AgCl film humidity-sensitive flexible intelligent writing board, preparation method thereof and intelligent writing flexible humidity sensing system

Abstract

The invention relates to an AgCl film humidity-sensitive flexible intelligent writing board, a preparation method thereof and an intelligent writing flexible humidity sensing system. The humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl thin film is of a layered structure and sequentially comprises a polyethylene glycol terephthalate (PET)-based flexible transparent electrode signal transmission layer, an AgCl inorganic plastic thin film humidity-sensitive layer and a patterned hollowed-out polydimethylsiloxane (PDMS) packaging layer from bottom to top.

Description

Technical Field

[0001] The present invention belongs to the technical fields of flexible electronics, new materials and sensors, and particularly relates to an intrinsically inorganic plastic AgCl film-based humidity-sensitive flexible intelligent writing board, a preparation method thereof, and an intelligent writing flexible humidity sensing system. Background Art

[0002] The flexible intelligent writing board is a new emerging wearable human-computer interaction mode and has gradually become a carrier with broad prospects in fields such as online teaching, calligraphy practice, and wearable sensing interaction. According to different sensing signals, flexible writing boards mainly include three types: pressure-sensitive type, temperature-sensitive type, and humidity-sensitive type. Among them, pressure-sensitive flexible devices are extremely vulnerable to interference from non-target signals and cause distortion, while temperature-sensitive devices greatly increase the difficulty of signal acquisition in practical applications due to the weak instantaneousness of signals. Therefore, humidity sensing, as a sensing mechanism with broad prospects, is expected to make the flexible writing board comparable to traditional brush writing and achieve a revolutionary breakthrough.

[0003] As a key component of the flexible intelligent writing board, high-performance humidity-sensitive materials need to have high detection sensitivity, fast response time, specific selectivity, and excellent flexibility. So far, traditional humidity-sensitive materials based on inorganic semiconductors have excellent humidity sensing performance, but their inherent rigidity makes them vulnerable to interference and distortion from non-target factors. Compared with inorganic materials, organic polymer materials exhibit good selectivity and flexibility, but the response hysteresis of the devices is very large. Organic / inorganic hybrid materials also attempt to balance sensing performance and flexibility, but their processability is poor, leading to key device-level problems in practical applications.

[0004] In recent years, it has been found that plastic inorganic semiconductors such as AgCl and Ag 2 S have been discovered, opening up a new type of material system and providing a new approach for the development of wearable electronic devices. It is worth noting that AgCl polycrystals exhibit excellent plasticity when stretched, bent, compressed, and rolled at room temperature. The mechanical properties similar to metals accurately reflect its excellent processability, which is attributed to the ionic characteristics of the Ag-Cl interaction, thus effectively meeting the requirements of flexible electronic devices for functional materials. However, typical AgCl is mainly used as a reference electrode in flexible electronic devices and is usually presented in the form of nanorods or nanofilms. For the intrinsically plastic inorganic semiconductor AgCl film with extraordinary mechanical properties, due to the lack of detailed information on its electrical characteristics under different environmental stimuli, its application in the field of flexible electronics is greatly limited.

[0005] As a widely used human-computer interaction platform, the flexible intelligent writing board should not only provide accurate and fast sensory interaction experiences but also have the ability to resist external deformation interference. Inspired by traditional brush writing, humidity-sensitive materials are expected to enable the realization of flexible intelligent writing boards. Although significant progress has been made in humidity-sensitive materials in recent years, it remains challenging to integrate these ideal functions into a single material. Summary of the Invention

[0006] Aiming at the above technical problems, the purpose of the present invention is to provide an intrinsically inorganic plastic AgCl thin film humidity-sensitive flexible intelligent writing board, its preparation method, and an intelligent writing flexible humidity sensing system.

[0007] In the first aspect, the present invention provides an intrinsically inorganic plastic AgCl thin film humidity-sensitive flexible intelligent writing board. The humidity-sensitive flexible intelligent writing board has a layered structure, which, from bottom to top, is successively: a polyethylene terephthalate PET-based flexible transparent electrode signal transmission layer, an AgCl inorganic plastic thin film humidity-sensitive layer, and a patterned and hollowed polydimethylsiloxane PDMS encapsulation layer.

[0008] Preferably, the electrode signal transmission layer includes a polyethylene terephthalate PET substrate and a bottom electrode layer deposited on the PET substrate; The thickness of the polyethylene terephthalate PET substrate is 20 - 120 μm, preferably 50 μm; the bottom electrode layer is an ITO-HfO 2 -ITO composite electrode or an Ag-HfO 2 -Ag composite electrode. The thickness of the ITO electrode layer is 100 nm, the thickness of the Ag electrode layer is 100 nm, and the thickness of the HfO 2 isolation layer is 60 nm.

