Flexible three-dimensional force touch sensor and preparation method thereof

Abstract

The invention discloses a flexible three-dimensional force tactile sensor and a preparation method thereof, and belongs to the technical field of flexible tactile sensors. The flexible three-dimensional force tactile sensor solves the problem that when an existing flexible three-dimensional force tactile sensor senses tangential force, the wide linear range and the high sensitivity contradict each other, and the requirements that the sensitivity and the linear range can be flexibly adjusted and customized are met. According to the invention, the sensitive layer with transverse gradient change of modulus is constructed in a manner of sleeving and splicing materials with different moduli, so that the sensitivity of the sensitive layer is changed transversely, and the sensitive layer is used for regulating and controlling the change of the sensitivity and the linear range when the sensor detects tangential force; the non-uniformity of the surface stress distribution of the sensitive layer under the action of the tangential load is utilized by utilizing the sensitivity of the non-uniform transverse distribution of the sensitive layer, so that the tangential force sensing performance of the device is further improved, the method is also effective under the normal load, and the three-dimensional force sensor prepared by the method has high sensitivity and wide linear range, and can be applied to the field of sensor devices. The method is widely applied to the aspects of three-dimensional force measurement, direction control and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a flexible three-dimensional force tactile sensor constructed by a suit assembly splicing strategy and a preparation method thereof, and belongs to the technical field of flexible tactile sensors. BACKGROUND

[0002] Flexible tactile sensors have a wide range of applications in human-computer interaction, tactile perception, medical detection, and other fields due to their lightness, thinness, and flexibility. However, traditional flexible tactile sensors can only detect normal pressure, which cannot meet the needs of complex and diverse scenarios. Therefore, the development of flexible three-dimensional force tactile sensors that can simultaneously detect normal force and tangential force has become a research hotspot.

[0003] In recent years, researchers have proposed many different structures of flexible three-dimensional force sensors to improve their performance in sensing three-dimensional forces. For example, the invention patent with application number 202410438410.8 and the name "Flexible piezoresistive three-dimensional force sensor and its preparation method and application" constructs a three-dimensional force sensor by combining a prism protrusion with four piezoresistive sensing units made of pressure-sensitive material. The invention patent with application number 202010264842.3 and the name "A fully flexible capacitive three-dimensional force tactile sensor" constructs a three-dimensional force sensor by combining a square flexible sensing electrode and a circular flexible common electrode with a semi-circular groove structure, which has higher sensitivity and faster response speed. The invention patent with application number 202410950523.6 and the name "A three-dimensional force dual-mode flexible strain sensor for fabric detection" combines capacitive strain sensors and piezoelectric strain sensors to expand the application range of three-dimensional force sensors. The invention patent with application number 202510093447.6 and the name "Flexible multi-dimensional force sensor based on centripetal gradient magnetic field design and its preparation method" constructs a magnetic field with gradient magnetic flux, which makes the sensor have different response slopes at different stress stages and improves the force measurement range of the device. As a three-dimensional force sensor, its performance in detecting tangential force is very important. Few of the above sensor structure designs optimize the performance of the device in detecting tangential force. When sensing tangential force, the stress distribution on the surface of the sensor's sensitive layer is uneven. No researcher has proposed a corresponding structure design to take advantage of this feature, and the device still needs to solve the contradiction between wide linear range and high sensitivity under tangential force.

[0004] In summary, a novel structure is proposed to address the stress characteristics of three-dimensional force sensors under tangential force, thereby enhancing the performance of three-dimensional force sensors in sensing tangential force or multi-dimensional force, solving the contradiction between wide linear range and high sensitivity, and having a profound significance for the performance improvement and application expansion of three-dimensional force tactile sensors. SUMMARY

[0005] In order to solve the conflicting problem between wide linear range and high sensitivity of existing flexible three-dimensional force tactile sensors when sensing tangential force, the present invention provides a flexible three-dimensional force tactile sensor and a preparation method thereof.

[0006] The technical solution of the present invention: One of the objectives of the present invention is to provide a flexible three-dimensional force tactile sensor, which comprises, from top to bottom, a protrusion, a sensitive layer, and an interdigital electrode layer; The sensitive layer is composed of a plurality of material sets with different moduli, wherein the low modulus material set is spliced ​​within the high modulus material; the lower surface of the sensitive layer has a microstructure, and the upper surface is bonded and fixed by PI tape; The protrusions are bonded to the PI tape on the upper surface of the sensitive layer by glue; and the interdigital electrode layer is assembled with the lower surface of the sensitive layer and then encapsulated by the PI tape.

[0007] It is further defined that the sensitive layer is composed of N kinds of materials with different moduli, and the high modulus material of the square ring with an outer side length of 10 mm is the outermost layer, and the outer side lengths are a N-1 , a N-2 , ...a2's square ring material is the middle layer, and the square material with a side length of a1 is the innermost layer, where 0 <a1<a2<…<a N-2 N-1 <10 mm, 1 <E 最外层 / E 最内层 ≤50.

[0008] It is further defined that N is an integer selected from 2-10.

[0009] It is further defined that the shape of the protrusion is a regular tetrahedron, a truncated cone, a cylinder or a hemisphere; the sensitive layer is composed of a set of square or circular low-modulus material and a square ring or circular ring high-modulus material.

[0010] It is further defined that the microstructure is one or more of a regular pyramid array, a regular hemispherical array, a bionic structure, a gradient structure or a random microstructure, and the size of a single microstructure is 1-50 μm.

[0011] It is further defined that the interdigitated electrode layer consists of a common negative electrode and four individual positive electrodes.

