer directly affects the complexity of the signal readout architecture and the level of crosstalk between channels. Using a continuous, full-surface common electrode simplifies the photolithography and wiring processes of flexible substrates, reduces the number of leads, and lowers parasitic capacitance and trace crosstalk interference during array integration, making it suitable for cost-sensitive consumer electronics or disposable medical patches. The full-surface electrode maintains a uniform potential equipotential surface under pressure, ensuring symmetrical electric field distribution across all lower electrode channels and improving the consistency of normal force detection. Using partitioned top electrodes corresponding one-to-one with the lower electrode layer allows for the application of independent bias voltages or frequency excitations to each sensing unit, facilitating multi-frequency impedance spectrum measurements and extracting richer force-temperature coupling characteristic parameters, making it suitable for high-precision industrial inspection or research-grade electronic skin. The partitioned design physically isolates the lateral electric field leakage between adjacent units, significantly reducing crosstalk in high-density arrays, but requires a multi-channel multiplexed readout circuit, increasing system complexity.

[0055] In a second aspect, the present invention provides a signal correction method based on the sensor of the first aspect, comprising: Simultaneously acquire the force signals output by the surrounding force electrodes and the temperature signals output by the central reference electrode; A temperature drift mapping relationship is established between temperature signals and force signals; The temperature drift mapping relationship is used to perform real-time temperature drift compensation on the force channel signal to generate a net force response signal; The three-dimensional force components are calculated and output based on the net force response signal.

[0056] Understandably, the signal correction method provided by this invention is based on the hardware structure of an ionized three-dimensional force sensor with a central reference electrode. Specifically, the hardware foundation for simultaneously acquiring the force signal output from the peripheral force electrodes and the temperature signal output from the central reference electrode lies in the integrated arrangement design of the peripheral force electrodes and the central reference electrode in the lower electrode layer of the sensor, as well as the mechanical isolation effect of the central cavity of the force-conducting structure layer on the central reference electrode. Since the surface of the central reference electrode is provided with a saturated contact ion membrane and is located in the projection coverage area of ​​the central cavity of the force-conducting structure layer, its electrical signal response is mainly modulated by the ambient temperature and has a weak response to mechanical pressure. Therefore, the temperature signal output by this electrode can truly characterize the temperature drift behavior when it is in the same ionized sensitive layer, the same process layer, and the same local thermal environment as the peripheral force electrodes. The temperature drift mapping relationship between the temperature signal and the force signal is established based on the fact that the peripheral force-bearing electrodes and the central reference electrode share the same ionization-sensitive material system. The physicochemical parameters such as ionic conductivity, interfacial double-layer capacitance, and polymer modulus exhibit consistent temperature-dependent changes in both types of electrode channels, allowing the temperature drift data of the central reference channel to be effectively mapped to the peripheral force-bearing channels. This mapping relationship is used to perform real-time temperature drift compensation on the force-bearing channel signal, generating a net force response signal. The technical effect is to eliminate common-mode signal drift caused by ambient temperature fluctuations and restore the pressure response component modulated only by mechanical deformation. The three-dimensional force component is calculated and output based on the net force response signal. This step relies on the mechanical decoupling capability of the normal and tangential forces inherent in the sensor's four-electrode hemispherical structure. The temperature-drift-compensated net force signal can be directly substituted into the pre-calibrated three-dimensional force decoupling matrix for component reconstruction. This method eliminates the need for an additional independent temperature sensing module or complex external compensation circuit; in-situ temperature drift reference can be achieved solely through the central reference electrode integrated within the sensor, significantly reducing the wiring complexity and integration cost of flexible array devices. Meanwhile, since the temperature reference signal and the force signal are synchronously acquired from the same sensing unit, the thermal field matching deviation caused by spatial separation of external temperature sensing schemes is avoided, improving the real-time performance and accuracy of temperature drift compensation, and enabling the sensor to maintain stable three-dimensional force measurement accuracy under wide temperature range and non-uniform thermal field conditions.

[0057] Understandably, the operation of establishing a temperature drift mapping relationship between temperature signals and force signals can specifically include: placing the sensor in a temperature-controlled environment before the sensor leaves the factory or during the initial calibration stage, collecting the temperature signal of the central reference electrode and the force signals of the surrounding force electrodes under zero load and standard load under different temperature gradients; using polynomial fitting or machine learning algorithms to construct a compensation coefficient matrix between temperature variables and zero-point drift and sensitivity attenuation of the force channel, and storing it in an external reading circuit or host computer as a mapping relationship during operation.