[0009] Preferably, the thickness of the AgCl inorganic plastic thin film humidity-sensitive layer is 10 - 200 μm, the length is 0.2 - 2 mm, and the width is 0.2 - 2 mm; preferably, the length is 1 mm, the width is 1 mm, and the thickness is 125 μm.

[0010] Preferably, the thickness of the patterned and hollowed polydimethylsiloxane PDMS encapsulation layer is 10 - 100 μm, preferably 50 μm; the proportion of the area of the patterned and hollowed part in the total area of the encapsulation layer is 9 - 64%; preferably, the patterned and hollowed part of the encapsulation layer is a square hole array of 0.6×0.6 mm 2 .

[0011] Preferably, the response time of the intrinsically inorganic plastic AgCl thin film humidity-sensitive flexible intelligent writing board can reach 0.008 s, and the maximum sensitivity can reach -8.24×10 6Ω / %RH, the humidity-temperature coefficient α can reach 0.167%RH / °C, the resistance change rate reaches 93.8%, the hysteresis is as low as 0.9%RH, and the resolution can reach 0.1%RH.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned humidity-sensitive flexible intelligent writing board based on the intrinsic plastic AgCl film, and the preparation method includes the following steps: (1) Sequentially deposit Ag / ITO, HfO 2 and Ag / ITO on the PET substrate to form a bottom electrode, and obtain a poly(ethylene terephthalate) PET-based flexible transparent electrode signal transmission layer; (2) Under vacuum pressurization conditions, perform spark plasma SPS densification sintering on AgCl powder to obtain an AgCl block, and then directly press the AgCl block into a uniform AgCl film by rolling at room temperature, and obtain the AgCl inorganic plastic film humidity-sensitive layer through physical slicing; (3) Use precision laser cutting technology to make a hollow pattern array on the PDMS film to obtain the patterned hollow polydimethylsiloxane PDMS encapsulation layer; (4) Place the AgCl inorganic plastic film humidity-sensitive layer on the bottom electrode of the PET-based flexible transparent electrode signal transmission layer and use the PDMS encapsulation layer to fix the position of the sensitive layer, ensure the electrical connection between AgCl and the bottom electrode, align the bottom electrode, the AgCl film and the PDMS encapsulation layer from bottom to top in sequence, and assemble to obtain the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film.

[0013] Preferably, in step (2), the vacuum degree of the vacuum pressurization is less than 20 Pa, and the pressure is 50-100 MPa; the temperature of the spark plasma SPS densification sintering is 180-250 °C, and the time is 8-20 minutes, preferably sinter at 200 °C for 10 minutes.

[0014] In a third aspect, the present invention provides an intelligent writing flexible humidity sensing system, and the intelligent writing flexible humidity sensing system includes: the above-mentioned humidity-sensitive flexible intelligent writing board sensor array as a signal acquisition unit, a flexible printed circuit board FPCB connected to the sensor array as a signal transmission module, and an App connected to the signal transmission module and serving as a signal output unit.

[0015] Preferably, the signal transmission module simultaneously collects 1-900 sensor signals, and the collection frequency is 1-10 Hz; preferably, the signal transmission module simultaneously collects 900 sensor signals, and the collection frequency is 10 Hz.

[0016] Preferably, the real-time display interface of the App of the signal output unit includes two modes: the real-time mode of humidity perception and the recording mode of humidity feedback.

[0017] Beneficial effects The humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film provided by the present invention has an ultra-fast response time, an extremely high maximum sensitivity, excellent anti-interference ability and outstanding stability; at the same time, the flexible intelligent sensing system integrating the AgCl-based humidity sensor array, flexible printed circuit board and OCR program can realize real-time and accurate perception and intelligent feedback of humidity stimulation, providing reference and inspiration for the development and application of new intrinsic plastic inorganic semiconductor materials in the field of flexible electronics. Description of the drawings

