Flexible temperature-sensitive device based on electrostatic automatic pattern filling and preparation method thereof

Abstract

The invention provides a flexible temperature-sensitive device based on electrostatic automatic pattern filling, a temperature-sensitive device body comprises a temperature-sensitive material, a flexible substrate material and a packaging layer, the temperature-sensitive material is a temperature-sensitive particulate matter cluster, and temperature-sensitive material powder does not need to be prepared into slurry or ink. An electric field loaded by corona discharge can be deposited on the flexible substrate, the conductive electrode is automatically identified and avoided, and only the non-conductive substrate area is filled. According to the method, the use of an adhesive is avoided, the sensitivity of the flexible temperature-sensitive device is improved, the cost is low, the process is simple, the preparation time of the device is saved, the production efficiency is improved, meanwhile, heat accumulation between the temperature-sensitive device and the skin can be avoided, the measurement error is reduced, and the real and reliable temperature measurement is ensured; the temperature-sensitive device is not sensitive to stress and strain, decoupling of various external signal stimulation is achieved, and the accuracy of measured data of the temperature-sensitive device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature-sensitive devices, and particularly to a flexible temperature-sensitive device based on electrostatic automatic graphic filling and a preparation method thereof. Background Art

[0002] Existing flexible temperature-sensitive devices generally consist of four parts, namely a temperature-sensitive material, a flexible substrate material, electrodes, and a packaging layer, which are stacked in a sandwich structure.

[0003] As the most important component of a flexible temperature-sensitive device, the temperature-sensitive material determines the mechanical and electrical properties of the temperature-sensitive device. The temperature-sensitive material characterizes the change of an external characteristic parameter (temperature) by changing its own parameters during the temperature change process. By combining the temperature-sensitive mechanism of the material and optimizing the material, a temperature-sensitive device with excellent electrical properties can be obtained.

[0004] For temperature-sensitive materials, the current mainstream preparation methods are mainly divided into two categories: wet preparation and dry preparation. The wet preparation process is simple and has a low cost. However, due to the presence of a binder in the slurry during the wet preparation process, a coating layer will be formed on the surface of the temperature-sensitive material particles. During the temperature sensing process, the coating layer will hinder the movement of carriers, resulting in a significant reduction in the sensitivity of the temperature-sensitive device and seriously affecting the performance of the temperature-sensitive device. The dry preparation process includes processes such as lithography and vapor deposition, which are mainly applied to the thin film deposition process of non-flexible materials such as metals and metal oxides. Although the dry process does not directly affect the performance of the prepared device, it has disadvantages such as high cost, energy-intensive, complex process, and limited types of preparation materials.

[0005] From the perspective of the overall device, the patterning of the temperature-sensitive material layer in a flexible temperature-sensitive device is often the top priority in determining the function of the temperature sensor. However, the patterning process often requires the use of various semiconductor manufacturing processes, resulting in a complex and costly process for preparing flexible temperature-sensitive devices. In addition, a temperature-sensitive material often responds to various external signal stimuli (such as temperature, humidity, and stress-strain). This makes it difficult for the temperature-sensitive device to decouple other signals except temperature, resulting in a decrease in the accuracy of the measurement data of the temperature-sensitive device. Summary of the Invention

[0006] The purpose of the present invention is to solve the above-mentioned technical deficiencies and provide a flexible temperature-sensitive device based on electrostatic automatic graphic filling and a preparation method thereof.

[0007] To this end, the present invention provides a flexible temperature-sensitive device based on electrostatic automatic graphic filling. The temperature-sensitive device body includes a temperature-sensitive material, a flexible substrate material, and a packaging layer. The temperature-sensitive material is a cluster of temperature-sensitive particulate matter, and the temperature-sensitive material is deposited on the flexible substrate by printing using an electric field loaded by corona discharge and then packaged.

[0008] Preferably, the temperature-sensitive material includes one or more of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate particles, graphene oxide particles, carbon nanotube particles, graphene nanosheet particles, reduced graphene oxide particles, polyaniline particles, and zinc oxide particles, and the particle size of the particles is 5-200 μm.

[0009] Preferably, the flexible substrate material includes one or more of polyethylene terephthalate, polyimide, polydimethylsiloxane, polytetrafluoroethylene, polyvinylidene fluoride, non-woven fabric, and medical tape.

[0010] Preferably, the encapsulation layer is encapsulated with a nano-film or a micro-film, and the preparation methods of the nano-film or the micro-film include spin coating, spin coating and lifting method, coating method, and spraying method.

