Flexible dual-mode sensor for underwater environment perception and method of manufacture

Abstract

The application discloses a flexible dual-mode sensor for underwater environment sensing and a preparation method, relates to the technical field of flexible pressure sensing, and comprises, from top to bottom, an upper hydrophobic packaging layer, an upper functional electrode layer, a pressure-sensitive layer, a lower functional electrode layer, a temperature-sensitive layer and a lower hydrophobic packaging layer, wherein the pressure-sensitive layer comprises a conductive fabric layer and an intermediate hydrophobic packaging layer. The application integrates pressure sensing and temperature sensing functions in a single flexible device, the two sensing modules share part of the electrode structure and the signals are independent of each other and do not interfere with each other, the synchronous detection of multiple physical quantities can be realized in a complex environment such as underwater, and the device structure is effectively simplified. The conductive fabric layer has three-dimensional interconnected pores, fiber surface micro-protrusions and rough structures, the number of contact points between fibers and the effective contact area are significantly improved with the increase of pressure under the stimulation of external pressure, the resistance change of the device is sensitive, the response amplitude is large, and the pressure sensing sensitivity is improved.

Description

Technical Field

[0001] This invention relates to the field of flexible pressure sensing technology, specifically to a flexible dual-mode sensor for underwater environmental sensing and its fabrication method. Background Technology

[0002] In recent years, the development of marine resources and deep-sea exploration have become increasingly frequent, creating an urgent need for sensing technologies capable of monitoring underwater environments. Underwater tactile sensing, as a key parameter reflecting ocean dynamics, has significant research value for accurate measurement in fields such as underwater rescue, deep-sea exploration, marine ecological research, and underwater wearable devices. Unlike ordinary natural environments, underwater environments typically exhibit complex characteristics such as high hydrostatic pressure and strong corrosivity, placing extremely high demands on the reliability, environmental adaptability, and long-term stability of sensing equipment. Therefore, it is necessary to develop novel flexible sensing technologies capable of long-term stable operation underwater.

[0003] Pressure sensors based on flexible materials have attracted much attention due to their excellent flexibility, high sensitivity, and good conformal adhesion. However, existing flexible sensors still face challenges when applied to practical underwater applications. For example, (1) the sensing mode is limited. Most underwater sensors are based on a single capacitance or resistance mechanism and can only detect changes in a single physical quantity. Especially in complex underwater operation scenarios, it is often necessary to acquire multi-dimensional information such as pressure and temperature (e.g., water temperature stratification detection, deep-sea hydrothermal monitoring); (2) it is difficult to achieve both underwater interface adaptability and waterproof reliability. Water molecule penetration can easily lead to sensor swelling, electrode corrosion, or interface peeling failure, resulting in distortion of underwater signal acquisition.

[0004] To address the aforementioned issues, researchers have begun exploring dual-mode sensing strategies that simultaneously sense multiple physical quantities. Existing research primarily focuses on two approaches: first, using a single sensing material to achieve pressure and temperature sensing through its dual-response characteristics; however, such schemes often face severe signal coupling problems, making it difficult to accurately distinguish between the two excitations; second, isolating the pressure and temperature sensing units, which, while achieving dual-parameter detection to some extent, suffers from structural complexity, low integration, and poor interface sealing reliability, hindering miniaturized underwater applications. Therefore, how to achieve independent detection and stable output of pressure and temperature signals through integrated design while ensuring sensor flexibility and underwater sealing, and avoiding crosstalk between the two sensing modes during operation, has become a critical technical challenge urgently needing breakthroughs in the field of flexible underwater sensing.