[0018] Figure 1 It is a schematic structural diagram of the AgCl film humidity-sensitive flexible intelligent writing board of the example of the present invention; Figure 2 It is a process flow chart for manufacturing the humidity-sensitive flexible intelligent writing board based on the intrinsic plastic AgCl film of the example of the present invention; Figure 3 In (a), it is the comparison result of the sensing sensitivity and response time of different humidity-sensitive materials, in (b), it is the comparison result of the key device indexes of different humidity sensors, including humidity temperature coefficient, linear correlation coefficient, resolution, hysteresis loop, resistance change rate, in (c), it is the schematic structural diagram of the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film of the example of the present invention and the mechanical flexibility display diagram of the AgCl film (bottom left), and the scale is 10 mm; Figure 4 In (a), it is a photo of the flexible transparent electrode based on PET, and the conductive layer is composed of layers of Ag, HfO 2 and Ag stacked layer by layer, and the scale is 2 cm, in (b), it is an optical micrograph of the PET flexible electrode; Figure 5 It is a schematic diagram of the patterned electrode and its key geometric parameters; Figure 6 In (a), it is a photo of the AgCl film after physical sectioning, and the scale is 8 mm, in (b), it is an optical micrograph of the square AgCl film with a size of 1×1 mm 2 ; Figure 7 It is a photo of the patterned PDMS with a 0.6×0.6 mm 2 square hole array; Figure 8Figure (a) is a schematic diagram of the test system for the AgCl flexible humidity sensor. Figure (b) is the I-V scanning curve of the flexible humidity sensor based on AgCl. Figure (c) is the resistance-relative humidity curve of the flexible sensor based on AgCl. Figure (d) is the response-recovery curve from 25% RH to 76% RH. Figure (e) is a schematic diagram of the hysteresis characteristic of the humidity sensor based on AgCl under the condition of 25-90% RH. Figure (f) is the functional relationship between the relative resistance change-relative humidity curve and temperature. Figure (g) is the stability test curve of the humidity sensor based on AgCl between 25% RH and 90.75% RH. Figure (h) is the resistance change of the AgCl thin film after different numbers of bending cycles. Figure (i) is the change of the resistance of AgCl with external humidity stimulation during the finger touch loading and unloading process; Figure 9 is the humidity distribution map of the 30×30 sensor array based on AgCl; Figure (a) is the normalized resistance spatial distribution of the sensor array under the conditions of 25% RH, 63% RH, 71% RH, and 85% RH. Figures (b-c) are the non-contact humidity sensing performances of the sensor array when one finger and two fingers are approaching respectively; Figure (d) is the distance sensing performance of the sensor array and the functional relationship between the resistance of the humidity sensor and the distance; Figure 10 is the application of the humidity sensor array based on AgCl in a flexible intelligent writing board. Figure (a) is a flexible intelligent humidity sensing system based on AgCl, including a sensor module, a signal acquisition module, a wireless transmission module, and a mobile display module. Figure (b) is a schematic diagram of the intelligent writing perception-feedback process based on the optical character recognition network application programming interface (API), including two recognition modes. One is the real-time acquisition mode, which includes 2 2 color gamuts. The other is the logical recognition mode ("0" / "1"). Figures (c-d) show the finger touch photos at different positions of the sensor array and the corresponding normalized real-time perception results. Figures (e-g) show the demonstration of the logical recognition results of the wearable wireless flexible intelligent writing board. Detailed implementation manners

[0019] The present invention will be further described below through the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention and do not limit the present invention.

[0020] First, as Figure 1 shown, the present invention provides an intrinsically inorganic plastic AgCl thin film humidity-sensitive flexible intelligent writing board. Among them, the humidity-sensitive flexible intelligent writing board is a layered structure, which is successively from bottom to top: a polyethylene terephthalate PET-based flexible transparent electrode signal transmission layer, an AgCl inorganic plastic film humidity-sensitive layer, and a patterned and hollowed polydimethylsiloxane PDMS encapsulation layer.

[0021] In some embodiments, the electrode signal transmission layer may include a polyethylene terephthalate (PET) substrate and a bottom electrode layer deposited on the PET substrate.

[0022] Among them, the thickness of the polyethylene terephthalate (PET) substrate may be 20 - 120 μm, preferably 50 μm.

[0023] Among them, the bottom electrode layer may be an ITO - HfO 2 -ITO composite electrode or an Ag - HfO 2 -Ag composite electrode, where HfO 2 is an isolation layer for preventing the interconnection between ITO or Ag electrodes; preferably, in the ITO - HfO 2 -ITO and Ag - HfO 2 -Ag composite electrodes, the thickness of the ITO electrode layer may be 100 nm, the thickness of the Ag electrode layer may be 100 nm, and the thickness of the HfO 2 isolation layer may be 60 nm.

[0024] In some embodiments, the thickness of the AgCl inorganic plastic film humidity - sensitive layer may be 10 - 200 μm, the length may be 0.2 - 2 mm, and the width may be 0.2 - 2 mm; preferably, the thickness is 125 μm, the length is 1 mm, and the width is 1 mm. If the thickness is too small, it will cause difficulties in film processing and poor material consistency.

