A patch-type temperature and humidity sensing system, its preparation method and application

Abstract

The present invention relates to the technical field of composite sensing systems, and particularly to a patch-type temperature and humidity sensing system, a preparation method thereof, and an application. The patch-type temperature and humidity sensing system, the preparation method thereof, and the application provided by the present invention use screen printing to simultaneously print a self-made temperature sensing ink pattern and humidity sensing ink on an FPCB circuit board, realizing an integrated design of the patch-type temperature and humidity sensor. On the temperature and humidity ink sensing pattern, a staggered stacking method is adopted, and each layer in the pattern is composed of multiple sequentially connected chevron shapes, obtaining the maximum linear length and a larger specific surface area; which is beneficial to increasing the absolute value of the resistance change of the temperature and humidity sensor and improving the detection sensitivity. The present invention solves the problems existing in traditional humidity sensors, such as complex preparation processes and the inability to balance high stability, high sensitivity, miniaturization, etc.

Description

Technical Field

[0001] This invention relates to the field of composite sensing system technology, specifically to a patch-type temperature and humidity sensing system, its preparation method, and its application. Background Technology

[0002] Chronic trauma is a global medical challenge affecting millions of people and is associated with high morbidity, limb loss, and mortality rates. Microbial infection is a significant problem in wounds resulting from chronic trauma, significantly hindering the healing process. Therefore, accurate and timely detection of wound infection and continuous monitoring of various infection-related biomarkers, such as temperature and humidity levels, are crucial for the treatment and care of chronic wounds.

[0003] Traditional clinical wound assessment methods have many drawbacks. On the one hand, they require patients to visit medical facilities frequently; on the other hand, frequent dressing changes are not only time-consuming but may also interfere with the wound healing process. Furthermore, this practice of frequent dressing changes is costly, placing a heavy economic burden on the healthcare system.

[0004] Currently, the treatment of skin trauma typically relies on medical bandages, whose main function is to protect the wound from pathogens. In clinical practice, doctors generally conduct 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 healing process.

[0005] Maintaining proper humidity balance is crucial for creating an ideal healing environment, but until recently, physicians were unable to monitor the humidity level of dressings without disturbing them. Wound humidity may exceed the range required for optimal healing, but this is difficult to verify precisely because the humidity level under the dressing is unclear. Effective humidity management can shorten healing time, reduce dressing changes, thereby reducing nursing workload and improving patient comfort. However, currently, assessing wound healing still relies heavily on the physician's clinical experience, introducing subjectivity in the process and hindering quantifiable medical diagnosis. Key reasons for this are technological and cost limitations, making the development of low-cost patch-type sensing systems highly valuable. Medical dressings include various types such as hydrogels, hydrocolloids, alginates, hydrocellulose, and foam dressings. While these dressings are effective in controlling and absorbing exudate, the actual humidity level inside the dressing remains unclear, and the dressing itself does not emit signals.

[0006] Therefore, researching an integrated sensing system that is simple in process, low in cost, and capable of simultaneously collecting two key human body data—temperature and humidity—is of great significance for the quantifiable progress of patient rehabilitation and medical testing. Summary of the Invention

[0007] The purpose of this invention is to provide a patch-type temperature and humidity sensing system, its preparation method and application. It adopts a multi-sensor integrated structure, which solves the problems of complex preparation process and inability to achieve high stability, high sensitivity and miniaturization of traditional humidity sensors.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A surface-mount temperature and humidity sensing system includes an FPCB circuit board, on which pin headers, a temperature sensor, and a humidity sensor are mounted. The temperature sensor and humidity sensor are independent of each other and are connected to a back-end circuit via pin headers to achieve the acquisition and processing of resistance signals from the two sensors. This surface-mount temperature and humidity sensing system is fabricated according to the following steps:

[0010] Step 1: Prepare the ink for the temperature device.

[0011] First, PEO is added to deionized water and mixed evenly. Then, graphite is added and mixed evenly to obtain a first mixture. DMF and PVDF are added to the first mixture, and after ultrasonic crushing and stirring evenly, temperature device ink is obtained. DMF is a dispersant for PVDF, and the ratio of graphite, PEO and PVDF is 4:3:3.