[0011] Preferably, the temperature-sensitive device body adopts a capacitive sensing mechanism, and the sensitivity of the temperature-sensitive device body is characterized by the temperature coefficient of capacitance. The temperature coefficient of capacitance TCC = ΔC / C0×ΔT, where ΔC / C0 represents the relative change in capacitance, and ΔT represents the temperature change.

[0012] A preparation method of a flexible temperature-sensitive device based on electrostatic automatic pattern filling includes the following steps:

[0013] S1. Prepare a pre-patterned electrode and print or deposit the electrode on the flexible substrate;

[0014] S2. Use a discharge needle to generate a corona discharge to form an electric field, place two substrates in the electric field, and form a controllable electric field between the two substrates;

[0015] S3. Place the flexible substrate between the two substrates;

[0016] S4. The temperature-sensitive material particles move between the two substrates under the action of the electric field. Based on the principle that the temperature-sensitive material particles bounce off the conductive regions on the flexible substrate and fill the non-conductive regions, the temperature-sensitive material particles avoid the conductive regions and automatically fill the non-conductive regions between the electrodes on the flexible substrate to form a temperature-sensitive pattern;

[0017] S5. Encapsulate the flexible substrate.

[0018] Preferably, the printing voltage of the temperature-sensitive material particles is 5-25 KV, the distance between the discharge needle and the upper substrate is 1-7 cm, and the deposition time is 500 ms-10 s.

[0019] Preferably, the electrode includes one or more of gold, silver, copper, aluminum, titanium, indium tin oxide, and carbon-based electrodes.

[0020] The beneficial effects of the present invention are as follows: The present invention provides a flexible temperature-sensitive device based on electrostatic automatic pattern filling and a preparation method thereof, having the following beneficial effects.

[0021] (1) The temperature-sensitive material does not need to be prepared into a slurry or ink. It can be deposited on a flexible substrate by using the electric field loaded by corona discharge, and it can automatically identify and avoid conductive areas, only filling non-conductive areas. This method avoids the use of adhesives, improves the sensitivity of flexible temperature-sensitive devices, has low cost, simple process, saves the preparation time of devices, and improves production efficiency;

[0022] (2) Using breathable materials such as non-woven fabrics as flexible substrates, they have good air permeability, can avoid heat accumulation between the temperature-sensitive device and the skin, reduce measurement errors, ensure the true and reliable temperature measurement, and significantly improve the performance of temperature-sensitive devices;

[0023] (3) Adopting a capacitive sensing mechanism makes the temperature-sensitive device insensitive to stress, strain, humidity signals, etc., realizes the decoupling of various external signal stimuli, and improves the accuracy of the measurement data of the temperature-sensitive device;

[0024] (4) Encapsulation with a nano-film or micro-film has a thin thickness, meeting the needs of the development of multi-functionalization and miniaturization of temperature-sensitive devices. Description of the Drawings

[0025] Figure 1 is the in-situ temperature change comparison diagram of Pedot:pss particle clusters at 28°C and 80°C in this embodiment;

[0026] Figure 2 is the principle of the automatic patterning electrostatographic printing technology in this embodiment;

[0027] Figure 3 is the detailed schematic diagram of the automatic patterning electrostatographic printing technology in this embodiment;

[0028] Figure 4 is the change curve of the capacitance of the flexible temperature-sensitive device at 20 - 90°C and the linear fitting diagram of each temperature segment in this embodiment;

[0029] Figure 5 is the comparison diagram of the capacitance change amount during the heating and cooling process from 21°C to 50°C and the bending process from 0° to 180° of the flexible temperature-sensitive device in this embodiment;

[0030] Figure 6 is the capacitance change state diagram of the nano-film encapsulation and non-encapsulation in this embodiment;

[0031] Figure 7 is the average time histogram of the temperature-sensitive material layer of the flexible temperature-sensitive device prepared by the automatic patterning electrostatographic printing technology in this embodiment;

[0032] Figure 8 is the preparation flow chart of the flexible temperature-sensitive device in this embodiment;

[0033] Figure 9 It is a schematic structural diagram of a flexible temperature-sensitive device with a non-woven fabric as the substrate in this embodiment;

[0034] Figure 10 It is a stable cycle diagram of 150 times of the flexible temperature-sensitive device in the temperature range of 21°C to 50°C in this embodiment;

[0035] Figure 11 It is a change diagram of the flexible temperature-sensitive device with a resolution lower than 0.1°C in the temperature range of 37°C to 38°C in this embodiment. Specific implementation manners

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments to help understand the content of the present invention. The methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified.

