WO2022116383A1 - 三维力柔性触觉传感器及其制备方法与解耦方法 - Google Patents

三维力柔性触觉传感器及其制备方法与解耦方法 Download PDF

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WO2022116383A1
WO2022116383A1 PCT/CN2021/073336 CN2021073336W WO2022116383A1 WO 2022116383 A1 WO2022116383 A1 WO 2022116383A1 CN 2021073336 W CN2021073336 W CN 2021073336W WO 2022116383 A1 WO2022116383 A1 WO 2022116383A1
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electrode
layer
force
dimensional force
sensor
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PCT/CN2021/073336
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English (en)
French (fr)
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聂宝清
刘坚
陈新建
耿佳蕾
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苏州大学
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Priority to US17/631,479 priority Critical patent/US20220349764A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
    • G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/16—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force
    • G01L5/165—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force using variations in capacitance

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  • the invention relates to the technical field of flexible sensors, in particular to a three-dimensional force flexible tactile sensor and a preparation method and decoupling method thereof.
  • the resistive three-dimensional force sensor is composed of conductive sensing elements such as conductive rubber or metal. Its working principle is that when the sensor is subjected to external force, the built-in conductive unit is compressed or stretched, so that the corresponding local resistance Variety.
  • this approach still suffers from many technical limitations, including complex structural design, resistance to thermal changes, and crosstalk between sensing pixels. Capacitive sensing has led another trend in the development of 3D force sensors due to its high sensitivity, excellent linearity, low power consumption and thermal noise resistance.
  • the technical problem to be solved by the present invention is to provide a three-dimensional force flexible tactile sensor and its preparation method and decoupling method. force detection.
  • the present invention provides a three-dimensional force flexible tactile sensor, comprising a first flexible layer, a porous elastic layer and a second flexible layer arranged in sequence, and a plurality of first electrodes are arranged on the first flexible layer , a second electrode is arranged on the second flexible layer, and both the first electrode and the second electrode are arranged in close contact with the porous elastic layer.
  • the first flexible layer is fabric, plastic or polymer film.
  • the porous elastic layer is prepared from Ecoflex or PDMS.
  • a plurality of first electrodes are prepared on the first elastic layer to obtain a first electrode/elastic composite layer, comprising the following steps:
  • the conductive paste is conductive silver paste or conductive polymer.
  • the preparation of the solution of the porous elastomer includes the following steps:
  • the mixed solution is mixed with the high molecular polymer to obtain a solution of the porous elastomer.
  • the high molecular polymer is Ecoflex-0030.
  • the mold includes a first sub-mold and a second sub-mold, the first sub-mold cooperates with the second sub-mold to form a mold cavity, and the S3 includes:
  • a mold is placed on the second electrode/elastic composite layer, and the cavity of the mold is filled with a solution of the porous elastomer, after which the first electrode/elastic composite layer is covered.
  • the present invention discloses a method for decoupling a three-dimensional force-flexible tactile sensor. Based on the above-mentioned three-dimensional force-flexible tactile sensor, the method includes the following steps:
  • ⁇ Cn is the absolute change of the corresponding capacitance unit
  • a three-dimensional force F' is applied to the sensor, the components Fx', Fy', and Fz' of the three-dimensional force F' are known, and the absolute changes ⁇ C1', ⁇ C2', ⁇ C3' of the capacitances composed of the first electrode and the second electrode are obtained. and ⁇ C4';
  • each group of the sample data includes F x ', F y ', F z ' under the three-dimensional force and the absolute value change of the sensor's capacitance ⁇ C1', ⁇ C2 ', ⁇ C3', ⁇ C4';
  • the m groups of sample data are fitted to obtain the matrix coefficient A', and the updated relationship between the force and capacitance of the sensor is obtained:
  • the present invention proposes a three-dimensional force detection flexible capacitive sensor (PDiF) based on porous elastomer and its decoupling method by introducing porous elastomer as a dielectric layer. It consists of an electrode layer and a porous elastic layer. Due to the coordination of the electrodes, it is equivalent to a plurality of parallel plate capacitors, so that the sensor in the present invention can not only detect the positive mechanical load, but also measure the force tangent to the surface of the sensor, thereby realizing three-dimensional force detection.
  • PiF three-dimensional force detection flexible capacitive sensor
  • the porous elastic layer is used as a dielectric layer, and its porous structure reduces the Young's modulus of the solid elastomer and increases the effective dielectric constant under compression, thereby improving the sensitivity to capacitance.
  • the normal and tangential loads have a synergistic effect on the pores, thereby improving the nonlinear relationship between the capacitance output and the three-dimensional contact force amplitude.
  • the decoupling method can realize the three-dimensional force decoupling analysis, with high calculation efficiency and accurate results.
