Preparation Method and Application of a Self-Driving Impact Sensor Device for Uniform Microdroplet Jet Printing

Abstract

A preparation method and application of a self-driven impact sensor device for uniform micro-droplet jet printing belong to the field of flexible electronics manufacturing. First, a sensor substrate mixture is prepared, and then a graphene fork-shaped conductive electrode is printed. The conductive graphene sinks and embeds into the interior of the PTFE / PDMS / NaCl mixture under the action of its own gravity and the wrapping effect of the viscous PTFE / PDMS / NaCl mixture to obtain the initial state of the sensor. Finally, NaCl in the PTFE / PDMS / NaCl flexible substrate is removed to generate tiny holes, and a PTFE / PDMS-graphene electrode generator sensor device, that is, a self-driven impact sensor device, is obtained. When the sensor of the present invention is excited by an external impact load, affected by the friction / electrostatic induction between the conductive electrode and the electret, charge directional transfer occurs inside the device to form a current. Corresponding to the load peak values of different excitations, the open-circuit voltage of this sensor is also different, and shows a linearly corresponding relationship with the load peak value within a certain range. Therefore, by observing the voltage signal of the sensor, the external impact excitation can be directly measured.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronics manufacturing, and particularly relates to a preparation method and application of a self-driven impact sensor device with uniform micro-droplet jet printing. Background Art

[0002] The rapid development of smart cities and smart wearables has put forward higher requirements for high-performance flexible sensor devices, such as self-adaptive stretching, bending and other deformations, sensitive feedback, temperature and humidity tolerance, etc. To meet such strict requirements, the conductors of sensors usually need to be encapsulated and protected by elastomers. Therefore, flexible sensor devices usually include a conductive electrode part and a flexible substrate part. The current preparation methods mainly focus on the preparation of flexible conductive electrodes, the preparation of flexible substrates, and the lamination and encapsulation molding of the two. Among them, the main preparation methods of flexible conductive electrodes include laser cutting, screen printing, 3D printing, etc. However, such preparation methods all need to transfer the formed electrodes and encapsulate them with flexible substrates, and this process will inevitably affect the electrode patterns, especially when the conductive electrodes have complex shapes. Therefore, it is of great significance to develop a flexible sensor device preparation technology that does not require electrode transfer and can self-encapsulate.

[0003] The prior art discloses the use of 3D printing technology to prepare sensors. This method is suitable for preparing the flexible conductor part, but it is difficult to adapt to complex detection environments due to the lack of external substrate protection. In addition, the currently prepared flexible sensors by 3D printing all require external power supply. With the gradual maturity of smart cities and smart wearables, frequent battery replacement or using additional power supply will greatly reduce the detection efficiency and reliability of sensors. Therefore, fast power supply is becoming one of the development goals of flexible sensor devices. Summary of the Invention

[0004] Technical Problems to be Solved:

[0005] To avoid the deficiencies of the prior art, the present invention provides a method for preparing a self-driven impact sensor device by uniform micro-droplet jet printing. This sensor is a self-encapsulated and self-powered flexible sensor device. Using the uniform micro-droplet jet 3D printing technology, a triboelectric nanogenerator flexible sensor with polytetrafluoroethylene (PTFE) / polydimethylsiloxane (PDMS) as the electrification part and graphene interdigital electrodes as the conductive electrodes is prepared. When this flexible sensor is excited by an external impact load, due to the friction / electrostatic induction between the conductive electrode and the electret, it promotes the occurrence of directional charge transfer inside the device to form a current. Corresponding to the load peaks of different excitations, the open-circuit voltage of this sensor will also be different, and it shows a linear corresponding relationship with the load peak within a certain range. Therefore, by observing the voltage signal of the sensor, the external impact excitation can be directly measured.

[0006] The technical solution of the present invention is: a method for preparing a self-driven impact sensor device by uniform micro-droplet jet printing, and the specific preparation method is as follows:

[0007] Step 1: Preparation of the electret-enhanced sensor substrate mixture;

[0008] Mix polydimethylsiloxane PDMS and a curing agent in a mass ratio of 10:1 to obtain mixture A; add polytetrafluoroethylene PTFE to mixture A to obtain mixture B, and add powdered sodium chloride NaCl to mixture B to obtain mixture C. Stir well to mix evenly to obtain the PTFE / PDMS / NaCl mixture; use a spin coater to spin coat the PTFE / PDMS / NaCl mixture in a polyimide PI container and pre-cure it at 70 °C for 3 - 5 min to increase the viscosity of the mixture.