[0005] Therefore, a flexible dual-mode sensor for underwater environmental sensing and its fabrication method are proposed to solve the above problems. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for fabricating a flexible dual-mode sensor for underwater environmental sensing, comprising the following steps: Step 1: Prepare polydimethylsiloxane / polytetrafluoroethylene composite solution; drop the composite solution onto a 3D printing mold and a flat substrate respectively, and heat to cure after vacuum degassing to obtain a patterned middle hydrophobic encapsulation layer and a thin film-like upper and lower hydrophobic encapsulation layer. Step 2: Using a polyimide film as a flexible substrate, a pressure sensing electrode pattern is prepared on one side of the film by magnetron sputtering or spraying with a pattern template to obtain an upper functional electrode layer; another clean polyimide film is taken, and a pressure sensing electrode pattern and an interdigitated temperature sensing electrode pattern are prepared on both sides of the polyimide film to obtain a lower functional electrode layer integrating pressure and temperature dual electrodes. Step 3: Cut the fabric and immerse it in the conductive dispersion solution for impregnation and drying. After drying, a conductive fabric layer with a continuous conductive network is formed. The conductive fabric layer is embedded inside the middle hydrophobic encapsulation layer to obtain the pressure-sensitive layer. Step 4: Prepare MXene / CNT composite temperature-sensitive ink, and uniformly apply it to the interdigitated temperature-sensitive electrode pattern area of ​​the lower functional electrode layer by spraying or scraping to obtain a temperature-sensitive layer located on the lower side of the lower functional electrode layer. Step 5: Device assembly and packaging to obtain a flexible dual-mode sensor for underwater environmental sensing.

[0007] Preferably, in step 1, the preparation steps of the polydimethylsiloxane / polytetrafluoroethylene composite solution are as follows: Polydimethylsiloxane prepolymer and curing agent in a mass ratio of 10:1 were added together to n-hexane and stirred to obtain a uniform dispersion. Polytetrafluoroethylene particles were added to the dispersion, with a mass ratio of polytetrafluoroethylene particles to polydimethylsiloxane prepolymer of 1:10. The mixture was stirred until the polytetrafluoroethylene particles were completely dispersed. The mixture was then stirred under heating conditions at 70°C to remove n-hexane and obtain a uniform polydimethylsiloxane / polytetrafluoroethylene composite solution.

[0008] Preferably, the middle hydrophobic encapsulation layer has a through hole for embedding the conductive fabric layer; in step 3, the fabric is cut to a size that matches the through hole of the middle hydrophobic encapsulation layer.

[0009] Preferably, in step 4, the preparation steps of the MXene / CNT composite temperature-sensitive ink are as follows: MXene nanosheets and carbon nanotubes were mixed at a mass ratio of 5:1. Deionized water was added to the deionized water to adjust the total solid content of the solution system to 20 wt%, and a mixed slurry was obtained. Then, the mixture was magnetically stirred and ultrasonically prepared to obtain a uniformly dispersed MXene / CNT composite thermosensitive ink.

[0010] Preferably, in step 4, after the MXene / CNT composite temperature-sensitive ink is coated onto the interdigitated temperature-sensitive electrode pattern area of ​​the lower functional electrode layer, the lower functional electrode layer is placed in a vacuum oven at 60-80°C and dried for 15-25 minutes. After being removed and cooled, a temperature-sensitive layer located on the lower side of the lower functional electrode layer is obtained.

[0011] As a preferred embodiment, step 5 specifically involves: The upper hydrophobic encapsulation layer, upper functional electrode layer, pressure-sensitive layer, lower functional electrode layer, temperature-sensitive layer, and lower hydrophobic encapsulation layer are stacked sequentially from top to bottom and bonded together with an adhesive. The pressure sensing electrode on the lower side of the upper functional electrode layer and the pressure sensing electrode on the upper side of the lower functional electrode layer are respectively attached to the upper and lower sides of the pressure-sensitive layer to obtain a flexible dual-mode sensor for underwater environmental sensing.

[0012] Preferably, the concentration of the conductive dispersion in step 3 is 5 mg / mL to 10 mg / mL, and the conductive dispersion is one of MXene dispersion, carbon nanotube dispersion, graphene dispersion, and carbon black dispersion.

