Surface-mounted temperature and humidity sensing system and preparation method and application thereof

Abstract

The invention relates to the technical field of composite sensing systems, in particular to a patch type temperature and humidity sensing system and a preparation method and application thereof. According to the patch type temperature and humidity sensing system and the preparation method and application thereof, the self-made temperature sensing ink pattern and the humidity sensing ink are printed on the FPCB at the same time in a silk-screen printing mode, and the integrated design of the patch type temperature and humidity sensor is achieved. On a temperature and humidity ink sensing pattern, a staggered layer superposition mode is adopted, and each layer in the pattern is composed of a plurality of n shapes which are connected in sequence, so that the maximum linear length and the larger specific surface area are obtained; the absolute value of resistance change of the temperature and humidity sensor is improved, and the detection sensitivity is improved. The problems that a traditional humidity sensor is complex in preparation process, and high stability, high sensitivity, miniaturization and the like cannot be considered at the same time are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite sensing systems, and in particular to a patch-type temperature and humidity sensing system and a preparation method and application thereof. Background Art

[0002] Chronic wounds are a global medical challenge that affects millions of people and is associated with high morbidity, limb loss and mortality. Microbial infection is a serious problem in wounds caused by these chronic wounds, which can significantly hinder the healing process. Therefore, it is crucial to accurately and promptly detect whether a wound is infected and continuously monitor multiple biomarkers related to infection, such as temperature and humidity values, for the treatment and care of chronic wounds.

[0003] Traditional clinical wound assessment methods have many drawbacks. On the one hand, it requires patients to frequently visit medical institutions. On the other hand, frequent dressing changes not only take up a lot of time, but may also interfere with the wound healing process. In addition, this frequent dressing change is costly, which has brought a heavy economic burden to the medical system.

[0004] Currently, the treatment of skin trauma usually relies on medical bandages, which mainly protect the wound from pathogens. In clinical practice, doctors generally make visual assessments based on various indicators such as the amount and color of wound exudate. However, this assessment method requires doctors to frequently remove the dressing, which may interrupt the wound's healing process.

[0005] It is well known that maintaining a proper moisture balance is critical to creating an ideal healing environment, but until recently, doctors have been unable to monitor the moisture status of dressings without disturbing them. The moisture content of a wound may exceed the range required for optimal healing, but this is difficult to verify because the moisture status under the dressing cannot be clearly determined. Effective moisture management can shorten healing time and reduce the frequency of dressing changes, thereby reducing nursing workload and improving patient comfort. However, for now, the judgment of wound healing status still mainly relies on the clinical experience of doctors, and there are subjective problems in the specific operation links, and the quantification of medical diagnosis is not enough. The main reason for this phenomenon is the technical and cost limitations, so the development of low-cost patch-type sensing systems is of great practical value. Medical dressings include hydrogels, hydrocolloids, alginates, hydrofibers and foam dressings. Although these dressings can play a better role in controlling and absorbing exudate, the actual moisture status inside the dressing is still not clear, and the dressing itself does not send out signals.

[0006] Therefore, researching an integrated sensing system with simple process, low cost and the ability to simultaneously collect two key human data, temperature and humidity, is of great significance to patient rehabilitation and the quantifiable progress of medical testing. Summary of the invention

[0007] The purpose of the present invention is to provide a patch-type temperature and humidity sensing system and its preparation method and application, which adopts a multi-sensor integrated structure to solve the problems of traditional humidity sensors, such as complex preparation process and inability to take into account high stability, high sensitivity and miniaturization.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A patch type temperature and humidity sensing system comprises an FPCB circuit board, on which a pin header, a temperature sensor and a humidity sensor are arranged; the temperature sensor and the humidity sensor are independent of each other, and are connected to a back-end circuit via the pin header to realize the collection and processing of resistance signals of the two sensors.

[0010] Furthermore, the temperature sensor and humidity sensor are both sensing ink patterns made of conductive ink by screen printing, the pattern adopts a staggered layer stacking design, and each layer in the pattern is composed of a plurality of "J" shapes connected in sequence.

[0011] Furthermore, the conductive ink includes: deionized water, graphite, PEO, PVDF, and DMF, wherein DMF is used as a dispersant for PVDF, and the mass ratio of graphite, PEO and PVDF is 4:3:3.

