Three-dimensional hollow hemispheroid flexible pressing sensor, test system and preparation method

Abstract

The invention discloses a three-dimensional hollow hemispheroid flexible pressing sensor, a test system and a preparation method, and the sensor comprises a silicone rubber matrix which is a hollow hemispheroid; the silicone rubber matrix is formed by printing silica gel ink in a support matrix; the sensing path is embedded in the silicon rubber matrix; the sensing path is formed by printing sensing ink; when the sensor is subjected to external pressure, the sensor sinks inwards to cause local deformation of the silicon rubber base body, so that the physical dimension of the sensing path embedded in the silicon rubber base body is changed, and the resistance value of the sensing path is changed. According to the invention, the hemispherical sensor is prepared by using a multi-material embedded 3D printing process, the sensing conductive path can be directly embedded into the sensor shell substrate for manufacturing, synchronous manufacturing and molding of the sensing path and the silica gel shell substrate are realized, and secondary processing is not needed; and the preparation method is simple. The method can be widely applied to the technical field of flexible sensing.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensing technology, and in particular to a three-dimensional hollow hemispherical flexible pressure sensor, a testing system and a preparation method. Background Art

[0002] Collision detection is particularly important in the fields of robotics, autonomous driving, and medical devices because it is directly related to the safety and accuracy of equipment operation. Traditional collision detection sensors are mostly based on rigid materials or structures, which are difficult to adapt to irregular surfaces or complex environments, and are easily worn or damaged due to frequent force. With the development of smart devices and robotics technology, the application demand for flexible sensors in tactile perception, force feedback, and safety monitoring is increasing. At present, flexible sensors generally have only simple structures, and their conductive paths are generally two-dimensional planar structures. When the sensor is expanded from a simple three-dimensional solid structure to a hollow three-dimensional structure, complex processes or additional support structures are required, and when its conductive path changes from a two-dimensional planar structure to a three-dimensional spatial structure, it is difficult to manufacture, which seriously restricts the design of flexible sensors with complex shapes and structures and limits their potential applications. Therefore, in order to overcome these limitations, there is an urgent need for a simple and universal method that can build a flexible sensor with a three-dimensional complex structure through one-step manufacturing without additional support structures and complex processes, realize the simultaneous manufacturing and molding of its silicone shell substrate and conductive sensing path, increase the flexibility of design and preparation, and use it for collision detection.

[0003] The first prior art scheme discloses a three-dimensional flexible structure tactile sensor and a preparation method thereof. The tactile sensor is formed by closely stacking a fingerprint imitation layer, a piezoresistive sensing layer, a stretchable electrode layer and a flexible substrate layer from top to bottom. The method mainly uses laser processing technology to cut the flexible substrate and form an arch bridge-shaped three-dimensional flexible structure through directional bending, uses printed electronics technology or template method to manufacture a stretchable electrode layer on the surface of the flexible substrate, uses a composite material formed by chitosan and multi-walled carbon nanotubes to manufacture a piezoresistive sensing layer, and uses a template method to manufacture the surface fingerprint imitation layer microstructure of the sensor, thereby enhancing the sensing ability for friction and vibration, and uses a flexible bonding technology to encapsulate the sensor to obtain a three-dimensional flexible structure tactile sensor that can work continuously and stably. However, the scheme uses laser processing technology, printed electronics technology, and template method to manufacture each component of the sensor separately, and then uses flexible bonding technology to encapsulate the sensor to obtain a three-dimensional flexible structure tactile sensor. It requires multiple steps of preparation, the preparation process is relatively complicated, and each component is prepared separately and cannot be integrated as a whole.

