Janus fabric strain sensor with switchable wettability and preparation method thereof
By constructing an MXene/CNTs composite conductive layer and a PFDMS/TiO2 hydrophobic layer on the surface of a flexible strain sensor, and utilizing ultraviolet light and heat treatment to achieve reversible wetting switching of the sensor interface, the problems of signal stability and structural reliability of the sensor in humid environments are solved, and the performance of the sensor in complex environments is improved.
Patent Information
- Application Number
- CN202610026124.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-04-17
AI Technical Summary
Existing flexible strain sensors lack stability in humid environments. Sweat penetration causes signal distortion, and multi-physics coupling caused by human movement leads to signal crosstalk and drift. They also lack environmental adaptability.
A Janus fabric strain sensor was constructed by coating an MXene/CNTs composite conductive sensing layer with a PFDMS/TiO2 hydrophobic functional layer and achieving reversible switching of wettability at the sensor interface through ultraviolet light irradiation and heat treatment.
It enables the sensor to adapt to different humidity environments, actively guides the directional transport of liquids such as sweat, keeps the sensing interface dry and stable, and improves signal reliability and sensor structural integrity.
Smart Images
Figure CN121876793A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of stress sensing technology, specifically relating to a Janus fabric strain sensor with switchable wettability and its preparation method. Background Technology
[0002] Flexible strain sensors, as a key branch of flexible electronics, have shown great promise in fields such as human-computer interaction, health monitoring, and electronic skin due to their excellent flexibility and stretchability. However, in practical wearable applications, their reliability faces two major challenges: first, environmental factors such as sweat and moisture can penetrate and interfere with the electrical properties of force-sensitive materials, leading to signal distortion; second, multi-physics coupling during human movement can cause signal crosstalk and drift, reducing recognition accuracy. To address these challenges, current research mainly improves stability on two levels: in terms of environmental stability, hydrophobic modifications or encapsulation layers are typically used to physically isolate water molecules; in terms of signal stability, multimodal sensing or sensor arrays are often used to decouple complex mechanical stimuli to suppress noise.
[0003] Janus materials offer unique advantages for directional liquid transport due to their inherent chemical or physical asymmetry. Current fabrication methods mainly fall into two categories: layer-by-layer construction (e.g., electrospinning) and surface asymmetry modification (e.g., plasma treatment). These methods generate a Laplace pressure difference through a wetting gradient, driving the directional movement of the liquid. This characteristic makes them highly promising for wearable sensors, as they can maintain interface dryness by self-driving the transport of sweat, thus improving signal stability. Currently, the field of flexible strain sensors primarily uses electrospinning to construct the wetting gradient; however, multilayer structures are prone to weak interfacial bonding and easy separation under dynamic conditions. While single-layer post-processing strategies maintain mechanical consistency, their static wettability is difficult to adapt to complex environmental changes. Therefore, developing an adaptive Janus interface that can dynamically switch between moisture-wicking and protective states according to the environment is crucial for realizing next-generation high-reliability wearable sensors. Summary of the Invention
[0004] This invention addresses the technical problems of existing fabric strain sensors, such as limited functionality, lack of environmental adaptability, and insufficient sensing stability in humid environments, by providing a method for fabricating a Janus fabric strain sensor with switchable wettability.
[0005] The structure of a Janus fabric strain sensor with switchable wettability according to the present invention is as follows: an MXene / CNTs composite conductive sensing layer is coated with a PFDMS / TiO2 hydrophobic functional layer, one side of the PFDMS / TiO2 hydrophobic functional layer is an ultraviolet light irradiation layer, and the other side is a polydimethylsiloxane layer.
[0006] The fabrication method of the Janus fabric strain sensor with switchable wettability is carried out according to the following steps:
[0007] Step 1: Preparation of MXene / CNTs composite conductive sensing layer. The cleaned TPU nonwoven fabric is swollen and its shape is fixed using a mold. It is placed in a hexadecyltrimethylammonium bromide solution and surface modified by ultrasonic assistance. After drying, it is immersed in an MXene / CNTs mixed dispersion solution, dried and demolded to obtain an MXene / CNTs composite conductive sensing layer with a micro-wrinkled structure.
[0008] Step 2: Integration of the PFDMS / TiO2 hydrophobic functional layer: The TPU nonwoven fabric with the MXene / CNTs composite conductive sensing layer with micro-wrinkled structure is immersed in the PFDMS / TiO2 mixed solution, ultrasonically dried;
[0009] Step 3: Fabrication of Janus fabric strain sensor with switchable wettability. One side of the fabric sensor with hydrophobic functional layer is irradiated with ultraviolet light, while the other side, which is not irradiated, is sprayed with polydimethylsiloxane solution.