[0013] Preferably, in step 3, the immersion and drying steps are repeated 3 to 5 times, with each immersion lasting 3 to 5 minutes and each drying process performed at a temperature of 60 to 80°C for 10 minutes.

[0014] The present invention also provides a flexible dual-mode sensor for underwater environmental sensing, which is prepared by the method described above.

[0015] The present invention has the following beneficial effects: This invention achieves simultaneous pressure-temperature dual-mode sensing in a single device, demonstrating high integration. The two sensing modules share some electrode structures, and their signals are independent and do not interfere with each other. This enables simultaneous detection of multiple physical quantities in complex environments such as underwater, effectively simplifying the device structure and improving integration and environmental adaptability.

[0016] Based on the three-dimensional porous structure of conductive fabric, the sensing sensitivity is high. The conductive fabric layer used in the pressure-sensitive layer has a three-dimensional interconnected porous structure, micro-protrusions on the fiber surface, and a rough structure. Under external pressure, the number of contact points between fibers and the effective contact area increase significantly with increasing pressure, making the device more sensitive to changes in resistance and with a larger response amplitude, thereby improving the pressure sensing sensitivity. At the same time, the fabric substrate is low in cost, flexible, and has fast deformation recovery, which is conducive to realizing wide-range and highly stable mechanical signal detection.

[0017] The device is fully encapsulated with superhydrophobic material, enabling stable operation in underwater environments. The upper and lower superhydrophobic encapsulation layers, together with the middle hydrophobic encapsulation layer, form a fully encapsulated superhydrophobic protective structure, providing complete waterproof and anti-fouling protection for the device. This solves the problem of short circuits and device damage that traditional flexible sensors are prone to under underwater and high humidity conditions. Furthermore, the overall fabrication process is simple and low-cost, making it suitable for large-scale fabrication and practical engineering applications. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the flexible dual-mode sensor for underwater environmental sensing according to the present invention. Figure 2 This is a schematic diagram of the structure of the upper functional electrode layer, the middle hydrophobic encapsulation layer, and the conductive fabric layer in this invention; Figure 3 This is a schematic diagram of the pressure working mechanism of the flexible dual-mode sensor used for underwater environmental sensing in this invention.

[0019] In the figure: 1, upper hydrophobic encapsulation layer; 2, upper functional electrode layer; 3, pressure-sensitive layer; 31, conductive fabric layer; 32, middle hydrophobic encapsulation layer; 4, lower functional electrode layer; 5, temperature-sensitive layer; 6, lower hydrophobic encapsulation layer. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0022] Example 1: refer to Figure 1 , Figure 2A flexible dual-mode sensor for underwater environmental sensing includes, from top to bottom, an upper hydrophobic encapsulation layer 1, an upper functional electrode layer 2, a pressure-sensitive layer 3, a lower functional electrode layer 4, a temperature-sensitive layer 5, and a lower hydrophobic encapsulation layer 6. The pressure-sensitive layer 3 includes a conductive fabric layer 31 and an intermediate hydrophobic encapsulation layer 32. The intermediate hydrophobic encapsulation layer 32 has a through hole in its center for embedding the conductive fabric layer 31. The upper hydrophobic encapsulation layer 1, the lower hydrophobic encapsulation layer 6, and the intermediate hydrophobic encapsulation layer 32 together constitute the hydrophobic protective structure of the device. The upper hydrophobic encapsulation layer 1 and the lower hydrophobic encapsulation layer 6 are symmetrically distributed on the outermost side of the device. Sensing electrodes attached to the conductive fabric layer 31 are provided on the lower side of the upper functional electrode layer 2 and the upper side of the lower functional electrode layer 4. Sensing electrodes attached to the temperature-sensitive layer 5 are provided on the lower side of the lower functional electrode layer 4. The upper functional electrode layer 2 and the lower functional electrode layer 4 are used to transmit mechanical signals. The lower functional electrode layer 4 is also used to connect to the temperature-sensitive layer 5 and output signals.