[0037] As Figures 1 to 10 shown, the present invention provides a flexible temperature-sensitive device based on electrostatic automatic graphic filling. The temperature-sensitive device body includes a temperature-sensitive material, a flexible substrate material, an electrode, and a packaging layer. The temperature-sensitive material is a temperature-sensitive particulate cluster, and the temperature-sensitive material is printed and packaged on the flexible substrate by being deposited using an electric field loaded by corona discharge.

[0038] This embodiment will be elaborated from the following aspects:

[0039] 1. Solve the problem of low sensitivity of the flexible temperature-sensitive device.

[0040] Most of the existing flexible temperature-sensitive devices have the problem of low sensitivity, mainly due to the temperature-sensitive material itself, the deposition process of the temperature-sensitive material on the flexible substrate, and the influence of the packaging layer on heat transfer.

[0041] (1) The temperature-sensitive material itself.

[0042] The temperature-sensitive material includes one or more of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate particles, graphene oxide particles, carbon nanotube particles, graphene nanosheet particles, reduced graphene oxide particles, polyaniline particles, zinc oxide particles, and the particle size is 5 - 200 μm.

[0043] The temperature-sensitive material is preferably a ball-milled particulate cluster of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (abbreviated as Pedot:pss) with a particle size less than 50 μm. The printing voltage of Pedot:pss particles is 3 - 15 KV, the distance between the discharge needle and the upper substrate is 1 - 7 cm, and the deposition time is 500 ms - 10 s.

[0044] In one embodiment of the present invention, the temperature-sensitive material adopts a particulate cluster of graphene oxide particles, with a printing voltage of 5 - 20 KV, the distance between the discharge needle and the upper substrate being 1 - 5 cm, the deposition time being 1 - 10 s, and the particle diameter being less than 200 μm.

[0045] In one embodiment of the present invention, the temperature-sensitive material adopts a particulate cluster of carbon nanotube particles or graphene nanosheet particles, with a printing voltage of 15 - 25 KV, the distance between the discharge needle and the upper substrate being 2 - 5 cm, the deposition time being 3 - 10 s, and the particle diameter being less than 100 μm.

[0046] In one embodiment of the present invention, the temperature-sensitive material adopts a particulate cluster of reduced graphene oxide particles, with a printing voltage of 10 - 25 KV, the distance between the discharge needle and the upper substrate being 1 - 5 cm, the deposition time being 1 - 10 s, and the particle diameter being less than 200 μm.

[0047] In one embodiment of the present invention, the temperature-sensitive material adopts a particulate cluster of polyaniline (PANI) particles, with a printing voltage greater than 20 KV, the distance between the discharge needle and the upper substrate being 2.5 - 5 cm, the deposition time being 5 - 10 s, and the particle diameter being less than 100 μm.

[0048] In one embodiment of the present invention, the temperature-sensitive material adopts a particulate cluster of zinc oxide (ZnO) particles, with a printing voltage of 15 - 25 KV, the distance between the discharge needle and the upper substrate being 2 - 5 cm, the deposition time being 2 - 8 s, and the particle diameter being less than 50 μm.

[0049] Further, the ball milling of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate includes the following steps:

[0050] 1. Put poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate particles with a size of 3 - 5 mm and two steel balls with a diameter of 2 - 5 mm into a ball milling jar in a glove box. The volume ratio of the particles is 1 / 3 - 2 / 3. The glove box is filled with argon to prevent the Pedot:pss particles from reacting with oxygen or moisture in the air before ball milling, thus affecting their performance.

[0051] 2. Take out the ball milling jar from the glove box and put it into a ball mill, with the working time being 15 - 30 min.

[0052] 3. After ball milling, take out the ball milling jar and put it into the glove box. Then open the ball milling jar and use a small spoon to put the particles into a glass bottle to obtain the ball-milled Pedot:pss particles.

[0053] 4. The size of the ball-milled Pedot:pss particles is 10 - 200 μm. Use a sieve to screen out particles with a size of 10 - 50 μm to be used as the material for the temperature-sensitive layer.

[0054] Microcracks will be generated on the surface of Pedot:pss after ball milling, which can significantly improve the temperature sensitivity of the material. At the same time, the volume of Pedot:pss particles will expand during the process of temperature increase, resulting in closer contact between particles. This increases the electron transport pathways in the temperature-sensitive material layer, improves the overall conductivity of the temperature-sensitive material layer, and thus enhances the sensitivity of the flexible temperature-sensitive device.