  • FIG. 1 is a schematic structural diagram and a schematic schematic diagram of the present invention, wherein (a) is a schematic structural diagram of a PDiF sensor, (b) a schematic cross-sectional view of the sensor under the action of normal force and tangential force;
  • Figure 2.1 is a flow chart of electrode fabrication, in which (a) a layer of tape is laminated on cotton cloth (b) the layer of tape is laser cut to obtain the desired pattern. (c) coating the surface of the substrate with silver paste (d) scraping the silver paste into the pattern of the tape layer (e) curing the silver paste and tearing off the remaining tape on the substrate;
  • Figure 2.2 is the flow chart of the preparation of the porous elastomer solution and the flow chart of the sensor assembly, in which (a) the SLD solution is prepared (b) the SLD solution is mixed with Ecoflex A and B in a mass ratio of 1:1 ( c) Preparation of the ECOFLX solution (d-e) Pour and fill the Ecoflex mixture into a rectangular annular cavity (f) Cover the top electrode layer on the Ecoflex solution (g) cure the Ecoflex solution and remove the U-shaped acrylic mold;
  • Figure 3 is a test chart of the sensor, where (a) when one force component (Fy, case A), two force components (Fx and Fy, case B) and three directions (Fx, Fy and Fz, case C) When the external force acts on the sensor, the schematic diagrams of the side view and the top view, (b) and (c) are the differential capacitance and total capacitance changes of the four capacitive units in response to the tangential load of the sensor under different normal forces;
  • Figure 4 is a comparison diagram of the solid elastic layer and the porous elastic layer, in which (a) is the photo of the two, (b) is the electron microscope image of the two, and (c) is the dielectric constant of the two samples with mechanical compression. Schematic diagram of the change of , (d) is a schematic diagram of the relative capacitance change of the two samples under normal load;
  • FIG. 5 is a schematic diagram of the sensor detection in the present invention, wherein (a) is the minimum detectable force in the normal direction, (b) is the minimum detectable force in the tangential direction, (c) is a schematic diagram of the corresponding speed and recovery time, (d) ) is a schematic diagram of the time-resolved response of the sensor to dynamic mechanical loads of 0-6.3N.
  • the present invention discloses a three-dimensional force flexible tactile sensor, which includes a first flexible layer, a porous elastic layer and a second flexible layer arranged in sequence, and a plurality of first electrodes are arranged on the first flexible layer.
  • a second electrode is arranged on the two flexible layers, and both the first electrode and the second electrode are arranged in close contact with the porous elastic layer.
  • the first flexible layer is fabric, plastic or polymer film.
  • the first electrodes may have four.
  • the poroelastic layer can be a flexible polymer material with pores therein, such as PDMS, Ecoflex, and the like.
  • a plurality of first electrodes and second electrodes form a capacitive unit. When the sensor is subjected to three-dimensional pressure, the capacitance value of each capacitive unit is tested to obtain the magnitude and direction of the three-dimensional pressure.
  • the first flexible layer contains four individual electrodes, and the bottom second flexible layer uses a large square common electrode.
  • the first flexible layer and the second flexible layer are separated by a porous elastic layer. This is achieved by forming four parallel plate capacitive cells in the overlapping region between the top and bottom electrodes, where the initial capacitance (C 0 ) in each cell follows the following expression:
  • ⁇ 0 is the vacuum permittivity
  • ⁇ r is the effective relative permittivity of the porous dielectric material
  • a e and d are the overlapping area and distance of the upper and lower electrodes, respectively.
  • the invention also discloses a preparation method of a three-dimensional force-flexible tactile sensor, comprising the following steps:
  • Step 1 Prepare a plurality of first electrodes on the first elastic layer to obtain a first electrode/elastic composite layer; prepare a second electrode on the second elastic layer to obtain a second electrode/elastic composite layer.
  • a plurality of first electrodes are prepared on the first elastic layer to obtain the first electrode/elastic composite layer, comprising the following steps:
  • a tape (50 ⁇ m thick, 3M) is covered on a piece of 150 ⁇ m thick cotton cloth (the base material can be fabric, plastic, polymer film, etc.), using a photolithography machine (VLS2.30 , Universal Laser) in a pre-designed geometric pattern, then the patterned area is peeled off, and the remaining area in the tape is used as a mask (Fig. 2.1b).
  • a conductive silver paste with a volume resistivity of 100 m ⁇ mm was applied to the surface of the cotton/tape (Fig. 2.1c).
  • the electrode material can be pure metal, conductive silver paste, conductive polymer, etc., or the conductive tape can be directly cut into the required pattern, which is directly attached to the base material.
  • Step 2 preparing the solution of the porous elastomer, specifically comprising the following steps:
  • SDS, BBI sodium dodecyl sulfate
  • Li2SO4 , ALDRICH lithium sulfate
  • DI deionized water
  • VORTEX-5 Kylin-Bell
  • Step 3 using the second electrode/elastic composite layer as a base, pouring a porous elastomer solution on the second electrode/elastic composite layer, and covering the first electrode/elastic composite layer;
  • the invention also includes a mold, the mold includes a first sub-mold and a second sub-mold, the first sub-mold cooperates with the second sub-mold to form a mold cavity, the mold is placed on the second electrode/elastic composite layer, and the mold cavity of the mold is The porous elastomer solution is filled in, after which the first electrode/elastic composite layer is covered.
  • Step 4 The solution-curing molding of the porous elastomer between the first electrode/elastic composite layer and the second electrode/elastic composite layer to obtain a flexible sensor.
