Self-correcting wearable temperature and humidity sensing system, preparation method and application thereof

Abstract

The application discloses a self-correcting wearable temperature and humidity sensing system and a preparation method and application thereof, and belongs to the field of flexible sensors. The application integrates a self-correcting wearable temperature and humidity sensing system composed of a temperature and humidity sensor and a Joule heater on a flexible substrate by using a method combining silk screen printing, drop coating and electrodeposition, and preparing silk fibroin-reduced graphene oxide (SF-rGO) as a dual-functional temperature and humidity sensing material. The sensor device not only shows high sensitivity and linear response in a range of 6% to 97% RH, but also can solve the influence of temperature change on the humidity sensing process under the correction of the Joule heater and the temperature sensor, and can be directly applied to fingertip humidity detection under non-contact conditions, and shows great potential in various human-computer interaction fields.

Description

Technical Field

[0001] The present invention relates to the field of wearable sensor devices, and in particular to the design, construction and application of a self-calibrating wearable temperature and humidity sensing system. Background Art

[0002] Wearable humidity sensors can be used not only in precision medicine fields such as respiratory monitoring, but their potential in contactless sensing has also attracted widespread attention. For example, by detecting fingertip humidity under contactless conditions, screen unlocking, instrument switching, and other functions can be achieved, thereby realizing various human-computer interaction applications. Therefore, the development of highly sensitive and fast-response wearable humidity sensors is particularly important. However, the development of wearable humidity sensors still has some limitations. For example, the irreversible adsorption of water molecules can lead to performance degradation, and there is a lack of temperature correction to eliminate the influence of temperature on humidity sensing. Most humidity-sensitive materials cannot simultaneously achieve high sensitivity, a wide detection range, and a fast response recovery process. To address these problems and meet application requirements, the preparation of high-performance humidity sensing materials and the development of wearable temperature and humidity sensing systems with self-correction functions are important research topics. Summary of the Invention

[0003] The main objectives of the present invention include: providing a method for preparing a high-performance temperature and humidity sensing material; designing and constructing a self-calibrating wearable temperature and humidity sensing system; and applying this wearable sensing system to fingertip temperature / humidity detection.

[0004] To achieve the above objectives, the present invention proposes a method for constructing a self-calibrating wearable temperature and humidity sensing system, comprising the following steps:

[0005] A method for preparing a self-calibrating wearable temperature and humidity sensing system, the method comprising the following steps:

[0006] 1) Preparation of silk protein-reduced graphene oxide (SF-rGO) material: Graphene oxide GO solution and silk protein SF solution incubated with LiBr were mixed, the pH was adjusted to 9-11, a reducing agent was added, and the mixture was heated for 3-6 hours to obtain a SF-rGO dispersion;

[0007] 2) Using an insulating material as a flexible substrate, a cross-finger electrode pattern is printed on the front of the flexible substrate using screen printing technology. After drying, a corresponding Joule heater pattern is printed on the back of the flexible substrate using printing paste;

[0008] 3) Modify the SF-rGO dispersion on the surface of the screen-printed interdigitated electrode and allow it to stand to form a film to obtain a temperature and humidity sensor;

[0009] 4) On the other side of the PET, a metal film is deposited in an electroplating solution composed of chloroplatinic acid and dilute sulfuric acid using cyclic voltammetry technology to obtain a Joule heater, which together with the temperature and humidity sensor on the front side forms a self-calibrating wearable temperature and humidity sensing system.

[0010] In the technical solution of the present invention: the reducing agent in step (1) is one or more of glucose, ascorbic acid, sodium citrate, potassium tartrate, and sodium phosphite; preferably: the reducing agent is glucose.

[0011] In the technical solution of the present invention: the reaction temperature in step (1) is 90-100°C.

[0012] In the technical solution of the present invention: in step (1), the mass ratio of graphene oxide GO to silk protein SF after incubation with LiBr is 1-5:1-5.