[0058] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0059] like Figure 1 and Figure 2 As shown, this embodiment provides an ionized three-dimensional force sensor with a central reference electrode, including a lower electrode layer 10, an ionized sensitive layer 20, an upper electrode layer 30, and a force-conducting structure layer 40.

[0060] The lower electrode layer 10 includes four peripheral force-bearing electrodes 11 and a central reference electrode 12. The four peripheral force-bearing electrodes 11 are each a quarter-circle, arranged at equal angular intervals along the same circumference to form an annular force-bearing area. The central reference electrode 12 includes a first semi-circular electrode and a second semi-circular electrode arranged at intervals along a central axis of symmetry, together forming a circular central reference area. The outer diameter of the annular force-bearing area is 10 mm, and the inner diameter is 4 mm; the diameter of the circumscribed circle of the central reference area is 1 mm.

[0061] An ionization-sensitive layer 20 is disposed above the lower electrode layer 10, forming contact interfaces with the peripheral force-bearing electrode 11 and the central reference electrode 12, respectively. The ionization-sensitive layer 20 above the peripheral force-bearing electrode 11 has a microstructure, which is a spherical array of protrusions formed by a phase separation process. This microstructure generates a significant change in contact area under external pressure, thereby achieving a high-sensitivity response to mechanical loads. The ionization-sensitive layer 20 on the surface of the central reference electrode 12 undergoes saturated contact treatment to form a saturated contact ion membrane 21. The saturated contact ion membrane 21 is formed by in-situ dripping and curing an ion gel mother liquor onto the surface of the central reference electrode 12. After curing, there are no interface gaps between the saturated contact ion membrane 21 and the central reference electrode 12, so that the electrical signal response of the central reference electrode 12 is mainly modulated by ambient temperature and exhibits a weak response to mechanical pressure.

[0062] The upper electrode layer 30 is disposed on the side of the ionization sensitive layer 20 away from the lower electrode layer 10. The upper electrode layer 30 is a continuous conductive layer covering the entire area corresponding to the surrounding force-bearing electrode 11.

[0063] A force-conducting structure layer 40 is disposed on the side of the upper electrode layer 30 opposite to the ionization-sensitive layer 20. The force-conducting structure layer 40 is a hollow hemispherical structure made of PDMS material, and has a central cavity 41. The projection of the central cavity 41 covers the central reference electrode 12. The ratio of the diameter of the central cavity 41 to the diameter of the bottom surface of the force-conducting structure layer 40 is 1:5. An annular contact area 42 is formed at the bottom edge of the force-conducting structure layer 40, and the force projection of the annular contact area 42 covers the peripheral force-receiving electrodes 11.

[0064] In this embodiment, the thickness of the ion-sensitive layer 20 above the peripheral force-bearing electrode 11 is 60 μm, and the thickness of the saturated contact ion membrane 21 on the surface of the central reference electrode 12 is 20 μm. The thicker peripheral ion-sensitive layer 20 provides sufficient elastic compression stroke for the microstructure interface, ensuring that the contact area changes significantly under external pressure, thus achieving a highly sensitive pressure response. The thinner saturated contact ion membrane 21, combined with the mechanical isolation effect of the central cavity 41, ensures that the central reference electrode 12 is in a mechanically weakened region when the force-conducting structure layer 40 is compressed. Furthermore, the initial contact area between the saturated contact ion membrane 21 and the central reference electrode 12 reaches the ion-electric double-layer saturation state, and the change in contact area under pressure approaches zero, thereby ensuring that the electrical signal response of the central reference electrode 12 is mainly modulated by the ambient temperature.

[0065] The working principle of this embodiment is as follows: When a normal pressure is applied from the outside, the force-guiding structure layer 40 transmits the load to the four peripheral force-receiving electrodes 11 through the annular contact area 42. The ionization-sensitive layer 20 above the peripheral force-receiving electrodes 11 undergoes compression deformation, and the contact area between the microstructure and the upper electrode layer 30 changes, causing the electrical signal output by the peripheral force-receiving electrodes 11 to modulate with the pressure. At the same time, since the projection of the central cavity 41 covers the central reference electrode 12, and there is no initial interface gap between the saturated contact ion membrane 21 and the central reference electrode 12, the central reference electrode 12 basically does not participate in the mechanical load transmission, and its output electrical signal mainly changes with the ambient temperature. By synchronously acquiring the force channel signal output by the peripheral force-receiving electrodes 11 and the temperature reference signal output by the central reference electrode 12, a temperature drift mapping relationship between the two is established, and real-time temperature drift compensation is performed on the force channel signal. The normal force and tangential force components can be accurately reconstructed under different ambient temperatures, achieving high-precision three-dimensional force sensing.