[0004] The second prior art scheme discloses a flexible bending sensor based on a three-dimensional electrode structure and a processing method. The sensor includes a flexible substrate layer, a conductive medium layer and a three-dimensional electrode located on the substrate layer, and an outer packaging and wrapping protective layer. The method treats impurities in the flexible substrate, solidifies liquid metal on the substrate to obtain a three-dimensional electrode; transfers the prepared conductive medium layer of a preset thickness to a substrate with a three-dimensional electrode, presses the conductive medium layer to contact the substrate, and the preset thickness is less than the thickness of the three-dimensional electrode; and packages and wraps the sensor with a protective layer. However, this scheme uses a multi-step complex process to sequentially construct the sensor from the bottom up starting from the substrate, and the process is complicated and has poor versatility.

[0005] The third prior art scheme discloses a flexible pressure sensor based on liquid metal photocuring printing technology. The sensor includes a flexible sensor, a wire and a packaging layer. The flexible sensor is prepared by photocuring printing; the flexible sensor has a microchannel structure inside; the microchannel structure includes two centrally symmetrical channels; each channel is mainly composed of an arc channel I, an arc channel II and a curved channel, and one end of the arc channel I of the two channels is respectively connected to two inlets in the microchannel structure; the curved channel is triangular and convex toward the upper end; the lower part of the flexible sensor is a columnar structure and the upper part is a circular vault structure; the inlets on both sides of the flexible sensor are respectively connected to the wire; the flexible sensor connected to the wire is encapsulated with PDMS to obtain an encapsulation layer of the encapsulated flexible sensor. However, this scheme requires the preparation of an additional encapsulation mold. After the flexible sensor is placed in the groove of the encapsulation mold, PDMS is poured into the encapsulation mold until it just covers the top of the flexible sensor, and the whole is placed on a heating table and heated at a constant temperature for 30 minutes until it is cured and taken out to obtain a flexible pressure sensor based on liquid metal photocuring printing technology. This invention still requires the preparation of an encapsulation mold for casting, and has poor flexibility. Summary of the invention

[0006] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the object of the present invention is to provide a three-dimensional hollow hemispherical flexible pressure sensor for collision detection, a test system and a preparation method.

[0007] The first technical solution adopted by the present invention is:

[0008] A three-dimensional hollow hemispherical flexible pressure sensor, comprising:

[0009] The silicone rubber matrix is ​​in the shape of a hollow hemisphere; the silicone rubber matrix is ​​printed in a supporting matrix using silicone ink;

[0010] A sensing path is embedded in the silicone rubber matrix; the sensing path is printed with sensing ink;

[0011] When the sensor is subjected to external pressure, the sensor will sink inward, causing local deformation of the silicone rubber matrix, which in turn causes the geometric dimensions of the sensing path embedded in the silicone rubber matrix to change, causing the resistance value of the sensing path to change.

[0012] Furthermore, the sensing path includes:

[0013] The conductor body is arranged on the hemisphere in a circuitous structure;

[0014] Two sections of guide wires are respectively connected to two ends of the wire body and are used for external connection wires.

[0015] Furthermore, the diameter of the hemispherical sensor is 30 mm, the thickness of the silicone rubber substrate is 2.2 mm, and in the top view of the hemispherical sensor, the distance between two adjacent conductive paths of the wire body is 2 mm.

[0016] Furthermore, the three-dimensional hollow hemispherical flexible pressure sensor includes a silicone rubber matrix with one or more embedded sensing paths.

[0017] The second technical solution adopted by the present invention is:

[0018] A method for preparing the above-mentioned three-dimensional hollow hemispherical flexible pressure sensor comprises the following steps:

[0019] preparing a support matrix, and transferring the support matrix into a printing container;

[0020] Preparation of silicone ink and sensor ink;

[0021] Model the silicone rubber matrix and slice it to generate the G-code file for printing the silicone rubber matrix and the sensing path;

[0022] Based on the G-code file, silicone ink and sensing ink are used for printing to obtain a hemispherical flexible pressure sensor;

[0023] Insert the wires into the guide wires at the bottom of the sensor and use sealant to bond and encapsulate.