[0010] Further, the preparation method of the MXene / CNTs composite conductive sensing layer in step one is as follows: ① The TPU nonwoven fabric is soaked in chloroform for 3-5 min and then fixed on a mold; ② The fixed TPU nonwoven fabric is placed in a cetyltrimethylammonium bromide solution and sonicated for 25-35 min and then dried in a 60 ℃ oven for 30 min; ③ The dried TPU nonwoven fabric is placed in an MXene / CNTs mixed solution and sonicated for 25-35 min and then dried in a 60 ℃ oven for 30 min and then demolded to obtain the MXene / CNTs composite conductive sensing layer.
[0011] Further, in step 1, the mass ratio of hexadecyltrimethylammonium bromide to deionized water in the hexadecyltrimethylammonium bromide solution is (20-60) mg: 100 mL.
[0012] Further, in step 1, the ratio of Mxene: carboxylated carbon nanotubes: water in the MXene / CNTs mixed dispersion solution is (150-200) mg: (5-10) mg: 200 mL.
[0013] Further, step 2 specifically involves dispersing titanium dioxide in a mixed solution composed of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and ethanol, stirring at room temperature, immersing the MXene / CNTs composite conductive sensing layer prepared in step 1 into the above solution, sonicating, drying and curing, and constructing a PFDMS / TiO2 hydrophobic functional layer on the surface of the sensing layer.
[0014] Further, in step 2, the mass ratio of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane to the volume ratio of ethanol in the mixed solution of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is (300-500) mg: 50 ml.
[0015] Furthermore, in step 2, the mass ratio of titanium dioxide to 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is (1-3):1.
[0016] Further, step 3 specifically involves performing asymmetric surface treatment on the fabric sensor with a hydrophobic functional layer obtained in step 2 to construct a Janus structure: one side is irradiated with 254 nm ultraviolet light to reduce the surface energy of that side, thereby exhibiting hydrophilicity; the other side is sprayed with a polydimethylsiloxane solution, which is then dried and cured to form a stable hydrophobic layer, thus obtaining a Janus fabric strain sensor with reversible switching.
[0017] Furthermore, the duration of ultraviolet irradiation in step 3 is 2 to 2.5 hours.
[0018] Furthermore, in step 3, the spray concentration is 1% polydimethylsiloxane.
[0019] The Janus fabric strain sensor with switchable wettability described in this invention is prepared by the method described above.
[0020] The sensor prepared in this invention is constructed through a swelling and in-situ adsorption process, possessing a hydrophobic inner layer and an outer layer with tunable light / thermal response. It can become hydrophilic under ultraviolet irradiation and revert to a hydrophobic state after heat treatment. This invention achieves dynamic wetting management of the sensing interface, significantly improving the signal stability and wearability of the sensor in complex humid environments, and has significant value for the development of next-generation adaptive smart textiles.
[0021] The advantages of this invention are:
[0022] (1) The present invention enables the sensor interface to respond to external light / heat stimuli and realizes the reversible switching of its wettability between hydrophilic and hydrophobic states.
[0023] (2) The sensor can adapt to different humidity environments and actively guide the directional transport of liquids such as sweat, thereby effectively maintaining the dryness and stability of the sensing interface and improving signal reliability.
[0024] (3) By integrating the sensing layer, functional layer and Janus structure into a single substrate through integrated technology, the separation between layers is avoided, and the sensor maintains structural integrity under dynamic bending and stretching, ensuring the reliability of long-term use. Attached Figure Description
[0025] Figure 1 The image shows the microstructure of the Janus fabric strain sensor with switchable wettability obtained in Example 1.
[0026] Figure 2 for Figure 1 Enlarged image;
[0027] Figure 3 The contact angle change of the Janus fabric strain sensor with switchable wettability obtained in Example 1 under ultraviolet irradiation;
[0028] Figure 4 The directional water-guiding performance diagram of the Janus fabric strain sensor with switchable wettability obtained in Example 1;
[0029] Figure 5 This is a diagram illustrating the directional water-guiding process of the Janus fabric strain sensor with switchable wettability obtained in Example 1.
[0030] Figure 6 The strain sensing performance diagram of the Janus fabric strain sensor with switchable wettability obtained in Example 1 is shown.
