Sensor for measuring touch and temperature of human body and preparation method thereof

Abstract

The invention belongs to the technical field of sensors, and particularly relates to a sensor for measuring human touch and temperature and a preparation method thereof. A sensor for measuring human body touch and temperature comprises a sensitive layer, a bottom surface AB silica gel layer, a top surface AB silica gel layer and at least one flexible circuit. The flexible circuit is attached to one side of the sensitive layer, the bottom AB silica gel layer is formed by coating AB silica gel on the side, away from the flexible circuit, of the sensitive layer, and the top AB silica gel layer is formed by coating AB silica gel on the side, attached with the flexible circuit, of the sensitive layer. The top surface AB silica gel layer and the bottom surface AB silica gel layer act together to wrap the sensitive layer pasted with the flexible circuit between the top surface AB silica gel layer and the bottom surface AB silica gel layer. The sensor prepared through the method is of a flexible structure and can adapt to a human body curve, the whole sensor is easy and convenient to operate, high in response speed, good in stability and high in sensitivity, and therefore the sensor can serve as wearable electronic equipment to measure human body touch and temperature changes.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible electronic device manufacturing, and specifically relates to a sensor for measuring human touch and temperature based on material extrusion technology and electrospray printing technology, and a preparation method thereof. Background Art

[0002] A sensor is a detection device that can sense the information being measured and can change the sensed information into electrical signals or other required forms of information output according to certain rules to meet the requirements of information transmission, processing, storage, display, recording and control. Traditional sensors for the human body include human tactile sensors and temperature sensors. Both human tactile sensors and temperature sensors are generally rigid structures, which makes it impossible to accurately measure the tactile and temperature processes of the human body. For example, temperature sensors such as mercury thermometers, electronic thermometers, and forehead temperature guns are all rigid structures. Mercury thermometers and electronic thermometers need to be placed in the armpits, mouths and other areas before they can be used, making the operation more cumbersome, and the response time of this type of thermometer is also long. Although the forehead temperature gun has a short response time, it can only obtain a temperature value once during measurement, just like mercury thermometers and electronic thermometers, and cannot display human temperature data and trends in real time, resulting in its low practicality.

[0003] Existing tactile sensors are generally rigid structures, which means that when used on the human body, they cannot adapt well to the curves of the human body, resulting in inconvenience in use and low accuracy. Summary of the invention

[0004] In order to solve the problems of complex operation, inconvenient use and low accuracy of existing tactile sensors and temperature sensors, the present invention provides a sensor for measuring human touch and temperature and a preparation method thereof.

[0005] The present invention is implemented by the following technical scheme: a sensor for measuring human touch and temperature, comprising a sensitive layer, a bottom AB silicone layer, a top AB silicone layer and at least one flexible circuit; the sensitive layer is used to measure changes in human touch and temperature, the sensitive layer comprises carbon nanotubes, AB silicone and PEDOT:PSS solution, the carbon nanotubes, the AB silicone and the PEDOT:PSS solution are mixed in a ratio of 1:10:1; the flexible circuit is bonded to one side of the sensitive layer, and the flexible circuit is used to transmit the changes in human touch and temperature measured by the sensitive layer to the sensor. The changes are converted into electrical signals; the bottom AB silicone layer is formed by coating the AB silicone on the side of the sensitive layer away from the flexible circuit; the top AB silicone layer is formed by coating the AB silicone on the side of the sensitive layer on which the flexible circuit is attached, and the bottom AB silicone layer and the top AB silicone layer work together to wrap the sensitive layer attached with the flexible circuit therebetween; the AB silicone comprises a main agent A and a curing agent B, the main agent A is one of epoxy resin, silicone or acrylic modified epoxy resin; the mixing ratio of the main agent A and the curing agent B is 1:1.

[0006] As a further improvement of the present invention, the carbon nanotubes are hexagonal carbon nanotubes with a purity greater than 98%, a tube diameter of 10nm-15nm, and a tube length of 15nm-30nm.

[0007] The present invention also includes a method for preparing a sensor for measuring human touch and temperature, which comprises the following steps:

[0008] S1, preparing the sensitive layer and the AB silica gel;

[0009] S2, use Solidworks to draw the casting mold model, and use FDM3D printing technology to make the mold;

[0010] S3, drawing a fluid-jet-printed regular array flexible circuit, and printing the flexible circuit on a substrate by an electrojet printing device, and then sintering at 150° C. for 30 minutes to obtain the flexible circuit;

[0011] S4, coating the mold prepared in step S2 with a portion of AB silicone to form the bottom AB silicone layer, loading the prepared sensitive layer into a 3D printer, and printing the sensitive layer on the solidified bottom AB silicone layer through the material extrusion 3D printer;