[0024] Further, the material of the support matrix includes high viscosity vinyl silicone oil MP5000, hydrogen-containing silicone oil MH180 and fumed silica A380, wherein high viscosity vinyl silicone oil MP5000 and hydrogen-containing silicone oil MH180 are basic reactants, and fumed silica A380 is a rheology modifier for adjusting the rheology of the support matrix;

[0025] The step of preparing the support matrix and transferring the support matrix into the printing container comprises:

[0026] Adding vinyl silicone oil, hydrogenated silicone oil and fumed silica into a stirring container according to a preset preparation ratio and stirring to obtain a uniformly mixed support matrix;

[0027] The uniformly mixed support matrix is ​​transferred into a printing container, and the printing container is placed in a vacuum degassing barrel for a preset time to remove all bubbles inside the support matrix.

[0028] Furthermore, the preset preparation ratio is: high viscosity vinyl silicone oil mass ratio: 70% to 90%, hydrogen-containing silicone oil mass ratio: 5% to 20%, and fumed silica mass ratio: 2% to 10%.

[0029] Furthermore, the silicone ink is a mixture of Karstedt catalyst ACS-Pt10 and low-viscosity vinyl silicone oil MP450; the sensing ink is a mixture of silicone ink and multi-walled carbon nanotubes. It should be noted that in addition to multi-walled carbon nanotubes, other conductive materials (such as carbon black, etc.) can also be used to prepare sensing inks to construct conductive sensing paths of sensors.

[0030] Furthermore, the silicone rubber matrix is ​​modeled and sliced ​​to generate a G code file for printing the silicone rubber matrix and the sensing path, including:

[0031] Use Solidworks software to model the silicone rubber matrix, slice it using IdeaMaker slicing software, and generate a G-code file for printing the silicone rubber matrix;

[0032] For the G-code file of the sensing path, the spatial coordinates of each point on the designed path are first calculated using the spatial polar coordinate formula, and then the generated spatial coordinate list is converted into a G-code file.

[0033] Furthermore, the hemispherical flexible pressure sensor is obtained by printing with silicone ink and sensing ink based on the G code file, including:

[0034] On the basis of the support matrix, a hemispherical silicone matrix is ​​printed using silicone ink by an embedded 3D printing method;

[0035] Printing the sensing ink in the silicone rubber matrix according to a preset path to form a conductive path embedded in the silicone rubber matrix, so that the silicone rubber matrix and the conductive sensing path are seamlessly integrated;

[0036] After printing is completed, the printed container is placed in a blast heating box for curing to obtain a hemispherical flexible pressure sensor with a three-dimensional hollow structure.

[0037] The third technical solution adopted by the present invention is:

[0038] A collision detection system comprises a hemispherical sensor, a signal processing circuit and a control board. The hemispherical sensor is connected to the control board via the signal processing circuit. The hemispherical sensor is implemented by the three-dimensional hollow hemispherical flexible pressure sensor as described above.

[0039] The beneficial effects of the present invention are as follows: the present invention uses a multi-material embedded 3D printing process to prepare a hemispherical sensor, and the sensing conductive path can be directly embedded in the sensor housing matrix for manufacturing, thereby realizing the synchronous manufacturing and molding of the sensing path and the silicone housing matrix without the need for secondary processing. In addition, the preparation method of the present invention is simple, and thanks to the supporting effect of the supporting matrix on the printing ink, the integrated manufacturing of sensors with a three-dimensional hollow structure can be realized without the need for additional supporting structures and complex preparation processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 This is a structural design diagram of a three-dimensional hollow hemispherical flexible pressure sensor in an embodiment of the present invention;

[0042] Figure 2 is a schematic diagram of a printing path of a hemispherical flexible sensor in an embodiment of the present invention;

[0043] Figure 3 This is a physical picture of a three-dimensional hollow hemispherical flexible pressure sensor in an embodiment of the present invention;

[0044] Figure 4 Schematic diagram of the effect of pressing speed on the change of resistance value of the hemispherical sensor in an embodiment of the present invention;

