A dual-mode flexible sensor for detecting dental caries and periodontitis and its preparation method

Abstract

The present invention is applicable to the technical field of medical devices, and provides a dual-mode flexible sensor for detecting dental caries and periodontitis, including: a flexible gas-sensitive sensor unit, the flexible gas-sensitive sensor unit includes a PET base layer, one side of the PET base layer is provided with an Au interdigital electrode layer, the side of the Au interdigital electrode layer away from the PET base layer is provided with a gas-sensitive sensing layer, and the side of the gas-sensitive sensing layer away from the Au interdigital electrode layer is provided with a PTFE waterproof and breathable membrane; and a flexible pressure-sensitive sensing unit, the flexible pressure-sensitive sensing unit includes a TPU / MWCNTs conductive foam layer. The device monitors exhaled gas through the flexible gas-sensitive sensor unit, detects muscle and joint movements through the flexible pressure-sensitive sensing unit, and through a dual-mode diagnosis method for early dental caries and periodontal disease patients' exhaled biomarkers and abnormal bite force, and multi-modal recognition of different signal molecules, makes the monitoring more comprehensive and accurate, and can obtain the results of the progress of patients' oral diseases and the comprehensive oral health status.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and particularly relates to a dual-mode flexible sensor for detecting dental caries and periodontitis and a preparation method thereof. Background Art

[0002] Oral health is an important part of overall health, and the World Health Organization has listed oral health as one of the ten standards for human health. Dental caries and periodontitis are two major diseases that endanger human oral health. They not only affect functions such as chewing, speech, and aesthetics, causing difficulties in social interaction and psychological barriers, but also are closely related to overall health. In principle, early intervention in dental caries and periodontitis can achieve a curative effect. Unfortunately, due to the lack of obvious early symptoms, dental caries and periodontitis are usually discovered only in the late stage, accompanied by irreversible damage to the hard tissues and periodontal tissues of the teeth. Therefore, the early diagnosis and monitoring of dental caries and periodontitis are very important for the prevention and control of diseases. However, traditional clinical diagnostic methods (such as visual inspection, probing, and imaging examinations) are difficult to operate and costly. They are not only not applicable to pregnant women and patients allergic to radiation, but also can only reflect the cumulative damage of the disease rather than the current situation of the disease, and cannot monitor the progression of periodontitis. Therefore, developing a low-cost, accurate, sensitive, and self-detectable multifunctional flexible wearable platform that can perform early diagnosis and prognostic monitoring of dental caries and periodontal disease patients throughout the process and from multiple angles has important value for maintaining overall oral health.

[0003] In recent years, breath analysis has provided a simple, non-invasive, rapid, and effective sensing method in the fields of medical diagnosis and disease monitoring, and can detect trace disease markers in exhaled gas. Some studies have shown that the concentrations of NO and NO2 in the oral cavities of patients with dental caries and periodontal disease are significantly increased, and the oxygen in the exhaled gas accounts for about 16%. The NO exhaled by humans immediately reacts with oxygen to form NO2. Through thermodynamic data calculation, the equilibrium constant of the reaction NO(g) + 1 / 2O2(g) = NO2(g) at a temperature of 298.15K (25°C) is 1.49×10 6 , and since NO reacts with oxygen, it can be almost 100% converted to NO2 very quickly. More importantly, compared with healthy people, their levels are significantly increased and change with the progression and treatment of disease damage. Therefore, rapid and accurate detection of changes in the concentration of NO2 in exhaled gas is of great significance for the early intervention and control of dental caries and periodontitis. More importantly, during the process of periodontal inflammation spreading to the periodontal supporting tissues, there will also be an impact on the biting force. In fact, a large number of studies have shown that multi-modal simultaneous detection is more feasible for disease diagnosis.

[0004] Therefore, quickly and accurately grasping the changes in NO2 and the changes in biting force in the early oral environment is of great significance for the early and precise diagnosis of dental caries and periodontal disease.