[0012] S5, after printing is completed, the conductive silicone is evenly applied to both ends of each flexible circuit, ensuring that the conductive silicone covers the end points of the flexible circuit when applied, and at the same time, multiple circuits are respectively attached to the same side of the sensitive layer, and the flexible circuit is attached to the side of the sensitive layer away from the bottom AB silicone layer, so as to obtain a mold sample, and then the mold sample is placed at 120° C. for curing for 30 minutes;

[0013] S6, evenly apply another part of the AB silicone on one side of the cured sensitive layer with the flexible circuit to form the top AB silicone layer, and encapsulate the sensitive layer with the flexible circuit through the bottom AB silicone layer and the top AB silicone layer. After the encapsulation is completed, heat it at 80°C for 30 minutes to obtain the sensor for measuring human touch and temperature.

[0014] As a further improvement of the present invention, the bottom surface AB silicone layer is mixed in a ratio of 1:1 and evenly applied in the mold, and the thickness of the layer applied in the mold is 2 mm.

[0015] As a further improvement of the present invention, the flexible circuit is an S-shaped structure.

[0016] As a further improvement of the present invention, the ink material of the flexible circuit in the preparation process is nano silver ion conductive ink, the base material is polyethylene terephthalate, the thickness of the base material is 125 μm, and the length and width are both 100 mm.

[0017] As a further improvement of the present invention, the diameter of the glass nozzle in the electrospray printing device is 40 μm, the height of the glass nozzle is 150 μm, the bias voltage is 700 V, and the printing speed is 0.15 mm / s.

[0018] As a further improvement of the present invention, the preparation method of the sensitive layer includes the following steps: weighing 1g of carbon nanotubes and placing them in a beaker; then weighing 5g of main agent A and 5g of curing agent B respectively, pouring the main agent A and curing agent B into the beaker containing the carbon nanotubes respectively, and then pouring 1g of PEDOT:PSS solution, mixing and stirring the various raw materials in the beaker until no bubbles are generated, and thus the sensitive layer is obtained.

[0019] As a further improvement of the present invention, the inner diameter of the dispensing nozzle in the material extrusion 3D printer is 0.4dm, and the air pressure is 0.2MPa.

[0020] As a further improvement of the present invention, the material used by the FDM 3d printer is any one of PLA, ABS, and TPU.

[0021] The technical solution provided by the present invention has the following beneficial effects:

[0022] (1) The sensor prepared by the present invention has a flexible structure and can adapt to the curve of the human body. The operation of the entire sensor is simple and convenient, with fast response speed, good stability and high sensitivity. The sensor of the present invention can monitor the changes in human touch and temperature in real time, so it can be worn for a long time as a wearable electronic device to measure the changes in human touch and temperature.

[0023] (2) The method for preparing the sensor of the present invention is simple to operate, and the process of preparing the sensor does not produce harmful substances, making it safer. In addition, it can be worn for a long time as a wearable electronic device, and can also be close to the skin to measure the temperature or tactile changes of the human body, and has a fast response speed.

[0024] (3) The present invention uses carbon nanotubes, AB silica gel and PEDOT:PSS solution as raw materials for the sensitive layer, so that the sensitive layer has good conductivity, thereby improving its measurement accuracy and sensitivity. At the same time, the prepared sensor is also flexible and can be bent at will, and the bending has almost no effect on the resistance, which proves that it has high stability and can be applied to the human body.

[0025] (4) By setting up multiple flexible circuits, the sensitive layer can be fully covered, and measurements can be performed at all locations of the sensitive layer, thereby improving its practicality. At the same time, multiple flexible circuits can also effectively avoid the situation where the entire sensor cannot be used when one of the circuits is damaged, thereby greatly improving the service life of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of a sensor for measuring human touch and temperature provided by the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of the flexible circuit provided by the present invention.

[0028] Figure 3 A schematic diagram of the preparation process of the sensor for measuring human touch and temperature provided by the present invention.

[0029] Figure 4 This is a dimensional parameter diagram of the casting mold provided by the present invention.

[0030] Figure 5 The G-code code of the printing sensitive layer provided by the present invention.

[0031] Figure 6 A scatter plot showing the resistivity of the sensor provided by the present invention changing with the bending angle.

[0032] Figure 7 A curve diagram showing the relationship between the resistance and temperature of the sensor provided by the present invention.

[0033] Figure 8 This is a diagram showing the resistance change of the sensor provided by the present invention when in a stretched or rebounded state.

[0034] Fig. 9 This is a sensitivity fitting curve diagram of the sensor provided by the present invention.

[0035] Fig.10 This is a temperature cycle stability test chart of the sensor provided by the present invention.