[0055] Figure 1 It is an in-situ variable-temperature SEM test on Pedot:pss particle clusters. During the temperature change process from 28 °C to 80 °C, there is a certain relative displacement between Pedot:pss particles. As Figure 1 can be seen, the distance between the two left particles is 0.665 μm at 28 °C and 1.274 μm at 80 °C, the distance between the two bottom particles is 5.318 μm at 28 °C and 5.873 μm at 80 °C, and the distance between the two upper particles is 23.491 μm at 28 °C and 22.992 μm at 80 °C. It can be seen that the volume of Pedot:pss particles will expand with the increase of temperature, which indirectly explains the internal reason for the significant increase in conductivity of the temperature-sensitive material layer during the temperature change process. The above Pedot:pss particles sense through direct contact, without the need to prepare a slurry, but directly utilize the ball-milled particles. The contact between particles will be closer during heating, improving the sensitivity of the temperature-sensitive device.

[0056] (2) Deposition process of temperature-sensitive material on flexible substrate.

[0057] To save costs and simplify the manufacturing process, technicians often choose the wet preparation method with a relatively simple process, that is, mixing the temperature-sensitive material with some resin materials to prepare a slurry and then printing the temperature-sensitive material on the flexible substrate. Since there is a binder in the slurry, after the temperature-sensitive material is cured, a coating layer will be formed on the surface of the temperature-sensitive material particles, which will hinder the movement of electrons between the temperature-sensitive material particles and reduce the conductivity of the temperature-sensitive layer, thus significantly reducing the sensitivity of the temperature-sensitive device. In view of this, this application adopts an automatic patterning electrostatic printing technology to achieve ultra-fast non-contact printing of temperature-sensitive material particles on a pre-patterned flexible substrate.

[0058] Specifically, as Figure 2 and Figure 3 shown, the temperature-sensitive material is deposited on the flexible substrate by using the electric field loaded by corona discharge for printing, including the following steps:

[0059] 1. Attach the flexible substrate to the bottom of the upper substrate. A pre-patterned electrode is arranged at the bottom of the flexible substrate facing the lower substrate;

[0060] 2. Apply an electric field between the upper substrate and the lower substrate using a corona discharge device, where the upper substrate is made of an insulating material and the lower substrate is made of a metal material;

[0061] 3. The temperature-sensitive material particles move between the upper substrate and the lower substrate under the action of the electric field;

[0062] 4. Based on the principle that the conductive regions of the electrodes on the flexible substrate bounce back and the non-conductive regions are filled, the conductive regions are the electrodes and the non-conductive regions are the regions other than the metal electrodes. The temperature-sensitive material particles are deposited on the flexible substrate according to a preset pattern, so that the temperature-sensitive material particles are directly filled between the electrode patterns, realizing fast contactless printing.

[0063] Automatic patterning electrostatic printing technology (AEP) is a dry printing process that does not require the use of adhesives for printing, which enables the direct contact between the particles of the temperature-sensitive material without the barrier of a coating layer, and can greatly improve the sensitivity of the temperature-sensitive device.

[0064] Most of the existing flexible temperature-sensitive devices use resistive or capacitive sensing, that is, the change in the resistance or capacitance of the temperature-sensitive material is used to characterize the change in temperature. The flexible temperature-sensitive device involved in this application uses a capacitive sensing mechanism, which has stable linearity and ultra-high sensitivity. The fundamental reason is that the temperature-sensitive material particles are in direct contact without the barrier of other non-conductive substances such as adhesives and coating layers.

[0065] For the temperature-sensitive device involved in this application, a temperature and humidity test chamber is used to control the temperature change, and an LCR digital bridge is synchronously used to test the capacitance change of the temperature-sensitive material layer of the temperature-sensitive device during the temperature change process. Based on the relative capacitance change amount (ΔC / C0), a stable characterization of the temperature change is achieved.