[0012] A method for preparing a patch-type temperature and humidity sensing system comprises the following steps:

[0013] Step 1, preparing humidity device ink: first, PEO is added to deionized water, and graphite is added and mixed evenly to obtain a first mixture; dimethylformamide (DMF) and polyvinylidene fluoride (PVDF) are added to the first mixture, and then ultrasonically crushed and stirred to obtain humidity device ink; the DMF is a dispersant of PVDF, and the ratio of graphite, polyethylene oxide (PEO) and PVDF is 4:3:3;

[0014] Preparation of humidity device ink: mixing graphene and conductive carbon raw materials in a mass percentage of 1:50, and then ultrasonically crushing and stirring to obtain humidity device ink;

[0015] Step 2: Use the temperature device ink and the humidity device ink to print the temperature sensing ink pattern and the humidity sensing ink pattern on the FPCB circuit board by screen printing process;

[0016] Step 3: heat-treating the product obtained in step 2 to obtain a patch-type temperature and humidity integrated system.

[0017] Furthermore, the implementation method of step 2 includes the steps of:

[0018] The temperature device ink and humidity ink patterns are printed on the FPCB circuit board by screen printing. Both the temperature device ink pattern and the humidity ink pattern are designed with staggered layers, that is, each pattern is printed multiple times. After each printing, the substrate and the screen are shifted by 0.1 mm, so that the printed pattern after each movement is 0.1 mm shorter than the previous one, so that it appears stepped in the horizontal viewing angle.

[0019] Furthermore, the mesh size of the screen printing screen used in step 2 is 300 meshes.

[0020] Furthermore, the implementation method of step 3 includes:

[0021] The printed samples were placed in a hot air oven for heat treatment at a temperature of 70°C for 4 hours.

[0022] The above-mentioned patch-type temperature and humidity sensing system is applied in the fields of smart Band-Aids and the like.

[0023] The present invention provides a patch-type temperature and humidity sensing system and its preparation method and application. The system uses screen printing to print a self-made temperature sensing ink pattern and humidity sensing ink on an FPCB circuit board at the same time, thereby realizing an integrated design of a patch-type temperature and humidity sensor. On the temperature and humidity ink sensing pattern, a staggered layer superposition method is adopted, and each layer in the pattern is composed of a plurality of sequentially connected "J" shapes, thereby obtaining a maximum linear length and a larger specific surface area; this is beneficial to increasing the absolute value of the resistance change of the temperature and humidity sensor and improving the detection sensitivity. For the temperature sensor, by controlling the material ratio in the humidity sensor ink, the resistance change from 35°C to 42°C is amplified, so that its sensitivity and other performances are greatly improved within the temperature range commonly seen in human skin; the temperature sensor resistance value is linearly related to the temperature, and has the advantage of good stability; the relationship function between the resistance change rate of the temperature sensor and the temperature is easy to fit, and relatively small temperature changes can be monitored, which can accurately reflect the skin condition of the human epidermis, especially the information on the skin condition of the wound. For the humidity sensor, in the homemade humidity sensor device ink used, graphene is used as the humidity sensing functional material, which is the main reason why the device resistance changes with humidity; conductive carbon is the supporting material, which can quickly absorb or release water molecules, and its exchange of water molecules with the environment determines the sensitivity of the sensor; the combination of the mass percentage of graphene-conductive carbon gives the humidity sensor a unique threshold property, which means that the sensor hardly responds at low humidity (below 50% RH) and only responds to medium and high humidity (above 90% RH).

[0024] After adopting the above technical solution, the present invention has the following advantages:

[0025] 1. The present invention adopts screen printing technology to complete the printing of temperature and humidity sensing ink patterns, which has the characteristics of low cost, mature and simple process technology, easy large-scale automated production, etc., and has broad application prospects.