[0045] Figure 5 Schematic diagram of the effect of pressing depth on the change of resistance value of the hemispherical sensor in an embodiment of the present invention;

[0046] Figure 6 is a schematic diagram of a four-direction collision detection device based on a hemispherical sensor in an embodiment of the present invention;

[0047] Figure 7 is a schematic diagram of a collision test platform based on a hemispherical sensor in an embodiment of the present invention;

[0048] Figure 8 is a schematic diagram of a collision detection experiment scenario in an embodiment of the present invention;

[0049] Fig. 9 Schematic diagram of collision detection voltage output in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0051] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0052] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0053] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0054] In general, in the current flexible sensors, the conductive path is a two-dimensional planar structure, so the conductive and sensing materials can be printed on a flexible substrate according to the designed path by screen printing or using a DIW printing method, and the path is encapsulated with a flexible insulating material after printing. When the path changes from a two-dimensional planar structure to a three-dimensional space structure, the above method is difficult to manufacture effectively. In addition, most of the current sensors with three-dimensional structures require additional support structures or are recombined into a whole through distributed construction, and the process is complicated. Therefore, the present invention proposes a three-dimensional hollow hemispherical flexible press sensor for collision detection and a preparation method thereof, using a multi-material embedded 3D printing process, first printing silicone ink in a support matrix to construct a hollow hemispherical silicone matrix, and then directly embedding the sensing ink in an uncured silicone matrix to print a conductive sensing path, and finally curing and forming synchronously. Therefore, the present invention can realize the integrated manufacturing of a hemispherical flexible press sensor with a three-dimensional hollow structure without the need for additional support structures and molds, and complex processes, and successfully use it for collision detection. Meanwhile, a collision detection system based on a hemispherical sensor is developed, which can effectively distinguish between fast collision and slow pressing, and the hemispherical sensor can be used for collision detection. The present invention is explained in detail below in conjunction with specific embodiments.

[0055] like Figure 1 As shown, this embodiment proposes a three-dimensional hollow hemispherical flexible pressure sensor for collision detection. The three-dimensional hollow hemispherical flexible pressure sensor for collision detection designed in this embodiment (referred to as the detection hemispherical sensor) has a main body of a silicone rubber matrix, and a sensing ink serving as a resistor is embedded inside to sense the external pressure speed and depth. The resistance value R (Ω) of the resistor is related to the resistivity ρ (S / m) of the conductive material itself and the cross-sectional area S (mm 2 ) and the length of the resistor L(m), the calculation formula is:

[0056]

[0057] When subjected to external pressure, the hemispherical sensor will sink inward, causing local deformation of the silicone rubber matrix, which in turn causes the geometric dimensions of the internal embedded sensing path to change, causing the resistance value to increase. This mechanism in which the resistance value changes accordingly due to the change in the size of the conductive material itself is called the geometric effect. At the same time, in addition to the dimensional changes of the sensing path printed by the sensing ink filled with multi-walled carbon nanotubes used in the present invention under the influence of the deformation of the silicone rubber matrix, the microstructure and conductive network formed between the internal multi-walled carbon nanotubes will also be reconstructed under the action of external force, resulting in a change in resistivity ρ. Therefore, under external force pressure, the overall structure of the hemispherical sensor is deformed, and the internal sensing resistance value increases. After the external force is removed, the sensor returns to its original shape and the resistance value decreases.

[0058] As an optional implementation, see Figure 1 The diameter of the hemispherical sensor is 30mm, the thickness of the silicone rubber substrate is 2.2mm, the conductive path is zigzag in the top view, and is a hemispherical arc in three-dimensional space. The spacing of the conductive path after projecting to the horizontal plane is 2mm. There is a guide wire at the starting point and end point of the sensing path to facilitate external wire connection.