[0066] As Figure 4 shown, when the temperature is within the measurable range (20 - 80 °C) of the flexible temperature-sensitive device, compared with the existing flexible temperature-sensitive devices, when the maximum measurable temperature (80 °C) of the temperature-sensitive device is reached, the relative capacitance change amount (ΔC / C0) of the temperature-sensitive device can reach more than 20,000, which is much higher than that of the existing flexible temperature-sensitive devices. Looking at it in segments, in the temperature range of 20 - 65 °C, the temperature-sensitive device has excellent sensitivity (TCC = 6.60% / °C) and good linearity (R2 = 0.91452). The maximum capacitance change amount (maxΔC / C0) within this range can reach more than 300%. The maximum capacitance change amount of the temperature-sensitive device is more than 2 - 3 times that of the same type of capacitive temperature-sensitive device, which is better than most flexible temperature-sensitive devices; in the temperature range of 65 - 80 °C, the temperature-sensitive device has ultra-high sensitivity (TCC = 1478.95% / °C) and better linearity (R2 = 0.97336), and almost exceeds all reported flexible temperature-sensitive devices in terms of sensitivity.

[0067] Further, the capacitance temperature coefficient TCC = ΔC / C0×ΔT, where ΔC / C0 represents the relative change in capacitance and ΔT represents the temperature change.

[0068] (3) Influence of the encapsulation layer on heat transfer.

[0069] Most flexible temperature-sensitive devices use resin-based materials with a thickness ranging from dozens of microns to hundreds of microns as the encapsulation layer, which reduces the heat conduction speed from the outside to the temperature-sensitive material layer, resulting in a decrease in the sensitivity of the flexible temperature-sensitive device and an increase in the response time to temperature.

[0070] The encapsulation layer involved in this application is preferably encapsulated with a polyimide (PI) nanofilm or a polyvinyl formal (formvar) nanofilm, and the thickness of the encapsulation layer is about 200 nm. Encapsulation with a nanoscale thin film can accelerate the heat conduction speed from the outside to the temperature-sensitive material layer, and can improve the sensitivity of the temperature-sensitive device and reduce the response time of the temperature-sensitive device compared with thick film encapsulation.

[0071] In an embodiment of the present invention, the encapsulation layer can also be encapsulated with a polyimide (PI) microfilm or a polyvinyl formal (formvar) microfilm, or can also be encapsulated with a pmma nano / microfilm or a polydimethylsiloxane nano / microfilm.

[0072] Further, the preparation methods of the nanofilm or microfilm include spin coating method, spin coating and lifting method, coating method and spraying method.

[0073] Further, the preparation process of the nanofilm or microfilm by the spin coating and lifting method includes the following steps:

[0074] 1. Spin coat polyvinyl alcohol on the silicon wafer in multiple stages;

[0075] 2. Clamp the spin-coated silicon wafer on the lifting machine. After setting the lifting parameters, immerse the silicon wafer in the prepared nanofilm solution and lift it. In this embodiment, 30-40 ml of chloroform and 1-1.2 g of polyvinyl formal powder are used to prepare the polyvinyl formal solution, and the polyvinyl formal is filled in a square cylinder. Among them, the preparation of the pmma nano / microfilm does not require the above lifting process;

[0076] 3. Put one side of the lifted silicon wafer into a petri dish filled with deionized water. After one side of the polyvinyl alcohol is completely dissolved in water, the nanofilm on this side will warp. Gently float it on the water surface with tweezers. Then, push the silicon wafer 5-8 mm every 10 minutes until it is completely pushed into the deionized water. After the whole nanofilm floats on the water surface, fish it out with a ring and put it in a drying oven to dry at 40-60 °C for 1 h for use;

[0077] 4. Transfer the dried nanofilm onto the temperature-sensitive material layer.

[0078] Specifically, spin-coating polyvinyl alcohol includes a first stage, a second stage, and a third stage. The spin-coating speed in the first stage is 300 - 600 rpm, which is relatively slow. The purpose is to initially wet the surface of the silicon wafer with polyvinyl alcohol. The time is 50 - 70 s, and the acceleration is 80 - 100 rpm / s, which can enable the polyvinyl alcohol to spread evenly on the silicon wafer. The spin-coating speed in the second stage is 2000 - 4000 rpm. The increasing speed helps to remove the excess polyvinyl alcohol and make the film on the silicon wafer more uniform. The time is 100 - 130 s, and the acceleration is 90 - 110 rpm / s, further adjusting the thickness and uniformity of the film. The spin-coating speed in the third stage is 4000 - 6000 rpm, which is the highest spin-coating speed and is used to further reduce the thickness of the film and improve the uniformity. The time is 230 - 250 s, and the acceleration is 90 - 110 rpm / s. The long-time high-speed spin-coating helps to obtain a thinner and more uniform film.