[0005] Two-dimensional transition metal dichalcogenides (TMDCs) have received extensive attention due to their unique physical and chemical properties and wide applications. The interface between 2D-TMD and quantum dots (0D QDs) has become an extremely attractive hybrid-dimensional heterostructure in the fields of electronics and optoelectronics due to its advantages such as a variety of types, strong electron coupling, and efficient interfacial charge transfer. The WS2 / QDs heterostructure is considered to be the most promising strategy to improve the NO2 sensing performance based on TMD. In particular, the p-n heterostructure can effectively overcome the disadvantages of long response time and incomplete recovery. However, the oral cavity is a complex environment with a wide variety of exhaled gases and high relative humidity. In a high-humidity environment, it is difficult for gas sensors based on heterostructures to obtain reliable sensitivity and reversibility. On the other hand, water molecules from exhaled gases tend to absorb on the surface of the sensing material, thereby affecting the electronic interaction between NO2 and the sensing material. These limitations place higher requirements on the sensor. Therefore, high-sensitivity and specific multimodal combined sensors still face great challenges.

[0006] With the development of materials science and sensing technology, there are currently some biosensors used for diagnosing dental caries and periodontitis at the laboratory level. However, these biosensors can either only achieve single-modal sensing, which is not reliable for disease diagnosis; or they separately detect multiple signal molecules without truly integrating the multimodal sensor; or the changes between signal molecules are not interference-free, reducing the detection accuracy; or the sensor integration and fabrication process are complex, which is not conducive to operation and chairside detection. However, so far, the work based on light-enhanced WS2 NS@MoS2 QDs P-N heterostructures designed to specifically sense exhaled NO2 is very rare. In addition, there is a particular lack of a monitoring platform that combines gas sensing and pressure sensing for the early diagnosis and whole-process, multimodal monitoring of patients with dental caries and periodontitis. Summary of the Invention

[0007] The purpose of the embodiments of the present invention is to provide a dual-mode flexible sensor for detecting dental caries and periodontitis and its preparation method, aiming to solve the problems raised in the above background technology.

[0008] The embodiments of the present invention are implemented as follows. A dual-mode flexible sensor for detecting dental caries and periodontitis includes:

[0009] A flexible gas-sensitive sensor unit, the flexible gas-sensitive sensor unit includes a PET base layer, one side of the PET base layer is provided with an Au interdigital electrode layer, the side of the Au interdigital electrode layer away from the PET base layer is provided with a gas-sensitive sensing layer, and the side of the gas-sensitive sensing layer away from the Au interdigital electrode layer is provided with a PTFE waterproof and breathable membrane; and

[0010] A flexible pressure-sensitive sensing unit, which includes a TPU / MWCNTs conductive foam layer. The TPU / MWCNTs conductive foam layer is used to cooperate with the flexible gas-sensing sensor unit to build a monitoring platform for the whole process and multi-angle of caries and periodontal diseases.

[0011] Another object of the embodiments of the present invention is a preparation method of a dual-mode flexible sensor for detecting caries and periodontitis, including the following steps:

[0012] Step 1: Synthesize WS2 NSs / MoS2 QDs composite nanomaterials:

[0013] Step 2: Wash the Au interdigitated electrode layer on the PET substrate layer with deionized water and dry it at room temperature;

[0014] Step 3: Spin-coat 30 μL of WS2 NSs / MoS2 QDs composite nanomaterials on the surface of the Au interdigitated electrode layer and dry it under flowing N2, and repeat this 5 times;

[0015] Step 4: After attaching the gas-sensing layer to the Au interdigitated electrode layer, attach a PTFE waterproof and breathable membrane to the Au interdigitated electrode layer, and store the prepared electrode in an N2 environment for standby;

[0016] Step 5: Prepare a conductive flexible TPU / MWCNTs foam and cut it into different sizes for mechanical and electrical measurements.

[0017] A further technical solution is that in the above Step 1, the preparation steps of WS2 nanosheets (WS2 NSs) are as follows:

[0018] Step 1.1: Synthesis of two-dimensional tungsten disulfide nanosheets (WS2 NSs):

[0019] Mix 600 mg of bulk layered WS2 with 80 mL of ethanol and 120 mL of deionized water; then place the mixture in an ultrasonic machine with a frequency of 100 Hz and a temperature of 30 °C. After ultrasonic exfoliation for 21 h, collect the mixture by filtration, and then dry it overnight at 60 °C in a vacuum oven, and label it as WS2 nanosheets.

[0020] Step 1.2: Preparation of molybdenum disulfide quantum dots (MoS2 QDs):

[0021] Step 1.2.1: Synthesis of molybdenum disulfide quantum dots: Add 50 mg of MoS2 powder to 10 mL of sulfuric acid, and then ultrasonicate (200 W) at 65 °C for 20 hours. The obtained mixture is centrifuged at 4500 rpm for 30 minutes to remove large flakes of MoS2.