  • the entire device was left at room temperature for three days, during which time the deionized water was completely evaporated, leaving a large number of pores in the elastomer.
  • the formation of the pores of the porous elastomer can also be formed by 3D printing, or by a processing method such as a template method.
  • the internal pores can be irregular and randomly dispersed pores, or regular-shaped pores arranged in an orderly manner, and the pore size is in the range of 1 ⁇ m to 1 mm.
  • the present invention also discloses a method for decoupling a three-dimensional force-flexible tactile sensor, based on the above-mentioned three-dimensional force-flexible tactile sensor, comprising the following steps:
  • ⁇ Cn is the absolute change of the corresponding capacitance unit
  • each group of sample data includes F x ', F y ', F z ' under the three-dimensional force and the absolute value change of the sensor's capacitance ⁇ C1', ⁇ C2', ⁇ C3', ⁇ C4';
  • the m groups of sample data are fitted to obtain the matrix coefficient A', and the updated relationship between the force and capacitance of the sensor is obtained:
  • Figure 3 is a comparison between the results obtained by the least squares fitting (triangle points) and the experimental data (circle points). Differences between experimentally measured (circle dots) and fitted data (triangular dots) of the relative capacitance changes of the four cells C1, C2, C3 and C4 when the PDiF sensor is subjected to external loads in one, two and three directions Compare.
  • Equation (4)-(6) it can be known that: (1) if only tangential force is applied, C 13 and C 24 are proportional to F y and F x respectively; if only normal force is applied, C tot and F z a linear relationship. This conclusion is similar to that of the three-dimensional force sensor with solid elastomer as the dielectric layer. (2) C tot is largely influenced by the quadratic term of the tangential force in Eq. (6). It results from the convolution of the overlapping area change (increase or decrease) and the simultaneous increase in the permittivity of the dielectric material by the presence of Fx or Fy .
  • the present invention can detect the combined force, that is, can detect the normal force and the tangential force of the sensor at the same time, so as to detect the three-dimensional force.
  • the present invention provides useful clues for understanding how the components of any contact force affect the elastic porous structure and determining the capacitive output in a synergistic manner.