[0013] In the technical solution of the present invention: the flexible substrate in step (2) is PET, polyimide, polydimethylsiloxane, polyurethane, paper or fiber textile; preferably, the flexible substrate is PET.

[0014] In the technical solution of the present invention: the printing paste in step (2) is carbon paste, copper paste or silver paste; preferably the printing paste is carbon paste.

[0015] In the technical solution of the present invention: the modification method in step (3) can be drip coating, spray coating or printing;

[0016] Preferably, the SF-rGO solution with a dispersion concentration of 2 to 10 mg / ml is modified on the surface of the interdigitated electrode by drop coating.

[0017] In the technical solution of the present invention, the metal is Pt, Au, Ag or Cu, and the electrodeposition parameters are as follows: the potential window is -0.25-0.4V, the scan rate is 0.03-0.08V / s, and the number of deposition cycles is 40-60.

[0018] A self-calibrating wearable temperature and humidity sensing system is prepared using the above method.

[0019] In the technical solution of the present invention: the prepared system is used to detect fingertip temperature / humidity under non-contact conditions.

[0020] Advantageous Effects of the Invention

[0021] The present invention prepares SF-rGO material as a moisture / temperature sensitive dual-function sensing material, and integrates a self-correcting wearable temperature and humidity sensing system consisting of a temperature and humidity sensor and a Joule heater on a flexible substrate through a method combining screen printing, drop coating and electrodeposition. The sensing system can achieve highly sensitive humidity response in the range of 30-100°C and 6%-97% relative humidity (RH). Under the conditions of the Joule heater heating strips and the temperature sensor real-time temperature measurement, a constant temperature condition can be maintained during the humidity sensing test to avoid the influence of temperature changes on the humidity testing process. In addition, the self-correcting wearable temperature and humidity sensing system prepared by the present invention is also used in fingertip humidity detection. The system has a simple preparation process, low cost and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a diagram showing the components and design of the self-calibrating wearable temperature and humidity sensing system in Example 1 of the present invention. The entire sensing system uses a flexible material as a substrate and integrates a Joule heater, a humidity sensor, and a temperature sensor through screen printing and post-modification methods. The Joule heater and temperature sensor can calibrate temperature parameters by heating, ensuring temperature stability during humidity sensing testing.

[0024] Figure 2 The humidity sensor of Example 1 of the present invention shows a relationship curve between humidity response and RH in the range of 6%-97% RH. The results of five parallel tests show that the resistance response increases linearly with increasing relative humidity in the range of 6%-97% RH, proving that the humidity sensor has stable linear responsiveness in the range of 6%-97% RH.

[0025] Figure 3 The following are the continuous response curves for the same RH in Example 1 of the present invention, with and without the auxiliary correction conditions of the Joule heater and temperature sensor. Without the Joule heater correction condition, the humidity sensor was unable to fully recover to its initial state during the second and third test cycles. With the auxiliary correction of the Joule heater, the humidity sensing process exhibited reversibility, fully recovering to its initial state after five consecutive dynamic tests, demonstrating that this self-calibrating wearable temperature and humidity sensing system can effectively solve the problem of humidity test instability caused by temperature changes during humidity testing.

[0026] Figure 4 This is a response diagram of the wearable temperature and humidity sensing system used in Example 1 of the present invention for real-time non-contact detection of fingertip humidity. Dynamic testing of the fingertip humidity of five different volunteers demonstrates that the sensor can quickly identify fingertip humidity under non-contact conditions, with response and recovery times both within tens of seconds.

[0027] Figure 5 The ratio of the D band to the G band is obtained after Raman testing of the SF-rGO material at different reaction times in Examples 1-4 of the present invention. The higher the D / G ratio, the higher the reduction degree of the material. Characterization tests show that the reduction degree is highest after 5h.