[0022] Step 1.2.2, Purification of molybdenum sulfide quantum dots: Dilute the supernatant to 40 mL of water and dialyze it in a dialysis bag (retaining a molecular weight of 1000 Da) to remove sulfuric acid, and detect it with BaCl2 solution (1 M) for 1 day.

[0023] Step 1.2.3, Filtration of molybdenum sulfide quantum dots: The obtained suspension is filtered through a 0.22 μm microporous membrane to obtain uniform MoS2 quantum dots.

[0024] Step 1.3, Preparation of tungsten sulfide - molybdenum sulfide composite material (WS2 / MoS2): Mix WS2 NSs and MoS2 QDs in water and stir magnetically for 1.5 h, so that the two can obtain a stable composite solution of 1 mg / mL WS2 NSs containing different contents of MoS2 QDs through electrostatic adsorption.

[0025] A further technical solution is that W:Mo in the tungsten sulfide - molybdenum sulfide composite material is 300:1.

[0026] A dual - mode flexible sensor for detecting dental caries and periodontitis and its preparation method provided by the embodiments of the present invention monitor exhaled gas through a flexible gas - sensitive sensor unit, detect muscle and joint movements through a flexible pressure - sensitive sensing unit, and through a dual - mode diagnosis method for exhaled gas markers and abnormal bite force in patients with early dental caries and periodontal diseases, and multi - modal recognition of different signal molecules, making the monitoring more comprehensive and accurate. According to the change of resistance signal, the progress of patients' oral diseases and the results of oral comprehensive health status can be obtained. The operation is simple, the reagent consumption is small, it is convenient and fast, and it is a non - invasive early disease diagnosis method. It paves the way for the whole process of early diagnosis and prediction of the progress of dental caries and periodontitis and the late evaluation of disease treatment effects and prognosis in the future POCT mode. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a dual - mode flexible sensor for detecting dental caries and periodontitis provided by the embodiments of the present invention;

[0028] Figure 2 It is a morphology diagram of the prepared WS2 nanosheet / MoS2 quantum dot (WS2 NSs / MoS2 QDs) composite material;

[0029] Figure 3 It is a surface morphology analysis diagram of the prepared WS2 NSs / MoS2 QDs composite material;

[0030] Figure 4 It is an optimization diagram of the gas - sensitive sensing performance and experimental conditions of the gas - sensitive sensor;

[0031] Figure 5 It is an optimization diagram of the selectivity, flexibility and long - term stability of the gas - sensitive sensor

[0032] Figure 6 It is the piezoresistive sensing performance diagram of the piezoresistive sensor;

[0033] Figure 7 It is the actual application diagram of the composite sensor for exhaled breath detection and bite force detection;

[0034] Figure 8 It is the structural schematic diagram of the multifunctional sensor and the schematic diagram of the gas-sensing / piezoresistive dual-mode flexible sensor for the whole-process diagnosis and monitoring of dental caries and periodontitis.

[0035] In the attached drawings: 1-PTFE waterproof and breathable membrane; 2-gas-sensing layer; 3-Au interdigital electrode layer; 4-PET base layer; 5-TPU / MWCNTs conductive foam layer. Detailed implementation manners

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the attached drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The following describes the specific implementation of the present invention in detail in conjunction with specific embodiments.

[0038] As Figure 1 shown, a dual-mode flexible sensor for detecting dental caries and periodontitis provided by an embodiment of the present invention includes:

[0039] A flexible gas-sensing sensor unit, the flexible gas-sensing sensor unit includes a PET base layer 4, a Au interdigital electrode layer 3 is disposed on one side of the PET base layer 4, a gas-sensing layer 2 is disposed on the side of the Au interdigital electrode layer 3 away from the PET base layer 4, and a PTFE waterproof and breathable membrane 1 is disposed on the side of the gas-sensing layer 2 away from the Au interdigital electrode layer 3; and

[0040] A flexible piezoresistive sensing unit, the flexible piezoresistive sensing unit includes a TPU / MWCNTs conductive foam layer 5, and the TPU / MWCNTs conductive foam layer 5 is used to cooperate with the flexible gas-sensing sensor unit to build a monitoring platform for the whole process and multi-angle of dental caries and periodontal diseases.