[0025] In some embodiments, the thickness of the patterned and hollowed polydimethylsiloxane (PDMS) encapsulation layer may be 10 - 100 μm, preferably 50 μm; the proportion of the area of the patterned hollowed - out part in the total area of the encapsulation layer may be 9 - 64%. If the thickness of the encapsulation layer is too large, it will make it difficult for the humidity - sensitive material to receive environmental humidity - sensitive signals and affect the writing fluency; if the thickness is too thin, it will be difficult to ensure the fixation of the humidity - sensitive film and affect the device reliability. In addition, if the hollowed - out area is too large, the adhesion and fixation area of the encapsulation layer to the humidity - sensitive material will decrease, making it difficult to fix the position of the humidity - sensitive film; on the contrary, the area for the material to receive external humidity - sensitive signals is smaller, affecting the sensing performance of the device.

[0026] In some embodiments, the patterned and hollowed - out of the encapsulation layer may be a square - hole array of 0.6×0.6 mm 2 . Through the patterned and hollowed - out design of the encapsulation layer, the AgCl film can be directly exposed to external humidity stimuli.

[0027] The humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film provided by the present invention, when the external humidity stimulates the surface (encapsulation layer) through a stimulating device such as a finger or a writing brush, the stimulation will cause a change in the resistance of the AgCl sensitive layer, so as to achieve the purpose of converting the humidity signal into an electrical signal. In addition, the humidity-sensitive flexible intelligent writing board can be used to sense humidity non-contact signals, finger touch signals, writing trajectories of writing brushes, etc. in real time, and at the same time provide intelligent feedback of Chinese characters, letters, etc. on the App through an optical character recognition (OCR) strategy. Further, by verifying the application of the intrinsic plastic inorganic semiconductor material in the field of flexible electronics, wearable human-computer interaction can be designed and implemented targeted.

[0028] In some embodiments, the response time of the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film can reach 0.008 s, the maximum sensitivity can reach -8.24×10 6 Ω / %RH, the humidity temperature coefficient α can reach 0.167%RH / °C, the resistance change rate reaches 93.8%, the hysteresis loop is as low as 0.9%RH, the resolution can reach 0.1%RH, and the linearity can achieve logical sensing and recognition. The humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film provided by the present invention has excellent stress / temperature anti-interference ability and can maintain performance integrity even in cyclic bending tests.

[0029] Hereinafter, in combination with Figure 2 , an exemplary description will be given of the preparation method of the humidity-sensitive flexible intelligent writing board based on the intrinsic plastic AgCl film provided by the present invention. Among them, the preparation method may include the following steps: (1) Sequentially deposit Ag / ITO, HfO 2 and Ag / ITO on the PET substrate by physical vapor deposition process to form a bottom electrode, and obtain a polyethylene terephthalate PET-based flexible transparent electrode signal transmission layer; (2) Under vacuum pressure, perform spark plasma sintering (SPS) densification on AgCl powder to obtain an AgCl block, and then directly press the AgCl block into a uniform AgCl film by rolling method at room temperature, and obtain the AgCl inorganic plastic film humidity-sensitive layer after physical slicing; (3) Use precision laser cutting technology to make a hollow pattern array on the PDMS film to obtain the patterned hollow polydimethylsiloxane (PDMS) encapsulation layer; (4) Place the AgCl inorganic plastic film humidity-sensitive layer on the bottom electrode of the PET-based flexible transparent electrode signal transmission layer and use the PDMS encapsulation layer to fix the position of the sensitive layer, ensuring the electrical connection between the AgCl and the bottom electrode. Align the bottom electrode, the AgCl film, and the PDMS encapsulation layer in sequence from bottom to top to assemble the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film.

[0030] In some embodiments, in step (2), the degree of vacuum for the vacuum pressurization can be controlled to be less than 20 Pa, and the pressure can be 50 - 100 MPa (such as 50 MPa); the temperature for the spark plasma SPS densification sintering can be 180 - 250 °C, and the time can be 8 - 20 minutes. Preferably, sintering is performed at 200 °C for 10 minutes.

[0031] In addition, the present invention also provides an intelligent writing flexible humidity sensing system. Among them, the intelligent writing flexible humidity sensing system can include: the above-mentioned humidity-sensitive flexible intelligent writing board sensor array serving as a signal acquisition unit, a flexible printed circuit board FPCB connected to the sensor array and serving as a signal transmission module, and an App connected to the signal transmission module and serving as a signal output unit.