[0012] Ink for preparing humidity devices:

[0013] Graphene and conductive carbon raw materials are mixed at a mass ratio of 1:50, and after ultrasonic crushing and uniform stirring, humidity device ink is obtained.

[0014] Step 2: Using temperature sensor ink and humidity sensor ink, print temperature sensing ink patterns and humidity sensing ink patterns on the FPCB circuit board using screen printing technology. Specifically: print temperature sensor ink and humidity sensing ink patterns on the FPCB using screen printing. Both temperature sensor ink patterns and humidity ink patterns adopt a staggered layer design, that is, each pattern is printed multiple times. After each printing, the substrate and screen are shifted by 0.1 mm, so that the printed pattern after each shift is 0.1 mm shorter than the previous one.

[0015] Step 3: Heat treat the product obtained in Step 2 to obtain a patch-type integrated temperature and humidity system.

[0016] Further, both the temperature sensor and the humidity sensor are sensing ink patterns made of conductive ink through screen printing. The pattern adopts a staggered stacking design, and each layer in the pattern consists of multiple connected U-shaped elements in sequence.

[0017] Further, the temperature device ink includes: deionized water, graphite, PEO, PVDF, and DMF. Here, DMF serves as a dispersant for PVDF, and the mass ratio of graphite, PEO, and PVDF is 3.9 - 4.1:2.9 - 3.1:2.9 - 3.1.

[0018] Further, the mesh count of the screen printing stencil used in step 2 is 300 mesh.

[0019] Further, the implementation method of step 3 includes:

[0020] Put the printed sample into a hot air oven for heat treatment. The heat treatment temperature is 70 °C, and the heat treatment time is 4 hours.

[0021] A patch-type temperature and humidity sensing system, characterized in that the patch-type temperature and humidity sensing system described in claim 1 is applied in a smart wound dressing.

[0022] A patch-type temperature and humidity sensing system, its preparation method and application provided by the present invention adopt screen printing to simultaneously print a self-made temperature sensing ink pattern and humidity sensing ink on an FPCB circuit board, realizing an integrated design of the patch-type temperature and humidity sensor. On the temperature and humidity ink sensing pattern, a staggered stacking method is adopted, and each layer in the pattern consists of multiple connected U-shaped elements in sequence, obtaining the maximum linear length and a larger specific surface area; it is beneficial to increase the absolute value of the resistance change of the temperature and humidity sensor and improve the detection sensitivity. For the temperature sensor among them, by controlling the material ratio in the humidity sensor ink, the resistance change between 35 °C and 42 °C is amplified, significantly enhancing the sensitivity and other performance within the common temperature range of the human skin; the resistance value of the temperature sensor has a linear relationship with temperature, having the advantage of good stability; the relationship function between the resistance change rate of the temperature sensor and temperature is easy to fit, capable of monitoring relatively small temperature changes, and accurately reflecting the information of the human epidermal skin condition, especially the wound skin condition. For the humidity sensor among them, in the self-made humidity sensor ink used, graphene serves as the humidity sensing functional material, which is the main reason for the change of the device resistance with humidity; conductive carbon is the supporting material, capable of quickly absorbing or releasing water molecules, and its water molecule exchange situation with the environment determines the sensitivity of the sensor; the specific threshold property of the humidity sensor is achieved by coordinating the mass percentage of graphene - conductive carbon. The threshold property means that the sensor hardly responds at low humidity (below 50% RH) and only responds to medium and high humidity (above 90% RH).

[0023] By adopting the above technical solution, the present invention has the following advantages:

[0024] 1. This invention uses screen printing technology to complete the printing of temperature and humidity sensing ink patterns. It has the characteristics of low cost, mature and simple technology, and easy large-scale automated production, and has broad application prospects.