[0012] It is further defined that the sensitive layer is a material with a laterally varying modulus constructed by a pore-forming method, an ultraviolet curing method, or a 3D multi-material printing method.

[0013] It is further defined that the sensitive layer is a material with a laterally varying sensitivity constructed by constructing a microstructure with a laterally varying size on the lower surface.

[0014] ​A second object of the present invention is to provide a method for preparing the above-mentioned flexible three-dimensional force tactile sensor, the method comprising the following steps: (1) Preparation of protrusions; The polydimethylsiloxane prepolymer and the curing agent are mixed evenly in a mass ratio of 10:1, poured into a mold, and subjected to bubble removal treatment. The PMMA sheet is then covered on the mold, heated and cured, and demolded to obtain a bulge. (2) Preparation of sensitive layer; First, polydimethylsiloxane prepolymer and curing agent are mixed evenly in a mass ratio of 10:1, poured into a mold with a microstructure, and heated and cured after degassing. After demolding, a high-modulus flexible material with a microstructure on one side is obtained. Conductive ink is sprayed on the microstructured side of the high-modulus flexible material to obtain a low-sensitivity sensitive layer. Then, Ecoflex A liquid and Ecoflex B liquid were mixed in a volume ratio of 1:1 and poured into a mold with a microstructure. After degassing, the mixture was cured at room temperature. After demolding, a low-modulus flexible material with a microstructure on one side was obtained. Conductive ink was sprayed on the microstructured side of the low-modulus flexible material to obtain a highly sensitive layer. Finally, the low-sensitivity sensitive layer is cut into a square ring, and the high-sensitivity sensitive layer is cut into a square, and the square size of the high-sensitivity sensitive layer is consistent with the inner blank size of the square ring of the low-sensitivity sensitive layer, and the two are concentric and the corresponding sides are parallel; on the basis of ensuring that the microstructures of the two are located on the same side, the high-sensitivity sensitive layer is assembled into a whole by attaching PI tape to the other side opposite to the microstructure, thereby obtaining a sensitive layer with a microstructure on the lower surface and a PI tape on the upper surface; (3) Preparation of interdigitated electrode layer; The interdigitated electrode layer is obtained by laser etching a rectangular PET electrode with metallic silver on the surface; (4) Preparation of flexible three-dimensional force tactile sensors; The lower surface of the protrusion prepared in (1) and the upper surface of the sensitive layer prepared in (2) are bonded together with glue, and then the lower surface of the sensitive layer and the interdigitated electrode layer are assembled face to face and packaged with PI tape to obtain a flexible three-dimensional force tactile sensor.

[0015] It is further defined that the heating curing temperature in (1) and (2) is 70°C and the curing time is 3 h.

[0016] It is further defined that the conductive ink in (2) is a mixture of CNTs, TPU and DMF, wherein the concentration of CNTs is 2 mg / ml and the concentration of TPU is 0.67 mg / ml.

[0017] It is further defined that (2) before spraying the conductive ink on the medium-high modulus flexible material and the low modulus flexible material, the surface is subjected to plasma treatment and then placed at 80°C for spraying treatment.

[0018] It is further defined that the plasma surface treatment gas is oxygen and the time is 5 minutes.

[0019] The third object of the present invention is to provide another flexible three-dimensional force tactile sensor, in which the specific sensitive layer is a material with a laterally varying modulus constructed by a pore-making method, an ultraviolet curing method, or a 3D multi-material printing method, or a material with a laterally varying sensitivity is constructed by constructing a microstructure with a laterally varying size on the lower surface of the sensitive layer.

[0020] A fourth object of the present invention is to provide an application of the above-mentioned flexible three-dimensional force tactile sensor, specifically for measuring three-dimensional force of the interface, performing slip detection or game control and other scenarios.