[0031] Figure 7 The resistance response curve of the Janus fabric strain sensor with switchable wettability obtained in Example 1 during 8000 cyclic stretching cycles at 60% strain is shown as a function of time. Detailed Implementation
[0032] Example 1: Fabrication of a Janus fabric strain sensor with switchable wettability
[0033] The fabrication method of a Janus fabric strain sensor with switchable wettability according to this embodiment is carried out according to the following steps:
[0034] I. Preparation of MXene / CNTs composite conductive sensing layer: The cleaned TPU nonwoven fabric was swollen with chloroform for 3-5 min and its shape was fixed using a mold. Then, it was placed in a 0.2 mg / ml hexadecyltrimethylammonium bromide aqueous solution and surface modified by sonication for 25-35 min. After that, it was taken out and dried in an oven at 60 ℃ for 30 min. An MXene / CNTs mixed dispersion solution was prepared by mixing 195.5 mg MXene, 6.5 mg carboxylated carbon nanotubes and 200 mL of water. The TPU nonwoven fabric was then immersed in the MXene / CNTs mixed dispersion solution and sonicated for 25-35 min. Finally, it was placed in an oven at 60 ℃ for 30 min and then demolded to obtain an MXene / CNTs composite conductive sensing layer with a micro-wrinkled structure.
[0035] II. Integration of PFDMS / TiO2 hydrophobic functional layer: 0.6 g of titanium dioxide was dispersed in a mixed solution consisting of 0.3 g of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and 50 mL of ethanol, and stirred at room temperature until homogeneous. Subsequently, the MXene / CNTs composite conductive sensing layer prepared in step (1) was immersed in the above solution and ultrasonically treated at room temperature for 30 min to ensure full adhesion of the functional material. Finally, it was dried and cured to construct a PFDMS / TiO2 hydrophobic functional layer on the surface of the sensing layer.
[0036] III. Fabrication of a Janus Fabric Strain Sensor with Switchable Wetting Properties: The fabric sensor with a hydrophobic functional layer obtained in step (2) underwent asymmetric surface treatment to construct a Janus structure: one side was selectively irradiated with 254 nm ultraviolet light for 2 hours to reduce the surface energy of that side, thus exhibiting hydrophilicity; the other side was sprayed with 0.5 ml of 1% polydimethylsiloxane solution and dried and cured at 60 °C for 30 min to form a stable hydrophobic layer. After this treatment, a significant difference in wettability was formed on both sides of the sensor. In addition, this Janus structure has a reversible wettability switching capability: when it is necessary to restore the hydrophilic surface to a hydrophobic state, it can be simply heated in a 150 °C oven. Thus, a Janus fabric strain sensor with reversible switching was obtained.
[0037] Example 2
[0038] This example provides the fabrication of a Janus fabric strain sensor with switchable wettability. The difference between this example and Example 1 is that the mass ratio of PFDMS to TiO2 is 1:1, while the rest is the same as Example 1.
[0039] Example 3
[0040] This example provides the fabrication of a Janus fabric strain sensor with switchable wettability. The difference between this example and Example 1 is that the mass ratio of PFDMS to TiO2 is 1:4, while the rest is the same as Example 1.
[0041] Example 4 Detection Test
[0042] To investigate the resistance change of the Janus fabric strain sensor with reversible switching obtained after implementation, the following operations were performed after step two:
[0043] The conductive silver paste was evenly applied to the copper electrode, and then the two electrodes were fixed to the two ends of the fabric sensor with hydrophobic functional layer obtained in step two. The sensor was cured in an oven at 60 ℃ for 2 h. After curing, step three was performed.
[0044] (I) The morphology of the Janus fabric strain sensor with reversible switching obtained in Example 1 is as follows: Figure 1 As shown in the scanning electron microscope image. Figure 1 Enlarged image as shown Figure 2 As shown. From Figures 1-2 It can be seen that the surface of the prepared Janus fabric strain sensor exhibits a micro-wrinkled morphology, and TiO2 particles are uniformly loaded on it.
[0045] (II) The contact angle change of the Janus fabric strain sensor with reversible switching obtained in Example 1 under ultraviolet irradiation is as follows: Figure 3 As shown, with prolonged ultraviolet irradiation time, the water contact angle on the sensor surface gradually decreases, from an initial 141° to 29°. Furthermore, after high-temperature treatment at 150°C, the surface can be restored to a hydrophobic state, indicating that its wettability has reversible switching characteristics.
[0046] (III) The directional water transport performance diagram and process diagram of the Janus fabric strain sensor with reversible switching obtained in Example 1, from... Figures 4-5 It can be seen that the Janus fabric strain sensor with reversible switching can achieve rapid directional transport of moisture within 24 seconds under the action of gravity and antigravity.
[0047] (iv) The resistance response curve of the Janus fabric strain sensor with reversible switching obtained in Example 1 as a function of tensile stress is shown below. Figure 6 As shown. The strain range of the sensor can reach 0~150%.