[0025] 2. The humidity integrated sensing system of the present invention has a patch structure, which can be combined with medical supplies (such as smart bandages). On the one hand, it can help patients recover and promote the quantification and precision of medical diagnosis; on the other hand, the sensing system can be reused, saving costs. Attached Figure Description

[0026] Figure 1 Exploded view of the patch-type integrated temperature and humidity sensor system of the embodiment;

[0027] Figure 2 This is a schematic diagram of the sensor ink pattern of the multi-layered staggered temperature and humidity sensor in the patch-type integrated temperature and humidity sensing system of the embodiment.

[0028] Figure 3 The following are the test results of the temperature sensor in the patch-type integrated temperature and humidity sensing system of the embodiment, where a is the constant temperature test result diagram, b is the impact test result diagram, and c is the repeatability test result diagram.

[0029] Figure 4 This is a curve showing the relationship between the resistance change rate of the humidity sensor and time in a low-humidity environment in the patch-type integrated temperature and humidity sensing system of this embodiment.

[0030] Figure 5 This is a schematic diagram of the patch-type integrated temperature and humidity sensing system applied to a smart adhesive bandage.

[0031] Figure label: 1-pin header, 2-temperature sensor, 3-FPCB circuit board, 4-humidity sensor. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0033] Example 1

[0034] like Figure 1As shown, this embodiment provides a patch-type temperature and humidity sensing system, including an FPCB circuit board. The FPCB circuit board is provided with pin headers, a temperature sensor, and a humidity sensor. The temperature sensor and the humidity sensor are independent of each other and are connected to the back-end circuit through the pin headers to realize the acquisition and processing of the resistance signals of the two sensors.

[0035] The specific steps of the above-mentioned patch-type temperature and humidity sensing system and its preparation method are as follows:

[0036] Step 1: Prepare inks for temperature devices and humidity devices:

[0037] The temperature-sensitive ink consists of five components: deionized water, graphite, PEO, PVDF, and DMF. DMF acts as a dispersant for PVDF, and the ratio of graphite, PEO, and PVDF is 4:3:3. The preparation process of the temperature-sensitive ink in this embodiment is as follows: First, 10g of PEO is added to 20ml of deionized water and mixed thoroughly. Then, 13.4g of graphite is added and mixed thoroughly. Next, 20ml of DMF and 10g of PVDF are added, followed by ultrasonic fragmentation for 30 minutes and stirring for 2 hours to obtain a suitable temperature-sensitive device ink. "Suitable" means that under a microscope, continuous observation of the ink sample reveals that the length and width of the solid particles within the image are all less than 100 nanometers, the solid particles are uniformly distributed, and the overall fluidity of the ink is similar to a viscous liquid. The temperature-sensitive device ink prepared in this embodiment can amplify the resistance change within a temperature range of 35℃ to 42℃, significantly improving its sensitivity and other performance characteristics within the temperature range commonly found on human skin.

[0038] Preparation of Humidity Ink: Graphene and conductive carbon raw materials were mixed at a mass ratio of 1:50, and then homogenized by ultrasonic crushing for 2 hours and stirring for 2 hours to obtain a suitable humidity device ink. "Suitable" here means that under a microscope, continuous observation of the ink sample shows that the length and width of the solid particles within the image are all less than 100 nanometers, the solid particles are uniformly distributed, and the overall fluidity of the ink is similar to that of a viscous liquid.

[0039] Step 2: The pre-drawn polymer thick film FPCB circuit board is used as a fixed substrate for a surface-mount temperature and humidity sensing system. Then, temperature and humidity ink patterns are printed on the polymer thick film FPCB circuit board using screen printing. In this embodiment, the screen printing stencil has a mesh count of 300.

[0040] like Figure 2As shown, both the temperature ink pattern and the humidity ink pattern adopt a staggered stacked design, and each layer in the pattern is composed of multiple "几" - shaped elements connected 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 displaced by 0.1 mm, so that the printed pattern after each displacement is 0.1 mm shorter than the previous one, presenting a five - stage stepped shape as a whole from the horizontal perspective. Looking from the top - down perspective, 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 stacked design obtained through multiple screen printings increases the specific surface area, enabling the pattern to contact the environment more fully.