[0079] Furthermore, the lifting parameters for preparing polyimide (PI) nanofilm or polyvinyl formal (formvar) nanofilm include the lifting height, dipping time, and lifting speed. The lowest lifting height is 30 - 60 cm, the highest lifting height is 120 - 140 cm, the dipping time is 1 s, and the lifting speed is 200 - 600 μm / s. While the dipping time for preparing polyimide (PI) microfilm or polyvinyl formal (formvar) microfilm is 5 - 15 s, and the lifting speed is 500 μm / s - 5 mm / s.

[0080] II. Solve the problem of poor air permeability of the flexible substrate in flexible temperature-sensitive devices.

[0081] The flexible substrate material is made of breathable materials, which include one or more of polyethylene terephthalate (PET), polyimide (PI), polyurethane (PU), polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polybutylene adipate-co-terephthalate (Ecoflex), non-woven fabric, and medical tape to match the Young's modulus of human skin.

[0082] When using polyethylene terephthalate (PET) and polyimide (PI) materials, the printing voltage is 15 - 25 KV, and the deposition time is 1 - 3 s.

[0083] When using polydimethylsiloxane (PDMS), non-woven fabric, and medical tape, the printing voltage is 3 - 15 KV, and the deposition time is 500 ms - 10 s.

[0084] In this embodiment, non-woven fabric is preferably used as the flexible substrate. The non-woven fabric belongs to artificial fiber non-woven fabric, which is made of cellulose such as natural wood, reed, and cotton linter as raw materials through chemical processing. This non-woven fabric has excellent air permeability, can timely discharge the sweat and moisture on the skin surface, maintain the skin dry, and effectively reduce the occurrence probability of skin problems. At the same time, for the flexible temperature-sensitive device, good air permeability can avoid heat accumulation between the temperature-sensitive device and the skin, reduce measurement errors, ensure the authenticity and reliability of temperature measurement, and significantly improve the performance of the temperature-sensitive device.

[0085] III. Solve the problem that the flexible temperature-sensitive device is easily interfered by other external stimuli except temperature.

[0086] The flexible temperature-sensitive device characterizes the temperature change by the change of the physical properties of the temperature-sensitive material caused by the temperature change, mainly relying on the change of the capacitance or resistance of the temperature-sensitive material between the electrodes. However, the temperature-sensitive material is not only sensitive to temperature, but also responds to various external stimuli such as humidity, stress and strain. To ensure the measurement accuracy, it is necessary to decouple the signals generated by other external stimuli except temperature, which is the main difficulty for technicians to prepare high-precision flexible temperature-sensitive devices.

[0087] The flexible temperature-sensitive device involved in this application is extremely sensitive to temperature signals and insensitive to stress and strain. When bending strain occurs, according to C = ΔC / C0, the electrode spacing is not easy to change, so the capacitance is not easy to change. As Figure 5 shown, when the temperature-sensitive device is heated and cooled between 21 °C and 50 °C, the maximum relative change amount (maxΔC / C0) of the capacitance of the temperature-sensitive material is 300%. At the same time, when the temperature-sensitive device is bent 180° along its central axis, the maximum relative change amount (maxΔC / C0) of its capacitance is only 10%. When this temperature-sensitive device is attached to the human skin for use, since the maximum bending angle of the joint generally does not exceed 90°, the maximum interference caused by the bending strain to its relative capacitance change amount can be controlled within 3%. This means that the flexible temperature-sensitive device involved in this application, as a temperature-sensitive device that can measure body temperature, has a low sensitivity to bending strain.

[0088] The flexible temperature-sensitive device involved in this application can not only be insensitive to bending strain, but also achieve decoupling of humidity signals, and this function is mainly achieved through the surface encapsulation body. This application uses PI or formvar nanofilm to implement the encapsulation process. While ensuring good heat conduction performance, the nanofilm encapsulation body can efficiently isolate external water vapor, thus effectively playing the key role of humidity decoupling. As Figure 6As shown in the figure, when the surface encapsulation is not set, the temperature-sensitive device is extremely vulnerable to the interference of humidity factors, resulting in an unstable capacitance change of the temperature-sensitive material when the temperature changes. After the nano-film encapsulation is completed, the curve of the capacitance change of the temperature-sensitive device with time shows high stability, effectively improving the measurement accuracy and reliability of the temperature-sensitive device in a complex environment.

[0089] IV. Solve the problems of high preparation cost and complex process of high-sensitivity flexible temperature-sensitive devices.