[0041] In the embodiments of the present invention, during use, exhaled gas is monitored by a flexible gas sensor unit. Muscle and joint movements are detected by a flexible pressure sensor unit. Specifically, the prepared TPU / MWCNTs conductive foam layer is cut into different sizes and shapes and attached to different parts of the human body with the assistance of medical tape to detect subtle and large body movements. Through a dual-mode diagnostic method for exhaled gas markers and abnormal bite force in patients with early caries and periodontal diseases, and multimodal recognition of different signal molecules, the monitoring is more comprehensive and accurate, and the progression of the patient's oral diseases and the results of the comprehensive oral health status are obtained based on the change of the resistance signal.

[0042] A preparation method of a dual-mode flexible sensor for detecting caries and periodontitis provided by an embodiment of the present invention includes the following steps:

[0043] Step 1, synthesize WS2 NSs / MoS2 QDs composite nanomaterials:

[0044] Two-dimensional WS2 NSs and zero-dimensional MoS2 QDs are respectively synthesized through an ultrasonic exfoliation process, and the two are combined through electrostatic adsorption to obtain a stable WS2 NSs / MoS2 QDs composite material;

[0045] Step 2, clean the Au interdigital electrode layer on the PET substrate layer with deionized water and dry it at room temperature;

[0046] Step 3, spin-coat 30 μL of WS2 NSs / MoS2 QDs composite nanomaterials on the surface of the Au interdigital electrode layer and dry it under flowing N2, and repeat this 5 times;

[0047] Step 4, after attaching the gas-sensitive sensing layer to the Au interdigital electrode layer, attach a PTFE waterproof and breathable membrane to the Au interdigital electrode layer, and store the prepared electrode in an N2 environment for standby;

[0048] Step 5, prepare a conductive flexible TPU / MWCNTs foam and cut it into different sizes for mechanical and electrical measurements.

[0049] As a preferred embodiment of the present invention, in the step 1, the preparation steps of WS2 nanosheets (WS2 NSs) are as follows (see specifically Figure 2 , where: a is the transmission electron microscope image of few-layer WS2 NSs, b is the transmission electron microscope image of MoS2 QDs, c is the transmission electron microscope image of the WS2 NSs / MoS2 QDs composite material, d and e are the scanning transmission electron microscope images of the WS2 NSs / MoS2 QDs composite material, and f-i are the corresponding energy-dispersive X-ray spectroscopy images of the three elements W, Mo, and S):

[0050] Step 1.1. Synthesis of tungsten disulfide nanosheets (WS2 NSs):

[0051] Mix 600 mg of bulk layered WS2 with 80 mL of ethanol and 120 mL of deionized water; then place the mixture in an ultrasonic machine with a frequency of 100 Hz and a temperature of 30 °C. After ultrasonic exfoliation for 21 h, collect the mixture by filtration, and then dry it overnight at 60 °C in a vacuum oven and label it as WS2 nanosheets.

[0052] Step 1.2. Preparation of molybdenum disulfide quantum dots (MoS2 QDs):

[0053] Step 1.2.1. Synthesis of molybdenum disulfide quantum dots: Add 50 mg of MoS2 powder to 10 mL of sulfuric acid, and then ultrasonicate (200 W) at 65 °C for 20 h. The resulting mixture is centrifuged at 4500 rpm for 30 min to remove large flakes of MoS2.

[0054] Step 1.2.2. Purification of molybdenum disulfide quantum dots: Dilute the supernatant to 40 mL in water and dialyze it in a dialysis bag (with a molecular weight cut-off of 1000 Da) to remove sulfuric acid, and detect it with BaCl2 solution (1 M) for 1 day.

[0055] Step 1.2.3. Filtration of molybdenum disulfide quantum dots: The resulting suspension is filtered through a 0.22 μm microporous membrane to obtain uniform MoS2 quantum dots.

[0056] Step 1.3. Preparation of tungsten disulfide - molybdenum disulfide composite (WS2 / MoS2): Mix WS2 NSs and MoS2 QDs in water and stir magnetically for 1.5 h to obtain a stable composite solution of 1 mg / mL WS2 NSs with different contents of MoS2 QDs through electrostatic adsorption. The morphology of the material is shown in Figure 2 (c), and the high - resolution transmission electron microscopy image and energy - dispersive X - ray spectroscopy image are shown in Figure 2 (d) - 2(i).