[0009] Step 2: Printing of graphene interdigital conductive electrodes;

[0010] Place the container spin-coated with the PTFE / PDMS / NaCl mixture after pre-curing in step one on the printing platform, facing the nozzle; the spraying device prepares conductive graphene with an interdigital electrode pattern as the conductive electrode according to the interdigital electrode pattern and spraying process requirements; the conductive graphene is finally sunk and embedded inside the PTFE / PDMS / NaCl mixture under the action of its own gravity and the wrapping of the viscous PTFE / PDMS / NaCl mixture to obtain the initial state of the sensor.

[0011] Step 3: Post-treatment of the sensor;

[0012] Place the initial state of the sensor obtained in Step 2 in a vacuum drying oven, adjust the temperature to 170 - 220 °C, and allow it to fully cure for 60 min; place the fully cured sensor device in clear water, and through slow bending and stretching, dissolve the NaCl in the PTFE / PDMS / NaCl flexible substrate of the sensor device in water to generate tiny pores; then fully volatilize and release the surface insulating substances in the conductive electrodes; finally, obtain a PTFE / PDMS-graphene electrode generator sensor device, that is, a self-powered impact sensor device.

[0013] A further technical solution of the present invention is that in Step 1, polytetrafluoroethylene (PTFE) is added at 30% of the mass fraction of the mixed solution A.

[0014] A further technical solution of the present invention is that in Step 1, powdered sodium chloride (NaCl) is added at 20% of the mass fraction of the mixed solution B.

[0015] A further technical solution of the present invention is that in Step 1, the uniformly mixed mixed solution C is subjected to vacuum treatment to discharge the air bubbles in the mixed solution C.

[0016] A further technical solution of the present invention is that in Step 2, a conductive graphene interdigital electrode pattern is printed using a uniform micro-droplet ejection device.

[0017] A further technical solution of the present invention is that in Step 2, the designed interdigital electrode pattern is input into a computer, and the parameters of the uniform micro-droplet ejection device are adjusted to: voltage 5 V, pulse width 10 - 30 μS, and frequency 0.1 - 0.2 Hz.

[0018] A further technical solution of the present invention is that in Step 3, the sensor device after removing NaCl is wiped dry, and then placed in a vacuum drying oven again. The temperature is adjusted to 200 - 220 °C, and the heat treatment time is 60 - 80 min to fully volatilize and release the surface insulating substances in the conductive electrodes.

[0019] An application of a uniform micro-droplet ejection printing self-powered impact sensor device, characterized in that:

[0020] First, connect wires A and B to both ends of the PTFE / PDMS-graphene electrode generator sensor device. The other end of wire A is connected to a voltage detection instrument, and the other end of wire B is grounded;

[0021] Then, use nano tape to fully adhere the PTFE / PDMS-graphene electrode generator sensor device to the surface of the object to be measured, apply an impact excitation with a fixed frequency and load peak value, and record the voltage signal V of the PTFE / PDMS-graphene electrode generator sensor device due to the influence of friction / electrostatic induction between the conductive electrode and the PTFE / PDMS electret i, complete the detection and sensing of the object under test under any impact load.

[0022] A further technical solution of the present invention is: for the impact load detection of the PTFE / PDMS-graphene electrode generator sensor device: gradually increase the peak load P of the excitation 1 -P n , and record the corresponding voltage signals V 1 -V n . In view of the significant linear relationship between the peak voltage signal and the peak load, therefore, for any voltage V within the maximum detection range i , the corresponding peak impact load is:

[0023]

[0024] where n represents the total number of impact tests, and i represents the specific i-th test.

[0025] A further technical solution of the present invention is: the peak load P 1 -P n is within 100 N.

[0026] Beneficial effects

[0027] The beneficial effects of the present invention are as follows: The present invention first prepares a mixture of PTFE electret-enhanced PDMS and NaCl, places the mixture tank on the printing platform, and uses the uniform micro-droplet jetting 3D printing technology to form the designed graphene interdigital electrode pattern in the viscous mixture. After washing with water to remove the NaCl powder inside the fully cured and self-encapsulated sensor device and form microporous channels, heat the sensor device to discharge the insulating substances in the conductive electrodes from the micropores, and form a triboelectric nanogenerator sensor device with good conductivity enhanced by electret. Finally, wire the device and fully adhere it to the surface of the object under test, gradually adjust the peak excitation load, and record the corresponding voltage signals respectively, so as to detect and sense any impact load.

[0028] The difficulty of the preparation method proposed by the present invention lies in: combining the self-gravity of conductive graphene with the viscous characteristics of the PTFE / PDMS / NaCl mixture to realize the self-encapsulation molding of the conductive electrode and the flexible substrate, that is, the conductive graphene of the interdigital electrode pattern prepared by uniform micro-droplet jetting printing finally sinks and embeds into the PTFE / PDMS / NaCl mixture under the action of its own gravity and the wrapping of the viscous PTFE / PDMS / NaCl mixture to complete self-encapsulation; this technology does not require processes such as electrode transfer and encapsulation.