[0021] Beneficial effects of the present invention: The present invention constructs a sensitive layer with a transverse modulus gradient by combining materials of different moduli. This allows for a lateral sensitivity variation, which is then used to control the sensitivity and linear range of the sensor when detecting tangential forces. The non-uniform sensitivity distribution of the sensitive layer exploits the uneven stress distribution on the surface of the sensitive layer under tangential loads, thereby improving the device's performance in sensing three-dimensional forces. This effectively reconciles the conflict between high sensitivity and a wide linear range when sensing tangential forces, enhancing the performance of the three-dimensional force sensor. Compared to existing technologies, the present invention also offers the following advantages: (1) It can improve the sensitivity of the three-dimensional force sensor in sensing tangential force and reconcile the contradictory relationship between high sensitivity and wide linear range, and the effect is better than simply adjusting the modulus of the entire sensitive layer; (2) This strategy can also reconcile the contradiction between high sensitivity and wide linear range when detecting normal force; (3) This strategy can achieve a variety of flexible and rich ways to adjust the performance of the three-dimensional force sensor. By adjusting the number of splicing seeds, splicing size, and modulus difference, the sensitivity and linear range of the sensor can be flexibly adjusted, and the performance of the three-dimensional force sensor in detecting normal force and tangential force can be customized. (4) The three-dimensional force sensor prepared by the present invention has high sensitivity and a wide linear range, can measure the three-dimensional force of the interface, and is applicable to scenarios such as robotic arm grasping and slip detection; (5) The three-dimensional force sensor prepared by the present invention has a relatively small angular resolution and can be applied to angle and direction-related control, such as game control. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A schematic structural diagram of a flexible three-dimensional force tactile sensor provided in Example 1 of the present invention; Figure 2 A flow chart for preparing the flexible three-dimensional force tactile sensor provided in Example 1 of the present invention; Figure 3 SEM photos of the joints of the sensitive layer set prepared in Example 1 (at different magnifications); Figure 4 Schematic diagram of the interdigitated electrode layer prepared in Example 1; Figure 5 Schematic diagram of splicing N sensitive layers with different moduli (2≤N≤10) (unit: mm), where (a) N=2, (b) N>2; Figure 6 Schematic diagram of the E1 element area division when N different modulus sensitive layers are spliced ​​(unit: mm); Figure 7 Performance comparison of the flexible three-dimensional force tactile sensors prepared in Example 1 and Comparative Examples 1-3, where (a) is the electromechanical curve under tangential force Fx, (b) is the electromechanical curve under normal force Fz, and (c) is the linear sensing factor (the product of sensitivity and linear range). Figure 8 Performance comparison of the flexible three-dimensional force tactile sensors prepared in Examples 1 to 3, where (a) is the electromechanical curve under tangential force Fx, (b) is the electromechanical curve under normal force Fz, and (c) is the linear sensing factor (the product of sensitivity and linear range). Figure 9 These are the finite element simulation results of the flexible three-dimensional force sensors prepared in Examples 1-3 and Comparative Examples 1-2 under a tangential force Fx of 1 N, where (a) is a cloud diagram of stress and displacement distribution on the surface of the sensitive layer, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is a comparison diagram of sensitivity under tangential force; Figure 10 These are the finite element simulation results of the flexible three-dimensional force sensors prepared in Examples 1-3 and Comparative Examples 1-2 under a normal force Fz of 1 N, where (a) is a cloud diagram of stress and displacement distribution on the surface of the sensitive layer, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is a sensitivity comparison diagram under normal force; Figure 11Finite element simulation results for the splicing of two modulus sensitive layers when the tangential force Fx is 1 N and the modulus ratio of the outer and inner layers varies. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer along the x-axis, (c) displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 12 Finite element simulation results for the splicing of two modulus sensitive layers when the normal force Fz is 1 N and the modulus ratio of the outer and inner layers varies. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer along the x-axis, (c) displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 13 Finite element simulation results under a tangential force Fx = 1 N when three sets of sensitive layers with different moduli are assembled. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) surface stress distribution curve of the sensitive layer along the x-axis, (c) surface displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 14 Finite element simulation results under a normal force Fz = 1 N when three sets of sensitive layers with different moduli are spliced ​​together. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) surface stress distribution curve of the sensitive layer along the x-axis, (c) surface displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 15 Finite element simulation results for the splicing of three types of modulus sensitive layers when the tangential force Fx is 1 N and the modulus ratio of the outer and inner layers varies. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer along the x-axis, (c) displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 16 Finite element simulation results for the splicing of three types of modulus sensitive layers when the normal force Fz is 1 N and the modulus ratio of the outer and inner layers varies. (a) Surface stress and displacement distribution cloud diagram of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer along the x-axis, (c) displacement distribution curve of the sensitive layer along the x-axis, and (d) relative size of equivalent sensitivity. Figure 17Finite element simulation results under a tangential force Fx = 1 N when splicing sensitive layer sets with different seeding densities, including (a) stress and displacement distribution cloud diagram of the sensitive layer surface, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer surface along the x-axis, (c) displacement distribution curve of the sensitive layer surface along the x-axis, and (d) relative size of equivalent sensitivity. Figure 18 Finite element simulation results under a normal force Fz = 1 N when splicing sensitive layer sets with different splicing inoculum numbers, including (a) stress and displacement distribution cloud diagram of the sensitive layer surface, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve of the sensitive layer surface along the x-axis, (c) displacement distribution curve of the sensitive layer surface along the x-axis, and (d) relative size of equivalent sensitivity. Figure 19 Other properties of the flexible three-dimensional force tactile sensor prepared in Example 1 under tangential load, where (a) is step loading, (b) is loading at different frequencies, (c) is detection limit, (d) is response and recovery time, and (e) is cyclic fatigue test; Figure 20 Other properties of the flexible three-dimensional force tactile sensor prepared in Example 1 under normal load, where (a) is step loading, (b) is loading at different frequencies, (c) is detection limit, (d) is response and recovery time, and (e) is cyclic fatigue test; Figure 21 Schematic diagram of other types of LVS sensitive layers; Figure 22 The three-dimensional force tactile sensor prepared in Example 1 is applied to the measurement of the three-dimensional force of the gripping interface of a robotic arm, where (a) shows the key action of the robotic arm in gripping a glass, and (b) shows the real-time test result curve of the three-dimensional force of the gripping interface; Figure 23 The three-dimensional force tactile sensor prepared in Example 1 is applied to slip detection, where (a) shows the scene where slip occurs, (b) shows the real-time three-dimensional force curve of the test interface, (c) shows the DWT processing of the Fz force signal, (d) shows the DWT processing of the Fx force signal, and (e) shows the DWT processing of the Fy force signal. Figure 24 The test results of the sensor prepared in Example 1 for tangential forces at different angles, where (a) is the test result when Δα=30°, (b) is the test result when Δα=15°, and (c) is the test result when Δα=10°; Figure 25 The three-dimensional force tactile sensor prepared in Example 1 is applied to game control, wherein (a) is the "Snake" game control system, and (b) is the effect of game control; In the figure, 1-bump, 2-PI tape, 3-sensitive layer, 4-conductive layer, 5-interdigitated electrode, 6-flexible PET substrate. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0024] Example 1 like Figure 1 and Figure 2 As shown, the method for preparing a flexible three-dimensional force tactile sensor in this embodiment includes the following steps: (1) Preparation of protrusions; Dow Corning DC184 polydimethylsiloxane prepolymer and curing agent were mixed in a 10:1 ratio by weight and poured into a polytetrafluoroethylene mold, with the liquid volume slightly exceeding the mold's capacity. The mold was then placed in a vacuum pump to remove air bubbles. A smooth PMMA sheet was placed over the mold opening to drain excess liquid. A 50 g weight was placed on the PMMA sheet and the mold was placed in an oven at 70°C for 3 hours to cure. The mold was then removed to obtain a regular square pyramid-shaped protrusion 1, which was then set aside. The specific dimensions of protrusion 1 were: 9.5 × 9.5 mm on the upper surface, 10 × 10 mm on the lower surface, and 4.2 mm in height.