[0023] The temperature-sensitive layer 5 is a conductive composite material made of MXene and carbon nanotubes; the conductive fabric layer 31 is prepared by immersing the fabric in a conductive dispersion and then drying it. The conductive dispersion is one or any combination of MXene dispersion, carbon nanotube dispersion, graphene dispersion, and carbon black dispersion. It is loaded onto the fabric substrate by solution impregnation to form a continuous conductive network structure. The conductive fabric layer 31 is in close contact with the upper functional electrode layer 2 and the lower functional electrode layer 4 and forms a closed conductive path.

[0024] The upper hydrophobic encapsulation layer 1, the lower hydrophobic encapsulation layer 6, and the middle hydrophobic encapsulation layer 32 are all made of polytetrafluoroethylene (PTFE) particles doped with polydimethylsiloxane (PDMS), which gives the device a stable superhydrophobic performance; the sensing electrode on the lower side of the lower functional electrode layer 4 is an interdigitated sensing electrode. Both the upper functional electrode layer 2 and the lower functional electrode layer 4 are based on polyimide (PI). The electrodes can be prepared by magnetron sputtering or spraying. The target material used for magnetron sputtering is selected from one or more of silver (Ag), titanium (Ti), aluminum (Al), copper (Cu), gold (Au), and ITO. The conductive materials used in the spraying process include silver nanowires, MXene, MXene / silver nanowire conductive ink, carbon black, carbon nanotubes, etc.

[0025] This embodiment also provides a method for fabricating a flexible dual-mode sensor for underwater environmental sensing, which includes the following steps: Step 1: Prepare a hydrophobic layer of polydimethylsiloxane (PDMS) / polytetrafluoroethylene (PTFE). 10g of polydimethylsiloxane (PDMS) prepolymer and 1g of curing agent were added to 20mL of n-hexane and magnetically stirred at 500r / min for 30min at room temperature to obtain a uniform dispersion. Then, 1g of polytetrafluoroethylene (PTFE) particles were added to the dispersion and stirred until the PTFE particles were completely and uniformly dispersed. The mixture was then placed in a 70℃ oil bath and stirred for 1-2h to remove the n-hexane solvent, thus obtaining a uniform polydimethylsiloxane (PDMS) / polytetrafluoroethylene (PTFE) composite solution. The composite solution was then drop-coated onto a 3D printing mold and a flat substrate, respectively. After vacuum degassing for 15min, it was transferred to an 80℃ oven for heating and curing for 2-4h. After naturally cooling to room temperature, it was demolded to obtain a patterned middle hydrophobic encapsulation layer 32, a thin film-like upper hydrophobic encapsulation layer 1, and a lower hydrophobic encapsulation layer 6. Step 2: Prepare functional electrode layers (upper functional electrode layer 2 and lower functional electrode layer 4). A 0.015 mm thick polyimide (PI) film was cut into a preset rectangular size and then ultrasonically cleaned alternately with deionized water and anhydrous ethanol for 10–15 min. After drying in a vacuum oven at 60 °C for 20 min, it was ready for use. Using the clean polyimide film as a flexible substrate, a silver (Ag) electrode was sputtered onto one side of the film using a pattern template-assisted magnetron sputtering process to form a pressure sensing electrode pattern. The sputtering power was 80 W and the sputtering time was 120 s, resulting in the upper functional electrode layer 2. Another clean polyimide film was taken, and silver (Ag) electrodes were sputtered onto both sides of the polyimide film using a magnetron sputtering process. A pressure sensing electrode pattern matching the upper functional electrode layer 2 was prepared on the upper side, and an interdigitated temperature sensing electrode pattern was prepared on the lower side. The sputtering parameters were the same as those used for the upper functional electrode layer 2. After sputtering, the film was transferred to a 70 °C oven for heating and curing for 1 h, and then cooled to room temperature to obtain the lower functional electrode layer 4, which integrates pressure and temperature electrodes. Step 3, prepare pressure-sensitive layer 3. Cut the fabric to the size that matches the through holes of the intermediate hydrophobic encapsulation layer 32, clean it with alcohol and dry it for later use; immerse the fabric in an MXene dispersion with a concentration of 5 mg / mL to 10 mg / mL, and perform multiple immersion and drying cycles (immersion for 3 to 5 min / time, drying at 60 to 80℃ for 10 min / time, cycle 3 times) to uniformly load the conductive material onto the surface of the fabric fibers. After drying, a conductive fabric layer 31 with a continuous conductive network is formed. Then, the conductive fabric layer 31 is embedded inside the intermediate hydrophobic encapsulation layer 32 to obtain pressure-sensitive layer 3. Step 4, prepare the temperature-sensitive layer 5. Mix MXene nanosheets and carbon nanotubes at a mass ratio of 5:1. Use deionized water as a dispersant and add it to the deionized water to adjust the total solid content of the solution system to 20wt% to obtain a mixed slurry. Then, stir magnetically at 1000r / min for 2h and then sonicate for 30min to obtain a uniformly dispersed MXene / CNT composite temperature-sensitive ink. Then, uniformly coat it onto the interdigitated temperature-sensitive electrode pattern area of ​​the lower functional electrode layer 4 by a scraping method. Then, place the lower functional electrode layer 4 in a vacuum oven at 60℃ for 20min to dry it, so that the temperature-sensitive material and the interdigitated temperature-sensitive electrode are tightly bonded. After cooling, the temperature-sensitive layer 5 can be obtained on the interdigitated temperature-sensitive electrode pattern area on the lower side of the lower functional electrode layer 4. Step 5, Device Assembly and Packaging. The upper hydrophobic encapsulation layer 1, upper functional electrode layer 2, pressure-sensitive layer 3, lower functional electrode layer 4, temperature-sensitive layer 5, and lower hydrophobic encapsulation layer 6 are stacked sequentially from top to bottom and bonded together with adhesive to obtain a flexible dual-mode sensor for underwater environmental sensing.