[0090] When preparing flexible temperature-sensitive devices by wet process, it is necessary to prepare slurry, and the binder and coating layer contained therein will significantly reduce the sensitivity of the device. Therefore, for flexible temperature-sensitive devices with high sensitivity requirements, dry process is mostly used for preparation. Common dry preparation processes for depositing temperature-sensitive materials on flexible substrates include photolithography, laser direct writing, magnetron sputtering, evaporation coating, etc. These processes directly deposit temperature-sensitive materials, avoiding the influence of the coating layer on the device sensitivity. However, these processes have problems such as expensive equipment and complex preparation processes, greatly increasing the preparation cost, preparation time and process complexity of flexible temperature-sensitive devices.

[0091] As Figure 8 shown, a preparation method of a flexible temperature-sensitive device based on electrostatic automatic pattern filling includes the following steps:

[0092] S1. Prepare a pre-patterned electrode and print or deposit the electrode on a flexible substrate. The pre-patterned electrode is prepared by means of screen printing, inkjet printing, spin coating printing, photocuring printing, photolithography, magnetron sputtering + mask plate, etc. The electrode includes one or more of gold (Au), silver (Ag), copper (Cu), aluminum (Al), titanium (Ti), indium tin oxide (ITO), and carbon-based electrode (carbon-based material + polymer resin), and the electrode is arranged at the bottom of the flexible substrate;

[0093] S2. Use a discharge needle to generate a corona discharge to form an electric field, place two substrates in the electric field, and form a controllable electric field between the two substrates; the substrates include an upper substrate and a lower substrate, the upper substrate is located above the lower substrate, and the discharge needle is arranged above the upper substrate;

[0094] S3. Place the flexible substrate between the upper substrate and the lower substrate;

[0095] S4. Automatic patterning of temperature-sensitive materials: By using a discharge needle set above the upper substrate to generate corona discharge and accumulate charges on the upper substrate, a potential difference is formed between the upper substrate and the lower substrate, which promotes the rapid movement of temperature-sensitive material particles between the upper substrate and the lower substrate. Based on the principle that the temperature-sensitive material particles bounce off the conductive regions and fill the non-conductive regions, the temperature-sensitive material particles avoid the conductive regions and automatically fill the non-conductive regions between the electrodes on the flexible substrate, forming a temperature-sensitive pattern, thus realizing the automatic patterned deposition of the temperature-sensitive material on the flexible substrate;

[0096] S5. Encapsulate the flexible substrate with a nano-film. First, prepare the nano-film based on processes such as spin coating, spin coating and lifting, coating, or spraying, and then transfer the nano-film onto the patterned temperature-sensitive material layer by transfer printing to achieve the encapsulation of the temperature-sensitive device.

[0097] The preparation process of this application is based on a dry process, ensuring the high sensitivity of the device. The deposition process of the temperature-sensitive material is only completed by an electrostatographic printing device, which consists of a high-voltage power supply and a corona discharge needle, and the equipment cost is very low. As an ultra-fast printing method, the deposition process of the temperature-sensitive material only takes hundreds of milliseconds to several seconds (as Figure 7 shown), greatly reducing the cost of fabricating flexible temperature-sensitive devices by dry processes, significantly improving the device production efficiency, and at the same time greatly reducing the complexity of the preparation process.

[0098] The flexible temperature-sensitive device involved in the present invention generally presents a sandwich structure, which is composed of a flexible substrate material, an electrode and a temperature-sensitive material, and a surface encapsulation layer from bottom to top.

[0099] The flexible substrate material at the bottom layer can select various flexible substrates, such as PET, PI, PDMS, and non-woven fabric, etc. Different beneficial effects can be obtained according to different flexible substrates. Taking non-woven fabric as an example (as Figure 9 shown), as a flexible skin-friendly material, it has good biocompatibility. At the same time, its breathable and porous structure can prevent the aggregation of skin moisture from affecting the lifespan of the temperature-sensitive device. In addition, the non-woven fabric substrate has a small thickness, low cost, safety and environmental protection, which can reduce the overall thickness and volume of the electronic skin temperature-sensitive device and lower the overall cost of the temperature-sensitive device.

[0100] The middle layer is composed of interdigital electrodes and temperature-sensitive materials distributed between the fingers. The two-dimensional overall size of the interdigital electrodes is about 50×25 mm, and it has a double-layer structure of titanium-gold longitudinally (both prepared by magnetron sputtering process), with a thickness in the order of hundreds of nanometers. The temperature-sensitive material distributed in the gaps between the fingers of the interdigital electrodes is a granular conductive polymer (the single particle size is within 40 μm), and this material realizes the filling behavior of the temperature-sensitive material in the gaps between the fingers of the interdigital electrodes by using the ultra-fast printing technology of automatic patterning electrostatic printing technology (AEP).