[0059] Based on the above three-dimensional hollow hemispherical flexible pressure sensor, this embodiment also provides a method for preparing the sensor, which is as follows:

[0060] First, prepare the support matrix. The main materials of the support matrix are high viscosity vinyl silicone oil MP5000, hydrogen-containing silicone oil MH180 and fumed silica A380. Among them, MP5000 and MH180 are basic reactants, and A380 is a rheology modifier to adjust the rheology of the support matrix. Add the above materials to a stirring container according to a certain preparation ratio (high viscosity vinyl silicone oil mass ratio: 70% to 90%, hydrogen-containing silicone oil mass ratio: 5% to 20%, fumed silica mass ratio: 2% to 10%), use a revolution and rotation vacuum mixer to stir at a speed of 1500 to 2000rpm at normal pressure for 2 to 5 minutes, and then stir at an air pressure of 1kPa for 3 to 7 minutes to obtain a uniformly mixed support matrix. Transfer the matrix to the printing container. Since a small amount of bubbles will be introduced during the transfer process, it is necessary to place the container in a vacuum degassing barrel and degas for 10 to 20 minutes at an air pressure of 1kPa to remove the bubbles inside.

[0061] Then, silicone ink and sensor ink are prepared. The silicone ink is a mixture of Karstedt catalyst ACS-Pt10 and low-viscosity vinyl silicone oil MP450, wherein the Karstedt catalyst ACS-Pt10 contains a platinum catalyst for catalyzing the hydrosilylation reaction, and the concentration of the platinum catalyst is 1000ppm. This concentration is still too high for the required concentration of the platinum catalyst in the ink. Therefore, the catalyst is further diluted with low-viscosity vinyl silicone oil MP450 to obtain a silicone ink with a certain mass fraction (where the mass fraction of the catalyst in MP450 is: 0.8% to 5%), and the silicone ink is stirred for 2 minutes at a speed of 2000rpm and an air pressure of 1kPa using a self-rotating and revolving vacuum mixer. The sensor ink for printing the sensor path is mixed by adding 3% to 7% of multi-walled carbon nanotubes to the silicone ink. After adding the multi-walled carbon nanotubes, first use a glass rod to stir the multi-walled carbon nanotubes into the silica gel ink, and then use a rotary vacuum mixer at a speed of 1500-2000 rpm and an air pressure of 1 kPa for 5-10 minutes to obtain a uniformly mixed sensing ink.

[0062] Next, the hemispherical silicone rubber matrix was modeled using Solidworks software and sliced ​​using IdeaMaker slicing software to generate a G-code file for printing the silicone rubber matrix. As for the G-code file of the sensing path, the spatial coordinates of each point on the design path were first calculated using the spatial polar coordinate formula:

[0063]

[0064] Where R(m) is the radius of the sphere, θ and Represents the altitude angle and polar angle (°) respectively. The generated spatial coordinate list is then converted into a G-code file using an open source Python script. The final printing path of the hemispherical silicone rubber substrate and the sensor path is as follows: Figure 2 shown.

[0065] During the printing process, the hemispherical silicone matrix is ​​first printed using silicone ink through an embedded 3D printing method. Thanks to the supporting effect of the support matrix on the printing ink, the silicone ink can print a hemispherical silicone matrix with a three-dimensional hollow structure without any additional support structure. Since it takes a long time for the silicone ink to cure the support matrix at room temperature, the printing path of the silicone ink remains uncured after the silicone rubber matrix is ​​printed. Therefore, the sensing ink can be directly printed in the silicone rubber matrix according to the specified path to form a conductive path embedded in the silicone shell matrix, so that the silicone shell matrix and the conductive sensing path can be seamlessly integrated. After printing is completed, the printing container is placed in a blast heating box and heated at 70 to 90°C for 2 to 3 hours to accelerate curing. After heating is completed, the cured printed sample can be removed from the supporting matrix, and the uncured silicone oil on the surface can be wiped off with dust-free paper to obtain a hemispherical flexible press sensor with a three-dimensional hollow structure. The actual picture of the printed hemispherical sensor is as follows Figure 3 Then insert the wire into the guide wire at the bottom of the sensor and use sealant to bond and encapsulate it, which is convenient for subsequent testing and wiring in the application.