[0025] (2) Preparation of sensitive layer; ① Mix Dow Corning DC184 polydimethylsiloxane prepolymer and curing agent in a mass ratio of 10:1, pour into a mold with a microstructure (the microstructure is a random microstructure, and the specific diameter of a single microstructure is about 50 μm). After vacuuming, leveling and degassing, place it in an oven at 70°C for insulation and curing for 3 hours, and demold to obtain a high-modulus flexible material with a thickness of about 500 μm and a microstructure on one side. The microstructured side of the high modulus flexible material was subjected to plasma surface treatment (oxygen gas for 5 min), placed on a hot plate at 80°C, and sprayed with conductive ink (the conductive ink was a mixture of CNTs, TPU and DMF, with a CNTs concentration of 2 mg / ml and a TPU concentration of 0.67 mg / ml) (using an ultrasonic spraying device, with a spraying pressure of 0.4 MPa, an ultrasonic power of 3.5 W, a conductive ink flow rate of 0.225 ml / min, and a conductive layer thickness of 1-2 μm) to obtain a low-sensitivity sensitive layer with a conductive layer 4.

[0026] ② Smooth-On Ecoflex 00-30 Ecoflex A and Ecoflex B were mixed in a 1:1 ratio by volume and poured into the same microstructured mold used in step ①. The mold was then placed on a flow platform and cured at room temperature for 4 hours. The mold was then demolded, resulting in a low-modulus flexible material with a microstructure on one side and a thickness of approximately 500 μm. The microstructured side of the low-modulus flexible material was plasma treated (oxygen gas for 5 minutes), placed on an 80°C hot plate, and sprayed with a conductive ink (combined with CNTs, TPU, and DMF, with a CNT concentration of 2 mg / ml and a TPU concentration of 0.67 mg / ml) using an ultrasonic spray device at a pressure of 0.4 MPa, an ultrasonic power of 3.5 W, and a conductive ink flow rate of 0.225 ml / min, resulting in a conductive layer thickness of 1-2 μm) to form a highly sensitive layer with conductive layer 4.

[0027] ③ Use a large square cutter (15×15 mm) to cut the low-sensitivity layer prepared in ① (the active area is only 10×10 mm, with the excess for packaging purposes), resulting in a large square low-sensitivity layer. Then, use a small square cutter (6×6 mm) to cut the center of the large square low-sensitivity layer, resulting in a square ring-shaped low-sensitivity layer. Use a small square cutter (6×6 mm) to cut the high-sensitivity layer, resulting in a small square high-sensitivity layer. Ensure that the microstructures of the small square high-sensitivity layer and the square ring low-sensitivity layer are on the same side. Fit the small square high-sensitivity layer into the inner square blank of the square ring low-sensitivity layer. PI tape 2 is adhered to the side opposite the microstructure to form a single unit, resulting in a sensitive layer 3 with a microstructure on the lower surface and PI tape 2 on the upper surface.

[0028] The microscopic morphology of the splicing of the obtained sensitive layer 3 is characterized, and the SEM picture is as follows Figure 3 As stated by Figure 3 It can be seen that the gap at the joint of the suit is very small, and the high-sensitivity and low-sensitivity sensitive layers of the suit have the same random microstructure. The size of a single microstructure is about 50 μm, and a carbon nanotube conductive layer is attached to the surface of the microstructure.

[0029] (3) Preparation of interdigitated electrode layer; The interdigitated electrode layer having interdigitated electrodes 5 is obtained by laser etching a rectangular flexible PET substrate 6 having metallic silver on its surface; Figure 4As shown, the interdigitated electrode 5 consists of a common negative electrode and four individual positive electrodes, and the total working area of ​​the interdigitated electrode is 10×10 mm; each unit is 5×5 mm, each unit has 10 fingers, and the finger gap is 150 μm.

[0030] (4) Preparation of flexible three-dimensional force tactile sensors; The lower surface of the protrusion 1 prepared in (1) and the PI tape 2 on the upper surface of the sensitive layer 3 prepared in (2) are bonded with 8008 glue, and then the lower surface of the sensitive layer 3 is aligned with the interdigital electrodes 5 of the interdigital electrode layer and assembled, and encapsulated with PI tape to obtain a flexible three-dimensional force tactile sensor, abbreviated as LVS-a6 (indicating a sensor prepared by a sensitive layer with lateral variation of sensitivity).

[0031] Example 2 The difference between this embodiment and embodiment 1 is that: (2) in the preparation of the sensitive layer, a small-sized square cutter (4×4 mm) is specifically used to prepare the sensitive layer, and the remaining process steps and parameters are the same as those in embodiment 1, thereby obtaining a flexible three-dimensional force tactile sensor, referred to as LVS-a4.