[0057] To further prove the successful preparation of the WS2 / MoS2 composite, its surface morphology was analyzed, as shown in Figure 3 (where a is the X - ray diffraction pattern of WS2, MoS2, and WS2 / MoS2 composites, b is the Raman spectrum, and c - e are X - ray photoelectron spectroscopy images). X - ray diffraction analysis, Raman spectroscopy analysis, and X - ray photoelectron spectroscopy analysis were respectively carried out on it, and characteristic signals of the material could be obtained; all of the above results can prove the successful synthesis of the WS2 / MoS2 composite.

[0058] As a preferred embodiment of the present invention, in order to obtain the best gas-sensing performance, the experimental conditions were optimized through gas-sensing performance tests, such as the material ratio and the light wavelength, and the performance of the device was tested under the optimal conditions (see Figure 4 , where a is the response diagram of different WS2 / MoS2 ratios to 0.25 ppm - 10 ppm NO2 under dark conditions, b is the response diagram of the WS2 / MoS2 composite material to 1 ppm NO2 under light of different wavelengths, c is the five-cycle response diagram of the device to light response, to 1 ppm NO2 under dark conditions, and to 1 ppm NO2 under ultraviolet light conditions, d is the dynamic response diagram of the device to different concentrations of NO2 under dark conditions, e is the response and recovery time of the device to 1 ppm NO2 under dark conditions, f is the curve diagram of the device response varying with gas concentration under dark conditions, g is the dynamic response diagram of the device to different concentrations of NO2 under ultraviolet light conditions, h is the response and recovery time of the device to 1 ppm NO2 under ultraviolet light conditions, and i is the curve diagram of the device response varying with gas concentration under ultraviolet light conditions).

[0059] (1) Optimization of the WS2 / MoS2 concentration ratio: Since the gas-sensing performance is affected by the different ratios of the two substances in the composite material, the atomic ratio of WS2 NSs to MoS2 QDs in the composite material was optimized, namely 200:1; 300:1; 400:1. As Figure 4 (a) shows, the response of the device to different concentrations of NO2 under dark conditions reaches the highest value when the atomic ratio of W to Mo is 300:1. Therefore, the WS2 / MoS2 composite material containing W:Mo = 300:1 was selected as the final material for modifying the electrode.

[0060] (2) Optimization of the light wavelength: Since light of different wavelengths can affect the response value of the device to NO2 and the length of the response and recovery time; therefore, we used four different wavelengths of light: white light, red light (620 nm), blue light (465 nm), and ultraviolet light (375 nm), and respectively tested the response value of the device to 1 ppm NO2 under the excitation of four different wavelengths of light; from Figure 4 (b), it can be seen that under the excitation condition of ultraviolet light (375 nm), the response value of the sensor to 1 ppm NO2 reaches the maximum. Therefore, the excitation condition of ultraviolet light (375 nm) was selected for subsequent tests.

[0061] As a preferred embodiment of the present invention, the gas-sensing detection of the dual-mode flexible sensor for detecting dental caries and periodontitis:

[0062] Detection of different concentrations of NO2 under dark conditions and under ultraviolet light illumination (see Figure 4, where c is the five-cycle response diagram of the device to light, 1 ppm NO2 under dark conditions, and 1 ppm NO2 under ultraviolet light conditions, d is the dynamic response diagram of the device to different concentrations of NO2 under dark conditions, e is the response and recovery time of the device to 1 ppm NO2 under dark conditions, f is the curve diagram of the device response varying with gas concentration under dark conditions, g is the dynamic response diagram of the device to different concentrations of NO2 under ultraviolet light conditions, h is the response and recovery time of the device to 1 ppm NO2 under ultraviolet light conditions, i is the curve diagram of the device response varying with gas concentration under ultraviolet light conditions; see Figure 5 , where a is the selectivity diagram of the flexible sensor; b is the anti-bending characteristic diagram of the flexible sensor; c is the long-term stability diagram of the flexible sensor under dark conditions and ultraviolet light excitation).

[0063] (1) Configure NO2 with different concentrations: Dilute NO2 with N2 to configure NO2 gas with different concentrations.

[0064] (2) Modify the working electrode: Spin-coat the prepared WS2 / MoS2 solution on the gold interdigitated electrode of the flexible PET substrate, dry it in a flowing N2 environment, and repeat the above process 5 times to obtain the modified electrode to be measured.