[0041] Step 3: Put the sample obtained in Step 2 into a hot - air oven and heat - treat it at 70 °C for 4 hours to obtain a patch - type temperature - humidity sensing system. When the external temperature - humidity conditions change, the resistance of the temperature - humidity sensor in this system will change. The temperature sensor and the humidity sensor are independent of each other, and each change amount corresponds to a specific temperature - humidity value one by one. The change amount is processed and transmitted through the RC front - end - FLL - Wheatstone bridge system circuit on the FPCB. After connecting to the reading instrument, the current temperature - humidity value can be read according to the change rate.

[0042] The temperature - humidity sensing system of this embodiment is composed of a self - made sensing ink and a sensing ink pattern formed by staggered stacking of multiple layers, enabling the temperature sensor to have advantages such as high sensitivity and good stability within the temperature range common to human skin. The humidity sensor realizes the threshold characteristic, does not collect and transmit data changes below 50%RH, filtering out errors caused by normal changes in the environment itself such as weather and geographical location. For environments above 90%RH, it can reach a reaction in seconds, having the advantages of high sensitivity and high variation.

[0043] The performance test of a patch - type temperature - humidity sensing system prepared in Example 1 is as follows:

[0044] In this embodiment, an ADC sampling circuit is used to test the temperature sensor of the prepared patch - type integrated temperature - humidity sensing system. The test method is:

[0045] After connecting the device in series with an 85 kΩ resistor to the MSP430 development board, the device was fixed on a constant-temperature heating platform. Temperatures were set to 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, and 65 ℃. An ADC sampling circuit was used to sample the data, and the average value was taken from multiple samples. The fitted TV function was: T[℃] = -742.55463 + 874.08949 * Vtt / VDD. It can be seen that the sensor exhibits good linearity with temperature changes, and the voltage divider changes significantly with temperature, making it suitable for temperature sensing.

[0046] The temperature sensor underwent stability, high-temperature shock, and repeatability tests according to this method, specifically:

[0047] Stability Test: The temperature sensor was placed on a constant-temperature heating platform. A multimeter was connected to record the resistance change. Temperatures were set to 30℃, 35℃, and 40℃ respectively, and measurements were taken continuously for 30 minutes at a constant temperature, recording data every 5 minutes to record the fluctuation of the temperature sensor's resistance value over 30 minutes. During the test, if... Figure 3 As shown in the figure, the resistance value of the temperature sensor did not change significantly under different temperatures. The maximum relative change rates of the temperature sensor's resistance value at 25 ℃, 30 ℃, and 35 ℃ were 1.504%, 1.51%, and 0.94%, respectively, indicating that the temperature sensor exhibits good temperature measurement stability. The test results are as follows... Figure 3 As shown in (a).

[0048] High-temperature shock test: The temperature sensor was placed in an environment of 30 ℃ for 5 minutes, and the resistance value was measured. Then, it was transferred to a high-temperature environment of 50 ℃ and the temperature value was measured again. This cycle was repeated 6 times. When the temperature changed, the resistance value immediately changed 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 As shown in (b).

[0049] Repeatability Test: The linear temperature sensor was subjected to three consecutive cyclic tests within the temperature range of 25 °C to 60 °C. The resistance-temperature characteristic curves of the temperature sensor showed excellent overlap across the three cycles. The average fluctuation of the resistance change rate over the three cycles was 4.922%. This further demonstrates the stability and accuracy of the temperature sensor in temperature measurement. The test results are as follows: Figure 3 As shown in (c).

[0050] In this embodiment, an external computer connected to a bridge circuit was used to test the humidity sensing unit of the fabricated patch-type integrated temperature and humidity sensing system. The test method was as follows:

[0051] The humidity in the sealed bag was controlled to a constant value using a saturated solution method. The principle is that different chemical salt solutions have a fixed saturated vapor pressure in a stable environment, which allows the ambient humidity to remain constant. Various physicochemically stable saturated salt solutions, such as NaCl, NaBr, and KCl, were used to control the humidity. Anhydrous sodium carbonate was used as a solid desiccant to prepare a low-humidity environment. A series of humidity levels, ranging from 30% RH to 94% RH, were prepared in a sealed environment of 10 cm × 10 cm × 20 cm. The bridge test leads were stably connected to the device via a PCB adapter board. The real-time time and resistance values ​​could be obtained from the computer, thus providing the response speed and resistance change curves of the humidity sensor under different humidity environments. To reduce measurement error, the above process was repeated three times and the average value was taken. Then, the process was repeated three more times with devices from the same batch to eliminate randomness.