  • Figure 3a illustrates when an external force with one force component (F y , case A), two components (F x and F y , case B) and three directions (F x , F y and F z , case C) acts on
  • the differential capacitance C24 exhibits a linear response to the tangential load ( Fx ) under constant normal force (Fig.
  • the capacitance value of a parallel plate capacitor is determined by the separation distance between electrodes (d), the total overlapping area (A e ), and the effective dielectric constant ( ⁇ r ) of the porous dielectric layer.
  • the presence of porous structures in the elastomer reduces the stiffness of the material. Therefore, the material will deform more under the same external load than a solid elastomer.
  • the pores are gradually closed, and the gas content in the elastomer decreases, resulting in an effective increase in the relative permittivity ⁇ r .
  • FIG. 4a shows photographs and electron microscope images without and with porous elastomer morphology, respectively.
  • Figure 4c compares the dielectric constant of the two samples as a function of mechanical compression.
  • the effective dielectric constant remains at ⁇ 5 throughout the compression range, while the dielectric constant of cellular elastomers increases by 35.58%. This is largely attributable to the closure of air pores, which expel air out of the elastomer and increase the overall dielectric constant.
  • the presence of the porous structure helps to increase the capacitance change under compressive load.
  • the relative capacitance change of the porous elastomer sensor under compressive load is 2.9 times that of the solid elastomer.

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Abstract

本发明公开了一种三维力柔性触觉传感器及其制备方法与解耦方法，包括依次设置的第一柔性层、多孔弹性层和第二柔性层，所述第一柔性层上设置有多个第一电极，所述第二柔性层上设置有第二电极，所述第一电极与第二电极皆与所述多孔弹性层紧贴设置。其传感器不仅可以检测正向的机械负载，而且可以测量与传感器表面相切的力，从而实现三维力的检测。

Description

三维力柔性触觉传感器及其制备方法与解耦方法 技术领域
本发明涉及柔性传感器技术领域，具体涉及一种三维力柔性触觉传感器及其制备方法与解耦方法。
背景技术
随着人工智能的发展，对柔性电子设备的需求越来越大，包括柔性传感器、可穿戴式能量发生器、可穿戴式有机二极管和软体机器人等。在这些最先进的电子设备中，要求许多柔性传感器不仅可以检测到传感器表面的法向力/压力，还需可以同时感测切向载荷。
目前有很多传感原理来检测三维负载，包括压电、电阻、电容和光学技术。作为最常用的方法之一，电阻式三维力传感器由导电橡胶或金属等导电传感元件构成，其工作原理是当传感器受到外力时，导致内置导电单元的压缩或拉伸，使得局部电阻的相应变化。然而，这种方法仍存在许多技术上的限制，包括复杂的结构设计、对热变化和感测像素之间的串扰。而电容式传感由于其高灵敏度、出色的线性度、低功耗和抗热噪声能力引领了三维力传感器发展的另一趋势。
对于柔性传感器的研究，存在以下问题：一方面，不能实现任意方向解耦，灵敏度不佳或不稳定；另一方面，传感器的解耦方法复杂，误差大。
发明内容
本发明要解决的技术问题是提供一种三维力柔性触觉传感器及其制备方法与解耦方法，其传感器不仅可以检测正向的机械负载，而且可以测量与传感器 表面相切的力，从而实现三维力的检测。