[0036] The markings in the figure are: 1. bottom surface AB silicone layer; 2. sensitive layer; 3. flexible circuit; 4. top surface AB silicone layer. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0038] In the description of the present invention, it should be noted that for directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicating directions and positional relationships are based on the directions or positional relationships shown in the drawings, which 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 direction, be constructed and operated in a specific direction, and cannot be understood as limiting the specific protection scope of the present invention. The terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. The terms "including" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device including a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] This embodiment provides a sensor for measuring human touch and temperature, such as Figure 1As shown, it includes a sensitive layer 2, a bottom AB silicone layer 1, a top AB silicone layer 4 and at least one flexible circuit 3. The flexible circuit 3 is attached to one side of the sensitive layer 2, the bottom AB silicone layer 1 is formed by coating AB silicone on the side of the sensitive layer 2 away from the flexible circuit 3, and the top AB silicone layer 4 is formed by coating AB silicone on the side of the sensitive layer 2 where the flexible circuit 3 is attached. The top AB silicone layer 4 and the bottom AB silicone layer 1 work together to wrap the sensitive layer 2 where the flexible circuit 3 is attached between the top AB silicone layer 4 and the bottom AB silicone layer 1. By wrapping the top AB silicone layer 4 and the top AB silicone layer 4 on both sides of the sensitive layer 2 where the flexible circuit 3 is attached, the sensitive layer 2 can be protected to prevent it from being worn during use and extend its service life.

[0040] The sensitive layer 2 is used to measure the changes in human touch and temperature, and the changes in human touch and temperature are converted into electrical signals through the flexible circuit 3, so people only need to observe the changes in resistance to know the changes in human touch and temperature. The sensitive layer 2 includes carbon nanotubes, AB silicone and PEDOT:PSS solution, and the carbon nanotubes, AB silicone and PEDOT:PSS solution are mixed in a ratio of 1:10:1.

[0041] In this embodiment, the effect of adding carbon nanotubes makes the mixed material conductive, because the carbon atoms on the carbon nanotubes form covalent parts through sp2 hybridization, forming a large range of delocalized π bonds. This structure makes the valence band and conduction band of the carbon nanotubes partially overlap, which is equivalent to a half-full energy band, and electrons can move freely, thereby giving the carbon nanotubes metallic conductivity. The effect of adding AB silica gel is to make the sensitive layer 2 flexible, so that it can be stretched and folded and ensure that it will not break, and can be restored to its original shape. The prepared sensitive layer 2 can adapt to the curve of the human body and improve its practicality. Adding PEDOT:PSS solution, which can be used as a conductive polymer, has high conductivity and stability, and this solution has a good response to temperature. Therefore, by adding PEDOT:PSS solution, rapid temperature measurement can be achieved, and the response speed of the prepared sensor to temperature is improved. In addition, this solution can also be used to adjust the consistency of the mixed material, so that the prepared sensitive layer 2 can have good flexibility and good response speed to temperature.

[0042] In this embodiment, the carbon nanotubes have a diameter of 10 nm-15 nm, a length of 15 μm-30 μm, a purity of more than 98%, and a hexagonal crystal lattice.

[0043] The AB silicone is selected from Smooth-On platinum-cured silicone (ecofiex TM 00-20), where Smooth-On is the brand of the material, ecofiex TM 00-20 is the code name of the material. The material itself does not contain metal, but the name contains platinum because it is made by a two-component molding vulcanizer and uses platinum as a catalyst. The advantage of using platinum as a catalyst is that the prepared AB silicone is stronger and more elastic, can be stretched to many times its original size without tearing, and will rebound to its original shape without deformation, making it have good recoverable deformation properties. In addition, the use of Smooth-On platinum-cured silicone (ecofiex TM 00-20) enables it to withstand sudden changes in temperature and has stable chemical properties. In this embodiment, the two components of AB silicone can be a main agent A and a curing agent B, wherein the main agent A can be one of epoxy resin, silicone or acrylic modified epoxy resin. Curing agent B can be mixed in a ratio of 1:1 to initiate a polymerization reaction, thereby achieving the purpose of curing AB silicone.

[0044] The AB silicone can be prepared by mixing the main agent A and the curing agent B in a certain proportion and then stirring them evenly.

[0045] It can be understood that the AB silicone in this embodiment includes a main agent A and a curing agent B. Therefore, in the actual preparation of the sensitive layer 2, the ratio of each component is as follows: carbon nanotubes: main agent A: curing agent B: PEDOT: PSS solution is 1:5:5:1.

[0046] The above ratio was selected because experiments with different ratios were conducted in the early stage and it was found that the performance of the sensor prepared under this ratio was the best. The specific experimental results are shown in Table 1 below.