[0065] (3) Parameter settings of LED lights with different wavelengths: White light (working voltage = 3.3 V), red light (620 nm, working voltage = 2.6 V), blue light (465 nm, working voltage = 3.2 V), ultraviolet light (375 nm, working voltage = 3.7 V).

[0066] (4) Calculation of the gas concentration injected into the gas chamber:

[0067] The gas concentration injected into the gas chamber is calculated according to the following formula:

[0068] C1*V1 = C2*V2

[0069] where C1 is the concentration of NO2 injected into the gas chamber, and V1 is the volume of NO2 injected into the gas chamber;

[0070] where C2 is the concentration of NO2 to be measured, and V2 is the volume of the gas chamber (20 L);

[0071] (5) Exploration of performance: Insert the prepared flexible gas sensor into the CGS-8 intelligent gas sensor analysis system (Beijing Elite Technology Co., Ltd., Beijing, China), and test the gas sensing performance of the flexible gas sensor under the above conditions. Such as Figure 4As shown in (c), under dark conditions, the response value of the device to 1 ppm of NO2 is 53.6%, while under ultraviolet light excitation, the response value of the device to 1 ppm of NO2 is 73.1%. Under the excitation of ultraviolet light, the response value of the device increases by 19.5%, demonstrating that the gas-sensing performance of the device has been improved under ultraviolet light excitation. Subsequently, by dynamically and continuously testing the gas response of the flexible gas sensor to different concentrations of NO2 under dark conditions, as Figure 4 shown in (d), the detection limit is 50 ppb, demonstrating the gas-sensing performance of the flexible sensor. And as Figure 4 shown in (e), under dark conditions, the response and recovery times of the flexible gas sensor to 1 ppm of NO2 are 362 s and 270 s, respectively. The curve of the response of the flexible gas sensor to gas concentration under dark conditions is as Figure 4 shown in (f). Then, by dynamically and continuously testing the gas response of the flexible gas sensor to different concentrations of NO2 under ultraviolet light conditions, as Figure 4 shown in (g), the detection limit is as low as 10 ppb, demonstrating that the gas-sensing performance of the flexible sensor has been further improved under ultraviolet light excitation. And as Figure 4 shown in (h), under ultraviolet light conditions, the response and recovery times of the flexible gas sensor to 1 ppm of NO2 are reduced to 244 s and 135 s, respectively, demonstrating that under ultraviolet light excitation, the response and recovery times of the sensor can be further reduced. The curve of the response of the flexible gas sensor to gas concentration under ultraviolet light conditions is as Figure 4 shown in (i).

[0072] In addition, in practical applications, no cross-interference between analytes and between analytes and other similar substances is an important prerequisite. Therefore, the cross-interference and selectivity of the flexible gas sensor with other gases were also investigated. As Figure 5 shown in (a), the response value of the fabricated flexible gas sensor only increases significantly in NO2 gas. In addition, by introducing 400-fold concentrations of other potential interfering gases such as ammonia (NH3), nitric oxide (NO), hydrogen sulfide (H2S), ethanol (C2H5OH), methanol (CH3OH), chloroform (CH2Cl2), formaldehyde (HCHO), and ethylene glycol (C2H6O2), the selectivity of the flexible gas sensor was further studied. As can be seen from the other columns in Figure 5 (a), even in the face of high concentrations of other interfering gases, the response value of the gas is very low, indicating that the immunosensor has good selectivity. The cross-reaction of the fabricated gas sensor with other high-concentration interfering substances can be ignored. Next, the good flexibility of the gas sensor device is crucial for wearable sensor applications in medical diagnosis and treatment. Therefore, the anti-bending characteristics of the flexible device under repeated bending conditions were continued to be investigated. AsFigure 5 (As shown in (b)), even after 500 mechanical deformation cycles, no change in the physical appearance of the sensor was observed, and the sensing performance only decreased slightly with the increase in the number of bending times, indicating its excellent mechanical stability and practical potential for application in wearable biosensors. Subsequently, the long-term stability of the flexible gas sensor was tested by continuously testing the response of the flexible gas sensor to 1 ppm NO2 for 11 days under dark conditions and under ultraviolet light excitation conditions, respectively. As Figure 5 (As shown in (c)), under dark conditions, the relative response of the sensor to 1 ppm NO2 fluctuated more significantly, while under ultraviolet light excitation, the relative response value fluctuated less within 11 days (<20%), showing good long-term stability.