为了解决上述技术问题，本发明提供了一种三维力柔性触觉传感器，包括依次设置的第一柔性层、多孔弹性层和第二柔性层，所述第一柔性层上设置有多个第一电极，所述第二柔性层上设置有第二电极，所述第一电极与第二电极皆与所述多孔弹性层紧贴设置。
作为优选的，所述第一柔性层为织物、塑料或高分子薄膜。
作为优选的，所述第一电极具有四个。
作为优选的，所述多孔弹性层为Ecoflex或PDMS制备而成。
作为优选的，包括以下步骤：
S1、在所述第一弹性层上制备多个第一电极，获得第一电极/弹性复合层；在所述第二弹性上制备第二电极，获得第二电极/弹性复合层；
S2、制备多孔弹性体的溶液；
S3、以第二电极/弹性复合层作为基底，在所述第二电极/弹性复合层上浇筑多孔弹性体的溶液，并覆盖第一电极/弹性复合层；
S4、所述第一电极/弹性复合层与第二电极/弹性复合层之间的多孔弹性体的溶液固化成型，获得柔性传感器。
作为优选的，所述S1中，在所述第一弹性层上制备多个第一电极，获得第一电极/弹性复合层，包括以下步骤:
在第一弹性层的一侧贴附胶层，在所述胶层上刻蚀以获得容纳槽；
在所述容纳槽内填设导电浆液，加热使得导电浆液固化；
去除胶层以获得第一电极/弹性复合层。
作为优选的，所述导电浆液为导电银浆或导电聚合物。
作为优选的，所述S2中，制备多孔弹性体的溶液，包括以下步骤：
将十二烷基硫酸钠和硫酸锂混合到去离子水中，获得混合液；
将所述混合液与高分子聚合物混合，获得多孔弹性体的溶液。
作为优选的，所述高分子聚合物为Ecoflex-0030。
作为优选的，还包括模具，所述模具包括第一子模具和第二子模具，所述第一子模具与第二子模具配合形成模腔，所述S3包括：
将模具置于第二电极/弹性复合层上，向所述模具的模腔中填充多孔弹性体的溶液，之后，覆盖第一电极/弹性复合层。
本发明公开了一种三维力柔性触觉传感器的解耦方法，基于上述的三维力柔性触觉传感器，包括以下步骤：
构建传感器受力与电容的关系式：
Figure PCTCN2021073336-appb-000001
其中，
Figure PCTCN2021073336-appb-000002
为第一电极与第二电极之间的初始电容值，ΔCn为对应电容单元的绝对变化量，F x、F y、F z为三维力的分量，n＝1,2,3,4；
检测各个第一电极与第二电极之间的初始电容值C 1 0、C 2 0、C 3 0和C 4 0；
对所述传感器施加三维力F’，三维力F’的分量Fx’、Fy’、Fz’已知，获取第一电极与第二电极组成的电容的绝对变化量ΔC1’、ΔC2’、ΔC3’和ΔC4’；
改变三维力F’的大小和方向，获取m组样本数据，每组所述样本数据包括三维力下的F x’、F y’、F z’和传感器的电容绝对值变化量ΔC1’、ΔC2’、ΔC3’、ΔC4’；
根据最小二乘法，对m组样本数据进行拟合，得到矩阵系数A’，获得更新后的传感器受力与电容关系式:
Figure PCTCN2021073336-appb-000003
对传感器施加未知测试力F 测，测量传感器的电容绝对值变化量ΔC1 测、ΔC2 测、ΔC3 测和ΔC4 测，代入更新后的传感器受力与电容关系式，获得未知测试力F 测力的三个分量F x测、F y测、F z测。
本发明三维力柔性触觉传感器的有益效果：
1、为了使柔性传感器实现更多功能，本发明通过引入多孔弹性体作为介电层，提出了一种基于多孔弹性体的三维力检测柔性电容式传感器(PDiF)及其解耦方法，该传感器由电极层和多孔弹性层组成。由于电极的配合，其相当于多个平行板电容器，使得本发明中的传感器不仅可以检测正向的机械负载，而且可以测量与传感器表面相切的力，从而实现三维力的检测。
2、本发明中多孔弹性层作为介电层，其多孔结构降低了固体弹性体的杨氏模量，并增加了压缩下的有效介电常数，从而提高了对电容的灵敏度。
3、本发明中，法向和切向载荷在多孔上产生协同效应，从而提高了电容输出与三维接触力幅度之间的非线性关系。
本发明三维力柔性触觉传感器的解耦方法的有益效果：解耦方法能够实现三维力解耦分析，计算效率高，结果准确。
附图说明
图1为本发明的结构示意图及原理示意图，其中，(a)为PDiF传感器的结 构示意图，(b)在法向力和切向力作用下传感器的横截面示意图；
图2.1为电极的制作流程图，其中，(a)在棉布上层压一层胶带(b)激光切割胶带层以得到所需图案。(c)在基材表面涂银浆(d)将银浆刮入胶带层的图案中(e)固化银浆并撕掉基材上剩余的胶带；
图2.2为多孔弹性体溶液的制备流程图及传感器组装的流程图，其中，(a)配制SLD溶液(b)将SLD溶液分别与Ecoflex A和B两种成分以1：1的质量比混合(c)制备ECOFLX溶液(d-e)将Ecoflex混合物倒入并填充到矩形环形腔中(f)在Ecoflex溶液上覆盖顶部电极层(g)固化Ecoflex溶液并移除U形丙烯酸模具；
图3为传感器的测试图，其中，(a)当一个力分量(Fy，情况A)、两个力分量(Fx和Fy，情况B)和三个方向(Fx、Fy和Fz，情况C)的外力作用在传感器上时，侧视图和俯视图的示意图，(b)和(c)为四个电容单元的响应传感器在不同法向力作用下对切向载荷的微分电容和总电容变化；
图4为实心弹性层与多孔弹性层的对比图，其中，(a)为两者的照片，(b)为两者的电子显微镜图，(c)为两种样品的介电常数随机械压缩的变化示意图，(d)为两种样品在法向负载作用下的相对电容变化示意图；
图5为本发明中传感器检测示意图，其中，(a)为法向上的最小可检测力，(b)为切向上的最小可检测力，(c)为相应速度与恢复时间的示意图，(d)为传感器对0-6.3N动态机械载荷的时间分辨响应示意图。
具体实施方式
下面结合附图和具体实施例对本发明作进一步说明，以使本领域的技术人员可以更好地理解本发明并能予以实施，但所举实施例不作为对本发明的限定。