[0047]

[0048] Through the above experiments with different proportions, it can be known that the sensitive layer 2 prepared under the proportions in the 1st, 2nd, 3rd and 4th groups of experiments either cannot be formed or is difficult to extrude, resulting in the inability to print and form the sensitive layer 2. The 5th to 10th groups of experiments can all print the sensitive layer 2, but the resistance of the sensitive layer printed by the 5th and 6th groups is very large, resulting in poor conductivity. The resistance of the sensitive layer 2 printed by the 8th, 9th and 10th groups is relatively small, resulting in good conductivity. When the diameter of the dispensing nozzle is selected as 0.8dm, the accuracy of printing the sensitive layer is poor, resulting in rough lines of the printed sensitive layer. When the dispensing nozzle is selected as 0.4dm, the effect is good, so the 10th group of parameters is selected in this embodiment to prepare the sensitive layer 2, that is, the ratio of the raw material carbon nanotubes: main agent A: curing agent B: PEDOT:PSS solution for preparing the sensitive layer 2 is 1:5:5:1.

[0049] In this embodiment, the preparation of the sensitive layer 2 includes the following steps: using an electronic balance to weigh 1g of carbon nanotubes and place it in a beaker, then weighing 5g of the main agent A and curing agent B in turn, placing them in beakers respectively, and then pouring 1g of PEDOT:PSS solution into the beaker, stirring the raw materials in the beaker for more than 30 minutes to ensure that they are stirred evenly, and to ensure that the mixed solution after stirring is free of bubbles and impurities. The prepared sensitive layer 2 is carefully loaded into the dispensing syringe of the material extrusion 3D printer using a glass rod or other suitable tools. During the filling process, pay attention to the uniformity and fullness of the material to avoid air bubbles or uneven distribution of the sensitive layer 2 in the dispensing syringe.

[0050] Please refer to Figure 2 In this embodiment, the flexible circuit 3 can be designed by AutoCAD professional electronic design software. Its structure can be composed of multiple curved S-shaped structures. There can be multiple flexible circuits 3, and multiple flexible circuits 3 can be arranged along the longitudinal direction of the sensitive layer 2. By arranging multiple flexible circuits 3 along the longitudinal direction of the sensitive layer 2, the flexible circuit 3 can cover various positions of the sensitive layer 2, thereby improving the sensitivity and coverage of the prepared sensor. By setting up multiple circuits, the resistance break in the circuit can be reduced to affect the detection performance of the entire sensor. The reason is as follows: If only one circuit is prepared, if this circuit is worn or otherwise, it will cause it to be broken, so that the sensor can no longer be used. If multiple circuits are used, the breakage of one or two circuits will not affect the use of the sensor. At the same time, according to the law of parallel resistance, the total resistance can be reduced.

[0051] It is understandable that in this embodiment, please refer to Figure 2The two ends of the flexible circuit 3 can be evenly coated with conductive silicone to ensure that the coated conductive silicone covers the end points of the flexible circuit 3. At the same time, the prepared flexible circuit 3 is attached to the sensitive layer 2 so that one end of the flexible circuit 3 has good contact with the sensitive layer 2, and the other end of the flexible circuit 3 can be in contact with an external power source, thereby converting the changes induced by the sensitive layer 2 into electrical signals, thereby realizing the detection of human touch and temperature.

[0052] Please refer to Figure 3 This embodiment also provides a method for preparing a sensor for measuring human touch and temperature, which comprises the following steps:

[0053] S1, prepare the sensitive layer 2 and AB silicone rubber separately for use.

[0054] S2, use SolidWorks software to build a three-dimensional model of the casting mold, the size of the construction is as follows Figure 4 As shown. After the drawing is completed, it is exported to STL format and imported into the slicing software for slicing. The slice layer height is set to 0.3mm and the temperature is set to 210℃. After slicing, the G-code code is generated. The G-code code can be post-processed according to the needs (some code parts may need to be manually modified), and then the G-code code is imported into the FDM3d printer. The FDM3d printer will print according to the program on the G-code, thereby printing out the mold.

[0055] S3, use AutoCAD professional electronic design software to draw the geometric structure of the flexible circuit 3. After completing the design of a single circuit, use an array setting to achieve simultaneous preparation of multiple circuits by setting them in the longitudinal direction. Save the designed circuit image in DXF format and import it into the electrojet printing device. Then, use the electrojet printing device to print the flexible circuit 3 on the substrate, thereby achieving simultaneous printing of multiple array-set flexible circuits 3.

[0056] S4, evenly apply AB silicone in the mold to ensure smooth application with a thickness of 2mm. Place the applied casting sample in a constant temperature and humidity chamber and cure it at 80°C for 30 minutes to obtain the bottom AB silicone layer 1. Then carefully load the spare sensitive layer 2 into the dispensing syringe of the material extrusion 3D printer through a glass rod or other suitable tools, and place the G-code code in the material extrusion 3D printer, and then print the sensitive layer 2 on the sample cured in step S4. During the printing process, the inner diameter of the dispensing nozzle is 0.4dm and the air pressure is 0.2MPa.