[0028] Figure 6 This is the continuous dynamic test curve of the SF-rGO material synthesized at different precursor ratios (GO:SF=3:1, 3:2, 1:1, 2:3) in Examples 1, 5-7 of the present invention under the same RH (97% RH) conditions. When the precursor ratio is 2:3, the responsiveness is the largest under the same RH. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings so that the present invention can be better understood by technical researchers in the field, thereby making a clear and definite definition of the protection scope of the present invention.

[0030] Example 1

[0031] First, the silk protein-reduced graphene oxide (SF-rGO) material is prepared by the following method:

[0032] 5g of silkworm cocoons were boiled in 0.02M NaHCO₃ solution to remove sericin. The sericin was then washed three times with deionized water and dried at room temperature. After drying, the sericin was dissolved in 100ml of 9.3M LiBr solution at 60°C. After dialysis for 48 hours, a 17.8mg / mL SF solution was obtained.

[0033] 80 mg of freshly prepared GO was dissolved in 100 mL of water. 4500 μL of the above-mentioned SF solution was added. Ammonia solution was added to adjust the pH to 10. 0.5 g of glucose was added as a reducing agent. The mixture was reacted at 95°C for 5 hours. Afterwards, the mixture was washed with deionized water to obtain a 5 mg / mL SF-rGO dispersion.

[0034] Construct a wearable temperature and humidity sensing system. The preparation process is as follows:

[0035] Design an interdigitated electrode pattern and a corresponding heater pattern, then process them into a screen printing template. Using PET as a flexible substrate and carbon paste as the slurry, print the interdigitated electrode pattern on the front of the PET and dry it at 80°C for 20 minutes. Then, use carbon paste to print the corresponding Joule heater pattern on the back of the PET and dry it at 80°C for another 20 minutes.

[0036] 5 mL of the prepared SF-rGO dispersion was drop-coated to modify the surface of the interdigitated electrode, and the film was allowed to form after standing to obtain a temperature and humidity sensor. On the other side of the PET, a Pt film was deposited in a plating solution consisting of 2 mM chloroplatinic acid and 0.5 M dilute sulfuric acid using cyclic voltammetry (deposition parameters: potential window of -0.25-0.4 V, scan rate of 0.05 V / s, and deposition cycle of 50) to obtain a Joule heater. Together with the temperature and humidity sensor on the front, it forms a self-calibrating wearable temperature and humidity sensing system. Figure 1 shown.

[0037] The device was placed in different RH environments for sensing tests, and the relationship curve between the humidity response of the device and RH in the range of 6%-97% RH was obtained. Figure 2 As shown in the figure, the results show that the response signal increases with the increase of RH, and the response signal changes linearly under different RH.

[0038] The humidity response at the same RH was tested with and without the auxiliary calibration of the Joule heater and temperature sensor. Figure 3 As shown in Figure 3, with the auxiliary correction of the Joule heater and temperature sensor, the humidity sensor can maintain a stable dynamic response process. Without the correction of the Joule heater and temperature sensor, it is difficult for the humidity sensor to return to its initial state.

[0039] Subsequently, the above-mentioned sensing system was applied to the fingertip humidity test, and the distance between the sensor and the fingertip was kept at 1mm, and the fingertip humidity signals of 5 volunteers were tested continuously. Figure 4 As shown, when a finger is placed over the sensor, the sensor immediately captures the signal. After the finger is removed, the response signal instantly decreases, with both response and recovery times within tens of seconds. This suggests that this sensing system has the potential to enable various human-computer interaction applications, such as unlocking screens and controlling instrument switches, by detecting fingertip moisture without contact.

[0040] Examples 2-4

[0041] The difference from Example 1 is that when preparing silk protein-reduced graphene oxide (SF-rGO) material, the reaction time is adjusted to 3 hours (Example 2), 4 hours (Example 3), and 6 hours (Example 4), and silk protein-reduced graphene oxide material can also be obtained. However, the reduction degree of graphene oxide is different. Characterization test verification shows that the reaction time of 5 hours is the optimal reaction time ( Figure 5 ).