[0066] In order to test the performance of the manufactured flexible pressure sensor, this experiment used a universal material testing machine to test the resistance change of the sensor for the pressing speed and pressing depth. For the pressing speed test, five sets of pressing and releasing speeds were set, ranging from 1mm / s to 5mm / s, and the pressing depth was constant at 13mm. After pressing to 13mm, it was held for 30s and then released. After being fully released, it was held for another 30s. The test results are as follows Figure 4As shown in the figure, the results show that the resistance change of the sensor is sensitive to the pressing speed. The faster the pressing speed, the higher the rate of change of the resistance value. This is because during the pressing process, the internal conductive material is stimulated by external force, and the conductive network will be destroyed and reconstructed, which will lead to an increase and decrease in resistivity. During the pressing process, destruction and reconstruction occur simultaneously. When the pressing speed is accelerated, the speed of conductive network destruction is higher than the speed of reconstruction, which will lead to a rapid increase in resistivity, making the resistance value increase faster and the peak value of the resistance value change rate larger. After pressing to the lowest point, the pressing rod remains stationary for 30s. At this time, the reconstruction speed of the conductive network of the internal conductive material is greater than the destruction speed, which is reflected in the change of resistance value, that is, the resistance continues to decrease. Since the silicone rubber matrix will also deform when the hemispherical press sensor is pressed, resulting in a change in the size of the sensing path, even if the resistivity of the conductive material is constantly decreasing due to the reconstruction of the conductive network, the overall resistance value will still be higher than the resistance value when it is not pressed. During the release process, the lifting of the pressing rod will also bring external stimulation, which will lead to the destruction and reconstruction of the conductive network inside the conductive material, causing the resistance value to increase. After complete release, the conductive network inside the material is reconstructed, causing the resistance value to slowly drop to the initial value.

[0067] The pressing depth was tested and 6 groups of pressing depths were set, ranging from 2mm to 12mm. The pressing speed was set to 8.33mm / s (500mm / min). The results are as follows: Figure 5 As shown. The results show that the rate of change of the resistance value increases with the increase of the pressing depth. Even at a pressing depth of 2mm, the resistance value will increase to a certain extent. However, due to the small deformation of the silicone rubber matrix, the geometric dimensions of the sensing path are less affected, so the resistance value gradually returns to the initial resistance. At the same time, it can be observed from the pressing force data that since the flexible sensor has a hollow structure, when the pressing depth reaches 12mm, the required pressing force is less than 4N.

[0068] Since the sensor is sensitive to the pressing speed, when the sensor is pressed slowly, the resistance value changes slowly and the resistance value increases less. When the sensor is pressed quickly, the resistance value will increase greatly and change faster. Therefore, the hemispherical sensor can be used for collision detection. Figure 6 As shown, four hemispherical sensors are attached to the four faces of the cube, representing the four directions of "up", "down", "left" and "right", respectively, to detect collisions in the four directions. A rod is connected to the back of the cube to facilitate hand-holding of the device.

[0069] In order to test the collision detection performance of the hemispherical sensor, a collision detection platform was built, such as Figure 7As shown. There is a Python program running in the computer, which is used to detect the voltage value collected by the ADC acquisition module. When a sudden voltage change is detected, the program sends a signal to the Arduino control board through the serial port, and the content is the index value of a certain direction. After receiving the information, the Arduino control board will light up the corresponding indicator light, indicating that a collision has occurred in that direction. After analyzing the resistance value change signal generated by the sensor and the voltage signal in the corresponding voltage divider circuit in advance, the voltage signal detection method set in the experiment is to detect whether the voltage signal on the channel increases by more than 0.5V within 200ms. If it exceeds, it means that a collision has occurred, otherwise no collision has occurred. The test process is to use your hands to quickly collide the four directions in the order of "up", "down", "left" and "right" three times, and then press slowly three times. The actual scenario of collision detection and the experimental effect are shown below. Figure 8 As shown in the figure, in the experiment, every time a quick collision occurs, the indicator light of the corresponding direction will light up, but in the case of slow pressing, the indicator light will not light up, which shows that the detection method used in the experiment can effectively distinguish between collision and pressing. The collected voltage signal is as follows Fig. 9 As shown, it can be observed that in each channel, the voltage signal has a larger and faster increase when a quick collision occurs, while the voltage increase is slower and the growth rate is slower when a slow press occurs. Therefore, through the difference in voltage signals, it is possible to distinguish whether a collision or a slow press occurs.