[0032] In some embodiments, the specification of the sensor array of the signal acquisition unit can be 30×30.

[0033] In some embodiments, the signal transmission module can simultaneously collect 1 - 900 sensor signals, and the collection frequency can be 1 - 10 Hz; preferably, the signal transmission module simultaneously collects 900 sensor signals, and the collection frequency is 10 Hz.

[0034] In some embodiments, the real-time display interface of the App of the signal output unit can include two modes: the real-time mode of humidity perception and the recording mode of humidity feedback. The former can monitor the position in real time when a finger or a writing brush touches the humidity sensor array; the latter can retain the touch trajectory of the finger or the writing brush for intelligent display.

[0035] In summary, the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film provided by the present invention has an ultra-fast response time, an extremely high maximum sensitivity, excellent anti-interference ability, and excellent stability; at the same time, the flexible intelligent sensing system integrating the AgCl-based humidity sensor array, the flexible printed circuit board, and the OCR program can realize the real-time and accurate perception and intelligent feedback of humidity stimuli, providing reference and inspiration for the development and application of new intrinsic plastic inorganic semiconductor materials in the field of flexible electronics.

[0036] The following are further examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0037] Example 1

[0038] The humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl film provided in this example, its preparation method, and the intelligent writing flexible humidity sensing system are as follows: 1. The humidity-sensitive flexible intelligent writing board provided in this example from bottom to top is successively: a polyethylene terephthalate PET-based flexible transparent electrode signal transmission layer, an AgCl inorganic plastic film humidity-sensitive layer, and a patterned and hollowed polydimethylsiloxane PDMS encapsulation layer; the electrode signal transmission layer includes a polyethylene terephthalate PET substrate and a bottom electrode layer deposited on the PET substrate; The thickness of the polyethylene terephthalate PET substrate is 50 μm; the bottom electrode layer is an Ag-HfO 2 -Ag structural composite electrode, the thickness of the Ag electrode layer is 100 nm, and the thickness of the HfO 2 isolation layer is 60 nm; The length of the AgCl inorganic plastic film humidity-sensitive layer is 1 mm, the width is 1 mm, and the thickness is 125 μm; The thickness of the patterned and hollowed polydimethylsiloxane PDMS encapsulation layer is 50 μm; the patterned and hollowed part of the encapsulation layer is a square hole array of 0.6×0.6 mm 2 ; the proportion of the area of the patterned and hollowed part in the total area of the encapsulation layer is 36%. 2. The preparation method of the humidity-sensitive flexible intelligent writing board based on the intrinsic plastic AgCl film provided in this example includes the following steps: (1) Deposit Ag, HfO 2 and Ag on the PET substrate successively through physical vapor deposition process to form a bottom electrode, and obtain a polyethylene terephthalate PET-based flexible transparent electrode signal transmission layer; (2) The AgCl powder is subjected to spark plasma sintering (SPS) densification under vacuum pressure to obtain an AgCl bulk, and then the AgCl bulk is directly pressed into a uniform AgCl thin film by rolling at room temperature. After physical slicing, the humidity-sensitive layer of the AgCl inorganic plastic thin film is obtained; the degree of vacuum for the vacuum pressure is less than 20 Pa, and the pressure is 50 MPa; the temperature for the spark plasma sintering (SPS) densification is 200 °C, and the sintering time is 10 minutes; (3) The precision laser cutting technology is used to fabricate a hollow pattern array on the PDMS thin film to obtain the patterned and hollowed polydimethylsiloxane (PDMS) encapsulation layer; (4) The humidity-sensitive layer of the AgCl inorganic plastic thin film is placed on the bottom electrode of the PET-based flexible transparent electrode signal transmission layer, and the PDMS encapsulation layer is used to fix the position of the sensitive layer to ensure the electrical connection between the AgCl and the bottom electrode. The bottom electrode, the AgCl thin film, and the PDMS encapsulation layer are aligned in sequence from bottom to top to assemble the humidity-sensitive flexible intelligent writing board based on the intrinsic inorganic plastic AgCl thin film. 3. The intelligent writing flexible humidity sensing system provided in this embodiment includes: the humidity-sensitive flexible intelligent writing board sensor array as the signal acquisition unit described above, the flexible printed circuit board (FPCB) as the signal transmission module connected to the sensor array, and the App as the signal output unit connected to the signal transmission module; the specification of the sensor array of the signal acquisition unit is 30×30; the signal transmission module simultaneously acquires 900 sensor signals, and the acquisition frequency is 10 Hz. Among them, the implementation process of the readout circuit of the intelligent writing flexible humidity sensing system is as follows: The humidity sensor array consists of 30×30 sensing pixels; one end of each row of sensors is connected to a row pin, that is, there are 30 row signal lines from R0 to R29; similarly, the other end of each column of sensors is connected to form a column pin, that is, there are 30 column signal lines from C0 to C29; two CMOS logic 16-channel analog multiplexers connected to R0 to R29 can realize the function of a single-pole 30-throw switch; the row selection signal lines are controlled by 5 ports of the microcontroller, and the specific row pin of the selected humidity array is connected to the common input / output port in the upper half; this port is connected to the analog-to-digital converter (ADC) of the microprogram control unit (MCU); similarly, the specific column pin of the selected humidity array can be connected to the common input / output port in the lower half of the column selection signal line through the other five ports of the MCU; these ports are also connected to the ADC of the MCU; in this way, the ADC can measure the pin level of a specific row at any end of the humidity sensor; the microcontroller polls through all the sensors and processes the humidity of each sensor on the humidity sensor array through an algorithm; then it communicates with the host computer through the Bluetooth communication function of the single-chip microcomputer; the host computer is an Android mobile phone with Bluetooth communication function, and installs the application program developed in this project; it can visually display the data collected and processed by the single-chip microcomputer in real time through Bluetooth communication, and realize character recognition through the OCR network API.