[0101] This printing method loads an electric field through corona discharge and utilizes the special behavior of charged particles bouncing off in the conductive area and filling in the non-conductive area to achieve the direct non-contact printing of temperature-sensitive material particles. Moreover, there is no need to prepare slurries, enabling direct contact between temperature-sensitive material particles without the barrier of binders, which can greatly improve the sensitivity of the prepared temperature-sensitive devices.

[0102] In summary, the flexible temperature-sensitive device of the present invention is prepared by using a low-cost and fast-speed electrostatic printing device, significantly reducing the production cost of the device and greatly improving the preparation speed of the device. Compared with other flexible temperature-sensitive devices, this flexible temperature-sensitive device has excellent output signal linearity and stability (as Figure 10 shown). In addition, since the resolution is closely related to the sensitivity, the higher the sensitivity, the greater the slope of the ΔC / C0-Temperature curve. At the same temperature, the capacitance of the temperature-sensitive device in this embodiment changes faster and has a high resolution. Therefore, this temperature-sensitive device also has a resolution lower than 0.1 °C and can detect temperature changes lower than 0.1 °C (as Figure 11 shown), and the measurement data is more accurate.

[0103] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "left", "right", "upper", "lower", "top", "bottom", "front", "rear", "inner", "outer", "back", "middle", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as a limitation of the present invention.

[0104] However, the above are only specific embodiments of the present invention, and the scope of implementation of the present invention cannot be limited thereby. Therefore, the replacement of equivalent components or equivalent changes and modifications made according to the scope of protection of the present invention patent should still fall within the scope covered by the claims of the present invention.

Claims

1. A flexible temperature-sensitive device based on electrostatic automatic graphic filling, the temperature-sensitive device body includes a temperature-sensitive material, a flexible substrate material, and a packaging layer, characterized in that, The temperature-sensitive material is a cluster of temperature-sensitive particles, and the temperature-sensitive material is printed and encapsulated on a flexible substrate by being deposited using an electric field loaded by corona discharge.

2. The flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 1, characterized in that, The temperature-sensitive material includes one or more of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate particles, graphene oxide particles, carbon nanotube particles, graphene nanosheet particles, reduced graphene oxide particles, polyaniline particles, zinc oxide particles, and the particle size is 5 - 200 μm.

3. The flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 1, wherein The flexible substrate material includes one or more of polyethylene terephthalate, polyimide, polydimethylsiloxane, polytetrafluoroethylene, polyvinylidene fluoride, non-woven fabric, and medical tape.

4. A flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 1, characterized in that, The encapsulation layer is encapsulated with a nano-film or a micro-film, and the preparation methods of the nano-film or the micro-film include spin coating, spin coating and lifting method, coating method and spraying method.

5. A flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 1, characterized in that The temperature-sensitive device body adopts a capacitive sensing mechanism, and the sensitivity of the temperature-sensitive device body is characterized by the capacitance temperature coefficient. The capacitance temperature coefficient TCC = ΔC / C0×ΔT, where ΔC / C0 represents the relative change in capacitance, and ΔT represents the temperature change.

6. A preparation method of a flexible temperature-sensitive device based on electrostatic automatic graphic filling, characterized in that, It includes the following steps: S1. Prepare a pre-patterned electrode and print or deposit the electrode on the flexible substrate; S2. Use a discharge needle to generate a corona discharge to form an electric field. Place two substrates in the electric field to form a controllable electric field between the two substrates; S3. Place the flexible substrate between the two substrates; S4. The temperature-sensitive material particles move between the two substrates under the action of the electric field. Based on the principle that the temperature-sensitive material particles bounce off the conductive regions on the flexible substrate and fill the non-conductive regions, the temperature-sensitive material particles avoid the conductive regions and automatically fill the non-conductive regions between the electrodes on the flexible substrate to form a temperature-sensitive pattern; S5. Encapsulate the flexible substrate.

7. The preparation method of a flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 6, characterized in that, The printing voltage of the temperature-sensitive material particles is 5 - 25 KV, the distance between the discharge needle and the upper substrate is 1 - 7 cm, and the deposition time is 500 ms - 10 s.

8. The preparation method of a flexible temperature-sensitive device based on electrostatic automatic graphic filling according to claim 6, wherein, The electrode includes one or more of gold, silver, copper, aluminum, titanium, indium tin oxide, and carbon-based electrodes.

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