[0032] Example 3 The difference between this embodiment and embodiment 1 is that: (2) in the preparation of the sensitive layer, a small-sized square cutter (8×8 mm) is specifically used to prepare the sensitive layer, and the remaining process steps and parameters are the same as those in embodiment 1, thereby obtaining a flexible three-dimensional force tactile sensor, referred to as LVS-a8.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 lies in: (2) Preparation of the sensitive layer. Specifically, the low-sensitivity sensitive layer prepared by cutting ① with a large-size square cutter (15×15 mm) is directly used as the sensor sensitive layer. The remaining process steps and parameters are the same as those in Example 1, and a flexible three-dimensional force tactile sensor is obtained, abbreviated as LS (representing a low-sensitivity sensitive layer sensor prepared with a pure high-modulus sensitive layer).

[0034] Comparative Example 2 The difference between this comparative example and Example 1 lies in: (2) Preparation of the sensitive layer. Specifically, the highly sensitive sensitive layer prepared by cutting ② with a large-size square cutter (15×15 mm) is directly used as the sensor sensitive layer. The remaining process steps and parameters are the same as those in Example 1, and a flexible three-dimensional force tactile sensor is obtained, abbreviated as HS (representing a highly sensitive sensitive layer sensor prepared with a pure low modulus sensitive layer).

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that: (2) the preparation of the sensitive layer, specifically, the polydimethylsiloxane prepolymer of Dow Corning DC184 and the curing agent are mixed uniformly in a mass ratio of 10:1 to obtain a PDMS glue to be cured, which is set aside; the Ecoflex A liquid and the Ecoflex B liquid of Smooth-On Ecoflex 00-30 are mixed uniformly in a volume ratio of 1:1 to obtain an Ecoflex glue to be cured, which is set aside; the PDMS glue to be cured and the Ecoflex glue to be cured are mixed in a volume ratio of 1:2, poured into a mold with a microstructure, and after vacuuming, leveling and degassing, placed in an oven at 70°C for heat preservation and curing for 3 hours, and demolded to obtain a medium modulus flexible material with a microstructure on one side. The microstructured side of the medium-modulus flexible material was plasma-treated (oxygen gas for 5 minutes), placed on an 80°C hot plate, and sprayed with a conductive ink (combined with CNTs, TPU, and DMF, with a CNT concentration of 2 mg / ml and a TPU concentration of 0.67 mg / ml) using an ultrasonic spraying device at a pressure of 0.4 MPa, an ultrasonic power of 3.5 W, and a conductive ink flow rate of 0.225 ml / min, resulting in a conductive layer thickness of 1-2 μm) to form a medium-sensitivity sensing layer. The prepared medium-sensitivity sensing layer was cut using a large square cutter (15×15 mm) and used directly as the sensor sensing layer. The remaining process steps and parameters were the same as in Example 1, resulting in a flexible three-dimensional force tactile sensor, abbreviated as MS (denoting a medium-sensitivity sensing layer sensor prepared using a pure medium-modulus sensing layer).

[0036] Application Examples A single 3D force sensor consists of four elements, E1-E4, manufactured identically. Theoretically, their output electrical signals are similar under the same load. However, actual assembly and packaging processes can cause variations in the consistency of the four element output signals. This can be reduced by normalizing the electrical signals of each element to approximately the average of the four elements. Normalized data from all four elements is similar, allowing each element to independently characterize the device's performance. Here, the normalized data from element E1 is used as a representative representation for each device (the equivalent sensitivity in the simulation also extracts data from the E1 region). Furthermore, due to the symmetry of the four-element arrangement, the device's performance when sensing Fx and Fy is similar. Here, the data at Fx represents the device's sensing of tangential force, and the data at Fz represents the device's sensing of normal force.

[0037] (1) The performance of the flexible three-dimensional force tactile sensor prepared in Example 1 and Comparative Examples 1 to 3 was characterized. The results are as follows: Figure 7As shown in the figure, compared with LS, MS and HS sensors, LVS sensor improves sensor sensitivity while taking into account a better linear range. Figure 7 As can be seen in (a), the LVS device has a sensitivity of 14.59 μA / N and a linear range of 0-10 N under the tangential force Fx. Figure 7 As can be seen in (b), the LVS device has a sensitivity of 17.57 μA / N and a linear range of 0-10 N under the action of the normal force Fz. In order to evaluate the comprehensive performance of the device and whether it has both high sensitivity and a wide linear range, the overall performance of the sensor can be intuitively presented by calculating the product of sensitivity and linear range LSF (Linear Sensing Factor). The larger this value is, the better the overall performance of the sensor. Figure 7 As shown in (c), it can be seen from the figure that the LSF of the LVS sensor is the largest under both tangential and normal forces, indicating that the LVS sensor has both high sensitivity and wide linear range in both tangential and normal directions, and the effect is better under tangential force.

[0038] (2) The performance of the flexible three-dimensional force tactile sensor prepared in Examples 1 to 3 above was characterized. The results are as follows: Figure 8 As shown in the figure, under the two modulus sensitive layer splicing modes, as the inner layer size a gradually increases (see splicing size Figure 5 (a)), the sensitivity of the sensor gradually increases, but the linear range gradually decreases. By comparing the LSF of different sensors, when a is 6 (Example 1), the sensor performance is the best.