[0039] Figure 3 In (a), the comparison results of the sensing sensitivity and response time of different humidity-sensitive materials are shown. It can be seen that the traditional organic humidity-sensitive material has good flexibility, but its response time and sensitivity are both low; the inorganic humidity-sensitive material has poor intrinsic flexibility and cannot have both high sensitivity and fast response time; although the organic / inorganic composite humidity-sensitive material can endow the material with certain flexibility, it still cannot have both high sensitivity and fast response time; in contrast, the AgCl film has the flexibility of a metal-like material and realizes ultra-high sensitivity and ultra-fast response time. Figure 3 In (b), the comparison results of the key device indicators of different humidity sensors are shown, including humidity temperature coefficient, linear correlation coefficient, resolution, hysteresis, and resistance change rate. The results show that the AgCl-based flexible humidity sensor has a high humidity temperature coefficient, resolution, hysteresis, and resistance change rate, laying a foundation for realizing logical sensing and recognition. Figure 3 In (c), the humidity-sensitive flexible smart writing board and structure schematic diagram based on the intrinsic inorganic plastic AgCl film of the present invention and the mechanical flexibility display diagram of the AgCl film (lower left corner) are shown, with a scale of 10 mm.

[0040] Figure 4 In (a), a photo of a flexible transparent electrode based on PET is shown. The conductive layer consists of Ag and HfO 2It is formed by stacking layers of Ag, with a scale of 2 cm. (b) is an optical micrograph of the PET flexible electrode. It can be seen from the figure that the electrode structure is clear. Through the HfO 2 The isolation layer can effectively avoid the risk of short - circuit between the horizontal - vertical Ag electrodes. In addition, the overall electrode has good transparency.

[0041] Figure 5 It is a schematic diagram of the patterned electrode and its key geometric parameters. It can be seen from the figure that the boundary size of the sensing part electrode is 1 mm × 1 mm, the size of a single sensing module is 2 mm × 2 mm, and each sensing module is independent of each other.

[0042] Figure 6 In (a) is a photo of the AgCl thin film after physical sectioning, with a scale of 8 mm. (b) is an optical micrograph of the square AgCl thin film, and its size is 1 × 1 mm 2 . It can be seen from the figure that the cutting process has high precision, and the obtained AgCl thin film has a complete structure and accurate size, ensuring the preparation of the sensing array.

[0043] Figure 7 It is a photo of the patterned PDMS with a 0.6 × 0.6 mm 2 square - hole array. The entire cutting process is realized by physical laser cutting. The humidity signal contacts the surface of the AgCl thin film through the hollow PDMS square holes, and the un - hollowed part plays a fixing role for the AgCl thin film.