[0026] It should be noted that in step 1, the average particle size of polytetrafluoroethylene (PTFE) is 1µm; and the thickness of the upper hydrophobic encapsulation layer 1 and the lower hydrophobic encapsulation layer 6 is controlled to be 0.5mm. In step 2, the four electrode terminals (the interdigitated temperature sensing electrode on the lower side of the lower functional electrode layer 4 has two electrode terminals, and the pressure sensing electrode on the upper side of the lower functional electrode layer 4 and the pressure sensing electrode on the lower side of the upper functional electrode layer 2 each have one electrode terminal) are reinforced with silver paste and lead wires are drawn out. In step 3, the dispersant for MXene is deionized water, which is used to prepare the MXene dispersion.

[0027] The working mechanism of the flexible dual-mode sensor used for underwater environmental sensing in this embodiment is as follows: refer to Figure 1 , Figure 3 The pressure sensing unit consists of an upper functional electrode layer 2, an MXene-based conductive fabric sensitive layer (conductive fabric layer 31), and a lower functional electrode layer 4. The pressure working mechanism is as follows: when the sensor is subjected to pressure, the external pressure is transmitted to the conductive fabric layer 31 through the encapsulation layers (upper hydrophobic encapsulation layer 1 and lower hydrophobic encapsulation layer 6). The pores between the fabric fibers are compressed, thereby significantly increasing the contact area between fibers and between fibers and the electrodes of the functional electrode layer, forming more conductive pathways. Simultaneously, the contact sites of MXene nanosheets on the surface of the fabric fibers increase, and the equivalent resistance of the MXene-based conductive fabric sensitive layer decreases sharply. Quantitative sensing of the pressure signal can be achieved by detecting changes in current.