[0026] 2. The humidity integrated sensing system of the present invention is a patch-type structure, which can be combined with medical supplies (such as smart Band-Aids). On the one hand, it only helps patients recover and promotes the quantification and precision of medical diagnosis; on the other hand, the sensing system can be reused, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 An exploded view of the patch-type integrated temperature and humidity sensing system of an embodiment;

[0028] Figure 2 Schematic diagram of sensor ink pattern in which multiple layers of temperature and humidity sensors are stacked in the patch-type temperature and humidity integrated sensing system of the embodiment;

[0029] Figure 31 is the test result of the temperature sensor in the patch-type integrated temperature and humidity sensing system of the embodiment, wherein a is a constant temperature test result diagram, b is an impact test result diagram, and c is a repeatability test result diagram;

[0030] Figure 4 is a curve showing the relationship between the resistance change rate and time of the humidity sensor in the patch-type temperature and humidity integrated sensing system of the embodiment in a low humidity environment;

[0031] Figure 5 is a schematic diagram of the patch-type temperature and humidity integrated sensing system of the embodiment being applied to a smart band-aid;

[0032] Reference numerals: 1-pin header, 2-temperature sensor, 3-FPCB circuit board, 4-humidity sensor. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, a patch-type temperature and humidity sensing system provided in this embodiment includes an FPCB circuit board, on which a pin header, a temperature sensor and a humidity sensor are provided; the temperature sensor and the humidity sensor are independent of each other, and are connected to the back-end circuit through the pin header to realize the collection and processing of the resistance signals of the two sensors.

[0036] The above-mentioned patch-type temperature and humidity sensing system and its preparation method have the following specific steps:

[0037] Step 1: Prepare temperature device ink and humidity device ink:

[0038] The temperature ink consists of 5 components including deionized water, graphite, PEO, PVDF, and DMF. Here, DMF serves as the dispersant for PVDF, and the ratio of graphite, PEO, and PVDF is 4:3:3. The preparation process of the temperature ink in this embodiment is as follows: First, add 10 g of PEO to 20 ml of deionized water. After mixing evenly, add 13.4 g of graphite and mix them evenly. Then add 20 ml of DMF and 10 g of PVDF. After ultrasonic fragmentation for 30 minutes and stirring for 2 hours, a suitable temperature device ink is obtained. The term "suitable" means that when continuously observing the ink sample under a microscope, the length and width dimensions of the solid particles within the visible image are both less than 100 nanometers, the solid particles are evenly distributed, and the overall fluidity of the ink is similar to that of a gluey liquid. The temperature device ink prepared in this embodiment can amplify the resistance change in the temperature range of 35°C to 42°C, significantly improving its sensitivity and other performance within the common temperature range of the human skin.

[0039] Prepare the humidity ink: After mixing graphene and conductive carbon raw materials in a mass percentage of 1:50, and subjecting them to ultrasonic fragmentation for 2 hours and stirring for 2 hours for homogenization, a suitable humidity device ink is obtained. Here, "suitable" means that when continuously observing the ink sample under a microscope, the length and width dimensions of the solid particles within the visible image are both less than 100 nanometers, the solid particles are evenly distributed, and the overall fluidity of the ink is similar to that of a gluey liquid.

[0040] Step 2: Use the pre-drawn polymer thick film FPCB circuit board as the fixed substrate of a patch-type temperature and humidity sensing system. Then, use screen printing to print the temperature ink pattern and the humidity ink pattern on the polymer thick film FPCB circuit board respectively. In this embodiment, the mesh number of the screen printing stencil is 300 meshes.

[0041] As Figure 2 shown, both the temperature ink pattern and the humidity ink pattern adopt a staggered layer design, and each layer in the pattern consists of multiple connected "J" shapes in sequence. Taking the FPCB circuit board as the reference plane, in this embodiment, both the temperature ink pattern and the humidity ink pattern are printed five times. After each printing, the substrate and the screen are misaligned and moved 0.1 mm, so that the printed pattern after each movement is 0.1 mm shorter than the previous one, presenting a five-stage stepped shape in the horizontal view as a whole. From the top view of the printed pattern, the width of the pattern lines is 0.5 mm, the vertical lines are 5 mm long, the horizontal lines between every two vertical lines are 0.5 mm long, the vertical lines and the horizontal lines appear alternately, the total width of the pattern is 5.5 mm, and the total length is 5 mm. The staggered layer design obtained through multiple screen printings increases the specific surface area, enabling the pattern to come into contact with the environment more fully.