[0057] S5, after printing is completed, the conductive silicone is evenly applied to both ends of each flexible circuit 3, ensuring that the conductive silicone covers the end points of the flexible circuit 3 when applied, and the prepared flexible circuit 3 is attached to one side of the sensitive layer 2, so that the same side of the sensitive layer 2 has multiple flexible circuits 3. The flexible circuit 3 is attached to the side of the sensitive layer 2 away from the bottom AB silicone layer 1, and a mold sample is obtained, and then the mold sample is placed at 120°C for curing for 30 minutes.

[0058] S6, evenly apply another part of the AB silicone on one side of the cured sensitive layer 2 with the flexible circuit 3 to form the top AB silicone layer 4, and encapsulate the sensitive layer 2 with the flexible circuit 3 through the bottom AB silicone layer 1 and the top AB silicone layer 4. After the encapsulation is completed, put it in a constant temperature and humidity chamber and heat it at 80°C for 30 minutes to obtain the sensor for measuring human touch and temperature.

[0059] Among them, the G-code code for printing sensitive layer 2 can be referred to Figure 5 shown.

[0060] Among them, FDM3d printers can use PLA materials, and pay attention to cleaning the nozzle before printing. It is understandable that PLA material is the most common material for FDM3d printers. This printer melts the PLA material at high temperature and then prints it into a fixed shape through the nozzle. PLA is replaceable, and usually the materials of FDM3d printers can be PLA, ABS, TPU and other materials. The reason why the temperature is set to 210 degrees Celsius in this embodiment is based on the characteristics of the selected PLA material, because the melting temperature of PLA material is 190℃-220℃. If the set temperature is too low, the PLA material will not melt and cannot be printed into the required shape. If the temperature is too high, the PLA material will carbonize and turn black, and in severe cases, it will cause blockage. Therefore, in actual operation, the temperature of the FDM3d printer can be set according to the printed material.

[0061] In this embodiment, after the circuit design is completed, in order to ensure the physical implementation of the circuit, the flexible circuit 3 is saved in DXF format and imported into the electro-jet printing device.

[0062] In this embodiment, the conductive ink in the electrospray printing device is nano silver ion ink, and before use, it is stirred evenly to ensure that the nano silver ions in the ink are evenly dispersed and the printing effect is improved. The substrate is polyethylene terephthalate, and the thickness of the substrate is 125 mm, and the length and width are 100 mm respectively. Before printing, the adhesion performance between the conductive ink and the substrate is ensured, and the wetting angle is guaranteed to be 36°, so as to improve the quality and accuracy of the printed flexible circuit 3. At the same time, the electrospray printing device needs to clean the surface dust before use to prevent any dust or impurities from affecting the adhesion and printing quality of the conductive pattern.

[0063] It can be understood that this embodiment combines the response surface and the genetic algorithm to obtain a set of optimized process parameters for the electro-jet printing equipment to ensure the stability and printing quality during the electro-jet printing process. Specifically, the diameter of the glass nozzle of the electro-jet printing equipment is 40 μm, the bias voltage is 700 V, the nozzle height is 150 microns, and the printing speed is 0.15 mm / s. The resistance stability of the flexible circuit 3 prepared under this parameter is good. Among them, a smaller glass nozzle diameter can usually achieve a more detailed printing effect. Appropriate bias voltage can prevent the resistance of the printed wire from being too large, and can also suppress the generation of the "coffee ring" effect. The height of the nozzle can affect the position and dispersion of the ink jet, thereby affecting the printing quality and progress.

[0064] In addition, after printing the flexible circuit 3, a sintering and curing treatment step is used to ensure the stability of the wire resistance. The purpose of this step is to make the printed silver ions undergo surface changes by heating under specific temperature conditions to promote the wire resistance to a stable state. In this embodiment, a constant temperature and humidity test box is used, the sintering and curing temperature is set to 150°C, and the heating time is 30 minutes.

[0065] Among them, the electrospray printing technology is a kind of 3D printing technology. The resolution of the printed circuit is very high and the precision is also high. Thus, the measurement accuracy of the prepared sensor can be improved. The purpose of preparing this flexible circuit 3 can be understood as a wire, because the sensitive layer 2 part in the sensor for measuring touch and temperature is to be plastic-sealed in AB silica gel later, so it is not easy to measure the resistance of the sensor. Therefore, in this embodiment, an electrospray printing circuit is selected, one end of which is connected to the sensitive layer in the sensor, and the other end is connected to the external power supply, thereby realizing the measurement of the resistance of the sensor, thereby realizing the conversion of the change of human touch and temperature into an electrical signal. At the same time, PET is selected as a substrate in this embodiment. PET material is a bendable material (non-stretchable), with the characteristics of high strength, high rigidity and good wear resistance, colorless and transparent, good chemical stability, so that the prepared circuit is a flexible structure, and the flexible structure can meet the requirements of the human body curve, and realize more benchmark measurement. This substrate can also use PDMS material, PDMS material is bendable and stretchable, but the price is much more expensive than PET, has good stretchability and resilience, and is usually used in artificial skin, flexible electronics and other fields. Therefore, PET material is preferably selected in this embodiment.