[0044] Figure 8 In (a) is a schematic diagram of the AgCl flexible humidity sensor test system. (b) is the I - V scanning curve of the AgCl - based flexible humidity sensor (the fitting curve shows that the contact resistance between the AgCl thin film and the Ag / HfO 2 / Ag electrode is approximately a fixed value, indicating good Ohmic contact between them). (c) is the resistance - relative humidity curve of the AgCl - based flexible sensor (as shown in the figure, as the ambient humidity gradually increases from 25%RH to 95%RH, the resistance of the AgCl - based flexible humidity sensor decreases by 93.8%. The resistance value of the device shows a non - linear decreasing trend, and the relative resistance change rate ΔR / R 0 reaches 63.8% in the medium - humidity range (70.6 - 83.2%RH), resulting in the device being approximately in the logic "0" and logic "1" states under low - humidity and high - humidity conditions respectively; the maximum sensitivity S of this humidity sensor is - 8.24 × 10 6Ω / %RH), (d) is the response-recovery curve from 25%RH to 76%RH (as shown in the figure, the response-recovery times are ~0.008 s and ~0.982 s respectively), (e) is a schematic diagram of the hysteresis characteristics of the AgCl-based humidity sensor under the condition of 25 - 90%RH (as shown in the figure, the adsorption and desorption humidity response curves of the sensor show that its hysteresis loop is about 0.9%RH, which is almost negligible), (f) is the functional relationship between the relative resistance change-relative humidity curve and temperature (as shown in the figure, in the range of 20 - 70 °C, the humidity-temperature coefficient α of the sensor is about 0.167%RH / °C. The extremely low α indicates that the sensor has high test accuracy at different ambient temperatures and will not affect its logical recognition ability at high and low humidities), (g) is the stability test curve of the AgCl-based humidity sensor between 25%RH and 90.7%RH (it can be seen from this curve that the device has good stability), (h) is the resistance change of the AgCl film after different numbers of bending cycles (indicating that the sensor is insensitive to stress stimulation and has strong anti-interference ability), (i) is the change of the resistance of AgCl with external humidity stimulation during the loading and unloading of finger touch (as shown in the figure, when the finger touches the humidity sensor, its resistance will change significantly and regularly).

[0045] Figure 9 is the humidity distribution map of the 30×30 sensor array based on AgCl; (a) is the normalized resistance spatial distribution of the sensor array under the conditions of 25%RH, 63%RH, 71%RH, and 85%RH. It can be seen from the figure that the sensor array can clearly distinguish different humidity levels, which proves that it has good consistency. Figures (b - c) are the non-contact humidity sensing performances of the sensor array when one finger and two fingers are approaching respectively; Figure (d) is the distance sensing performance of the sensor array and the functional relationship between the resistance of the humidity sensor and the distance. We use the water-soaked letter "A" to dynamically monitor the short-distance sensing. When the distance from the device decreases from 20 mm to 1 mm, the resistance of the humidity sensor decreases from 198 MΩ to 2.02 MΩ.

[0046] Figure 10 is the application of the AgCl-based humidity sensor array in a flexible intelligent writing board. Figure (a) is the AgCl-based flexible intelligent humidity sensing system, including a sensor module, a signal acquisition module, a wireless transmission module, and a mobile display module. Figure (b) is a schematic diagram of the intelligent writing perception-feedback process based on the optical character recognition network application programming interface (API), including two recognition modes. One is the real-time acquisition mode, which includes 2 2There are two recognition modes for the flexible intelligent writing board, one is the color gamut, and the other is the logical recognition mode ("0" / "1"). In the real-time mode, the writing board can directly display the touch position stimulated by humidity. To enrich the functions and intelligence of the writing board, an optical character recognition network API is added on the basis of real-time perception, realizing the accurate and intelligent recognition from the humidity-stimulated trajectory to text. The whole process mainly consists of four parts: humidity-stimulated trajectory collection, signal image preprocessing, image feature extraction, and matching and recognition. Figures (c-d) show the finger touch photos at different positions of the sensor array and the corresponding normalized real-time perception results. When different numbers of fingers touch the surface of the sensor array, the display interface can accurately identify the touch results, verifying the feasibility of the flexible intelligent writing board using humidity perception to achieve trajectory recognition in practical applications. Figures (e-g) show the demonstration of the logical recognition results of the wearable wireless flexible intelligent writing board, which can accurately identify different writing strokes and convert them into letters or Chinese characters. When the writing brush is dipped in water and moved on the surface of the sensor array, it can be seen from the results in the figure that the flexible intelligent writing board can achieve the accurate display of Chinese characters or English letters.

[0047] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A moisture-sensitive flexible smart writing board based on intrinsic inorganic plastic AgCl film, characterized in that: The humidity-sensitive flexible smart writing board is a layered structure, which comprises, from bottom to top: a polyethylene terephthalate (PET)-based flexible transparent electrode signal transmission layer, an AgCl inorganic plastic film humidity-sensitive layer, and a patterned hollow polydimethylsiloxane (PDMS) encapsulation layer.