[0029] In addition, the sensor has a self-powered sensing effect. Under the excitation of an external impact load, the electrification part and the conductive motor part of the sensor are subject to electrostatic induction and triboelectrification effects, resulting in the directional transfer of charges inside it and forming an electric current. Different impact excitations can generate different voltage signals, so no additional power supply is required during use. It can be used to detect impact loads on solid objects, human bodies, etc. Description of the Drawings

[0030] Figure 1 Schematic diagram of the sensor preparation device;

[0031] Figure 2 Self-driven impact force sensor and its application examples;

[0032] Figure 3 Schematic diagram of the sensor working principle;

[0033] Figure 4 Test results of the self-driven sensor under different loads.

[0034] Description of the reference numerals: 1. Mobile control system, 2. Temperature control system, 3. Pressure control system, 4. Liquid storage tank, 5. Pressure drive system, 6. Flexible and stretchable motor, 7. PTFE / PDMS container, 8. PDMS / PTFE, 9. Three-dimensional mobile printing platform. Detailed Embodiments

[0035] The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] To enable relevant technicians to better understand the implementation of the present invention, refer to the attached Figures 1-4 , the method for preparing a self-driven sensor for detecting damage to aircraft skin composite materials proposed by the present invention includes the following steps:

[0037] Step 1: Prepare an electret mixture: Mix polydimethylsiloxane (PDMS) and a curing agent in a mass ratio of 10:1 to obtain mixture A, add polytetrafluoroethylene PTFE at 30% of the mass fraction of mixture A to obtain mixture B; add powdered sodium chloride NaCl at 20% of the mass fraction of mixture B to obtain mixture C, stir well for 10 min, and perform vacuum treatment for 15 min to obtain a PTFE / PDMS / NaCl mixture; spin-coat the obtained PTFE / PDMS / NaCl mixture in a polyimide (PI) tank; pre-cure at 70 °C for 3 min to increase the viscosity of the mixture.

[0038] Step 2: Use uniform microdroplet jet 3D printing technology to prepare graphene interdigital electrodes in the mixture Figure 1)。Place the container spin-coated with the PTFE / PDMS / NaCl mixture after pre-curing in Step 1 on the printing platform, facing the nozzle directly; input the designed interdigital electrode pattern into the computer, and adjust the printer process parameters: voltage 5V, pulse width 20μs, printing frequency 0.2Hz. The graphene micro-droplets ejected from the nozzle gradually sink under the action of gravity and the viscous resistance of the mixture and complete restricted spreading. The printing platform moves in the XYZ directions according to the designed interdigital electrode pattern under computer control to complete electrode printing, and the printing process is completed within 3h. The formed graphene electrode is completely embedded inside the PTFE / PDMS / NaCl( Figure 2 ), obtaining the initial state of the sensor.

[0039] Step 3: Post-processing of the sensor and improvement of the self-powered level: Place the initial state of the sensor obtained in Step 2 in a vacuum drying oven and cure it fully at a temperature of 190°C for 60min. Place the fully cured sensor device in clean water, and by slowly bending and stretching, dissolve the NaCl powder in the PTFE / PDMS / NaCl flexible substrate of the sensor device to generate tiny pores. After drying the device, place it in the vacuum drying oven again and perform heat treatment at a temperature of 200°C for 80min to fully volatilize and release the surface insulating substances in the conductive electrodes. Obtain a PTFE / PDMS-graphene power generation device with excellent electrical conductivity, that is, a self-driven impact sensor device.

[0040] Step 4: Installation and use of the sensor: Connect wires A and B to both ends of the PTFE / PDMS-graphene power generation device prepared in Step 3. Connect the other end of wire A to the high-voltage probe of the oscilloscope for detecting electrical signals, and connect the other end of wire B to the ground. Use ultra-thin nano tape to adhere it firmly to the surface of the object to be measured( Figure 2 ), apply an impact excitation with a fixed frequency and peak load of 1Hz, 50N. Affected by the friction / electrostatic induction between the conductive electrode and the electret( Figure 3 ), record the output voltage signal V of the generator sensor at this time i = 150V;

[0041] Step 5: Real-time detection of impact load: Place the sensor on the surface of the object to be measured, fix the occurrence frequency of the excitation at 1Hz, and gradually increase the peak load P of the excitation in turn 1 -P 3 = 20N, 50N, 75N (within 100N), and record the corresponding voltage signals V 1 -V 3 = 105V, 150V, 241V( Figure 4 in Figure (a)), in view of the significant linear relationship between the peak voltage signal and the peak load (the linearity of the voltage increment and the load increment is higher than 96%), so for any voltage V within the maximum detection rangei The corresponding peak impact load can be calculated as:

[0042]

[0043] Although embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing, characterized in that the specific steps are as follows: Step 1: Preparation of an electret-enhanced sensor substrate mixture; Mix polydimethylsiloxane (PDMS) and a curing agent in a mass ratio of 10:1 to obtain mixture A; add polytetrafluoroethylene (PTFE) to mixture A to obtain mixture B, and add powdered sodium chloride (NaCl) to mixture B to obtain mixture C. Stir well to mix evenly to obtain the PTFE / PDMS / NaCl mixture; use a spin coater to spin coat the PTFE / PDMS / NaCl mixture in a polyimide (PI) container and pre-cure it at 70 °C for 3 - 5 min to increase the viscosity of the mixture; Step 2: Printing of a graphene interdigital conductive electrode; Place the container spin-coated with the PTFE / PDMS / NaCl mixture after pre-curing in Step 1 on a printing platform and align it with the nozzle; the spraying device prepares a conductive graphene with an interdigital electrode pattern as the conductive electrode according to the interdigital electrode pattern and spraying process requirements; The conductive graphene is affected by its own gravity and the wrapping effect of the viscous PTFE / PDMS / NaCl mixture, and finally sinks and embeds into the interior of the PTFE / PDMS / NaCl mixture to obtain the initial state of the sensor; Step 3: Post-treatment of the sensor; Place the initial state of the sensor obtained in Step 2 in a vacuum drying oven, adjust the temperature to 170 - 220 °C, and fully cure it for 60 min; place the fully cured sensor device in clear water, and by slowly bending and stretching, dissolve the NaCl in the PTFE / PDMS / NaCl flexible substrate of the sensor device in water to generate tiny pores; then fully volatilize to release the surface insulating substances in the conductive electrode; finally, obtain a PTFE / PDMS-graphene electrode generator sensor device, that is, a self-driven impact sensor device.

2. The preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing according to Claim 1, characterized in that: In Step 1, polytetrafluoroethylene (PTFE) is added according to 30% of the mass fraction of mixture A.

3. The preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing according to Claim 2, characterized in that: In Step 1, powdered sodium chloride (NaCl) is added according to 20% of the mass fraction of mixture B.

4. The preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing according to Claim 1, characterized in that: In Step 1, the uniformly mixed mixture C is subjected to vacuum treatment to discharge the air bubbles in mixture C.

5. The preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing according to Claim 1, characterized in that: In Step 2, a uniform micro-droplet spraying device is used to print a conductive graphene interdigital electrode pattern.

6. The preparation method of a self-driven impact sensor device by uniform micro-droplet jet printing according to Claim 1, characterized in that: In step 2, the designed interdigital electrode pattern is input into a computer, and the parameters of the uniform micro-droplet ejection device are adjusted as follows: voltage 5V, pulse width 10 - 30 μS, and frequency 0.1 - 0.2 Hz.

7. The preparation method of a uniform micro-droplet ejection printing self-driven impact sensor device according to claim 1, characterized in that: In step 3, the sensor device after removing NaCl is dried, and then placed in a vacuum drying oven again. The temperature is adjusted to 200 - 220 °C, and the heat treatment time is 60 - 80 min to fully volatilize and release the surface insulating substances in the conductive electrodes.

8. The application of a uniform micro-droplet ejection printing self-driven impact sensor device according to any one of claims 1 - 7, characterized in that: First, external wires A and B are connected to both ends of the PTFE / PDMS-graphene electrode generator sensor device. The other end of wire A is connected to a voltage detection instrument, and the other end of wire B is grounded; Then, use nano tape to fully adhere the PTFE / PDMS-graphene electrode generator sensor device to the surface of the object to be measured, apply an impact excitation with a fixed frequency and load peak, and record the voltage signal V of the PTFE / PDMS-graphene electrode generator sensor device under the influence of friction / electrostatic induction between the conductive electrode and the PTFE / PDMS electret i , and complete the detection and sensing of the object to be measured under any impact load.

9. The application of a uniform micro-droplet ejection printing self-driven impact sensor device according to claim 8, characterized in that: Impact load detection of the PTFE / PDMS-graphene electrode generator sensor device: Gradually increase the peak load P of the excitation 1 -P n , and record the corresponding voltage signals V 1 -V n . Given that there is a significant linear relationship between the peak voltage signal and the peak load, the peak impact load corresponding to any voltage V within the maximum detection range is i : where n represents the total number of impact tests, and i represents the specific i-th test.

10. The application of a uniform micro-droplet ejection printing self-driven impact sensor device according to claim 9, characterized in that: The peak load P 1 -P n is within 100 N.

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