[0066] In step S4, the sensitive layer 2 is printed by selecting a material extrusion 3D printer. 3D printing has low cost, is convenient and fast, and has high efficiency. The printed sensitive layer 2 has high precision.

[0067] In this embodiment, three printing technologies are used in total, namely, electrojet printing, material extrusion 3D printing and FDM 3D printing. Among them, electrojet printing is responsible for printing the flexible circuit 3, material extrusion 3D printing is responsible for printing the sensitive layer 2, and FDM 3D printing is responsible for printing the mold.

[0068] The sensor prepared by the present invention is light in weight and low in cost, so that it can be applied to various scenarios.

[0069] It can be understood that the sensor prepared by this embodiment can not only be used to detect changes in human touch and temperature, but can also be applied to industry.

[0070] When applied to the human body, it can be used as follows: 1. In the medical field, the sensor can be used on surgical robots. Since the sensor is a flexible structure, it can provide tactile feedback during surgery without causing harm to the human body, allowing doctors to feel the hardness, elasticity and other characteristics of tissues through remote control operations, thereby improving surgical accuracy. 2. In the medical field, the sensor can also be used to monitor the physical condition of vegetative patients. By wearing the sensor, if the vegetative patient's body moves, it can be expressed in the form of electrical signals, and people can understand the physical condition of the vegetative patient by observing the electrical signals. 3. In the medical field, the sensor can also monitor the patient's body temperature in real time. By wearing the sensor, it can help doctors judge the patient's body temperature fluctuations and thus formulate better treatment plans.

[0071] In the industrial field, the sensor of the present invention can be used as follows: 1. Since the sensor of the present invention is made of flexible material, it can be installed on an industrial robot and used as a tactile sensor to sense the position, shape, hardness, texture and other information of the contacted object, so that the industrial robot can make better judgments. 2. In precision assembly operations, the sensor of the present invention can be used as a tactile sensor to help the robot accurately sense the position, shape and contact force of the components, thereby achieving high-precision insertion, assembly or fastening operations. 3. For the grasping of irregularly shaped or fragile objects, the sensor of the present invention can be used as a tactile sensor to allow the robot to adjust the grasping strategy according to the pressure distribution when contacting the object, so as to achieve flexible grasping and reduce damage.

[0072] It can be understood that the above-mentioned uses are only part of the usage scenarios of the sensor prepared by the present invention. In actual processes, the sensor prepared by the present invention is not limited to the above-mentioned usage scenarios.

[0073] Performance Testing

[0074] In order to verify the various performances of the sensor for measuring human touch and temperature provided in this embodiment, the technicians designed a test plan and built a corresponding experimental platform and test system.

[0075] (I) Stability test

[0076] Since the sensor prepared in this embodiment is mainly used to measure human touch and temperature, some unevenness or incomplete joints may occur on the joints or skin surface of the human body. If the resistance of the sensor prepared in this embodiment is relatively stable at different bending angles, it means that the performance of the sensor prepared in this embodiment is relatively stable.

[0077] The specific operation is as follows: the prepared sensor is tested for resistance change, but the digital multimeter cannot achieve continuous monitoring processing, so in this test, the Arduino platform can be used to design a circuit to read the real-time resistance change of the sensor. Using the voltage division characteristics of the series circuit, the sensor resistance R can be obtained with the help of the known resistance voltage division. Where R0 is a known resistor, R is the output resistor, U is the total voltage, and U0 is a known resistor voltage divider. In order to ensure the stability of the bending angle, an FDM 3D printer was used in this experiment to print molds of 30°, 60°, and 90°, and the sensor was placed close to the mold. When the resistance was stable, the resistance value was read, and the result was as follows: Figure 6 Data shown.

[0078] Figure 6 This is a scatter plot of the sensor prepared in this embodiment as the bending angle changes. The stability test is performed by continuously changing the bending angle at 0°, 30°, 60° and 90° angle gradients. Figure 6 It can be seen that the resistance change rate of the sensor prepared in this embodiment does not change substantially with the change of the bending angle, which indicates that the sensor prepared in this embodiment has good stability and can adapt to the change of the human body curve.