[0042] Step 3: Place the sample obtained in step 2 in a hot air oven and heat treat it at 70°C for 4 hours to obtain a patch-type temperature and humidity sensing system. The temperature and humidity sensor of this system will change its resistance when the external temperature and humidity conditions change. The temperature sensor and humidity sensor are independent of each other, and each change corresponds to a specific temperature and humidity value. The change is processed and transmitted through the RC front-end-FLL-Wheatstone bridge system circuit on the FPCB. After connecting to the readout instrument, the current temperature and humidity values ​​can be read according to the change rate.

[0043] The temperature and humidity sensing system of this embodiment uses a sensing ink pattern composed of self-made sensing ink and multi-layer patterns staggered and superimposed to achieve the advantages of high sensitivity and good stability in the temperature range commonly seen on human skin. The humidity sensor realizes the threshold characteristic, does not collect and transmit data changes below 50% RH, and filters out errors caused by normal changes in the environment itself, such as weather and geographical location. For environments above 90% RH, it can achieve a response in seconds, with the advantages of high sensitivity and high change.

[0044] The performance test of a patch-type temperature and humidity sensor system prepared in Example 1 is as follows:

[0045] In this embodiment, the ADC sampling circuit is used to test the temperature sensor of the prepared patch-type integrated temperature and humidity sensing system. The test method is as follows:

[0046] After connecting the device in series with an 85KΩ resistor and the MSP430 development board, the device was fixed on a constant temperature heating table, and the temperatures were set to 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, and 65℃, respectively. The ADC sampling circuit was used for sampling, and the average value was taken after multiple sampling. The fitted TV function is: T[℃]=-742.55463+874.08949*Vtt / VDD. It can be seen that the sensor has good linearity with temperature changes, and the voltage divider changes significantly with temperature, which can be used to realize temperature sensing function.

[0047] The temperature sensor was tested for stability, high temperature shock, and repeatability according to this method. Specifically:

[0048] Stability test: Place the temperature sensor on a constant temperature heating table. Connect an electrometer to record the resistance change. Set the temperature to 30℃, 35℃ and 40℃ respectively, measure continuously for 30 minutes at a constant temperature, and record the data every 5 minutes to record the resistance fluctuation of the temperature sensor within 30 minutes. Figure 3As shown. Under different temperatures, the resistance value of the temperature sensor does not change in a large range. At 25℃, 30℃ and 35℃, the maximum relative change rate of the resistance value of the temperature sensor is 1.504%, 1.51% and 0.94% respectively. The temperature sensor has good temperature measurement stability. The test results are shown in Figure 3 (a) shown.

[0049] High temperature shock test: Place the temperature sensor in a 30℃ environment for 5 minutes, measure the resistance value, and then transfer it to a 50℃ high temperature environment to measure the temperature value again. Repeat this cycle 6 times. When the temperature changes, the resistance value changes to the corresponding resistance value at that temperature. This proves that the temperature sensor has good responsiveness and stability. The test results are as follows Figure 3 (b) as shown.

[0050] Repeatability test: The linear temperature sensor was tested three times in a row within the range of 25℃-60℃. In the three cycles, the resistance-temperature characteristic curve of the temperature sensor has good overlap. The average fluctuation of the resistance change rate generated by the three cycles is 4.922%. This further proves the stability and accuracy of the temperature sensor in measuring temperature. The test results are as follows: Figure 3 (c) as shown.

[0051] In this embodiment, a bridge is used to connect the computer to read the humidity sensor unit of the prepared patch-type temperature and humidity integrated sensor system, and the test method is as follows:

[0052] The saturated solution method is used to control the humidity in the sealed bag to a constant value. The principle is that different chemical salt solutions have a fixed saturated vapor pressure in a stable environment, which can make the environmental humidity a constant value; various saturated salt solutions with stable physical and chemical properties such as NaCl, NaBr, and KCl are used to control the humidity to be constant, and anhydrous sodium carbonate is used as a solid desiccant to configure a low humidity environment. A series of humidity values ​​from 30% RH to 94% RH are configured in a sealed environment of 10cm×10cm×20cm. The bridge test line is stably connected to the device through a PCB adapter board, and the real-time size of time and resistance can be obtained in the computer, thereby obtaining the reaction speed and resistance change curve of the humidity sensor in different humidity environments. In order to reduce the measurement error, the above process is repeated three times to take the average value; then the same batch of devices are taken to repeat the above process three times to eliminate contingency.