[0073] (6) Detection in the actual environment:

[0074] All clinical exhaled samples were obtained from the Stomatological Hospital of Jilin University. NO2 gas was mixed into the exhaled gas of healthy people to prepare a series of exhaled samples with different NO2 concentrations, so as to simulate the exhaled samples of patients with dental caries and periodontitis. The subjects were required not to eat, drink, brush their teeth or gargle within 1 hour before sampling, and the exhaled samples were collected between 9:00 am and 11:00 am. Before detection, the collected exhaled samples needed to be dried by a drying device to remove the water vapor in the exhaled gas to prevent the influence of the water vapor in the exhaled gas on the test. Thereafter, 500 mL of the simulated exhaled sample was injected into the gas chamber with a syringe for detection under dark conditions. The detection results are as Figure 7 (As shown in (a)), the response values of 8 healthy people were low, and the responses of the simulated exhaled samples of dental caries and periodontitis with different concentrations were significantly higher than those of healthy people, indicating that the sensor can not only perform exhaled gas diagnosis in the early stage of dental caries and periodontitis, but also has the ability to distinguish the severity of the disease, thus providing valuable evidence for guiding clinical treatment.

[0075] As a preferred embodiment of the present invention, the pressure-sensitive sensing detection of the dual-mode flexible sensor for detecting dental caries and periodontitis:

[0076] The prepared flexible conductive foam was cut into different sizes and shapes, and with the assistance of medical tape, it was respectively attached to different parts of the human body to detect subtle and large-scale body movements (such as Figure 6 (as shown, a is the temporomandibular joint movement test, b is the smile movement test, c is the masticatory muscle movement test, d is the swallowing movement test, e is the bite force test, f is the knee joint bending movement test, g is the finger bending movement test, h is the elbow joint bending movement test)):

[0077] (1) Prepare conductive flexible TPU / MWCNTs foam and cut it into different sizes for mechanical and electrical measurements.

[0078] (2) Attach copper tapes to both ends of the conductive flexible TPU / MWCNTs foam as electrodes, and connect them to a Fluke multimeter with wires for electrical testing.

[0079] (3) Attach the conductive flexible TPU / MWCNTs foam to different parts of the human body with medical tape:

[0080] When testing the movement of the temporomandibular joint, attach the conductive foam in front of the tragus (lateral to the condyle) of the subject, and ask the subject to open and close the mouth; when testing the movement of the masticatory muscles, attach the conductive foam to the mandibular angle of the subject, and ask the subject to open and close the mouth; when testing the smiling action, attach the conductive foam to the nasolabial fold of the subject, and ask the subject to smile; when testing the swallowing action, attach the conductive foam to the laryngeal prominence of the subject, and ask the subject to swallow; when testing the biting force, encapsulate the upper and lower layers of the conductive foam with PET film respectively to prevent saliva contamination, then place the conductive foam on the anterior teeth and posterior teeth of the subject respectively, and ask the patient to bite; when monitoring the flexion movement of finger joints, elbow joints and knee joints, attach the conductive foam to the finger joints, elbow joints and knee joints respectively, and ask the subject to perform finger joint flexion, elbow joint flexion and knee joint flexion movements.

[0081] (4) Exploration of performance: Connect the prepared flexible pressure sensor to a Fluke multimeter (USA), and test the pressure sensing performance of the flexible pressure sensor under the above conditions. As Figure 6 (a) shown, when testing the movement of the temporomandibular joint, the response value can reach 136.4%; as Figure 6 (b) shown, when testing the smiling movement, the response value can reach 44.0%; as Figure 6 (c) shown, when testing the movement of the masticatory muscles, the response value can reach 135.9%; as Figure 6 (d) shown, when testing the swallowing movement, the response value can reach 122.7%; when as Figure 6 (e) shown, when testing the biting force, the response value can reach 97.1%; as Figure 6 (f)-6(g) shown, when testing the flexion of fingers, elbow joints and knee joints, the responses can reach 419.9%, 352.2% and 723.6% respectively. It is proved that the flexible pressure sensor has the ability to monitor the movements of human subtle and large-amplitude joints and muscles.