[0039] (3) In order to discuss the effect of the change in splicing size on the device performance when the sensitive layer is composed of two materials with different moduli, finite element simulation is used to discuss the following: like Figure 5 As shown in (a), the side length of the inner material is a, and the outer side length of the outer material is 10, where 0 <a<10,在外层材质是PDMS,内层材质是Ecoflex时,模拟内层尺寸变化时,敏感层表面应力和位移的分布情况,以及等效灵敏度相对大小的变化(这里的等效灵敏度仅反映相对大小趋势,不反映实际数值和比例,后文同理)。

[0040] Specifically, the performance of the sensitive layers prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was simulated. The simulation results are shown in FIG. Figure 9 and 10 As shown ( Figure 9 is the simulation result under tangential force Fx=1 N, Figure 10is the simulation result under normal force Fz=1 N). As can be seen from the figure, as the size of the inner Ecoflex changes, the sensitivity also changes. The larger a is, the greater the sensitivity is, and it is between the LS and HS sensitivities. Figure 9 (d) and Figure 10 (d) It can be seen that the simulation and experimental rules are consistent, which shows that the device performance can be effectively adjusted and customized by adjusting the splicing size.

[0041] (4) In order to discuss the effect of the difference between the modulus of the outer layer material and the modulus of the inner layer material on the device performance when the sensitive layer is composed of two materials with different moduli, finite element simulation is used to discuss the following: like Figure 5 As shown in (a), the inner layer size a=6 is fixed and the inner layer material modulus E is maintained. 内 =0.1 MPa unchanged, adjust the outer material modulus E 外 The change of E 外 / E 内 =R, where 1 <R≤50,模拟了5种模量差异下的结果,即R=2、5、10、30、50时的情况。

[0042] The simulation results are as follows Figure 11 and 12 As shown ( Figure 11 is the simulation result under tangential force Fx=1 N, Figure 12 is the simulation result under normal force Fz=1 N). As can be seen from the figure, as the modulus of the outer layer continues to increase, the difference in stress and displacement distribution between the outer and inner layers becomes larger and larger, and the sensitivity of the device continues to decrease. It can be seen that by adjusting the difference in modulus of the inner and outer layers, the performance of the device can be effectively adjusted and customized.

[0043] (5) In order to discuss the effect of the change in splicing size on the sensor performance when the sensitive layer is composed of three sets of materials with different moduli, a finite element simulation is conducted as follows: like Figure 5 As shown in (b), the moduli of the three sensitive layers are fixed, where the moduli of the inner layer, middle layer and outer layer are 0.1, 0.5 and 1 MPa respectively, and the side length a1 of the inner layer material and the outer side length a2 of the middle layer material are adjusted, where 0 <a1<a2<10,模拟了6种套装拼接尺寸下的结果,即(a1,a2)=(2,4)、(2,6)、(2,8)、(4,6)、(4,8)、(6,8)时的情况。

[0044] The simulation results are as follows Figure 13 and 14 As shown ( Figure 13 is the simulation result under tangential force Fx=1N, Figure 14is the simulation result under the normal force Fz=1N). As can be seen from the figure, as the sizes of the inner and middle layers change, the stress and displacement distributions in the inner, middle, and outer layers also change accordingly. The device sensitivity is affected by both a1 and a2, showing a regular spatial distribution. It can be seen that by adjusting the sizes of the inner and middle layers, the device performance can be adjusted and customized more flexibly and richly.

[0045] (6) In order to discuss the effect of the change in modulus difference on the device performance when the sensitive layer is composed of three materials with different moduli, a finite element simulation is conducted as follows: like Figure 5 As shown in (b), the dimensions of the inner and middle layers are fixed, where the inner layer side length a1 = 3.33 and the middle layer outer side length a2 = 6.67, and the inner layer material modulus E is maintained. 内 =0.1 MPa unchanged, adjust the outer material modulus E 外 and the middle layer material modulus E 中 The change of E 外 / E 内 =R1,E 中 / E 内 =R2, where 1 <R2<R1≤50,模拟了6种模量差异下的结果,即(R1,R2)=(5,2.5)、(10,2.5)、(10,5)、(20,2.5)、(20,5)、(20,10)时的情况。

[0046] The simulation results are as follows Figure 15 and Figure 16 As shown ( Figure 15 is the simulation result under tangential force Fx=1 N, Figure 16 is the simulation result under the normal force Fz=1 N). As can be seen from the figure, with the change of the modulus of the middle and outer layers, the stress and displacement distribution in the inner, middle and outer layers also change accordingly. The device performance is jointly affected by R1 and R2, showing a regular spatial distribution. It can be seen that by adjusting the modulus difference between the materials of the three sensitive layers, the device performance can be adjusted and customized more flexibly and richly.

[0047] (7) In order to discuss the effect of the number of sensitive layers involved in the splicing on the performance of the device after splicing when the set splicing strategy is adopted, a finite element simulation is conducted, as follows: like Figure 5 As shown in the figure, when the splicing seed number is adjusted, the splicing size is evenly divided horizontally; the material modulus increases evenly from the innermost layer to the outermost layer, and the fixed E 最内 =0.1 MPa, E 最外= 1 MPa, and the sensitive layer is composed of N kinds of materials with different modulus, where 2 ≤ N ≤ 10. The simulation results of five different N values, i.e., N = 2, 3, 5, 7, and 10, are shown.

[0048] The simulation results are shown in Figs. Figure 17 and Figure 18 The simulation results of the tangential force Fx = 1 N are shown in Fig. Figure 17 The simulation results of the normal force Fz = 1 N are shown in Fig. Figure 18 It can be seen from the figures that as the number of splicing increases, the stress and displacement distribution on the different modulus material regions of the sensitive layer also changes. The performance of the device is greatly affected by the number of splicing. The tangential sensitivity first decreases and then increases with the increase of N, which indicates that the more the number of splicing, the more complete the utilization of the unevenly distributed stress. The normal sensitivity continuously decreases with the increase of N, and when N ≥ 5, the sensitivity change is not obvious. The more the number of splicing, the more complex the mutual restriction between the layers, and the more difficult the actual splicing operation. From the practical operation point of view, N = 2 or 3 is better.