[0052] The test results for the humidity sensor are as follows:

[0053] like Figure 4 As shown, the humidity sensor is extremely sensitive under medium to high humidity (above 70% RH), especially under high humidity of 94% RH, with a response and recovery time of up to seconds. The resistance change rate is also very significant, almost close to 100%, which gives the humidity sensor the advantage of immediate response to sudden situations such as bleeding.

[0054] To demonstrate the ability of the fabricated patch-type integrated temperature and humidity system to simultaneously monitor temperature and humidity and its application in real-life scenarios, this embodiment designs an application scenario based on a smart adhesive bandage, such as... Figure 5 As shown, this involves working on the skin of the back of a human hand. Clearly, the surface of human skin is a common application scenario in real life. Figure 5 As shown, the patch-type integrated temperature and humidity system is placed between the adhesive bandage and the skin, at the adhesive tape location. It is secured using the adhesive bandage's own fixation properties and is easily disassembled for reuse. Sunlight exposure simulates wound inflammation by causing temperature changes and raising the temperature, while a spray increases humidity to simulate wound suppuration and bleeding.

[0055] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment 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 within the scope of protection of the present invention.

Claims

1. A patch-type temperature and humidity sensing system, characterized in that: The system includes an FPCB circuit board, on which pin headers, a temperature sensor, and a humidity sensor are mounted. The temperature and humidity sensors are independent of each other and are connected to the back-end circuitry via pin headers to acquire and process the resistance signals of the two sensors. The fabrication method of this surface-mount temperature and humidity sensing system includes the following steps: Step 1: Prepare the ink for the temperature device. First, PEO is added to deionized water and mixed evenly. Then, graphite is added and mixed evenly to obtain a first mixture. DMF and PVDF are added to the first mixture, and after ultrasonic crushing and stirring evenly, temperature device ink is obtained. DMF is a dispersant for PVDF, and the ratio of graphite, PEO and PVDF is 4:3:

3. Ink for preparing humidity devices: Graphene and conductive carbon raw materials are mixed at a mass ratio of 1:50, and after ultrasonic crushing and uniform stirring, humidity device ink is obtained. Step 2: Using temperature sensor ink and humidity sensor ink, print temperature sensing ink patterns and humidity sensing ink patterns on the FPCB circuit board using screen printing technology. Specifically: print temperature sensor ink and humidity sensing ink patterns on the FPCB using screen printing. Both temperature sensor ink patterns and humidity ink patterns adopt a staggered layer design, that is, each pattern is printed multiple times. After each printing, the substrate and screen are shifted by 0.1 mm, so that the printed pattern after each shift is 0.1 mm shorter than the previous one. Step 3: Heat treat the product obtained in Step 2 to obtain a patch-type integrated temperature and humidity system.

2. The patch-type temperature and humidity sensing system according to claim 1, characterized in that: Both the temperature sensor and the humidity sensor are sensor ink patterns made by screen printing with conductive ink. The pattern adopts a staggered superposition design, and each layer of the pattern is composed of multiple sequentially connected zigzag shapes.

3. The patch-type temperature and humidity sensing system according to claim 1, characterized in that: The temperature device 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 3.9–4.1:2.9–3.1:2.9–3.

1.

4. The patch-type temperature and humidity sensing system according to claim 1, characterized in that: The screen printing stencil used in step 2 has a mesh count of 300.

5. The patch-type temperature and humidity sensing system according to claim 1, characterized in that: The implementation method of step 3 includes: The printed sample is placed in a hot air chamber for heat treatment at a temperature of 70°C for 4 hours.

6. A patch-type temperature and humidity sensing system, characterized in that: The patch-type temperature and humidity sensing system described in claim 1 is applied to a smart adhesive bandage.

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