[0082] (5) Detection of actual samples: We cut the prepared flexible conductive foam into pieces of 1 cm * 1 cm. Before testing, both the upper and lower layers of the flexible conductive foam are encapsulated with PET films to prevent saliva contamination. Then, the conductive foams are respectively placed on the anterior teeth and posterior teeth of the subjects, and the subjects are instructed to perform biting actions, thereby measuring the biting forces of the anterior teeth and posterior teeth. The detection results are as Figure 7 (b) shown. The response generated by the biting force of the anterior teeth of the subjects is significantly less than that generated by the biting force of the posterior teeth. As expected, the biting force generated by the anterior teeth is significantly less than that of the posterior teeth. This indicates that the strain sensor can not only test joint and muscle movements, but also test the magnitude of the biting force, thus providing valuable evidence for the construction of a dual-mode (gas-sensing and strain-sensing) early detection platform for caries and periodontitis patients and the whole process monitoring of the disease.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-mode flexible sensor for detecting dental caries and periodontitis, characterized in that, Comprising: A flexible gas sensor unit, the flexible gas sensor unit includes a PET base layer, on one side of the PET base layer is provided with an Au interdigital electrode layer, on the side of the Au interdigital electrode layer away from the PET base layer is provided with a gas sensing layer, the gas sensing layer is made of WS2 NSs / MoS2 QDs composite nanomaterials, and on the side of the gas sensing layer away from the Au interdigital electrode layer is provided with a PTFE waterproof and breathable membrane; and A flexible pressure sensor unit, the flexible pressure sensor unit includes a TPU / MWCNTs conductive foam layer.

2. A preparation method of the dual-mode flexible sensor for detecting dental caries and periodontitis as described in claim 1, characterized in that, Including the following steps: Step 1. Synthesize WS2 NSs / MoS2 QDs composite nanomaterials: Step 2. Wash the Au interdigital electrode layer on the PET base layer with deionized water and dry it at room temperature; Step 3. Spin-coat 30 μL of WS2 NSs / MoS2 QDs composite nanomaterials on the surface of the Au interdigital electrode layer and dry it under flowing N2, and repeat this 5 times; Step 4. After attaching the gas sensing layer to the Au interdigital electrode layer, attach a PTFE waterproof and breathable membrane to the Au interdigital electrode layer, and store the prepared electrode in a N2 environment for standby; Step 5. Prepare a conductive flexible TPU / MWCNTs foam and cut it into different sizes for mechanical and electrical measurements.

3. The preparation method of the dual-mode flexible sensor for detecting dental caries and periodontitis according to claim 2, characterized in that, In the said Step 1, the preparation steps of WS2 nanosheets are as follows: Step 1.

1. Synthesis of two-dimensional tungsten disulfide nanosheets: Mix 600 mg of bulk layered WS2 with 80 mL of ethanol and 120 mL of deionized water; then place the mixture in an ultrasonic machine with a frequency of 100 Hz and a temperature of 30 °C, after ultrasonic exfoliation for 21 h, collect the mixture by filtration, and then dry it overnight at 60 °C in a vacuum oven, and label it as WS2 nanosheets; Step 1.

2. Preparation of molybdenum sulfide quantum dots, i.e., MoS2 QDs: Step 1.2.

1. Synthesis of molybdenum sulfide quantum dots: Add 50 mg of MoS2 powder to 10 mL of sulfuric acid, and then ultrasonicate it at 65 °C for 20 hours. The obtained mixture is centrifuged at 4500 rpm for 30 minutes; Step 1.2.

2. Purification of molybdenum sulfide quantum dots: Dilute the supernatant to 40 mL of water, dialyze it in a dialysis bag, retain a molecular weight of 1000 Da, remove sulfuric acid, and detect it with 1 M BaCl2 solution for 1 day; Step 1.2.

3. Filtration of molybdenum sulfide quantum dots: The obtained suspension is filtered through a 0.22 μm microporous membrane to obtain uniform MoS2 quantum dots; Step 1.

3. Preparation of tungsten disulfide / molybdenum sulfide composite material, i.e., WS2 / MoS2: Mix WS2 NSs and MoS2 QDs in water and stir magnetically for 1.5 h to obtain a stable composite solution of 1 mg / mL WS2 NSs containing different contents of MoS2 QDs through electrostatic adsorption.

4. The preparation method of the dual-mode flexible sensor for detecting dental caries and periodontitis according to claim 3, characterized in that, In the tungsten disulfide molybdenum sulfide composite material, W:Mo = 300:1.

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