[0049] Further, the approximate expression of the force-electricity curve of the device after splicing is derived as follows: Under the splicing mode, by reasonably combining the normal force-electricity curve data of the unspliced device in the experiment and the average normal force data of each region obtained by simulation, the trend of the force-electricity curve of the spliced device can be roughly predicted. The principle is as follows: When the number of sensitive layers participating in splicing is N, the splicing condition is shown in Fig. Figure 5 Since the size distribution of the four elements is similar, the E1 element is taken as the analysis object, as shown in Fig. Figure 6 The E1 element region division schematic diagram after splicing is shown. Here, the different splicing regions are divided into A1-A N , and the electrical signal is taken as an example.

[0050] Since the A1-A N regions are in parallel relationship in the circuit, the total current of the E1 region is the sum of the currents provided by each region, as shown in equation (1) (1) wherein, I E1 I1 represents the total current of the E1 region, Ia i represents the current provided by the A

[0051] The current provided by the A i region can be represented as the current size in the unspliced state (i.e., the E1 region material is all A i region material) and the area percentage of the A i region after splicing The product of , as shown in formula (2); (2) in and The expressions are (3) and (4) respectively; (3) (4) in A after splicing i The average normal force on the region under load F (obtained by extracting simulation data), Indicates A i The functional relationship between the normal force and the current in the unjointed state (which can be obtained experimentally); A after splicing i The area of ​​the region, It represents the total area of ​​E1 region.

[0052] set up 、 and A represents the external loads Fz, Fx and Fy respectively. i The average normal force on the region, combining equations (1)-(4), we can get the approximate expressions (5)-(7) of the current in region E1 under the corresponding uniaxial force; (5) (6) (7) in, 、 and represents the total current output from region E1 under uniaxial forces Fz, Fx, and Fy, respectively. λz, λx, and λy represent the device's correction coefficients in the z, x, and y directions, respectively, which can be obtained by comparing experimental data. This formula can be used to predict the electromechanical curve of the assembled device and further predict its more comprehensive performance, facilitating process parameter optimization and device performance customization.

[0053] Figure 19 The other performances of the sensor prepared in Example 1 under a tangential load Fx are demonstrated. As can be seen from the figure, the device exhibits a good step response under a step load of Fx = 0-10 N; the device can sense tangential loads of different frequencies; the minimum detection limit is 10 mN; the response and recovery times are 100 ms and 90 ms, respectively; and good stability is shown after 7200 cycle tests under a load of Fx = 0.1-1 N.

[0054] Figure 20 The other performances of the sensor prepared in Example 1 under a normal load Fz are demonstrated. As can be seen from the figure, the device exhibits a good step response under a step load of Fz=0-10 N; the device can sense normal loads of different frequencies; the minimum detection limit is 30 mN; the response and recovery times are 70 ms and 50 ms, respectively; and good stability is shown after 7200 cycle tests under a load of Fz=0.1-1 N.

[0055] (8) The sensitive layer with transversely varying sensitivity provided by the present invention can also be a material with transversely varying modulus constructed by a pore-forming method, an ultraviolet curing method, or a 3D multi-material printing method, thereby constructing a sensitive layer with transversely varying sensitivity; and by changing the size of the microstructure on the lower surface of the sensitive layer, a microstructure with transversely varying size is constructed, thereby constructing a sensitive layer with transversely varying sensitivity, such as Figure 21 shown.

[0056] (9) The flexible three-dimensional force tactile sensor prepared in Example 1 is applied to a robotic arm, such as Figure 22 As shown in the figure, the real-time measurement results of the three-dimensional force of the gripping interface during the process of the robot arm gripping the glass are as follows: Figure 22 As shown in (b), it can be seen from the figure that the prepared three-dimensional force sensor can measure the three-axis force components of the grasping interface in real time and correctly reflect the changes in the component forces under key actions in grasping. For example, 1. When clamping, the interface Fz and Fx increase (indicating that the mechanical claw is difficult to clamp in parallel and there is a tangential force component), 2. When lifting the cup or 3. pouring water into the cup, Fx and Fy decrease (the tangential force of the interface increases due to gravity), 4. When putting it down and releasing it, the three-axis force fluctuates and decreases to 0. It can be seen that the prepared sensor can realize real-time and accurate measurement of three-dimensional force.

[0057] (10) The flexible three-dimensional force tactile sensor prepared in Example 1 is applied to the detection of slippage during three-dimensional force detection on the interface, as shown in FIG. Figure 23 As shown, Figure 23 (a), Slip is a high-frequency action. The test device quickly moves the upper pressure plate left and right to simulate the slip scenario, such as Figure 23 (b) The entire test process is divided into five stages: I slow loading stage, II holding stage, III sliding stage, IV holding stage, and V slow unloading stage; Figure 23 (c)-(e), by performing discrete wavelet transform (DWT) on the three-axis force signal output by the sensor, the high-frequency components in the signal can be extracted, and the occurrence and time of slip can be discovered. Combining the data after the three-directional transformation and reasonably setting the detail coefficient threshold, the occurrence and approximate direction of slip can be accurately determined.

[0058] (11) The flexible three-dimensional force tactile sensor prepared in Example 1 was used to test the tangential forces at different angles. The results are as follows: Figure 24 As shown in the figure, the normal force Fz = 4 N is kept constant during the test, the tangential force Ft is kept constant at 1.6 N, and the angle α with the positive direction of the X axis changes in different increments Δα within 0-360°. Figure 24 As can be seen from (a)-(c), the prepared three-dimensional force sensor can accurately distinguish tangential forces at different angles, and the minimum distinguishable angle change is 10°.