[0079] (II) Test of the relationship between the resistance value and temperature of the sensor

[0080] This performance test also uses the Arduino platform to design a circuit to read the sensor's resistance change. However, in this test, we use a heating platform to place the sensor close to the heating platform. When the heating platform is heated to the specified temperature, we wait for 5 minutes to ensure that the sensor is also heated to the specified temperature. Then we read the sensor's resistance data and get the following: Figure 7 The graph shown.

[0081] Figure 7 It is the fitting diagram between different resistance values ​​and temperature. Figure 7 It can be seen that as the temperature rises, the resistance value of the sensor is also gradually reduced, which shows that the sensor prepared in this embodiment shows a negative temperature coefficient temperature-sensitive characteristic. The negative temperature coefficient means that as the temperature rises, the resistance of the sensor shows a decreasing trend, that is, each temperature will correspond to a resistance value, which can be achieved by measuring the resistance and converting the corresponding temperature, thereby achieving the purpose of measuring the temperature. In addition, the sensor prepared in this actual example is a flexible structure, and its resistance value is also relatively stable under bending. Therefore, in the actual operation process, the sensor can be worn for a long time, and the human body temperature can be monitored in real time by real-time monitoring of the resistance value.

[0082] (III) Testing of the stretching and resilience performance of the sensor

[0083] The test is performed as follows: a circuit is designed on the Arduino platform to read the real-time resistance change of the sensor, and then the sensor is stretched on a stretching platform. After the sensor resistance is stable, the resistance value of the sensor is read. The data in Table 2 are obtained.

[0084]

[0085] Among them, L0 is the initial sensor length, L is the sensor length after stretching, |L-L0| is the stretching amount, R1 is the stretching resistance, R2 is the rebound resistance, and R3 is the initial resistance of the sensor. Figure 8 It can be seen from the data that the resistance value of the sensor changes very little within a stretching amount of 3.5 mm, which proves that the sensor prepared in this embodiment can meet the stretching problem caused by skin viscoelasticity during use. In addition, it can be seen from the above experimental data that the resistance of the sensor changes very little under stretching, which shows that the sensor prepared by the present invention is not easily mechanically damaged, making it suitable for various complex environments, such as being used as a wearable device, and can also be placed in smart textile products for use.

[0086] (IV) Sensor sensitivity test

[0087] The operation is as follows: This performance test also uses the Arduino platform to design a circuit to read the sensor's resistance change, but in this test, we use a heating platform to place the sensor close to the heating platform. When the heating platform is heated to the specified temperature, wait for 5 minutes to ensure that the sensor is also heated to the specified temperature. Then read the sensor's resistance data and get the following Fig. 9 The graph shown.

[0088] Through the above operation, the sensitivity curve of the sensor can be obtained as follows: Fig. 9 As shown, Fig. 9 The linear fitting slope of the middle curve is -0.0068782, and the correlation coefficient R 2 It is 0.9969, which proves that the sensor prepared in this embodiment has good sensitivity to human body temperature.

[0089] In addition, the sensor prepared in this embodiment utilizes the thermal characteristics of the active material, from which it can be seen that the resistivity TCR is an important indicator of its sensitivity. The resistivity is defined as the relative change in resistance when the temperature changes by 1°C.

[0090] Among them, T0 refers to the initial temperature, T refers to the current temperature, R(T0) is the resistance at the initial temperature, R(T) is the resistance at the current temperature, and TCR is the "Temperature Coefficient of Resistance". It is a parameter that describes the degree to which the material's resistance changes with temperature, reflecting the sensitivity of the resistance to temperature changes, usually expressed as the resistance change per degree Celsius. Fig. 9 The graphs shown are the relationship between the resistance change R(T)-R(T0) and the relationship between the resistance relative change rate (R(T)-R(T0)) / R(T0) and the temperature T. The purpose of drawing these two graphs is to intuitively display the sensitivity characteristics of the sensor, understand the performance of the sensor in practical applications, and ensure its measurement accuracy and stability within a specific range. Fig. 9 The data of is used to calculate that the TCR of the sensor prepared in this embodiment is about -0.768% / °C, which means that the resistance decreases by 0.768% every time the temperature rises by 1°C. From this data, it can be seen that the sensor prepared in this embodiment has good sensitivity when used as a wearable device, which meets the requirements of sensor sensitivity in the field of wearable devices.

[0091] (V) Temperature cycle stability test of sensor

[0092] The results obtained by subjecting the sensor to a temperature cycle test are as follows Fig.10 shown.

[0093] Fig.10 This is a stable cycle stability test diagram of the sensor prepared in this embodiment. Fig.10 It can be seen that in the case of multiple temperature cycles, the deviation of the relative change of the resistance of the sensor is small, indicating that the sensor prepared in this embodiment has good stability and repeatability. Fig.10 It can also be seen that under multiple temperature cycles, the sensor can still show its sensitivity characteristics, proving that the sensor can still be used normally after multiple cycles.