[0028] The temperature sensing unit consists of a lower functional electrode layer 4 and an MXene / CNT composite thermosensitive material sensitive layer (thermosensitive layer 5). Its sensing mechanism is as follows: the MXene / CNT composite thermosensitive material exhibits a positive temperature coefficient (PTC) characteristic. When the sensor contact temperature increases, the carrier migration rate within the composite thermosensitive material decreases. Simultaneously, the thermal expansion of the polymer matrix leads to an increase in the spacing between the conductive networks of MXene and CNTs, causing the resistance of the composite thermosensitive material to increase with temperature. Conversely, when the temperature decreases, the resistance of the composite thermosensitive material decreases. Temperature sensing is achieved by detecting the resistance change of the thermosensitive material in the lower electrode circuit.

[0029] In summary, the flexible dual-mode sensor for underwater environmental sensing of the present invention integrates pressure sensing and temperature sensing functions in a single flexible device. The two sensing modules share some electrode structures and their signals are independent and do not interfere with each other. It can realize the simultaneous detection of multiple physical quantities in complex environments such as underwater, effectively simplifying the device structure and improving integration and environmental adaptability. The conductive fabric layer 31 used in the pressure-sensitive layer 3 of this invention has a three-dimensional interconnected porous structure, micro-protrusions on the fiber surface, and a rough structure. Under external pressure stimulation, the number of contact points between fibers and the effective contact area increase significantly with the increase of pressure, making the device more sensitive to changes in resistance and with a large response amplitude, thereby improving the pressure sensing sensitivity. At the same time, the fabric substrate has low cost, good flexibility, and fast deformation recovery, which is conducive to realizing wide-range and high-stability mechanical signal detection. The upper hydrophobic encapsulation layer 1, the lower hydrophobic encapsulation layer 6, and the middle hydrophobic encapsulation layer 32 of this invention together constitute a fully encapsulated superhydrophobic protective structure, which fully realizes the functions of waterproof and anti-fouling protection for the device, solving the problem that traditional flexible sensors are prone to short circuits and device damage under underwater and high humidity conditions; moreover, the overall manufacturing process is simple and low in cost, making it suitable for large-scale manufacturing and practical engineering applications.

[0030] Example 2: Based on Example 1, this example provides a method for fabricating a flexible device integrating pressure and temperature sensing functions, the difference being that the silver (Ag) target material used in magnetron sputtering in step 2 is replaced with one or more of titanium (Ti), aluminum (Al), copper (Cu), gold (Au), and ITO, and the sputtering process parameters are adjusted adaptively according to the characteristics of the target material. The remaining fabrication steps are exactly the same as in Example 1.

[0031] Example 3: Based on Example 1, this example provides a method for fabricating a flexible device integrating pressure and temperature sensing functions. The difference lies in that the magnetron sputtering process in step 2 is replaced by a spraying process, and the spraying materials used are silver nanowires, MXene, MXene / silver nanowire composite ink, carbon black, carbon nanotubes, etc. The remaining fabrication steps are exactly the same as in Example 1.

[0032] Example 4: Based on Example 1, this example provides a method for fabricating a flexible device integrating pressure and temperature sensing functions, the difference being that the MXene dispersion in step 3 is replaced with one or any combination of carbon nanotube dispersion, graphene dispersion, and carbon black dispersion. The remaining preparation steps are exactly the same as in Example 1.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating a flexible dual-mode sensor for underwater environmental sensing, characterized in that, Includes the following steps: Step 1: Prepare polydimethylsiloxane / polytetrafluoroethylene composite solution; drop the composite solution onto the 3D printing mold and the flat substrate respectively, and heat and cure it after vacuum degassing to obtain a patterned middle hydrophobic encapsulation layer (32) and a thin film upper hydrophobic encapsulation layer (1) and a lower hydrophobic encapsulation layer (6). Step 2: Using a polyimide film as a flexible substrate, a pressure sensing electrode pattern is prepared on one side of the film by magnetron sputtering or spraying with a pattern template to obtain an upper functional electrode layer (2); another polyimide film is taken, and a pressure sensing electrode pattern and an interdigitated temperature sensing electrode pattern are prepared on both sides of the polyimide film to obtain a lower functional electrode layer (4) integrating pressure and temperature dual electrodes. Step 3: Cut the fabric and immerse it in the conductive dispersion liquid for impregnation and drying. After drying, a conductive fabric layer (31) with a continuous conductive network is formed. The conductive fabric layer (31) is embedded inside the middle hydrophobic encapsulation layer (32) to obtain the pressure-sensitive layer (3). Step 4: Prepare MXene / CNT composite temperature-sensitive ink, and uniformly apply it to the interdigitated temperature-sensitive electrode pattern area of ​​the lower functional electrode layer (4) by spraying or scraping to obtain a temperature-sensitive layer (5) located on the lower side of the lower functional electrode layer (4). Step 5: Device assembly and packaging to obtain a flexible dual-mode sensor for underwater environmental sensing.

2. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, In step 1, the preparation steps of the polydimethylsiloxane / polytetrafluoroethylene composite solution are as follows: Polydimethylsiloxane prepolymer and curing agent in a mass ratio of 10:1 were added together to n-hexane and stirred to obtain a uniform dispersion. Polytetrafluoroethylene particles were added to the dispersion, with a mass ratio of polytetrafluoroethylene particles to polydimethylsiloxane prepolymer of 1:

10. The mixture was stirred until the polytetrafluoroethylene particles were completely dispersed. The mixture was then stirred under heating conditions at 70°C to remove n-hexane and obtain a uniform polydimethylsiloxane / polytetrafluoroethylene composite solution.

3. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, The middle hydrophobic encapsulation layer (32) has a through hole in the middle for embedding the conductive fabric layer (31); in step 3, the fabric is cut to a size that matches the through hole of the middle hydrophobic encapsulation layer (32).

4. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, In step 4, the preparation steps of the MXene / CNT composite temperature-sensitive ink are as follows: MXene nanosheets and carbon nanotubes were mixed at a mass ratio of 5:

1. Deionized water was added to the deionized water to adjust the total solid content of the solution system to 20 wt%, and a mixed slurry was obtained. Then, the mixture was magnetically stirred and ultrasonically prepared to obtain a uniformly dispersed MXene / CNT composite thermosensitive ink.

5. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, In step 4, after the MXene / CNT composite temperature-sensitive ink is coated on the interdigitated temperature-sensitive sensing electrode pattern area of ​​the lower functional electrode layer (4), the lower functional electrode layer (4) is placed in a vacuum oven at 60-80℃ and dried for 15-25 minutes. After being taken out and cooled, a temperature-sensitive layer (5) located on the lower side of the lower functional electrode layer (4) is obtained.

6. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, Step 5 specifically involves: The upper hydrophobic encapsulation layer (1), upper functional electrode layer (2), pressure-sensitive layer (3), lower functional electrode layer (4), temperature-sensitive layer (5) and lower hydrophobic encapsulation layer (6) are stacked from top to bottom and bonded together with adhesive. The pressure sensing electrode on the lower side of the upper functional electrode layer (2) and the pressure sensing electrode on the upper side of the lower functional electrode layer (4) are respectively attached to the upper and lower sides of the pressure-sensitive layer (3) to obtain a flexible dual-mode sensor for underwater environment sensing.

7. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, In step 3, the concentration of the conductive dispersion is 5 mg / mL to 10 mg / mL, and the conductive dispersion is one of MXene dispersion, carbon nanotube dispersion, graphene dispersion, and carbon black dispersion.

8. The method for fabricating a flexible dual-mode sensor for underwater environmental sensing according to claim 1, characterized in that, In step 3, the immersion and drying steps are repeated 3 to 5 times. Each immersion lasts for 3 to 5 minutes, and each drying is carried out at a temperature of 60 to 80°C for 10 minutes.

9. A flexible dual-mode sensor for underwater environmental sensing, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

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