[0066] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An ionized three-dimensional force sensor with a central reference electrode, characterized in that, include: The lower electrode layer includes a plurality of peripheral force-bearing electrodes arranged symmetrically, and at least two central reference electrodes located in the area enclosed by the peripheral force-bearing electrodes. An ionization sensitive layer is disposed above the lower electrode layer and forms contact interfaces with the peripheral force-bearing electrodes and the central reference electrode, respectively. The upper electrode layer is disposed on the side of the ionization sensitive layer opposite to the lower electrode layer; A force-conducting structure layer is disposed on or above the upper electrode layer, the force-conducting structure layer having a central cavity, the projection of the central cavity covering the central reference electrode; The electrical signal response of the peripheral force-bearing electrode is configured to be modulated by both external pressure and ambient temperature. The ionization sensitive layer on the surface of the central reference electrode is subjected to saturated contact treatment to form a saturated contact ion membrane, so that the electrical signal response of the central reference electrode is configured to be modulated only by ambient temperature.

2. The ionized three-dimensional force sensor with a central reference electrode according to claim 1, characterized in that, The peripheral force-bearing electrodes are arranged in a 2×2 square array, a circular array, a fan-shaped array, an arc array, or using interdigitated electrodes; The at least two central reference electrodes are arranged at intervals and together form a central reference region, which is circular, square, cross-shaped or annular island; the at least two central reference electrodes are split dual electrodes, interdigitated reference electrodes or semi-circular opposing electrodes.

3. The ionized three-dimensional force sensor with a central reference electrode according to claim 2, characterized in that, The number of peripheral force-bearing electrodes is four, each forming a quarter-circle, and they are arranged at equal angular intervals along the same circumference to jointly form a ring-shaped force-bearing area. The central reference electrode includes a first semicircular electrode and a second semicircular electrode arranged at intervals along the central axis of symmetry. The first semicircular electrode and the second semicircular electrode together form a circular central reference region. The outer ring diameter of the annular stress-bearing zone is 8mm~12mm, and the inner ring diameter is 3mm~5mm; The diameter of the central reference area is 0.5mm to 1.5mm.

4. The ionized three-dimensional force sensor according to claim 1, characterized in that, The force-guiding structure layer is a hollow hemisphere, hollow truncated hemisphere, annular boss, or micro-dome array structure made of flexible elastomer material.

5. The ionized three-dimensional force sensor according to claim 4, characterized in that, The ratio of the diameter of the central cavity to the diameter of the bottom surface of the force-conducting structure layer is (1:4) to (1:6); the bottom edge of the force-conducting structure layer forms an annular contact area, and the force projection of the annular contact area covers the surrounding force-conducting electrodes.

6. The ionized three-dimensional force sensor with a central reference electrode according to claim 1, characterized in that, The thickness of the saturated contact ion membrane is 15μm to 25μm, and the thickness of the ionization sensitive layer above the peripheral force electrode is 50μm to 70μm.

7. The ionized three-dimensional force sensor according to claim 1, characterized in that, The saturated contact ion membrane is formed by in-situ curing of the ion gel mother liquor on the surface of the central reference electrode. After curing, there is no interface gap between the saturated contact ion membrane and the central reference electrode, so that the electrical signal response of the central reference electrode is configured to be modulated only by the ambient temperature.

8. The ionized three-dimensional force sensor according to claim 1, characterized in that, The materials of the ionization sensitive layer include PVDF-HFP ion liquid system, TPU ion liquid system, PDMS-based ion gel system, CNT composite ionization layer or MXene composite ionization layer.

9. The ionized three-dimensional force sensor according to claim 1, characterized in that, The upper electrode layer is either a continuous conductive layer covering the area corresponding to the surrounding force-bearing electrodes, or a partitioned electrode that corresponds one-to-one with the lower electrode layer.

10. A signal correction method based on the sensor according to any one of claims 1 to 9, characterized in that, include: The force signals output by the peripheral force electrodes and the temperature signals output by the central reference electrode are collected simultaneously. A temperature drift mapping relationship is established between the temperature signal and the force signal; The temperature drift mapping relationship is used to perform real-time temperature drift compensation on the force channel signal to generate a net force response signal. The three-dimensional force components are calculated and output based on the net force response signal.

Images