[0094] The above describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A sensor for measuring human touch and temperature, characterized in that: It includes: A sensitive layer (2), the sensitive layer (2) is used to measure changes in human touch and temperature, the sensitive layer (2) comprises carbon nanotubes, AB silica gel and PEDOT:PSS solution, the carbon nanotubes, the AB silica gel and the PEDOT:PSS solution are mixed in a ratio of 1:10:1; at least one flexible circuit (3), the flexible circuit (3) being bonded to one side of the sensitive layer (2), the flexible circuit (3) being used to convert changes in human touch and temperature measured by the sensitive layer (2) into electrical signals; A bottom AB silicone layer (1), wherein the bottom AB silicone layer (1) is formed by coating the AB silicone on a side of the sensitive layer (2) away from the flexible circuit (3); A top surface AB silicone layer (4), wherein the top surface AB silicone layer (4) is formed by coating the AB silicone on the side of the sensitive layer (2) on which the flexible circuit (3) is attached, and the bottom surface AB silicone layer (1) and the top surface AB silicone layer (4) work together to wrap the sensitive layer (2) on which the flexible circuit (3) is attached; The AB silica gel includes a main agent A and a curing agent B, wherein the main agent A is one of epoxy resin, silicone or acrylic modified epoxy resin; the mixing ratio of the main agent A and the curing agent B is 1:

1.

2. The sensor for measuring human touch and temperature as claimed in claim 1, characterized in that: The carbon nanotubes are hexagonal carbon nanotubes with a purity greater than 98%, a tube diameter of 10nm-15nm, and a tube length of 15nm-30nm.

3. A method for preparing a sensor for measuring human touch and temperature, characterized in that: It includes the following steps: S1, preparing the sensitive layer (2) and the AB silica gel in the sensor for measuring human touch and temperature as described in any one of claims 1 to 2; S2, use Solidworks to draw the casting mold model, and use FDM3D printing technology to make the mold; S3, drawing a fluid-jet-printed regular array flexible circuit (3), and printing the flexible circuit (3) on a substrate using an electrojet printing device, and then sintering at 150° C. for 30 minutes to obtain the flexible circuit (3); S4, coating the mold prepared in step S2 with a portion of AB silicone to form the bottom AB silicone layer (1), loading the prepared sensitive layer (2) into a 3D printer, and printing the sensitive layer (2) on the solidified bottom AB silicone layer (1) through material extrusion by the 3D printer; S5, after printing is completed, the conductive silicone is evenly applied to both ends of each flexible circuit (3), ensuring that the conductive silicone covers the end points of the flexible circuit (3) when applied, and at the same time, a plurality of the flexible circuits (3) are respectively attached to the same side of the sensitive layer (2), and the flexible circuit (3) is attached to the side of the sensitive layer (2) away from the bottom AB silicone layer (1), so as to obtain a mold sample, and then the mold sample is placed at 120° C. for curing for 30 minutes; S6, evenly apply another portion of AB silicone on one side of the cured sensitive layer (2) with the flexible circuit (3) attached thereto to form the top AB silicone layer (4), and encapsulate the sensitive layer (2) with the flexible circuit (3) attached thereto through the bottom AB silicone layer (1) and the top AB silicone layer (4). After encapsulation, heat the layer at 80° C. for 30 minutes to obtain the sensor for measuring human touch and temperature.

4. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The bottom surface AB silicone layer (1) is mixed in a ratio of 1:1 and evenly applied to the mold. The thickness of the applied silicone layer in the mold is 2 mm.

5. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The flexible circuit (3) is an S-shaped structure.

6. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The ink material of the flexible circuit (3) during the preparation process is nano silver ion conductive ink, the base material is polyethylene terephthalate, the thickness of the base material is 125 μm, and the length and width are both 100 mm.

7. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The diameter of the glass nozzle in the electrospray printing device is 40 μm, the height of the glass nozzle is 150 μm, the bias voltage is 700 V, and the printing speed is 0.15 mm / s.

8. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The preparation method of the sensitive layer (2) comprises the following steps: weighing 1g of carbon nanotubes and placing them in a beaker; then weighing 5g of a main agent A and 5g of a curing agent B respectively, pouring the main agent A and the curing agent B into the beaker containing the carbon nanotubes respectively, and then pouring 1g of a PEDOT:PSS solution into the beaker, mixing and stirring the various raw materials in the beaker until no bubbles are generated, thereby obtaining the sensitive layer (2).

9. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The inner diameter of the dispensing nozzle of the material extrusion 3D printer is 0.4dm, and the air pressure is 0.2MPa.

10. The method for preparing a sensor for measuring human touch and temperature according to claim 3, characterized in that: The material used by the FDM 3d printer is any one of PLA, ABS, and TPU.

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