参照图1所示，本发明公开了一种三维力柔性触觉传感器，包括依次设置的第一柔性层、多孔弹性层和第二柔性层，第一柔性层上设置有多个第一电极， 第二柔性层上设置有第二电极，第一电极与第二电极皆与多孔弹性层紧贴设置。第一柔性层为织物、塑料或高分子薄膜。第一电极可具有四个。多孔弹性层可为柔性的聚合物材料，其内具有孔隙即可，如PDMS、Ecoflex等。多个第一电极与第二电极组成电容单元，当该传感器受到三维压力时,测试各个电容单元的电容值，即可计算获得三维压力的大小及方向。
参照图1a所示，以横截面图来说明PDiF传感器的工作原理。第一柔性层包含四个独立的电极，底部第二柔性层用一个大的方形公共电极。
第一柔性层和第二柔性层被一多孔弹性层隔开。这种实现方法是在顶部和底部电极之间的重叠区域中形成四个平行板电容单元，其中每个单元中的初始电容(C 0)遵循以下表达式：
Figure PCTCN2021073336-appb-000004
式中，ε 0为真空介电常数，ε r为多孔介质材料的有效相对介电常数，A e和d分别是上下电极的重叠面积和距离。
如图1b所示，当传感器受到法向力(F z)时，介电层会沿z轴方向变形，上下极板之间的距离距离(d)减小，使得电容增大。另外，介电层的机械压缩导致多孔的闭合，介电层的相对介电常数(ε r)增大而进一步提高了电容变化。当传感器受到x轴(F x)或y轴(F y)方向上的切向力时，弹性变形会沿力加载方向改变顶部电极和底部电极的重叠区域(A e)，从而导致相应的电容在此方向上发生变化。
本发明还公开了一种三维力柔性触觉传感器的制备方法，包括以下步骤：
步骤一、在第一弹性层上制备多个第一电极，获得第一电极/弹性复合层；在第二弹性上制备第二电极，获得第二电极/弹性复合层。
其中，在第一弹性层上制备多个第一电极，获得第一电极/弹性复合层，包括以下步骤:
S11、在第一弹性层的一侧贴附胶层，在胶层上刻蚀以获得容纳槽；
S12、在容纳槽内填设导电浆液，加热使得导电浆液固化，其中，导电浆液为导电银浆或导电聚合物；
S13、去除胶层以获得第一电极/弹性复合层。
具体的，如图2.1a所示，将胶带(厚度为50μm，3M)覆盖在一块厚度为150μm棉布(基底材料可以是织物、塑料、高分子薄膜等)上，使用光刻机(VLS2.30，Universal Laser)以预先设计的几何图案，然后剥去图案化区域，胶带中的其余区域用作掩膜(图2.1b)。将体积电阻率为100mΩ·mm的导电银浆涂到棉/胶带表面(图2.1c)。随后，用刮板刮平银浆，使得银浆与胶带的高度持平(图2.1d)，其中电极材料可以是纯金属、导电银浆、导电聚合物等，也可以直接将导电胶带切割成需要的图案，直接贴到基底材料上。用热风枪(SAIKE852D)以100W的功率加热基板20s，在此过程中，银浆完全干燥，然后除去棉布表面上的剩余胶带(图2.1e)，则图案化电极制作完成。
步骤二、制备多孔弹性体的溶液，具体包括以下步骤：
S21、将十二烷基硫酸钠和硫酸锂混合到去离子水中，获得混合液；
S22、将混合液与高分子聚合物混合，获得多孔弹性体的溶液。
具体的，首先，将十二烷基硫酸钠(SDS，BBI)和硫酸锂(Li 2SO4，ALDRICH)混合到去离子(DI)水中，质量比为1：20：100(SDS：Li 2SO4：DI)，然后在旋涡振荡器(VORTEX-5，Kylin-Bell)中震荡20分钟，形成SDS/Li 2SO4/DI(SLD)混合液(图2.2a)。然后将混合液与高分子聚合物混合，如PDMS、Ecoflex等，我们选取的是Ecoflex-0030，通过将制备的混合液分别添加到Ecoflex-0030(SMOOTH-ON)的A部分和B部分中(图2.2b)。具体操作是，将混合液以1：1的质量比添加到Ecoflex的A部分或B部分中，并手动搅拌两种 分离的溶液5分钟。再将两种类型的溶液以1：1的质量比放入烧杯中，再搅拌5分钟，在此期间，去离子水均匀地分散在混合物中。SLD，Ecoflex A部分和B部分的混合物，称为Ecoflex溶液(图2.2c)，再在真空室中抽气15分钟。
步骤三、以第二电极/弹性复合层作为基底，在第二电极/弹性复合层上浇筑多孔弹性体的溶液，并覆盖第一电极/弹性复合层；
本发明还包括模具，模具包括第一子模具和第二子模具，第一子模具与第二子模具配合形成模腔，将模具置于第二电极/弹性复合层上，向模具的模腔中填充多孔弹性体的溶液，之后，覆盖第一电极/弹性复合层。
具体的，如图1.2d所示，将两块U形丙烯酸模具放置在底部电极表面，形成矩形环形腔。将Ecoflex溶液倒入并填充到矩形环形腔中，然后覆盖上电极层(图2.2e，2.2f)。样品在室温下固化半小时，然后将丙烯酸模子从基板上移除(图2.2g)。
步骤四、第一电极/弹性复合层与第二电极/弹性复合层之间的多孔弹性体的溶液固化成型，获得柔性传感器。
具体的，将整个装置在室温下放置三天，在此期间，去离子水被完全蒸发，从而在弹性体中留下大量多孔。
本发明中，多孔弹性体的孔洞的形成还可以通过3D打印，或者通过模板法等加工方法形成。其内部孔可以是不规则随机分散的孔，也可以是排列有序的规则形状的孔洞，孔径大小在1μm～1mm范围内。
本发明还公开了一种三维力柔性触觉传感器的解耦方法，基于上述的三维力柔性触觉传感器，包括以下步骤：
构建传感器受力与电容的关系式：
Figure PCTCN2021073336-appb-000005
其中，
Figure PCTCN2021073336-appb-000006
为第一电极与第二电极之间的初始电容值，ΔCn为对应电容单元的绝对变化量，F x、F y、F z为三维力的分量，n＝1,2,3,4；
检测各个第一电极与第二电极之间的初始电容值C 1 0、C 2 0、C 3 0和C 4 0；
对传感器施加三维力F’，三维力F’的分量Fx’、Fy’、Fz’已知，获取第一电极与第二电极组成的电容的绝对变化量ΔC1’、ΔC2’、ΔC3’和ΔC4’；