2. The moisture-sensitive flexible smart writing board based on intrinsic inorganic plastic AgCl thin film according to claim 1, characterized in that: The electrode signal transmission layer includes a polyethylene terephthalate (PET) substrate and a bottom electrode layer deposited on the PET substrate; The thickness of the polyethylene terephthalate (PET) substrate is 20-120 μm, preferably 50 μm; the bottom electrode layer is an ITO-HfO2-ITO structure composite electrode or an Ag-HfO2-Ag structure composite electrode, the thickness of the ITO electrode layer is 100 nm, the thickness of the Ag electrode layer is 100 nm, and the thickness of the HfO2 isolation layer is 60 nm.

3. The moisture-sensitive flexible smart writing board based on intrinsic inorganic plastic AgCl thin film according to claim 1 or 2, characterized in that: The AgCl inorganic plastic film humidity sensitive layer has a thickness of 10-200 μm, a length of 0.2-2 mm, and a width of 0.2-2 mm; preferably, a length of 1 mm, a width of 1 mm, and a thickness of 125 μm.

4. The moisture-sensitive flexible smart writing board based on intrinsic inorganic plastic AgCl thin film according to any one of claims 1 to 3, characterized in that: The thickness of the patterned hollow polydimethylsiloxane PDMS encapsulation layer is 10-100 μm, preferably 50 μm; the area of ​​the patterned hollow part accounts for 9-64% of the total area of ​​the encapsulation layer; preferably, the patterned hollow of the encapsulation layer is 0.6×0.6 mm 2 An array of square holes.

5. The moisture-sensitive flexible smart writing board based on intrinsic inorganic plastic AgCl thin film according to any one of claims 1 to 4, characterized in that: The response time of the moisture-sensitive flexible smart writing board based on the intrinsic inorganic plastic AgCl film can reach 0.008s, and the maximum sensitivity can reach -8.24×10 6 Ω / %RH, the humidity temperature coefficient α can reach 0.167%RH / ℃, the resistance change rate can reach 93.8%, the hysteresis difference is as low as 0.9%RH, and the resolution can reach 0.1%RH.

6. A method for preparing a moisture-sensitive flexible smart writing board based on intrinsic plasticity AgCl thin film according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) Ag / ITO, HfO2 and Ag / ITO are sequentially deposited on a PET base substrate by a physical vapor deposition process to form a bottom electrode, thereby obtaining a polyethylene terephthalate (PET)-based flexible transparent electrode signal transmission layer; (2) performing spark plasma SPS densification sintering on AgCl powder under vacuum pressure conditions to obtain an AgCl block, and then directly pressing the AgCl block into a uniform AgCl film by a rolling method at room temperature, and obtaining the AgCl inorganic plastic film humidity sensitive layer by physical slicing; (3) using precision laser cutting technology to produce a hollow pattern array on the PDMS film to obtain the patterned hollow polydimethylsiloxane PDMS encapsulation layer; (4) placing the AgCl inorganic plastic film humidity sensitive layer on the bottom electrode of the PET-based flexible transparent electrode signal transmission layer and using the PDMS encapsulation layer to fix the position of the sensitive layer to ensure the electrical connection between the AgCl and the bottom electrode, aligning the bottom electrode, the AgCl film and the PDMS encapsulation layer from bottom to top in sequence, and assembling the intrinsic inorganic plastic AgCl film humidity sensitive flexible smart writing board.

7. The preparation method according to claim 6, characterized in that: In step (2), the vacuum degree of the vacuum pressurization is less than 20 Pa, and the pressure is 50-100 MPa; the temperature of the spark plasma SPS densification sintering is 180-250° C., and the time is 8-20 minutes, preferably sintering at 200° C. for 10 minutes.

8. An intelligent writing flexible humidity sensing system, characterized in that: The intelligent writing flexible humidity sensing system includes: the above-mentioned intrinsic inorganic plastic AgCl thin film humidity-sensitive flexible intelligent writing board sensor array as a signal acquisition unit, a flexible printed circuit board FPCB as a signal transmission module connected to the sensor array described in any one of claims 1-5, and an App connected to the signal transmission module and serving as a signal output unit.

9. The intelligent writing flexible humidity sensing system according to claim 8, characterized in that: The signal transmission module collects 1-900 sensor signals simultaneously, and the collection frequency is 1-10 Hz; preferably, the signal transmission module collects 900 sensor signals simultaneously, and the collection frequency is 10 Hz.

10. The intelligent writing flexible humidity sensing system according to claim 8 or 9, characterized in that: The App real-time display interface of the signal output unit includes two modes: a real-time mode of humidity perception and a recording mode of humidity feedback.

Images