[0070] Based on the above three-dimensional hollow hemispherical flexible pressure sensor, see Figure 7 This embodiment also provides a collision detection system based on a hemispherical sensor, including: a hemispherical sensor, a signal processing circuit, an Arduino control board, and an indicator light module.

[0071] In summary, the present invention has the following advantages and beneficial effects compared to the prior art:

[0072] (1) The preparation method of the present invention is simple. The present invention uses a multi-material embedded 3D printing process to prepare a hemispherical sensor, and prints the silicone ink and the sensing ink in a supporting matrix according to a specified path in a certain order. Thanks to the supporting effect of the supporting matrix on the printed ink, the integrated manufacturing of a hemispherical flexible pressure sensor with a three-dimensional hollow structure can be achieved without an additional supporting structure. In addition, since it takes a long time for the silicone ink to cure the supporting matrix at room temperature, the printing path of the silicone ink remains uncured after the silicone rubber matrix is ​​printed. Therefore, the sensing ink can be directly printed in the silicone matrix, and the conductive sensing path can be directly embedded in the silicone matrix, and finally the silicone matrix and the embedded sensing path can be simultaneously cured and formed at high temperature. Compared with other methods for manufacturing sensors with three-dimensional space, the present invention can achieve the integrated manufacturing of sensors with three-dimensional hollow structures without the need for additional supporting structures and complex preparation processes.

[0073] (2) In common flexible sensors, the conductive path is a two-dimensional planar structure. Therefore, the conductive and sensing materials can be printed on a flexible substrate according to the designed path by screen printing or using the DIW printing method. After printing, the path is encapsulated with a flexible insulating material. When the path changes from a two-dimensional planar structure to a three-dimensional structure, it is difficult to manufacture effectively. The present invention can realize the printing of a three-dimensional sensing path. In addition, the sensing conductive path of the present invention can be directly embedded in the sensor housing substrate for manufacturing, realizing the simultaneous manufacturing and molding of the sensing path and the silicone housing substrate without the need for secondary processing.

[0074] (3) A collision detection system based on a hemispherical sensor was invented and developed, including: a hemispherical sensor, a signal processing circuit, an Arduino control board, and an indicator light module. Since the hemispherical sensor is more sensitive to the pressing speed, when the sensor is pressed slowly, the resistance value changes slowly and the resistance value increases less; when the sensor is pressed quickly, the resistance value will increase significantly and change faster, and the voltage of the voltage divider circuit will suddenly change. After analyzing the resistance value change signal generated by the sensor and the corresponding voltage signal in the voltage divider circuit in advance, the voltage signal detection method set in the experiment is to detect whether the voltage signal on the channel increases by more than 0.5V within 200ms. If it exceeds, it means that a collision has occurred, otherwise no collision has occurred. Therefore, the developed collision detection system can effectively distinguish between fast collisions and slow pressing situations, and the hemispherical sensor can be used for collision detection.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0076] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-dimensional hollow hemispherical flexible pressure sensor, characterized in that: include: The silicone rubber matrix is ​​in the shape of a hollow hemisphere; the silicone rubber matrix is ​​printed in a supporting matrix using silicone ink; A sensing path, embedded in the silicone rubber matrix; The sensing path is printed with sensing ink; When the sensor is subjected to external pressure, the sensor will sink inward, causing local deformation of the silicone rubber matrix, which in turn causes the geometric dimensions of the sensing path embedded in the silicone rubber matrix to change, causing the resistance value of the sensing path to change.