改变三维力F’的大小和方向，获取m组样本数据，每组样本数据包括三维力下的F x’、F y’、F z’和传感器的电容绝对值变化量ΔC1’、ΔC2’、ΔC3’、ΔC4’；
根据最小二乘法，对m组样本数据进行拟合，得到矩阵系数A’，获得更新后的传感器受力与电容关系式:
Figure PCTCN2021073336-appb-000007
对传感器施加未知测试力F 测，测量传感器的电容绝对值变化量ΔC1 测、ΔC2 测、ΔC3 测和ΔC4 测，代入更新后的传感器受力与电容关系式,获得未知测试力F 测力的三个分量F x测、F y测、F z测。
具体的，本实施例m＝167，根据最小二乘法在m＝167个数据集上的拟合，得到矩阵系数A’：
Figure PCTCN2021073336-appb-000008
图3为最小二乘法拟合得到的结果(三角点)与实验数据(圆点)对比。当PDiF传感器受到一个、两个和三个方向的外部负载时，四个单元C1、C2、C3和C4的相对电容变化的实验测量值(圆点)和拟合数据(三角点)之间的比较。
结合方程(2-3)，力和电容可以通过以下方程进行预测：
C 13＝(σ t+m×F z)×F y            ⑷
C 24＝(σ t+m×F z)×F x             ⑸
Figure PCTCN2021073336-appb-000009
其中σ t＝0.10，σ n＝0.157，m＝0.05，n＝0.04，p＝0.31。C 13,C 24和C tot定义为:
C 13＝ΔC 1/C 1 0-ΔC 3/C 3 0                ⑺
C 24＝ΔC 2/C 2 0-ΔC 4/C 4 0                ⑻
C tot＝ΔC 1/C 1 0+ΔC 2/C 2 0+ΔC 3/C 3 0+ΔC 4/C 4 0              ⑼
根据方程式(4)-(6)，可知：(1)如果仅施加切向力，则C 13和C 24分别与F y和F x成正比；如果仅施加法向力，C tot与F z成线性关系。该结论与以固体弹性体作为介电层的三维力传感器的结论相似。(2)C tot在很大程度上受到公式(6)中切向力的二次项的影响。它是由于F x或F y的存在使重叠面积变化(增加或减少)和介电材料的介电常数同时增加的卷积而产生的。(3)如果法向力和切向力同时作用于传感器，则C 13，C 24和C tot，都会受到这两个力的协同作用，即F y×F z或F x×F z的影响。如图3，当PDiF传感器受到一个、两个和三个方向的外部负载时，四个单元C1、C2、C3和C4的相对电容变化的实验测量值(蓝点)和拟合数据(红点)之间的比较，结果显示实验数据与拟合数据的均方根误差在3.3％以内。本发明中的解耦方法，计算效率高，结果准确。
本发明具有以下技术效果：
1、本发明能够检测组合力，即能够同时检测传感器的法向力和切向力，从而检测到三维力。
2、现有的传感器解耦方法中，对于通过施加单一的力分量(即Fx、Fy或Fz)来测量电信号，然后建立方程来量化这些单独的力分量和电输出之间的关系，但是，此解耦方法不能适用于两个或三个分量的任意力解耦；而本申请中的解耦方法，能够适用于三维力的解耦，运算速度快，精度高。
3、本发明为理解任意接触力的分量如何影响弹性多孔结构和以协同方式确定电容输出提供了有用的线索。
下面结合具体的实施例对本发明的技术方案予以说明。
(1)对三维力的电容响应
图3a说明了当一个力分量(F y，情况A)、两个分量(F x和F y，情况B)和三个方向(F x、F y和F z，情况C)的外力作用于我们的PDiF传感器时，四个传感单元的相对电容变化(ΔC n/C n 0,n＝1,2,3 and 4)。如情况A所示，传感器在y轴方向的力作用下，四个单元中的相对电容变化都从初始值(平均C n 0＝3.3pF)增加，每个单元增加的范围不同。当切向力F y由0增加到2N时，C 1和C 3分别增加了21.1％和46.3％，在相同的力范围内C 2和C 4增加了31.0％。这主要归因于两个方面：1.在切向力作用下，多孔被拉伸孔隙变小，导致有效介电常数增加，从而使得各单元电容增大；2.切向力改变了上下电极的重叠区域，在这种情况下，C 3的重叠区域增大，C 1的重叠区域减小。最终导致两个相对单元之间电容变化的差异。在情况B中，当PDiF传感器在两个分量(F x和F y的大小相等)的力作用时，四个单元的电容变化可根据重叠区域变化分为两组。在切向力由0增加到2N时，C 1和C 2(第一组)增加了40.5％、C 3和C 4(第二组)增加了20.6％。在C的情况下，当传感器在法向力(3N)和切向力(0～1.5N)同时作用时，切向力方向改变使得四个单元的电容变化被重新分组(第一组C 1和C 4，第二组C 2、C 3)。此外，与情况B相比，两个组合变化多增加10％。所有结果都与上述规则一致。
图3b和3c绘制了传感器差分电容C 24(C 24＝ΔC 2/C 2 0-ΔC 4/C 4 0,)和总电容C tot(C tot＝ΔC 1/C 1 0+ΔC 2/C 2 0+ΔC 3/C 3 0+ΔC 4/C 4 0)相对于法向力(F z)和切向力(F x或 F y)的响应。差分电容C 24在恒定法向力作用下对切向负载(F x)呈现线性响应(图3b)，随着法向负载增加到5N,切向灵敏度σ t(C 24/F x)从0.12N -1增加到0.34N -1。另一方面，四个单元的总电容变化C tot由F z和F x共同控制，这表明两个力分量对四个电容器具有协同效应。如图3c所示，当F z保持不变时，C tot与F x呈非线性关系。同时，在2N的切向载荷下，随着F z从0增加到5N，C tot从1.3增加到2.5。
(2)固体和多孔弹性体的比较