[0053] The test results for the humidity sensor are as follows:

[0054] like Figure 4As shown, the humidity sensor is extremely sensitive under medium and high humidity (above 70% RH), especially under high humidity of 94% RH, and can achieve a response and recovery in seconds. The resistance change rate is also very significant, almost close to 100%, which makes the humidity sensor have the advantages of instant response to sudden situations such as bleeding.

[0055] In order to prove the ability of the prepared patch-type temperature and humidity integrated system to simultaneously monitor temperature and humidity and its application in real life scenarios, this embodiment designs an application scenario based on a smart band-aid, such as Figure 5 As shown in the figure, it works on the back of human hand. Obviously, in real life, the surface of human skin is a common application scenario. Figure 5 As shown, the patch-type temperature and humidity integrated system is placed between the band-aid and the skin, at the tape, and can be fixed by using the band-aid's own fixing ability. It is easy to disassemble and take out the system for reuse. The temperature change is simulated by sun exposure to simulate the increase in wound inflammation temperature, and the humidity is increased by spraying to simulate wound suppuration and bleeding.

[0056] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of 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 patch-type temperature and humidity sensing system, characterized in that: It includes an FPCB circuit board, on which a pin header, a temperature sensor and a humidity sensor are arranged; the temperature sensor and the humidity sensor are independent of each other, and are connected to a back-end circuit through a pin header to realize the collection and processing of resistance signals of the two sensors.

2. A patch-type temperature and humidity sensing system according to claim 1, characterized in that: The temperature sensor and the humidity sensor are both sensing ink patterns made by screen printing with conductive ink. The pattern adopts a staggered layer stacking design, and each layer in the pattern is composed of a plurality of "J" shapes connected in sequence.

3. A patch-type temperature and humidity sensing system according to claim 1, characterized in that: The conductive ink comprises: deionized water, graphite, PEO, PVDF, and DMF, wherein DMF is used as a dispersant of PVDF, and the mass ratio of graphite, PEO and PVDF is 3.9-4.1:2.9-31.:2.9-3.

1.

4. A method for preparing a patch-type temperature and humidity sensing system, comprising the following steps: Step 1, preparing humidity device ink: first, PEO is added to deionized water, and graphite is added and mixed evenly to obtain a first mixture; DMF and PVDF are added to the first mixture, and then ultrasonically crushed and stirred to obtain humidity device ink; the DMF is a dispersant for PVDF, and the ratio of graphite, PEO and PVDF is 4:3:3; Preparation of humidity device ink: mixing graphene and conductive carbon raw materials in a mass percentage of 1:50, and then ultrasonically crushing and stirring to obtain humidity device ink; Step 2: Use the temperature device ink and the humidity device ink to print the temperature sensing ink pattern and the humidity sensing ink pattern on the FPCB circuit board by screen printing process; Step 3: heat-treating the product obtained in step 2 to obtain a patch-type temperature and humidity integrated system.

5. A method for preparing a patch-type temperature and humidity sensor system according to claim 4, characterized in that: The implementation method of step 2 comprises the following steps: The temperature device ink pattern and the humidity ink pattern are printed on the FPCB by screen printing respectively. Both the temperature device ink pattern and the humidity ink pattern are designed with staggered layers, that is, each pattern is printed multiple times. After each printing, the substrate and the screen are shifted by 0.1 mm, so that the printed pattern after each movement is 0.1 mm shorter than the previous one.

6. A method for preparing a patch-type temperature and humidity sensor system according to claim 5, characterized in that: The mesh number of the screen printing screen used in step 2 is 300 meshes.

7. A method for preparing a patch-type temperature and humidity sensor system according to claim 6, characterized in that: The implementation method of step 3 includes: The printed samples were placed in a hot air oven for heat treatment at a temperature of 70°C for 4 hours.

8. A patch-type temperature and humidity sensing system, characterized in that: Apply the humidity integrated sensing system to smart Band-Aids.

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