[0042] Examples 5-7

[0043] The difference from Example 1 is that when preparing the silk protein-reduced graphene oxide (SF-rGO) material, the mass ratio of the reaction precursor GO to SF is adjusted from 1:1 to 3:1 (Example 5), 3:2 (Example 6), and 2:3 (Example 7), thereby obtaining SF-rGO materials with different ratios. The humidity performance and temperature performance tests show that when the precursor ratio is 2:3, the responsiveness is the largest at the same RH ( Figure 6 ).

[0044] Examples 8-9

[0045] The difference from Example 1 is that the base material is changed to polyimide (Example 8) and fiber fabric (Example 9).

[0046] Using polyimide as a flexible substrate, a cross-finger electrode pattern was printed on the front side using carbon paste and dried at 80°C for 20 minutes. The corresponding Joule heater pattern was then printed on the back side using carbon paste and dried at 80°C for another 20 minutes.

[0047] Using fiber fabric as the flexible substrate, first apply a layer of polyurethane dispersion, dry it at 90℃ for 1 hour, then use carbon paste as the slurry to print the interdigitated electrode pattern on the front, dry it at 80℃ for 20 minutes, and continue to use carbon paste to print the corresponding Joule heater pattern on the back, and dry it at 80℃ for 20 minutes.

[0048] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a self-calibrating wearable temperature and humidity sensing system, characterized by: The method comprises the following steps: 1) Preparation of silk protein-reduced graphene oxide (SF-rGO) material: mixing graphene oxide GO solution with silk protein SF solution after LiBr incubation, adjusting the pH to 10, adding a reducing agent, and heating the reaction for 3 to 6 hours to obtain a SF-rGO dispersion; the reducing agent in step (1) is glucose, and the reaction temperature is 90 to 100°C; in step (1), the mass ratio of graphene oxide GO to silk protein SF after LiBr incubation is 1 to 5:1 to 5; 2) Using an insulating material as a flexible substrate, printing an interdigitated electrode pattern on the front of the flexible substrate using screen printing technology, and after drying, continuing to use printing paste to print a corresponding Joule heater pattern on the back of the flexible substrate; wherein the flexible substrate in step (2) is PET, polyimide, polydimethylsiloxane, polyurethane, paper or fiber textile; 3) The SF-rGO dispersion was modified on the surface of the screen-printed interdigitated electrode and allowed to stand to form a film to obtain a temperature and humidity sensor; 4) On the other side of the PET, a metal film is deposited in an electroplating solution composed of chloroplatinic acid and dilute sulfuric acid using cyclic voltammetry technology to obtain a Joule heater, which together with the temperature and humidity sensor on the front side forms a self-calibrating wearable temperature and humidity sensing system.

2. The method for preparing the self-calibrating wearable temperature and humidity sensing system according to claim 1, characterized in that: The printing paste in step (2) is carbon paste, copper paste or silver paste.

3. The method for preparing the self-calibrating wearable temperature and humidity sensing system according to claim 2, characterized in that: The printing paste in step (2) is carbon paste.

4. The method for preparing the self-calibrating wearable temperature and humidity sensing system according to claim 1, wherein: The modification method in step (3) is drip coating, spray coating or printing.

5. The method for preparing the self-calibrating wearable temperature and humidity sensing system according to claim 1, wherein: In step (3), the SF-rGO solution with a dispersion concentration of 2~10 mg / ml is modified on the surface of the interdigitated electrode by drop coating.

6. The method for preparing the self-calibrating wearable temperature and humidity sensing system according to claim 1, wherein: The metal is Pt, Au, Ag or Cu, and the electrodeposition parameters are as follows: potential window is -0.25-0.4 V, scan rate is 0.03-0.08 V / s, and deposition cycle number is 40-60.

7. A self-calibrating wearable temperature and humidity sensing system, characterized by: The sensor system is prepared by the method according to any one of claims 1 to 6.

8. The system prepared according to claim 1 is used for detecting fingertip temperature and humidity under non-contact conditions.

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