如式1所示，平行板电容器的电容值由电极之间的间隔距离(d)，总重叠面积(A e)和多孔介电层的有效介电常数(ε r)确定。在我们的PDiF传感器的设计中，弹性体中存在多孔结构会降低材料的刚度。因此，与固体弹性体相比，该材料在相同的外部载荷下会产生更大的变形。此外，在外压作用下，多孔逐渐闭合，弹性体中的含气量降低，导致相对介电常数ε r有效增大。
在这里，我们通过实验比较了多孔和固体弹性体材料的介电性能和机械性能。图4a、图4b分别显示了不具有和具有多孔弹性体形态的照片和电子显微镜图像。图4c比较了两个样品的介电常数随机械压缩的变化。对于固体弹性体，有效介电常数在整个压缩范围内保持在～5，而多孔弹性体的介电常数增加了35.58％。这在很大程度上归因于气孔的闭合，孔将空气驱逐出弹性体并增加了整体介电常数。多孔结构的存在有助于增加压缩负载下的电容变化。如图4d所示，多孔弹性体传感器在压缩负载作用下的相对电容变化是固体弹性体2.9倍。
(3)检测限、重复性和响应/恢复时间
我们通过时间分辨实验确定了法向和切向方向上的最小可检测力。记录在5Hz的采样频率下单个传感单元的相对电容变化(图5a和5b)。测得在法向力为110mN、切向力为150mN时，电容的变化分别为0.85％和0.91％。通过分析电容输出曲线的下降沿和上升沿，可见在1.17N的正常负载下，响应和恢复时间大约分别为0.16s和0.71s(图5c)。此外，我们还研究了通过在法向方向 上施加不同的机械载荷(从0到6.3N)来研究机械重复性。对于该范围内所有机械载荷，传感器能够灵敏地响应动态载荷并返回其原始值(图5d)。结果表明，我们的传感器在所施加的力范围内具有出色的可重复性。
以上所述实施例仅是为充分说明本发明而所举的较佳的实施例，本发明的保护范围不限于此。本技术领域的技术人员在本发明基础上所作的等同替代或变换，均在本发明的保护范围之内。本发明的保护范围以权利要求书为准。

Claims (10)

  1. 一种三维力柔性触觉传感器，其特征在于，包括依次设置的第一柔性层、多孔弹性层和第二柔性层，所述第一柔性层上设置有多个第一电极，所述第二柔性层上设置有第二电极，所述第一电极与第二电极皆与所述多孔弹性层紧贴设置。
  2. 如权利要求1所述的三维力柔性触觉传感器，其特征在于，所述第一柔性层为织物、塑料或高分子薄膜。
  3. 如权利要求1所述的三维力柔性触觉传感器，其特征在于，所述第一电极具有四个。
  4. 如权利要求1所述的三维力柔性触觉传感器的制备方法，其特征在于，所述多孔弹性层为Ecoflex或PDMS制备而成。
  5. 一种三维力柔性触觉传感器的制备方法，其特征在于，包括以下步骤：
    S1、在所述第一弹性层上制备多个第一电极，获得第一电极/弹性复合层；在所述第二弹性上制备第二电极，获得第二电极/弹性复合层；
    S2、制备多孔弹性体的溶液；
    S3、以第二电极/弹性复合层作为基底，在所述第二电极/弹性复合层上浇筑多孔弹性体的溶液，并覆盖第一电极/弹性复合层；
    S4、所述第一电极/弹性复合层与第二电极/弹性复合层之间的多孔弹性体的溶液固化成型，获得柔性传感器。
  6. 如权利要求5所述的三维力柔性触觉传感器的制备方法，其特征在于，所述S1中，在所述第一弹性层上制备多个第一电极，获得第一电极/弹性复合层，包括以下步骤:
    在第一弹性层的一侧贴附胶层，在所述胶层上刻蚀以获得容纳槽；
    在所述容纳槽内填设导电浆液，加热使得导电浆液固化；
    去除胶层以获得第一电极/弹性复合层。
  7. 如权利要求6所述的三维力柔性触觉传感器的制备方法，其特征在于，所述导电浆液为导电银浆或导电聚合物。
  8. 如权利要求5所述的三维力柔性触觉传感器的制备方法，其特征在于，所述S2中，制备多孔弹性体的溶液，包括以下步骤：
    将十二烷基硫酸钠和硫酸锂混合到去离子水中，获得混合液；
    将所述混合液与高分子聚合物混合，获得多孔弹性体的溶液。
  9. 如权利要求5所述的三维力柔性触觉传感器的制备方法，其特征在于，还包括模具，所述模具包括第一子模具和第二子模具，所述第一子模具与第二子模具配合形成模腔，所述S3包括：
    将模具置于第二电极/弹性复合层上，向所述模具的模腔中填充多孔弹性体的溶液，之后，覆盖第一电极/弹性复合层。
  10. 一种三维力柔性触觉传感器的解耦方法，基于权利要求3所述的三维力柔性触觉传感器，其特征在于，包括以下步骤：
    构建传感器受力与电容的关系式：
    Figure PCTCN2021073336-appb-100001
    其中，
    Figure PCTCN2021073336-appb-100002
    为第一电极与第二电极之间的初始电容值，ΔCn为对应电容单元 的绝对变化量，F x、F y、F z为三维力的分量，n＝1,2,3,4；
    检测各个第一电极与第二电极之间的初始电容值C 1 0、C 2 0、C 3 0和C 4 0；
    对所述传感器施加三维力F’，三维力F’的分量Fx’、Fy’、Fz’已知，获取第一电极与第二电极组成的电容的绝对变化量ΔC1’、ΔC2’、ΔC3’和ΔC4’；
    改变三维力F’的大小和方向，获取m组样本数据，每组所述样本数据包括三维力下的F x’、F y’、F z’和传感器的电容绝对值变化量ΔC1’、ΔC2’、ΔC3’、ΔC4’；
    根据最小二乘法，对m组样本数据进行拟合，得到矩阵系数A’，获得更新后的传感器受力与电容关系式:
    Figure PCTCN2021073336-appb-100003
    对传感器施加未知测试力F 测，测量传感器的电容绝对值变化量ΔC1 测、ΔC2 测、ΔC3 测和ΔC4 测，代入更新后的传感器受力与电容关系式，获得未知测试力F 测力的三个分量F x测、F y测、F z测。
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