[0048] (V) The resistance response curve of the Janus fabric strain sensor with reversible switching obtained in Example 1 under repeated stretching as a function of time, and a partially enlarged view of some curves are shown below. Figure 7 As shown, under 60% strain conditions, the sensor maintained stable response performance after 8000 repeated cycles of testing.
[0049] (vi) The Janus fabric strain sensor with reversible switching obtained in Example 2 has a strain range of 0~180%, but it cannot achieve rapid directional transport of moisture.
[0050] (vii) The Janus fabric strain sensor with reversible switching obtained in Example 3 has a strain range of 0~130%, which can realize rapid directional transport of moisture.
Claims
1. A Janus fabric strain sensor with switchable wettability, characterized in that, The Janus fabric strain sensor with switchable wettability has the following structure: an MXene / CNTs composite conductive sensing layer is coated with a PFDMS / TiO2 hydrophobic functional layer. One side of the PFDMS / TiO2 hydrophobic functional layer is an ultraviolet light irradiation layer, and the other side is a polydimethylsiloxane layer.
2. The method for fabricating the Janus fabric strain sensor with switchable wettability as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of MXene / CNTs composite conductive sensing layer: The cleaned TPU nonwoven fabric is swollen and its shape is fixed using a mold. The surface of the material was modified by ultrasonic assistance in a cetyltrimethylammonium bromide solution; after drying, it was immersed in a mixed dispersion of MXene / CNTs, dried, and demolded to obtain a composite conductive sensing layer of MXene / CNTs with a micro-wrinkled structure. Step 2: Integration of the PFDMS / TiO2 hydrophobic functional layer: The TPU nonwoven fabric with the MXene / CNTs composite conductive sensing layer with micro-wrinkled structure is immersed in the PFDMS / TiO2 mixed solution, ultrasonically dried; Step 3: Fabrication of Janus fabric strain sensor with switchable wettability. One side of the fabric sensor with hydrophobic functional layer is irradiated with ultraviolet light, while the other side, which is not irradiated, is sprayed with polydimethylsiloxane solution.
3. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 1, characterized in that, In step 1, the preparation method of the MXene / CNTs composite conductive sensing layer is as follows: TPU nonwoven fabric is soaked in chloroform for 3-5 min and then fixed on a mold; the fixed TPU nonwoven fabric is placed in a cetyltrimethylammonium bromide solution and sonicated for 25-35 min and then dried in a 60 ℃ oven for 30 min; the dried TPU nonwoven fabric is placed in an MXene / CNTs mixed solution and sonicated for 25-35 min and then dried in a 60 ℃ oven for 30 min before demolding to obtain the MXene / CNTs composite conductive sensing layer.
4. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 1, characterized in that, In step 1, the ratio of the mass of hexadecyltrimethylammonium bromide to deionized water in the hexadecyltrimethylammonium bromide solution is (20-60) mg: 100 mL; in the MXene / CNTs mixed dispersion solution, the ratio of Mxene: carboxylated carbon nanotubes: water is (150-200) mg: (5-10) mg: 200 mL.
5. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 1, characterized in that, Step 2 specifically involves dispersing titanium dioxide in a mixed solution composed of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and ethanol to obtain a PFDMS / TiO2 mixed solution. The solution is stirred at room temperature, and the MXene / CNTs composite conductive sensing layer prepared in step 1 is immersed in the above solution. The solution is then sonicated, dried, and cured to construct a PFDMS / TiO2 hydrophobic functional layer on the surface of the sensing layer.
6. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 5, characterized in that, In step 2, the mass ratio of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane to the volume ratio of ethanol in the mixed solution of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and ethanol is (300-500) mg: 50 ml.
7. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 5, characterized in that, In step 2, the mass ratio of titanium dioxide to 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is (1-3):
1.
8. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 1, characterized in that, Step 3 specifically involves performing asymmetric surface treatment on the fabric sensor with hydrophobic functional layer obtained in step 2 to construct a Janus structure: irradiating one side with 254 nm ultraviolet light to reduce the surface energy on that side, thereby making it hydrophilic. On the other side, a polydimethylsiloxane solution was sprayed and dried to form a stable hydrophobic layer, thus creating a Janus fabric strain sensor with reversible switching.
9. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 8, characterized in that, In step 3, the duration of ultraviolet irradiation is 2 to 2.5 hours.
10. The method for fabricating a Janus fabric strain sensor with switchable wettability according to claim 8, characterized in that, In step 3, the spray concentration is 1% polydimethylsiloxane.