2. The three-dimensional hollow hemispherical flexible pressure sensor according to claim 1, characterized in that: The sensing path includes: The conductor body is arranged on the hemisphere in a circuitous structure; Two sections of guide wires are respectively connected to two ends of the wire body and are used for external connection wires.

3. The three-dimensional hollow hemispherical flexible pressure sensor according to claim 2, characterized in that: The three-dimensional hollow hemispherical flexible pressure sensor includes a silicone rubber matrix with one or more embedded sensing paths.

4. A method for preparing the three-dimensional hollow hemispherical flexible pressure sensor according to any one of claims 1 to 3, characterized in that: The following steps are involved: preparing a support matrix, and transferring the support matrix into a printing container; Preparation of silicone ink and sensor ink; Model the silicone rubber matrix and slice it to generate the G-code file for printing the silicone rubber matrix and the sensing path; Based on the G-code file, silicone ink and sensing ink are used for printing to obtain a hemispherical flexible pressure sensor; Insert the wires into the guide wires at the bottom of the sensor and use sealant to bond and encapsulate.

5. A preparation method according to claim 4, characterized in that: The materials of the support matrix include high viscosity vinyl silicone oil MP5000, hydrogen-containing silicone oil MH180 and fumed silica A380; The step of preparing the support matrix and transferring the support matrix into the printing container comprises: Adding vinyl silicone oil, hydrogenated silicone oil and fumed silica into a stirring container according to a preset preparation ratio and stirring to obtain a uniformly mixed support matrix; The uniformly mixed support matrix is ​​transferred into a printing container, and the printing container is placed in a vacuum degassing barrel for a preset time to remove all bubbles inside the support matrix.

6. A preparation method according to claim 5, characterized in that: The preset preparation ratio is: high viscosity vinyl silicone oil mass ratio: 70% to 90%, hydrogen-containing silicone oil mass ratio: 5% to 20%, fumed silica mass ratio: 2% to 10%.

7. A preparation method according to claim 4, characterized in that: The silicone ink is prepared by mixing Karstedt catalyst ACS-Pt10 and low-viscosity vinyl silicone oil MP450; the sensor ink is prepared by adding multi-walled carbon nanotubes to the silicone ink.

8. A preparation method according to claim 4, characterized in that: The silicone rubber matrix is ​​modeled and sliced ​​to generate a G code file for printing the silicone rubber matrix and the sensing path, including: Use Solidworks software to model the silicone rubber matrix, slice it using IdeaMaker slicing software, and generate a G-code file for printing the silicone rubber matrix; For the G-code file of the sensing path, the spatial coordinates of each point on the designed path are first calculated using the spatial polar coordinate formula, and then the generated spatial coordinate list is converted into a G-code file.

9. A preparation method according to claim 4, characterized in that: The method of printing based on the G code file using silicone ink and sensing ink to obtain a hemispherical flexible pressure sensor includes: On the basis of the support matrix, a hemispherical silicone matrix is ​​printed using silicone ink by an embedded 3D printing method; Printing the sensing ink in the silicone rubber matrix according to a preset path to form a conductive path embedded in the silicone rubber matrix, so that the silicone rubber matrix and the conductive sensing path are seamlessly integrated; After printing is completed, the printed container is placed in a blast heating box for curing to obtain a hemispherical flexible pressure sensor with a three-dimensional hollow structure.

10. A collision detection system, characterized in that: The invention comprises a hemispherical sensor, a signal processing circuit and a control board. The hemispherical sensor is connected to the control board through the signal processing circuit. The hemispherical sensor is implemented by the three-dimensional hollow hemispherical flexible pressure sensor as described in any one of claims 1 to 3.

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