[0059] (12) The flexible three-dimensional force tactile sensor prepared in Example 1 can be used to control the game. The results are as follows: Figure 25 As shown, Figure 25 (a) By combining the prepared sensor with back-end signal processing and related software modules, a "Snake" game control system was constructed; Figure 25 (b) It can be seen that the prepared three-dimensional force sensor can be used as a game controller to realize the manipulation of game characters. The movement of the target is controlled by applying forces of different sizes and directions to the sensor. The size of the normal force can be used as a judgment standard for starting or pausing the game. When the normal force is ≥1 N, the game starts, otherwise the game is paused. The tangential force can be used as a direction vector to control the movement direction of the game character.

[0060] The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A flexible three-dimensional force tactile sensor, characterized in that: From top to bottom, there are protrusions, sensitive layer and interdigital electrode layer; The sensitive layer is composed of a plurality of material sets with different moduli, wherein the low modulus material set is spliced ​​within the high modulus material; the lower surface of the sensitive layer has a microstructure, and the upper surface is bonded and fixed by PI tape; The protrusions are bonded to the PI tape on the upper surface of the sensitive layer by glue; and the interdigital electrode layer is assembled with the lower surface of the sensitive layer and then encapsulated by the PI tape.

2. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that: The sensitive layer is made of N kinds of materials with different moduli. The high modulus material of the square ring with an outer side length of 10 mm is the outermost layer. N-1 , a N-2 , ...a2's square ring material is the middle layer, and the square material with a side length of a1 is the inner layer, where 0 <a1<a2<…<a N-2 N-1 <10 mm, 1 <E 最外层 / E 最内层 ≤50.​ 3. The flexible three-dimensional force tactile sensor according to claim 2, characterized in that: Said N is selected from an integer of 2-10.

4. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that: The shape of the protrusion is a regular tetrahedron, a truncated cone, a cylinder or a hemisphere; the sensitive layer is composed of a square or circular low-modulus material and a square ring or circular high-modulus material; the microstructure is one or more of a regular pyramid array, a regular hemispherical array, a bionic structure, a gradient structure or a random microstructure, and the size of a single microstructure is 1-50 μm.

5. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that: The interdigitated electrodes consist of a common negative electrode and four individual positive electrodes.

6. A method for preparing the flexible three-dimensional force tactile sensor according to any one of claims 1 to 5, characterized in that: include: (1) Preparation of protrusions; The polydimethylsiloxane prepolymer and the curing agent are mixed evenly in a mass ratio of 10:1, poured into a mold, and subjected to bubble removal treatment. The PMMA sheet is then covered on the mold and heated and cured to obtain a protrusion. (2) Preparation of sensitive layer; First, polydimethylsiloxane prepolymer and curing agent are mixed evenly in a mass ratio of 10:1, poured into a mold with a microstructure, and heated and cured after degassing to obtain a high-modulus flexible material with a microstructure on one side. Conductive ink is then sprayed on the microstructured side of the high-modulus flexible material to obtain a low-sensitivity sensitive layer. Then, Ecoflex A liquid and Ecoflex B liquid were mixed in a volume ratio of 1:1 and poured into a mold with a microstructure. After degassing, the mixture was cured at room temperature to obtain a low-modulus flexible material with a microstructure on one side. Conductive ink was then sprayed on the microstructured side of the low-modulus flexible material to obtain a highly sensitive layer. Finally, the low-sensitivity sensitive layer is cut into a square ring, and the high-sensitivity sensitive layer is cut into a square, and the square size of the high-sensitivity sensitive layer is ensured to be consistent with the internal blank size of the square ring of the low-sensitivity sensitive layer, and the two are concentric and the corresponding sides are parallel; on the basis of ensuring that the microstructures of the two are located on the same side, the high-sensitivity sensitive layer is assembled into a whole by attaching PI tape to the other side opposite to the microstructure, thereby obtaining a sensitive layer with a microstructure on the lower surface and fixed on the upper surface by PI tape; (3) Preparation of interdigitated electrode layer; The interdigitated electrode layer is obtained by laser etching a rectangular PET electrode with metallic silver on the surface; (4) Preparation of flexible three-dimensional force tactile sensors; The lower surface of the protrusion prepared in (1) and the upper surface of the sensitive layer prepared in (2) are bonded together with glue, and then the lower surface of the sensitive layer and the interdigitated electrode layer are assembled face to face and packaged with PI tape to obtain a flexible three-dimensional force tactile sensor.

7. The preparation method according to claim 6, characterized in that (2) The conductive ink is a mixture of CNTs, TPU and DMF, where the concentration of CNTs is 2 mg / ml and the concentration of TPU is 0.67 mg / ml.

8. The preparation method according to claim 6, characterized in that (2) Before spraying conductive ink on medium and high modulus flexible materials and low modulus flexible materials, plasma surface treatment is performed and then placed at 80°C for spraying treatment.

9. A flexible three-dimensional force tactile sensor, characterized in that: The sensitive layer described in claim 1 is a material with a laterally varying modulus constructed by a pore-forming method, an ultraviolet curing method, or a 3D multi-material printing method, or a material with a laterally varying sensitivity constructed by constructing a microstructure with a laterally varying size on the lower surface of the sensitive layer.

10. An application of the flexible three-dimensional force tactile sensor according to claim 1 or 9, characterized in that: Used to measure three-dimensional interface forces, perform slip detection or game control.

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